INDEX OF TABLES TABLE NO. CONTENT PAGE CHAPTER 1 I

Tuberculosis 2. Natural Products 3. Polymeric nanoparticles 4. Encapsulation of natural compounds in polymeric nanoparticles 5. Drugs for the treatment of tuberculosis loaded in polymeric nanoparticles IV.

5

Antioxidant activity of the ethanol fraction from leaves of Leucophyllum frutescens (HF4) in its non-encapsulated and encapsulated form in biodegradable polymeric nanoparticles (NP). Ascorbic acid (AA) was taken as an antioxidant control ( ±σ, n=3).

CHAPTER 3 1

Effect of the sonication time on the hydrodynamic diameter ( ±σ, n=3).

2

Effect of the concentration of Tween 80 solution on the hydrodynamic diameter ( ±σ, n=3).

3

Effect of the ratio on the amount of oleic acid (oil phase) and 1% w/v of Tween 80 solution (aqueous phase) on the hydrodynamic diameter ( ±σ, n=3). Tuberculosis is an emergency disease worldwide, the emergence of resistant strains to the treatment has produced the use of natural products as alternative. Studies have shown that Leucophyllum frutescens extracts present antimicrobial effect, but the disadvantage is that the extracts are recovered in a vehicle that contains organic solvents. The preparation of polymeric nanoparticles (NP) involves the elimination of the solvent in which the active is solubilized, which makes possible to use them as vehicles for the administration of the extracts. Therefore, the aim of this study was to design and develop formulations of NP with an extract of L. frutescens, and rifampicin (RIF), in order to evaluate the in vitro biological activity against M. tuberculosis. Firstly, the methanolic extract of leaves and roots of L. frutescens and its fractions were obtained. The anti-M. tuberculosis activity was determined, being the root extract (EMR) and its hexane fractions (FHR and RF1) the most actives with a MIC of 100, 40 and 40 μg/mL, respectively. RIF, EMH, FHR and RF1 were incorporated into NP by nanoprecipitation. NP of ≈180 nm with homogeneous size distribution were obtained. The NP were evaluated on M. tuberculosis, being the formulation of NP-PLGA-RIF (MIC=0.10 μg/mL) and NP-PLGA-RF1 (CMI=80 μg/mL) with better activity. Finally, the anti-M. tuberculosis activity of the combined form formulations was evaluated, the combination of RIF with NP-PLGA-RF1 produced better behavior, reducing the MIC of both without showing toxic effect. The studies carried out in this work showed the potential use of an NP formulation contains a vegetable fraction of L. frutescens in combination with RIF as an alternative against M. tuberculosis.

II.

RÉSUMÉ La tuberculose est une maladie d'urgence dans le monde, l'apparition de souches résistantes au traitement a produit l'utilisation de produits naturels comme alternative. Des études ont montré que les extraits de Leucophyllum frutescens présentaient un effet antimicrobien, mais l'inconvénient est que les extraits sont récupérés dans un véhicule qui contient des solvants organiques. La préparation de nanoparticules polymériques (NP) implique l'élimination du solvant dans lequel l'actif est solubilisé, ce qui permet les utiliser comme véhicules pour l'administration des extraits. Par conséquent, le but de cette étude a été design et développer des formulations de NP avec un extrait de L. frutescens et de la rifampicine (RIF), afin d'évaluer l'activité biologique in vitro contre M. tuberculosis. Premièrement, l'extrait méthanolique de feuilles et de racines de L. frutescens et ses fractions a été obtenu. L'activité contre M. tuberculosis a été déterminée, l'extrait de racines (EMR) et ses fractions hexanique (FHR et RF1) ont été les plus actives avec une CMI de 100, 40 et 40 μg/mL, respectivement. RIF, EMH, FHR et RF1 ont été incorporés dans NP par nanoprécipitation. Des NP de ≈180 nm avec une distribution de taille homogène ont été obtenus. Les NP ont été évaluées sur M. tuberculosis, les formulations de NP-PLGA-RIF (CMI=0,10 μg/mL) et NP-PLGA-RF1 (CMI=80 μg/mL) ont montré la meilleure activité. Finalement, l'activité des formulations combinées contre M. tuberculosis a été évaluée, la combinaison de RIF avec NP-PLGA-RF1 a produit le meilleur comportement, réduisant la CMI des deux sans montrer un effet toxique. Les études réalisées dans ce travail ont montré l'utilisation potentielle d'une formulation de NP contient une fraction végétale de L. frutescens en combinaison avec le RIF comme alternative contre M. tuberculosis. INTRODUCTION

Tuberculosis

Tuberculosis (Tb) is an infectious disease caused by Mycobacterium tuberculosis (OMS, 2018), which is an acid-fast bacillus. It particularly affects the lungs, developing pulmonary Tb [START_REF] Ruiz-Manzano | Diagnóstico y tratamiento de la tuberculosis[END_REF]. Since 1993, it is considered by the World Health Organization (WHO) as an emergency disease worldwide. In 2016, 10.4 million people became ill with tuberculosis and 1.7 million died from this disease (OMS, 2018).

The current therapeutic scheme against Tb is based on the administration of four firstline antibiotics: isoniazid (INH), rifampicin (RIF), pyrazinamide (PZA) and streptomycin or ethambutol, for 6 months (WHO, 2005). Specifically, RIF is the only bactericidal drug that has activity on different populations that the bacteria present in the organism.

One limitation of the treatment is that, due to its long duration many patients do not follow it adequately, which causes the appearance of drug-resistant strains. Therefore, to improve the pharmacological therapy and avoid the resistance of the agent, it is urgent to find alternatives that reduce the time of treatment, or substances with a mechanism of action different to the existing drugs.

Natural Products

The plants have been used in traditional medicine to treat several diseases. WHO estimates that in many developed countries, from 70 to 80% of the population has tested a kind of alternative or complementary medicine (OMS, 2008).

Research in natural products has grown in recent years, numerous medicinal plant compounds that exhibit bioactivity have been described, including antimycobacterial activity (Camacho-Corona et al., 2009).

For this reason and in response to the urgency of obtaining new drugs against strains of M. tuberculosis, several studies based on natural products have been developed. Some plants of the north of Mexico have been evaluated with favorable activity, among them, extracts of Leucophyllum frutescens, commonly named "cenizo".

In the study by Molina-Salinas et al., extracts of L. frutescens against drug-resistant and drug-resistant strains of M. tuberculosis were tested. The extract of the leaves and roots were obtained by maceration. The evaluation by microdilution in broth showed an activity of the root extract of 62.5 μg/mL, for the sensitive and the resistant strain. For the leaves, a MIC of 125 μg/mL was obtained. This study supports that, the selection of plants by ethnobotanical criteria increases the possibility of finding species with activity, not only against M. tuberculosis, but also against other microorganisms (Molina-Salinas et al., 2007).

However, the disadvantage of the use of extracts is that they are recovered in vehicles containing organic solvents, therefore their application in vivo is not viable.

To overcome these limitations, new strategies have been proposed, including the use of polymeric nanoparticles (NP) as a vehicle for the administration of plant extracts.

Polymeric nanoparticles

The NP (Figure 1) are particles of less than 500 nm in diameter that are prepared from natural or synthetic, biodegradable or non-biodegradable polymers. Drugs, proteins, peptides or nucleotides can be incorporated into these polymeric systems for their therapeutic application. Among the features that stand out from these colloidal systems include the protection of the active, the targeting to an organ or cell and the sustained release of the encapsulated compound (Martínez Rivas et al., 2017), this last virtue allows to reduce the frequency of treatment dose. On the other hand, the preparation of NP involves the elimination of the solvent in which the active is solubilized (Figure 2), resulting in the encapsulation of the active compounds, free of organic solvents.

An additional advantage of NP is related to the versatility in their administration, depending their composition. NP can be applied topically (Martínez Rivas et al., 2017), oral or parenteral (Pilheu et.al., 2007).

Therefore, it is important to note that NP are a potential vehicle to increase the antimycobacterial activity of drugs used in the treatment of tuberculosis and to transport natural extracts that can not be administered directly to the body.

Encapsulation of natural compounds in polymeric nanoparticles

In recent years the interest in the encapsulation of plant extracts or derivatives has increased, an example is the encapsulation of resveratrol. Yao et al. incorporated the compound in chitosan NP with free amino groups on the surface. NP had a particle size of 487 nm and an polydispersity index of 0.144; in addition, chitosan NP showed sustained release in vitro [START_REF] Yao | Study on the preparation of resveratrol chitosan nanoparticles with free amino groups on the surface[END_REF].

In another study, Uthaman et al. extracted boswellic acid from the rubber resin of Boswellia serrata. The volumetric analysis showed a total of boswellic acid in the extract of 60%. Subsequently, formulations of NP were formulated with boswellic acid by nanoprecipitation method. NP had a diameter of 259 nm and a Z potential of -42.88 mV.

The in vitro cytotoxicity assays were performed with different cancer cell lines (pancreas, brain, prostate and melanoma). The PC3 prostate cancer cell line showed favorable cytotoxicity percentages. Therefore, they concluded that NP formulations containing boswellic acid can be used as potential anticancer agents in the treatment of prostate cancer [START_REF] Uthaman | Novel Boswellic Acids Nanoparticles Induces Cell Death in Prostate Cancer Cells[END_REF].

Drugs for the treatment of tuberculosis loaded in polymeric nanoparticles

Different studies have verified the protective properties [START_REF] Calleja-Avellanal | Desarrollo y caracterización de nanopartículas de rifampicina para su aplicación en el tratamiento de la tuberculosis. Tecnología Farmacéutica[END_REF], targeting [START_REF] Yolandy | Targeted nanodrug delivery systems for the treatment of Tuberculosis[END_REF] and sustained release (Maksimenko et al., 2010) from NP containing first-line drugs of the tuberculosis treatment, including RIF. NP improved the bioavailability of the drugs and reduced the frequency of the dose [START_REF] Pandey | Poly (DL-Lactide-Co-Glycolide) Nanoparticle-Based Inhalable Sustained Drug Delivery System for Experimental Tuberculosis[END_REF]Pandey y Khuller, 2006). In addition, there are several works that showed an effect against M. tuberculosis when they are encapsulated in NP. An example was observed in the study conducted by Yolandy et al., who demonstrated targeting of isoniazid (INH) in nanoparticulate delivery systems. The in vitro tests were performed on THP-1 and U937 monocyte-macrophages and microscopic analysis showed that targeting was achieved. After 1 and 2 days of exposure of INH loaded NP, a significant inhibition in the growth of the microorganism was observed, but with a reduced value in the toxicity/efficiency ratio compared with free INH [START_REF] Yolandy | Targeted nanodrug delivery systems for the treatment of Tuberculosis[END_REF]. And, Booysen et al. proved that RIF and INH loaded NP have activity against the strain of M. tuberculosis H37Rv. In addition, they carried out the oral administration of the formulations in mice and observed a sustained release of the drugs for 7 days. They also determined the distribution of RIF and INH in the liver and the lungs for up to 10 days. With these results, they conclude that NP containing drugs for the treatment of tuberculosis have the potential to improve Tb chemotherapy [START_REF] Booysen | In Vivo/in Vitro Pharmacokinetic and Pharmacodynamic Study of Spray-Dried Poly-(Dl-Lactic-Co-Glycolic) Acid Nanoparticles Encapsulating Rifampicin and Isoniazid[END_REF].

Therefore, the incorporation of plant compounds in NP as well as a first-line drug such as RIF is a promising alternative. In this context, the present work focused on the encapsulation of the extract and the fractions of L. frutescens in NP to generate a phytomedicine, as well as the incorporation of RIF, with the purpose of improving the activity against M. tuberculosis, and thus, proposing them as treatment for tuberculosis.

IV. JUSTIFICATION

The Tb is considered since 1993, by WHO, a worldwide emergency disease. One of the main causes of the great number of deaths, reported each year because of this disease, is due to the resistance that the bacillus strains have acquired in consequence to the inadequate monitoring of the treatment.

For this reason, it is urgent to find alternatives that reduce the treatment time and actives with a mechanism of action different from the existing drugs, to treat resistant strains. In recent years, natural products have been studied for the molecules with biological activity it contains, but their application is limited to the presence of organic solvents with which extracts are recovered.

The NP are a vehicle of biologically active compounds that offers multiple advantages, among them, the removal of the organic solvents in which the active compounds are dissolved. Therefore, the incorporation of plant compounds in NP is a promising alternative. In addition, NP provide sustained release to the encapsulated compound, making possible to reduce the dose frequency.

In this context, the present work is focused on incorporation of extracts and fractions of Leucophyllum frutescens plant to generate a phytomedicine, as well as encapsulation of RIF, in order to enhance the activity against M. tuberculosis and propose them as treatment for Tb.

V. HYPOTHESIS

The encapsulation of an extract or fraction of L. frutescens and rifampicin in polymeric nanoparticles allows the enhancement of the activity against M. tuberculosis.

VI. GENERAL OBJECTIVE

To design and develop NP formulations based on an extract or fraction of L. frutescens and RIF, in order to increase their biological activities against M. tuberculosis. , 2018). Four first-line antibiotics are administered to treat the disease, including rifampicin (RIF). However, the daily administration of the drugs for more than 6 months orally (NOM NOM-006-SSA2-1993).

VII. SPECIFIC OBJECTIVES

One limitation of the treatment is its long duration, patients do not follow it adequately, which causes the appearance of resistant strains to the drugs. Therefore, to improve drug therapy and to avoid the resistance of the agent, it is urgent to find alternatives that reduce the time of treatment or find substances with a different mechanism of action from the existing drugs.

Plants have been used in traditional medicine to treat different diseases. WHO estimates that 70 to 80% of the population has ever resorted to one or another form of alternative or complementary medicine (OMS, 2008). The phytochemical study has grown in recent years and have been described numerous compounds obtained from medicinal plants that exhibit biological activity, including antimycobacterial activity described (Camacho-Corona et al., 2009).

For this reason, and in response to the urgency of obtaining new treatments against M.

tuberculosis strains, natural products studies have been developed. Several plants in northern of Mexico have a favorable activity against this bacterium. Particularly, the extracts of L. frutescens plant, commonly known as "cenizo", were found among those that presents best activity.

Molina-Salinas et al., evaluated the methanol extract from leaves and roots of L.

frutescens on the sensitive and multi-drug resistant strain of M. tuberculosis. Leaves extract had no activity on the sensitive strain, whereas, in the resistant multi-drug strain showed a MIC of 125 μg/mL. Roots extract had a MIC of 62.5 μg/mL in both strains (Molina-Salinas et al., 2007).

However, the disadvantage of this type of extracts is they are recovered in vehicles that contain organic solvents, thus their application in vivo is not viable. To overcome this limitation, new strategies have been proposed such as polymeric nanoparticles (NP) use.

NP are systems that present sustained release allowing the reduction of the frequency of treatment doses; in addition, NP confer to the active: protection [START_REF] Yoo | pH-Sensitive Eudragit Nanoparticles for Mucosal Drug Delivery[END_REF], targeting to specific tissues and controlled delivery (Maksimenko et al., 2010;Pandey y Khuller, 2006). For example, Yao et al., carried out studies about the release of resveratrol (a compound present in grapes) incorporated in chitosan nanoparticles, the results showed that the nanoparticles had a sustained release and, therefore, a reduction in the frequency of the dose [START_REF] Yao | Study on the preparation of resveratrol chitosan nanoparticles with free amino groups on the surface[END_REF].

Antitubercular drugs have also been incorporated in NP for the enhancement of their activities. Booysen et. al. encapsulated RIF and isoniazid (INH) [START_REF] Booysen | In Vivo/in Vitro Pharmacokinetic and Pharmacodynamic Study of Spray-Dried Poly-(Dl-Lactic-Co-Glycolic) Acid Nanoparticles Encapsulating Rifampicin and Isoniazid[END_REF]. For this reason, RIF being an antibiotic used in the treatment of Tb, is a model drug for its incorporation into NP.

The promising use of extracts or fractions is accompanied by the term biocompatibility. Two aspects that should be considered in the study of sample compatibility are: cytotoxicity and hemocompatibility. Knowing this last aspect, extracts or non-toxic fractions can be proposed for the use in an organism.

The aim of the present work was to take advantage of anti-M. tuberculosis activity of the extracts and fractions from L. frutescens plant to formulate them in NP in order to make viable its application against M. tuberculosis. In addition, the combined effect of extracts and fractions free and encapsulated was evaluated to propose the use of an extract or fraction of L. frutescens as co-adjuvant of the antituberculosis drug RIF.

MATERIALS AND METHODS

Preparation of Leucophyllum frutescens extracts and their fractions

Leaves and roots of L. frutescens were collected in Monterrey, N. L., Mexico in July 2013. Consequently, the plant material was washed, dried at room temperature and pulverized. An amount of 50 g of powdered leaves or roots were weighed and 350 mL of methanol was added. The extracts were obtained by ultrasound (Ultrasonic Cleaners, VWR Symphony, USA). For a period of 1 h, the temperature for the extraction was increased from 25 to 60 ºC, once reached 60 ºC, three cycles of 10 min of sonication and 10 min of rest were performed. Subsequently, the samples were filtered to obtain the solvent, which was evaporated under reduced pressure (Laborota 4003 control, Heidolph) in order to obtain the methanol extract of leaves (EMH) and roots (EMR).

With respect to the fractionation of the extracts, two methods were used. In the method 1, EMH was solubilized in methanol, it was placed in a separatory funnel and hexane was added; subsequently, both solvents were mixed and the hexane part was recovered and evaporated under reduced pressure in order to obtain the hexane fraction (FHH). The same procedure was followed with the EMR in order to obtain the hexane fraction from roots (FHR).

In the method 2, hexane was added to the EMH and stirred to aid the solubilization of the compounds related to the solvent, then, it was filtered to obtain the solvent and evaporated obtaining the hexane fraction called HF1. Chloroform was added to the solid insoluble in hexane, stirred and filtered to obtain the solvent with the compounds related to chloroform and evaporated for obtaining the chloroform fraction (HF2). This procedure was repeated with other solvents of higher polarity (ethyl acetate, ethanol and methanol) in order to obtain the HF3-HF5 fractions.

The fractionation method 2 was also performed to the EMR, identifying the obtained fractions as RF1-RF5. The yield (%) of the extracts and the fractions were calculated according to equations 1 and 2, respectively:

where, Wextract is the weight (g) of the obtained extract once the solvent is evaporated, Wplant is the weight (g) of the dried and powdered leaves or roots, Wfraction is the weight (g) of the obtained fraction once the solvent is evaporated, and Wextract is the weight (g) of the extract for the fractionation.

Chromatographic analysis of the extracts and fractions of Leucophyllum frutescens

For obtaining of the chromatographic profile of the EMH, EMR and their fractions, the samples were dissolved separately in acetonitrile (J. T. Baker, USA)/methanol (Tedia, USA), each solution was filtered through a 0.45 μm filter (Millipore, USA) to be analyzed by HPLC (VARIAN 9065,9012,ProStar 410,USA). A Synergi™ 4 μm Fusion-RP 80 Å (150 mm x 2.0 mm x 4 μm) column, a flow of 0.2 mL/min and 30 °C was used. The mobile phase was formic acid (purity: 90%, Millipore, USA) at 0.1% v/v and methanol with an isocratic elution of 45:55 for 40 min for leaves and 60 min for roots. The profiles were detected at λ=215 nm.

Chromatographic analysis of rifampicin

The RIF analysis (Sigma-Aldrich, USA) was carried out by HPLC using a Zorbax

Eclipse XDB-C18 (150 mm x 2.1 mm x 5 μm) column, with a mobile phase formed by acetonitrile and water at 0.1% (v/v) of formic acid with an isocratic elution of 60:40 with a flow of 0.35 mL/min at 30 °C and at λ=334 nm.

Preparation of the calibration curve and method validation for the quantification of rifampicin

For the quantification of RIF a stock solution in acetonitrile was prepared. From this solution, the working solutions were prepared in a range from 5 to 30 μg/mL and filtered through a 0.45 μm membrane. The analysis was carried out by HPLC to obtain the calibration curve.

The chromatographic method was validated through the variables: linearity, limit of detection (LOD) and limit of quantification (LOQ) according to the International Conference on Harmonization (ICH). For the establishment of the linearity, the calibration curve was prepared and analyzed in triplicate. The LOD and LOQ were calculated by the following equations:

where, is the standard deviation of the response and S is the slope of the calibration curve.

The repeatability was established with three levels of concentration, six times each one the same day, while the reproducibility was obtained with three levels of concentration, six times each one in two different days.

Preparation of the calibration curve of the methanol extract from roots and their hexane fractions of Leucophyllum frutescens

For the quantification of the plant samples in NP, calibration curves of the EMR, FHR and RF1 were prepared. The samples were prepared in a mixture of acetonitrile/methanol at a concentration of 600 -1700 μg/mL, the solution was filtered through a 0.45 μm filter to be analyzed by HPLC.

Synergi™ 4 μm Fusion-RP 80 Å (150 mm x 2.0 mm x 4 μm) column was used.

The mobile phase was formic acid at 0.1% v/v and methanol in an isocratic elution of 45:55 for 60 min with a flow of 0.2 mL/min, 30 ºC and at λ=220 nm.

The chromatographic method for the sample RF1 was validated through the variables: linearity, LOD and LOQ according to the ICH.

Encapsulation and characterization of rifampicin, methanol extract and hexane fractions of Leucophyllum frutescens roots in biodegradable polymeric nanoparticles

Four different formulations of RIF loaded NP were prepared by the nanoprecipitation technique proposed by Fessi et al. (1989). Briefly, the organic phase was prepared containing polylactic acid (PLA; PURASORB) or polylactic-co-glycolic acid (PLGA; MEDISORB 85:15 DL) and 2 mg of RIF in 3 mL of a mixture of solvents (acetone:methanol). The organic phase was added to 10 mL of an aqueous phase, containing polyvinyl alcohol (PVAL) (Clariant, Mexico) or Lutrol F127 (BASF) as a tensoactive agent at a concentration of 1% (w/w).

Then, the organic solvent was evaporated under reduced pressure. In this way, four formulations of RIF loaded NP were obtained. The NP characterization was carried out determining the particle size and polydispersity index (PDI) by dynamic light scattering (Zetasizer Nano ZS90, Malvern Instruments, UK). The zeta potential was measured by electrophoretic light scattering (Zetasizer Nano ZS90, Malvern Instruments, UK).

Two different formulations EMR, FHR or RF1 in NP were prepared by the nanoprecipitation technique. The organic phase was prepared with the particle-forming polymer, 20 mg of PLA or 15 mg of PLGA, and the plant sample (8 mg for EMR or 4 mg for FHR or RF1) in solvent mixture (acetone: methanol). The organic phase was added to PVAL at 1% w/w in constant stirring. The NP characterization was carried out by determining the particle size, PDI and zeta potential.

To determine the drug loading and encapsulation efficiency (%L and %EE), the NP formulations were centrifuged at 25,000 rpm (Allegra 64R, Beckman Coulter, USA), the supernatant was decanted, and the pellets were lyophilized (Freeze Dry System, LABCONCO, USA). The lyophilized NP were dissolved in acetonitrile for NP-RIF and acetonitrile:methanol for NP-EMR, NP-FHR and NP-RF1.

The obtained solutions were analyzed according to the chromatographic method previously described to quantify the samples from the calibration curves of each one.

Subsequently, the %L and % EE for each formulation were determined by the following equations:

and NP-PLA-FHR was performed in duplicate. The experimental results were expressed as mean±standard deviation ( ±σ, n=3).

Analysis by Scanning Electron Microscopy

The surface morphology of the NP was observed through the scanning electron microscopy (SEM) (FEI Quanta 250 FEG) from the "Centre Technologique des

Microstructures" (CT ) of the Claude Bernard University Lyon 1, France. For the preparation of the samples, one drop of each NP suspension was deposited in a metal sample holder and dried at room temperature. Finally, the samples were plated with platinum under vacuum.

Anti-M. tuberculosis activity

The anti-M. tuberculosis activity was evaluated on the susceptible strain of M. of the first well and adding them to the second well of the row, then, of the second well, 100 μL was taken to add them to the third, this procedure was repeated until reaching the last well each row; the 100 μL taken from the last well was eliminated. Finally, 100 μL of the bacterial suspension was added to obtain a final volume in all wells of 200 μL. The final concentrations for the EMH, FHR and RF1 were from 0.7 to 400 μg/mL; for RIF from 0.1 to 50 μg/mL; for NP-RIF from 12.5 to 400 μg/mL; for NP-EMR, NP-FHR and NP-RF1 from 5 to160 μg/mL. The microplates were incubated at 37 °C for 5 days. At day 5, 20 μL of the blue alamar reagent and 12 μL of 10% v/v of tween 80 were added to all the work wells, and the microplates were reincubated at 37 °C for 24 h. The minimum inhibitory concentration (MIC) was determined from the color change of the blue to pink reagent. All tests were carried out at least in triplicate.

In a second stage of the study, the RIF was combined with the EMR, FHR and RF1 in order to determine the mixture with the best activity. The work carried out by [START_REF] Avijgan | Synergistic Activity between Echinophora Platyloba DC Ethanolic Extract and Azole Drugs against Clinical Isolates of Candida Albicans from Women Suffering Chronic Recurrent Vaginitis[END_REF] was taken as a reference. Then, RIF was combined with the formulation of NP-RF1 and NP-RIF formulation with NP-RF1 to determine if there was a synergism in the antimycobacterial activity. To carry out the evaluation, the concentration of RIF was varied by column and the concentration of the vegetable samples was varied by row. For example, for the RIF and RF1 combination, the RIF concentration was varied in the 1st row and the volume of the solution was kept constant with RF1 for a final concentration of 40 μg/mL; in the 2nd row the concentration of RIF was varied, and the volume of the solution was kept constant with RF1 for a final concentration of 20 μg/mL and, thus, downwards.

All analyzes were carried out in triplicate, except for the combination of RIF with EMR (n=1).

Hemolytic activity assay

The assay of hemolytic activity was carried out according by UNE-EN ISO 10993-4. A blood sample, from a healthy patient, was placed in a tube with ethylenediaminetetraacetic acid (EDTA), as an anticoagulant. The sample was centrifuged, discarding the plasma and the white cell pack, and preserving only the red blood cells (RBC) package. The RBC were washed three times with PBS (pH=7.4) in a 1:1 ratio (RBC:PBS). After washing, the supernatant was discarded and the RBC were resuspended in PBS in a 1: 1 ratio (RBC:PBS) in order to obtain the working suspension of RBC. On the other hand, stock solutions of EMR and hexane fractions were dissolved in DMSO/PBS at a concentration of 1 mg/mL. Different concentrations of these samples were prepared from the stock solution, as well as NP formulations that showed the best activity against M. tuberculosis (NP-RIF and NP-RF1) in a range of 10 to 200 μg/mL in DMSO from 0.1 to 2% v/v. The negative control to the hemolysis was prepared with 975 μL of PBS and the positive control to the hemolysis was prepared with 975 μL of milli-Q water. A 25 μL of the RBC suspension was added to all samples, including controls. The samples were incubated at 37 ° C for 1 h (VORTEMP 56, Labnet International, Inc., USA). After this time, the samples were centrifuged at 10,000 rpm for 10 min (Spectrafuge 24D, Labnet International, Inc., USA), recovering the supernatant of all the samples and adding them to a 96-well microplate. Finally, the absorbance of the supernatants was measure at λ = 575 nm in a microplate reader (Epoch, BioTek Instruments, Inc., USA). The hemolytic activity was expressed as a percentage according to equation 7:

(7)
where, ABSsample is the absorbance of the supernatant from the sample, ABSneg is the absorbance of the negative control, and ABSpos is the absorbance of the positive control.

All analyzes were carried out at least in triplicate. The experimental results were expressed as ±σ, n=3.

RESULTS AND DISCUSION

Yields of extracts of Leucophyllum frutescens and their fractions

The methanol extracts from the leaves and roots of L. frutescens were obtained by ultrasound. As shown in Table I, the highest yield was obtained with the leaves. In the study published by Sultana et al. the same tendency is observed, there was a higher yield in leaves than in roots. They obtained the methanol extracts from leaves and roots of Moringa oleifera by two extraction techniques, with an orbital agitator at room temperature and under reflux in a water bath for 6 h, obtaining a yield with M. oleifera leaves of 9.6 and 16.6%, respectively. The yields in roots were of 3.2 and 5.1%, respectively [START_REF] Sultana | Effect of extraction solvent/technique on the antioxidant activity of selected medicinal plant extracts[END_REF]. Even, the yields for EMH is higher than EMR, 19.30 and 7.92%, respectively. et al., 2006). In our case, the ultrasound method developed to obtain the methanol extracts from leaves and roots of L. frutescens required less time (2 h). The percentages of yield of the fractions, with the methodology described above, are shown in Table I. When the hexane fraction is obtained, by any method, there was a higher yield in the hexane fractions from roots, it is possible to attribute greater number of related compounds in hexane by roots than leaves. While, increasing the polarity of the solvents, yields of leaves are observed higher than roots.

Chromatographic profiles of the extracts and fraction of Leucophyllum frutescens

The extracts and fractions from leaves and roots were analyzed by HPLC to obtain their chromatographic profile. The variability within the plants of the same species depends on the collection station and the origin of the plant, among other factors [START_REF] Nguyen Hoai | Development of HPLC fingerprints for Mallotus species extracts and evaluation of the peaks responsible for their antioxidant activity[END_REF]. For this reason, the determination of the chromatographic profile is useful for the quality control of plant extracts [START_REF] He | Chemical Fingerprint Analysis for Quality Control and Identification of Ziyang Green Tea by HPLC[END_REF][START_REF] Kim | Quality Assessment of Ojeok-San, a Traditional Herbal Formula, Using High-Performance Liquid Chromatography Combined with Chemometric Analysis[END_REF][START_REF] Xie | Combinative Method Using HPLC Quantitative and Qualitative Analyses for Quality Consistency Assessment of a Herbal Medicinal Preparation[END_REF], Yang et al., 2013).

4 main peaks (Figure 1), while the chromatographic profiles of the extract and fractions from roots reveal the presence of 7 main peaks (Figure 2).

Anti-M. tuberculosis activity of the extracts and fractions obtained from de

Leucophyllum frutescens

The activity of extracts and fractions of L. frutescens against M. tuberculosis H37Rv was evaluated by the alamar blue microplate method. MIC obtained from the assay are presented in Table II In this case, the activity given by the fractions was greater than the extract [START_REF] Kahaliw | Evaluation of the antimycobacterial activity of crude extracts and solvent fractions of selected Ethiopian medicinal plants[END_REF].

According to the results published with other plants, root fractions are potential plant samples against M. tuberculosis. Following the mentioned chromatographic profile (Figure 2), in roots there are more peaks than in leaves.

RF3 fraction was discarded for the determination of the chromatographic profile, antioxidant and hemolytic activity, due to experimentally a low percentage of yield and low anti-M. tuberculosis H37Rv were obtained.

Chromatographic analysis of rifampicin

Among the analytical methods, HPLC highlight, it allows the separation of the compounds according to their physiochemical characteristics, even if they are in a polymeric matrix (Moreno-Exebio y Grande-Ortiz, 2014).

Initially, the chromatographic conditions that allowed the detection of RIF were developed. Figure 3 showed that the molecule was detected at a retention time of 2.0 min. chromatographic method for the quantification of antituberculosis drugs. The retention time of RIF was 2.85 min using acetonitrile: tetrabutylammonium hydroxide (42.5:57.5, v / v) (0.2 mM) at a pH of 3.10 (Glass et al., 2007).

Preparation of the calibration curve and method validation for the quantification of rifampicin

The validation was carried out to ensure that the analytical procedure is accurate for the quantification of RIF. Table 3 shows the validation parameters established for the developed method. The concentration range (5-30 μg/mL) had linearity, with a correlation coefficient greater than 0.99. LOD was 0.71 μg/mL, while LOQ was 2.14 μg/mL. On the other hand, repeatability and reproducibility were measured, obtaining a variation of 5.97 and 6.79%, respectively. These values are acceptable, below the ±15% previously established [START_REF] Glass | Optimization of a Stability-Indicating HPLC Method for the Simultaneous Determination of Rifampicin, Isoniazid, and Pyrazinamide in a Fixed-Dose Combination Using Artificial Neural Networks[END_REF], therefore the method is accurate.

Height (mAU) Time (min)

Table III. Validation parameters of the chromatographic method for the quantification of rifampicin

Preparation of the calibration curve of the methanol extract from leaves and roots of Leucophyllum frutescens

As part of the characterization, from the chromatographic methods previously developed, the calibration curve of each plant sample (EMR, FHR and RF1) was analyzed in order to quantify the most abundant peaks in them, being selected the peak no. 5 in all the samples, and the peaks no. 6 and 7 in RF1. The method for RF1 quantification was validated by linearity, LOD and LOQ (Table IV).

For extracts or fractions from plants, the known compounds of the plant are selected, and the chromatographic method is developed for their quantification. For

Encapsulation and characterization of rifampicin, methanol extract and hexane fractions from roots of Leucophyllum frutescens loaded in polymeric nanoparticles

Nanotechnology has emerged as a promising area to target the active to reservoirs such as macrophages [START_REF] Nasiruddin | Nanotechnology-Based Approach in Tuberculosis Treatment[END_REF]. M. tuberculosis resides for a long period of time in the alveolar macrophages of the lungs [START_REF] Jain | Targeted Drug Delivery to Macrophages[END_REF].

Due to the NP size, they are a promising vehicle for distribution through the body and to reach the target cells or organs. Nahar and Jain prepared NP with sizes of 150-200 nm and negative zeta potential. Subsequently, they determined the targeting of Amphotericin B in PLGA NP conjugated with mannose and PEG to organs rich in macrophages (liver, kidney, spleen, lung and lymph nodes) in a bioavailability study.

Swiss albino adult mice and males were injected with NP formulations, after the treatment they were sacrificed to analyze the organs. The results showed targeting of NP to organs rich in macrophages (Nahar y Jain, 2009). Comparing these results with our work, these characteristics of size and surface charge are favorable for their potential use. The surface charge measured by the zeta potential is important because it is related to the stability of NP and drug release profiles (Honary y Zahir, 2013). The use of some emulsifiers (surfactants) modifies the surface charge, although the emulsifiers used in this work are neutral [START_REF] Mura | Influence of Surface Charge on the Potential Toxicity of PLGA Nanoparticles towards Calu-3 Cells[END_REF], and their charge is modified depending on the pH of the medium. For example, PVAL has acetates groups that are negatively ionized as the Then, the formulations were analyzed by HPLC for the quantification of the drug, this HPLC method was developed to detect RIF without interference from the polymeric matrix. As seen in Table V, the encapsulation percentages changed according to the polymer and surfactant involved in particle formation. NP formulation with the highest encapsulation of RIF was PLA-PVAL-NP formulation, with an encapsulation efficiency of 35.9%, which indicates that 35.9% of total RIF is encapsulated in NP. While, the lowest encapsulation was PLGA-PVAL-NP. This difference is given, because the polymer PLA has lower hydrophilic affinity than PLGA [START_REF] Dalpiaz | Application of the 'in-Oil Nanoprecipitation' Method in the Encapsulation of Hydrophilic Drugs in PLGA Nanoparticles[END_REF]. Therefore, PLA is more macrophages at 4 h. Therefore, they conclude that the size and surface chemistry of the particles influences their absorption [START_REF] Nicolete | The Uptake of PLGA Micro or Nanoparticles by Macrophages Provokes Distinct in vitro Inflammatory Response[END_REF].

The peak no. 5 was selected to be quantified in NP, for being an abundant Finally, the surface morphology of the NP by MEB was determined. Figure 4 shows the micrographs obtained from the blank NP, RIF NP and RF1 NP. NP had a spherical shape and a smooth surface, with a size around 80 nm and homogeneous distribution in all formulations.

Anti-Mycobacterium tuberculosis activity of the nanoparticle formulations

Once the formulations of NP were obtained, they were evaluated against M.

tuberculosis. In Table VII, MIC of the formulations of NP with RIF are shown, the complete formulations (encapsulated and non-encapsulated active) and the formulations with the encapsulated active were evaluated. Likewise, MIC for RIF was determined (0.20 μg/mL). PLGA NP showed the best encapsulation, and it is the PLGA-PVAL formulation with encapsulated active that had the highest activity (0.10 μg/mL) even compared with the free drug. This enhancement in the antibacterial activity of the drug encapsulated in PLGA NP compared with its free form has already been observed in other studies.

As example is the work carried out by Darvishi et al., and, for S. epidermidis was of 35 and 10 μg/mL, respectively. The results revealed that GLA NP had better activity than free GLA [START_REF] Darvishi | Preparation and Antibacterial Activity Evaluation of 18-β-Glycyrrhetinic Acid Loaded PLGA Nanoparticles[END_REF]. As mentioned, the best antimycobacterial activities were given by EMR, FHR and RF1 (MIC=100, 40 and 40 μg/mL, respectively), so they were selected to be formulated in NP. Table VIII shows the results of the assay for the determination of the activity of the NP formulations containing EMH, FHR or RF1, being FHR-PLGA-NP and RF1-PLGA-NP with the best activities. These results suggest that PLGA-PVAL-NP enhanced the activity against M. tuberculosis compared to free forms of RIF, FHR and RF1. Subsequently, the combined effect between RIF and EMR, FHR or RF1 was evaluated, the best combination was achieved with RIF and RF1, MIC decreased from 0.20 to 0.10 μg/mL and 40 to 10 μg/mL, respectively (Table VIII). From this favorable combination, the combined effect of RIF with RF1-PLGA-NP and RIF-PLGA-NP with RF1-PLGA-NP was tested. The combination RIF-PLGA-NP with RF1-PLGA-NP did not have a better effect than the free combination. However, the combination of RIF with RF1-PLGA-NP, showed a better MIC for both, from 0.20 to 0.10 μg/mL and 80 to 20 μg/mL, respectively. It means, when RF1 is in NP, it is possible to enhance the effect of its free form. These results suggested that the combination of RIF with a hexane fraction from roots of L. frutescens against M. tuberculosis is favorable. The combination of drugs with natural agents increases the spectrum of activity and decreases the risk of emergence of resistant strains (Avijan et al., 2014).

Hemolysis assay

One of the techniques for measuring compatibility can be through the determination of hemolysis [START_REF] Fischer | In vitro Cytotoxicity Testing of Polycations: Influence of Polymer Structure on Cell Viability and Hemolysis[END_REF]. The test of the extracts and their fractions was carried out according by UNE-EN ISO 10993-4 which establish that a percentage lower than 5% is considered non-hemolytic, considering the value of 100% to the total amount of hemoglobin present in the RBC sample added. RF5 showed no hemolysis at the concentrations analyzed. In contrast, RF2 and RF4 maintain a nonhemolytic effect at ≤100 μg/mL, and EMR at ≤25 μg/mL, Finally, the hexane fractions FHR and RF1 are non-hemolytic at ≤10 μg/mL (Figure 5). Also, the hemolysis percentage was determined as an indicator of the toxicity of RIF and NP formulations. For the concentration of RIF with activity against M. tuberculosis MIC were determined: i) free form (0.20 μg/mL), ii) in combination (0.10 μg/mL) and iii) RIF-PLGA-PVAL, being the formulation with the best activity. The results showed there was no presence of hemolysis. While, RF1 and RF1-PLGA-NP at the MIC against M. tuberculosis (40 and 80 μg/mL, respectively) are hemolytic. However, when RF1 is combined with RIF, the concentrations decreased from 40 to 10 μg/mL for RF1 and from 80 to 20 μg/mL for the NP formulation, and at these concentrations there was no presence of hemolysis (Figure 6). Additionally, Figure 6 showed that the encapsulation of RF1 in NP favors the reduction of its toxicity.

CONCLUSION

In this study several evaluations were carried out in order to have a broader knowledge about the biological activity of L. frutescens where is concluded:

-With the ultrasound method developed to obtain the methanol extract of leaves and roots of L. frutescens was obtained a yield of 19.3 and 7.92%, respectively, in a short time (2 h).

-Similar yields of the two fractionation methods of the hexane fractions were observed. However, method 2 was selected to continue with the following partitions because it is a faster and easier to execute.

-The chromatographic profiles by HPLC of the extracts and fractions revealed four and seven peaks of major components in leaves and roots, respectively.

-The bactericidal activity of the extracts and fractions against M. tuberculosis revealed that the roots are more active, specifically, EMR, FHR and RF1 with MIC of 100, 40 and 40 μg/mL, respectively. However, hemolysis occurred at these concentrations.

-Biodegradable NP of RIF and plant samples (EMR, FHR and RF1) of L. frutescens were prepared by nanoprecipitation, with a size from 140 to 190 nm, with homogeneous distributions and negative zeta potential.

-When RIF is encapsulated in PLGA-PVAL-NP enhanced its activity against M. tuberculosis (0.10 μg/mL) compared to the PLA-PVAL-NP and the free drug. The extract and fractions had a higher MIC when they are encapsulated. The most active formulations were with the fractions, showing better activity with PLGA NP (80 μg/mL) compared to PLA NP (160 μg/mL).

-The combination of plant samples with RIF decreased the MIC in both cases, demonstrating a better effect.

-At the active concentrations against M. tuberculosis, RIF and RIF loaded NP did not present hemolysis.

-The RF1 and RF1 loaded NP showed hemolysis at the active concentrations against M. tuberculosis. However, when RF1 is combined with RIF, the concentrations decreased from 40 to 10 μg/mL for RF1 and from 80 to 20 μg/mL for the NP formulation, and at these concentrations there is no presence of hemolysis.

Based on the results, the encapsulation of RF1 in NP decreased the toxicity.

Therefore, a promising alternative for the treatment of Tb is the encapsulation of RF1 in NP and to combine it with conventional antituberculosis drugs.

CHAPTER 2. POTENTIAL USE OF Leucophyllum frutescens AS ANTIOXIDANT AGENT AND ITS ENCAPSULATION IN POLYMERIC NANOPARTICLES ABSTRACT

Leucophyllum frutescens has been studied mainly for its activity against Mycobacterium tuberculosis but other biological properties in the plant have been less studied. In addition, for advance in the investigation of the plant to the application in some organism, it would be promising to transport the natural components in polymeric nanoparticles (NP), thus avoiding the use of organic solvents. It should be noted that NP have different advantages that improve the biological activity of the contained active. The objective of this work was to encapsulate an extract or fraction, with antioxidant activity, obtained from the methanol extract of L. frutescens. With nanoencapsulation, the vegetable sample is incorporated in a vehicle free of organic solvents, without losing its property, making possible to administer it in the body. First, the antioxidant activity of the extracts and fractions from leaves and roots of L. frutescens were evaluated to select the ethanolic fraction from leaves (HF4) as the most active. The chromatographic profile of the ethanol fraction of leaves was determined by High Performance Liquid Chromatography (HPLC), selecting four peaks-components for their use as internal markers in order to quantify them once the plant sample was encapsulated in NP. For quantification of the component peaks in NP, firstly, the chromatographic method was partially validated. The regression equations of the four peaks were obtained, with correlation coefficients greater than 0.99. In addition, the limit of detection and limit of quantification of each peak was determined resulting in 43. 09 and 130.58, 38.62 and 117.03, 22.29 and 67.53 and, 45.86 and 138.97 μg/mL, for peaks 1, 2, 3 and 4, respectively. Suspensions of HF4 loaded NP were obtained by the nanoprecipitation method. NP had particle sizes around 200 nm with homogeneous distributions. While, the percentage of encapsulation of peaks 1, 2, 3 and 4 was 20, 23, 61 and 80%, respectively. Then, the antioxidant activity was evaluated using the oxidant peroxyl, 2,2-azo-bis-(2-amidinopropane) dihydrochloride (AAPH) in red blood cells. The fraction HF4 presented antioxidant activity at 100 μg/mL and when HF4 was encapsulated in NP, the activity was preserved. Finally, through the hemolysis test was concluded that HF4 and HF4-NP are not toxic to the active concentrations. Therefore, the potential use of HF4 loaded NP as an antioxidant agent is promising.

INTRODUCTION

Several compounds with biological activity from plants, have been isolated and identified. One of the most common examples is Taxol ® , which was obtained from the plant called Taxus breuifolia [START_REF] Wani | Plant Antitumor Agents. VI. Isolation and Structure of Taxol, a Novel Antileukemic and Antitumor Agent from Taxus Brevifolia[END_REF]. The large number of plants existing in the earth leads to the acquisition of new compounds or the promising discovery of

activities not yet known in species not yet studied.

Leucophyllum frutescens, of the family Scrophulariaceae, is a plant commonly known as "cenizo". In Nuevo León it is the bush par excellence. In Texas it is called "shrub barometer" because its flowering depends on humidity in the environment and rainfall [START_REF] Zaragoza | Guía de Árboles y Otras Plantas Nativas en la Zona Metropolitana de Monterrey[END_REF]. L. has been studied mainly for its activity against Mycobacterium tuberculosis (Alanís-Garza et al., 2012;Molina-Salinas et al., 2007, 2011). Some studies suggest other biological properties present in the metabolites of the plant.

However, a property not yet studied is its antioxidant capacity. Throughout the antioxidant effect, the body is protected from oxidative stress caused by free radicals. Free radicals play a fundamental role in different diseases such as cancer, inflammatory diseases or neurological disorders caused by age [START_REF] Lobo | Free Radicals, Antioxidants and Functional Foods: Impact on Human Health[END_REF].

There are several studies focused on the investigation of the antioxidant activity of plants. Generally, the antioxidant properties are attributed to a chemical group called polyphenols (Özkan y Özcan, 2017). In the study by Saeed et al., some extracts were obtained from the plant Torilis leptophylla, were studied, where the presence of phenols were found, which were related to their antioxidant activity. Likewise, an in vivo study suggested that methanol extract could be used against oxidative damage caused by carbon tetrachloride (CCl4) by its antioxidant property [START_REF] Saeed | Antioxidant Activity, Total Phenolic and Total Flavonoid Contents of Whole Plant Extracts Torilis Leptophylla L[END_REF].

To produce free radicals using the peroxyl initiator, 2,2-azo-bis-(2amidinopropane) dihydrochloride (AAPH) in red blood cells (RBC) causes hemolysis, however, adding an antioxidant prevents hemolysis. Therefore, this system is an adequate model to determine the antioxidant activities of extracts or fractions of plants [START_REF] An | Evaluation of the Antioxidant Activity of Cooked Gomchwi (Ligularia Fischeri) Using the Myoglobin Methods[END_REF]. This method allowed to Jiang et al. to investigate the protection conferred by the aqueous extract of Pueraria thomsonii and Pueraria lobata on the RBC damage of rats caused by free radicals. No antioxidant activity was shown by the aqueous extract of P.

thomsonii, with an IC50 around 1000 μg/mL. In contrast, the extract of P. lobata exhibited a potent activity, with an IC50 of 194.0±6.9 μg/mL [START_REF] Jiang | A comparative study on aqueous root extracts of Pueraria thomsonii and Pueraria lobata by antioxidant assay and HPLC fingerprint analysis[END_REF].

A limitation in the use of plant extracts with potential as antioxidant agents is on their in vitro or in vivo application because they are obtained in an organic solvent, which cannot be administered to an organism. A proposal to transport natural components is the use of polymeric nanoparticles (NP), because they show different advantages that improve the biological activity of the sample [START_REF] Christofoli | Insecticidal Effect of Nanoencapsulated Essential Oils from Zanthoxylum rhoifolium (Rutaceae) in Bemisia tabaci Populations[END_REF].

For this reason, the aim of this work was to encapsulate an ethanol fraction obtained from the methanol extract of L. frutescens leaves, with antioxidant activity in order to contain it in a vehicle free of organic solvents without loss of activity, and thus to obtain a formulation with potential administration in an organism.

MATERIALS AND METHODS

Obtaining of the extracts of Leucophyllum frutescens and their fractions

Chapter 1 describes the procedure for obtaining the extracts from leaves and roots of L. frutescens and its fractions.

Determination of the antioxidant activity of the extracts and fractions from

Leucophyllum frutescens

The antioxidant activity was measured by the damage of RBC producing free radicals with AAPH, the methodology described by [START_REF] Abajo | In vitro Study of the Antioxidant and Immunomodulatory Activity of Aqueous Infusion of Bidens Pilosa[END_REF]. was used as reference. A blood sample, from a healthy patient, was placed in a tube with ethylenediaminetetraacetic acid (EDTA), as an anticoagulant. The sample was centrifuged, discarding the plasma and the white cell pack, preserving only the RBC package. RBC were washed three times with a solution of phosphates with salt (PBS, pH 7.4) in a ratio of 1:1 (RBC: PBS). After the washing, the supernatant was discarded, and the RBC were resuspended in PBS to subsequently dilute them 1:10 (RBC:PBS) in order to obtain the working suspension of RBC.

On the other hand, stock solutions of EMH, EMR and fractions in DMSO were prepared. Also, one solution of AAPH at 400 mM in PBS was prepared. Then, a volume of each sample was taken to obtain the final concentrations in a range of 10 to 200 μg/mL in DMSO (0.15 to 3% v/v). The antioxidant control was ascorbic acid (AA), which was prepared at the same concentrations as the plant samples. 375 μL of the AAPH solution and 250 μL of the RBC suspension were added to all the samples.

The oxidant control was PBS, 375 μL of the AAPH solution and 250 μL of the RBC suspension. Two controls were added, one negative to the hemolysis (750 μL of PBS and 250 μL of RBC) and another positive to hemolysis (750 μL of milli-Q water and 250 μL of RBC). All test samples had a final volume of 1000 μL. Samples and controls were incubated at 37 ° C for 2.5 h with constant agitation (300 rpm) (VORTEMP 56, Labnet International, Inc., USA). After this time, the samples were centrifuged at 10,000 rpm for 10 min (Spectrafuge 24D, Labnet International, Inc., USA), recovering the supernatant of all the samples and adding them to a 96-well microplate. Finally, the absorbance of the supernatants at λ=575nm was measured in a microplate reader (Epoch, BioTek Instruments, Inc., USA). The oxidative damage was determined by equation 1:

where, ABSsample is the absorbance of the supernatant of the sample, ABSox is the absorbance of the supernatant of the oxidant control and ABSpos is the absorbance of the supernatant of the positive control to the hemolysis. From this result the antioxidant activity was determined:

All analyzes were carried out at least in triplicate. The experimental results were expressed as mean±standard deviation ( ±σ, n=3).

Determination of the hemolytic activity of the extracts and fractions from

Leucophyllum frutescens

The assay of hemolytic activity was carried out according by UNE-EN ISO 10993-4. A blood sample, from a healthy patient, was placed in a tube with ethylenediaminetetraacetic acid (EDTA), as an anticoagulant. The sample was centrifuged, discarding the plasma and the white cell pack, and preserving only the red blood cells (RBC) package. The RBC were washed three times with PBS (pH 7.4) in a 1:1 ratio (RBC:PBS). After washing, the supernatant was discarded and the RBC were resuspended in PBS in a 1: 1 ratio (RBC:PBS) in order to obtain the working suspension of RBC.

On the other hand, stock solutions of EMR and hexane fractions were dissolved in DMSO/PBS at a concentration of 1 mg/mL. Different concentrations of these samples were prepared from the stock solution, as well as NP formulations that showed the best activity against M. tuberculosis (NP-RIF and NP-RF1) in a range of 10 to 200 μg/mL in DMSO from 0.1 to 2% v/v. The negative control to the hemolysis was prepared with 975 μL of PBS and the positive control to the hemolysis was prepared with 975 μL of milli-Q water. 25 μL of the RBC suspension was added to all samples, including controls. The samples were incubated at 37 ° C for 1 h (VORTEMP 56, Labnet International, Inc., USA). After this time, the samples were centrifuged at 10,000 rpm for 10 min (Spectrafuge 24D, Labnet International, Inc., USA), recovering the supernatant of all the samples and adding them to a 96-well microplate. Finally, the absorbance of the supernatants was measure at λ = 575 nm in a microplate reader (Epoch, BioTek Instruments, Inc., USA). The hemolytic activity was expressed as a percentage according to equation 3:

(3)
where, ABSsample is the absorbance of the supernatant from the sample, ABSneg is the absorbance of the negative control, and ABSpos is the absorbance of the positive control.

All analyzes were carried out at least in triplicate. The experimental results were expressed as ±σ, n=3.

Chromatographic analysis

For the obtaining of the chromatographic profile of HF4, it was dissolved in acetonitrile (J. T. Baker, USA)/methanol (Tedia, USA), the solution was filtered through a 0.45 μm filter (Millipore, USA) to be analyzed by HPLC (VARIAN 9065,9012,ProStar 410,USA). A Synergi™ 4 μm Fusion-RP 80 Å (150 mm x 2.0 mm x 4 μm) column, a flow of 0.2 mL/min and 30 °C was used. The mobile phase was formic acid (purity: 90%, Millipore, USA) at 0.1% v/v and methanol with an isocratic elution of 45:55 for 40 min for leaves and 60 min for roots. The profiles were detected at λ=224 nm.

Preparation of the calibration curve and method validation

HF4 was weighted and disolved in methanol (Tedia, USA), to obtain a stock solution at 2000 μg/mL. From the stock, the working solutions were prepared in the range from 100 to 700 μg/mL and filtered through a 0.45 μm membrane (Millipore, USA), they were analyzed by the HPLC method before mentioned to obtain the calibration curve.

The chromatographic method was validated through the variables: linearity, limit of detection (LOD) and limit of quantification (LOQ) according to the International Conference on Harmonization (ICH). For the establishment of the linearity, the calibration curve was prepared and analyzed in triplicate. The LOD and LOQ were calculated by the following equations:

where, is the standard deviation of the response and S is the slope of the calibration curve.

Encapsulation of the ethanol fraction from leaves of Leucophyllum frutescens in polymeric nanoparticles and its characterization

Once the validation parameters were established, NP containing HF4 were prepared by the nanoprecipitation technique proposed by Fessi et al. (Fessi et al., 1989).

Briefly, the organic phase was prepared dissolved 15 mg of polylactic-co-glycolic acid (PLGA; MEDISORB 85 15 DL) and 4 mg of HF4 in 3 mL of a mixture of solvents

RESULTS AND DISCUSION

Determination of the antioxidant activity of the extracts and fractions of

Leucophyllum frutescens

Adding AAPH to RBC, free radicals are generated by oxidative damage in the lipids of the cell membrane, consequently, the hemolysis of the cell is induced. The In the present study with L. frutescens, the samples with the best activity were obtained from leaves. The EMH, and the fractions HF1, HF2, HF3 and HF4 reached a protection around 80% from 50 μg/mL. While, the HF5 fraction reached this percentage from 100 μg/mL (Figure 1). The ascorbic acid (AA) control presents antioxidant activity from 50 μg/mL (Figure 2). The results with L. frutescens revealed a protective effect at concentrations close to plants commonly reported with antioxidant activity. Karimi et al. investigated the aqueous and ethanol extracts of seeds of Nigella sativa L. and the aerial part of Portulaca oleracea L. in order to evaluate the cytoprotective effect of the extracts against the hemolytic damage induced by the free radical initiator AAPH. In general, the concentrations tested were from 25 to 1800 μg/mL, being from 150 μg/mL where an antioxidant effect is observed in the extracts [START_REF] Karimi | Protective Effects of Aqueous and Ethanolic Extracts of Nigella sativa L. and Portulaca oleracea L. on Free Radical Induced Hemolysis of RBCs[END_REF]. In contrast, FHH reached its highest protection capacity (around 70%) at 50 μg/mL, at higher concentrations this property decreases. This percentage decreases because at the same time, it has a hemolytic effect. Despite being obtained with the same solvent (hexane), the results for FHH and HF1 are different, therefore the fractionation method influenced the antioxidant activity of each fraction.

On the other hand, EMR reached 80% of protection from 25 to 50 μg/mL, however, when the tested concentration was 100 μg/mL, its antioxidant activity decreases (Figure 2). As evidenced in Figure 2, the same behavior of EMR can be seen in its fractions.

In the hexane fractions FHR and RF1, protection above the 80% is maintained in the range of 10 to 12.5 μg/mL, for RF2 and RF4 from 25-50 μg/mL and 50-150 μg/mL, respectively.

In contrast, the antioxidant activity in RF5 is maintained from 50 to 200 μg/mL. Probably, the protection of the EMR, FHR, RF1, RF2 and RF4 samples decreased as presented in Chapter 1, they have a hemolytic effect, while in RF5 there is no presence of hemolysis.

All these results demonstrated that, the EMH, HF1, HF2, HF3, HF4, HF5 and RF5, could be used in a range from 25 to 200 μg/mL and obtain an antioxidant effect, even, this effect can be comparable to AA control. Meanwhile, FHH, EMR, FHR, RF1, RF2 and RF4 could be used at specific concentrations.

Determination of the hemolytic activity of the methanol extract from leaves of

Leucophyllum frutescens and its fractions

Because, extracts and fractions obtained from L. frutescens leaves showed greater antioxidant activity, we proceeded to the determination of toxicity by hemolysis.

Calibration curve of HF4 and validation of the chromatographic method

The regression equation of each peak-component (1-4) was obtained from the calibration curve shown in Figure 4. As shown in Table 1, the correlation coefficients for the calibration curve of each peak-component were greater than 0.99. LOD and LOQ for each peak 1, 2, 3 and 4 were 43.09 and 130.58, 38.62 and 117.03, 22.29 and 67.53 and, 45.86 and 138.97 μg/mL, respectively.

In the area of natural products, when it is required to quantify a peak from a known molecule present in an extract, it is compared with the standard analyzed by the same chromatographic method. Such is the case of Assunção et al. who developed and validated a method by HPLC for the quantification of ellagic acid in the ethanol extracts from leaves of Eugenia uniflora L. (Myrtaceae) [START_REF] Assunção | Development and Validation of a HPLC-UV Method for the Evaluation of Ellagic Acid in Liquid Extracts of Eugenia uniflora L. (Myrtaceae) Leaves and Its Ultrasound-Assisted Extraction Optimization. Evidence-Based Complementary and Alternative Medicine[END_REF]. In our work a chromatographic method was developed and validated by HPLC using peaks-components as internal markers for the quantification of HF4 in NP. Once the method was validated, HF4 was encapsulated in NP by the nanoprecipitation method. The characterization of the formulation of NP with HF4 is shown in Table 2. NP sizes were obtained around 200 nm with a homogeneous size distribution (0.118). The lyophilized NP pellet with HF4 was dissolved in a mixture of acetonitrile: methanol, and the obtained solution was analyzed by HPLC. The area under the curve of each peak was replaced in its regression equation (Table 1), in order to obtain the concentration of the four component peaks in NP. Consequently, equations 6 and 7

were used to determine %L and %EE of peaks [START_REF] Amorim | HPLC-DAD Based Method for the Quantification of Flavonoids in the Hydroethanolic Extract of Tonina Fluviatilis Aubl. (Eriocaulaceae) and Their Radical Scavenging Activity[END_REF][START_REF] Abajo | In vitro Study of the Antioxidant and Immunomodulatory Activity of Aqueous Infusion of Bidens Pilosa[END_REF]3 and 4 in NP,being 4.13 and 19.83,4.89 and 23.48,12.81 and 61.52 and,16.56 and 79.53%, respectively.

The encapsulation of the peaks increased as the hydrophobic nature of the peaks increased, the highest hydrophobicity was observed with peak 4 and therefore the highest encapsulation. Sanna et al., obtained white tea extract by infusing the leaves in distilled water, after, it was encapsulated in poly-ɛ-caprolactone NP (PCL) and alginate as particleforming polymers using the nanoprecipitation technique. The optimal formulation had a size around 380 nm and a unimodal distribution. They determined the %EE of two catechins, (-)-epigallocatechin gallate and (-)epicatechin gallate, with values of 30.62 and 32.60%, respectively [START_REF] Sanna | Polymeric Nanoparticles Encapsulating White Tea Extract for Nutraceutical Application[END_REF]. In our work, higher %EE were determined, probably due to the nature of the components present in the L. frutescens fraction.

Peak-Component

Determination of the antioxidant and hemolytic activity of the ethanol fraction from

Leucophyllum frutescens leaves

The method used to determine the antioxidant activity of the HF4 NP was by the induction of oxidative damage of RBC with the reagent AAPH which generates hemolysis. Hemolysis of the RBC damage can be avoided with the presence of antioxidant substances. Figure 5 shows the antioxidant activity of HF4, HF4 NP and AA. HF4 fraction revealed around 80% of protection against oxidative damage (antioxidant activity) at 50 μg/mL. Achieving 100% antioxidant activity above 100 μg/mL. If this concentration is compared with the AA molecule evaluated as an antioxidant control, HF4 had better activity. When HF4 is encapsulated in NP, at 50 μg/mL the activity is around 80%; while 100% of antioxidant activity is reached at 100 μg/mL. In free HF4, total antioxidant activity is revealed at 100 μg/mL. Therefore, it is demonstrated that, although this fraction is formulated in NP, the antioxidant property is preserved. In the aforementioned research by Sanna et al., the antioxidant activity of the white tea extracts was evaluated by the in vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) method.

The best activity of PCL NP was of DPPH, observed at 300 μg/mL with 60% of inhibition compared to the free extract that shoed 100% of inhibition of DPPH at 25 μg/mL.

They attributed this difference to the low release of polyphenols from PCL NP [START_REF] Sanna | Polymeric Nanoparticles Encapsulating White Tea Extract for Nutraceutical Application[END_REF]. Less activity is obtained at a higher concentration if it is compared with our result, this may be due to the nature of the polymers, because PCL has a slower degradation rate compared with polylactics (Mahapatro y Singh, 2011), which is related to his low release. Likewise, the was evaluated by the hemolytic activity at active concentrations, determining that there is no presence of hemolysis. This test results in the potential use of HF4 fraction formulated or not formulated in NP for administration in the organism, however, it is in NP where the use of the organic solvents is avoided.

CONCLUSION

In the evaluation of the antioxidant activity of the extracts and fractions of L. frutescens is concluded:

58

-The extracts and fractions of L. frutescens plant showed protection, avoiding the toxicity lysis of RBC caused by the oxidation induced with the AAPH reagent.

The FHH, EMR, FHR, RF1, RF2 and RF4 samples presented their maximum antioxidant activity at low concentrations.

-The antioxidant activity of EMH, HF1, HF2, HF3, HF4, HF5 and RF5 was showed from 25 to 200 μg/mL and non-hemolytic effect.

-In roots, the antioxidant activity of FHR and RF1 was more than 90% at 10 μg/mL and non-hemolytic effect. However, the activity was decreased when the concentration was increased due to hemolysis production. Similar effect was produced with other root samples.

-The HF4 fraction was selected for the studies that proceeded for its relevant antioxidant activity at a concentration of 100 μg/mL, similar to the reference antioxidant molecule AA.

-The chromatographic method was validated to be used for the quantification of major peaks-components in NP presented in the fraction and revealed a favorable incorporation of the L. frutescens fraction.

-The nanoprecipitation method for the preparation of NP loaded with HF4 was appropriate, a particle size around 200 nm with a homogeneous distribution was obtained, its properties are preserved, and it is non-toxic at the active concentrations. tuberculosis.

INTRODUCTION

NE are systems thermodynamically unstable and kinetically stable are on nanometric scale [START_REF] Gupta | Nanoemulsions: Formation, Properties and Applications[END_REF]. The interest for NE is related to the prospects of applications such disperse systems in medicine, in pharmaceutical and cosmetic industries [START_REF] Koroleva | Nanoemulsions: The Properties, Methods of Preparation and Promising Applications[END_REF]. A nanoemulsion is constituted by oil, water and emulsifier [START_REF] Gupta | Nanoemulsions: Formation, Properties and Applications[END_REF]. The emulsifier or emulsifying agent is a surfactant that reduces the interfacial tension between the immiscible phases, provide a barrier around the droplets and prevent coalescence of the droplets [START_REF] Manoharan | Various Pharmaceutical Disperse Systems[END_REF].

The methods for the emulsion preparation are classified in high-and low-energy.

The high-energy methods include mechanical shear such as that produced by high-shear stirring, ultrasonic emulsification, high-pressure homogenization. The low-energy method most widely used is phase inversion temperature [START_REF] Koroleva | Nanoemulsions: The Properties, Methods of Preparation and Promising Applications[END_REF].

They can be administrated by oral [START_REF] Devalapally | Evaluation of a Nanoemulsion Formulation Strategy for Oral Bioavailability Enhancement of Danazol in Rats and Dogs[END_REF], intranasal [START_REF] Kumar | Intranasal Nanoemulsion Based Brain Targeting Drug Delivery System of Risperidone[END_REF], topical [START_REF] Hussain | Nanoemulsion Gel-Based Topical Delivery of an Antifungal Drug: In Vitro Activity and in Vivo Evaluation[END_REF] and parenteral routes [START_REF] Araújo | Development and Characterization of Parenteral Nanoemulsions Containing Thalidomide[END_REF]. They can be formulated in variety of formulations such as foams, creams, liquids, sprays [START_REF] Jaiswal | Nanoemulsion: An Advanced Mode of Drug Delivery System[END_REF] or gels [START_REF] Hussain | Nanoemulsion Gel-Based Topical Delivery of an Antifungal Drug: In Vitro Activity and in Vivo Evaluation[END_REF]. As drug delivery systems studies have demonstrated many advantages such as incorporation of hydrophobic drug into a hydrophilic medium, targeting, cellular uptake and bioavailability.

A study carried out by Kumar et al., .4) and AmB-NE gel, respectively. Also, the irritation potential of topical formulations was evaluated on Wistar albino rats. In this study, the results showed that no severe irritation symptoms such as erythema (redness)

and edema (swelling) during 72 h except reference positive [START_REF] Hussain | Nanoemulsion Gel-Based Topical Delivery of an Antifungal Drug: In Vitro Activity and in Vivo Evaluation[END_REF].

In recent years, special interest has been placed in the encapsulation of natural products as extracts and essential oils obtained from plants to enhance their biological effects [START_REF] Blanco-Padilla | Food Antimicrobials Nanocarriers[END_REF]. Donsì et al. proved al., 2007). However, few compounds obtained from L. frutescens have been identified (Alanís-Garza et al., 2012;Molina-Salinas et al., 2011).

In this context, the aim of the study was to optimize and characterize of a NE to encapsulate an active fraction obtained from the methanol extract of roots of L. frutescens, as well as, the antituberculosis drug RIF, and the in vitro evaluation against M.

tuberculosis.

MATERIALS AND METHODS

Preparation of Leucophyllum frutescens hexane fraction

Chapter 1 describes the procedure for obtaining the hexane fraction by method 2, called RF1 .

Preparation, optimization and characterization of nanoemulsions

Briefly, oleic acid (OA) as oil phase was emulsified in a tween 80 solution as aqueous phase with ultrasonic emulsification (Homogeneizador, OPTIC IVYMEN SYSTEM) with 80% amplitude. The influence of different variables in the preparation of emulsions were proved. Firstly, different times of sonication (3, 5, 6, 7 and 8 min) were tested with 4g of oleic acid and 96g of a tween 80 solution at 2%w/v. Then, the concentration of tween 80 was changed (1, 1.5, 2, 3 and 4% w/v). Finally, different amounts in oil/aqueous phase were proved (1.5/98.5, 2/98, 3/97, 3.5/96.5 and 4/96 g). All the formulations were prepared in triplicated. The hydrodynamic diameter, polydispersity index (PDI) and zeta potential of each emulsion were measured by dynamic light scattering (Zetasizer Nano ZS90, MALVERN). Zeta potential was determined at 5 different pH (3, 5, 7, 9 and 11). Their stabilities were followed by hydrodynamic diameter, PDI and the separation of oil/aqueous phases over time.

Preparation and characterization of hexane fraction of Leucophyllum frutescens and rifampicin loaded emulsions

Different formulations of RF1 and RIF were prepared by ultrasonic emulsification.

Briefly, the organic phase containing RF1 or RIF in oleic acid was emulsified in the aqueous phase containing a solution of T-80 (1% w/v). Then, NE were characterized by the measurement of hydrodynamic diameter, polydispersity index (PDI), zeta potential and stability. The actives in NE were quantified by high performance liquid chromatography (HPLC) (WATERS).

RF1 quantification was carried out indirectly, centrifuging the samples (Eppendorf 5415 centrifuge) at 5000 rpm for 30 min, to separate the aqueous phase from the globules.

The aqueous phase was taken and analyzed on a Phenomenex C18 column with a flow of 0.2 mL/min at 30 °C. The mobile phase was water (A) and methanol (B) in a isocratic elution 45:55 (A: B) for 60 min. The detection of the RIF peak was at λ=210 nm.

RIF quantification was carried out indirectly, centrifuging the samples (Eppendorf 5415 centrifuge) at 5000 rpm for 30 min, to separate the aqueous phase from the globules.

The aqueous phase was taken and analyzed on a Phenomenex C18 column with a flow of 0.35 mL/min at 30 °C. The mobile phase was water (A) and acetonitrile (B) in an isocratic

RESULTS AND DISCUSION Preparation, optimization and characterization of nanoemulsions

The emulsions were prepared with oleic acid as oil phase and tween 80 as surfactant. Oleic acid was chosen due to M. tuberculosis has shown the ability to utilize this fatty acid complexed with triton as a source of carbon for growth was determined [START_REF] Hedgecock | Complexing of Fatty Acids by Triton WR1339 in Relation to Growth of Mycobacterium tuberculosis[END_REF], and with a nanocarrier based in oleic acid will be possible M.

tuberculosis takes it more effectively than others.

As part of the optimization, different preparation variables of NE were evaluated.

Firstly, the influence of the sonication time [START_REF] Ahmed | Potential of Nanoemulsions for Intravenous Delivery of Rifampicin[END_REF]5,6,7 and 8 min) on the particle size and PDI was determined (Figure 1). When time was increased the hydrodynamic diameter and PDI decreased from 215.7±3.2 nm to 155.6±0.2 nm and from 0.319±0.025 to 0.244±0.009, respectively. The ultrasonic emulsification is very efficient in reducing droplet size. Here, the energy is provided through a sonicator probe. It contains piezoelectric quartz crystal which can expand and contract in response to alternating electric voltage. As the tip of sonicator contacts the liquid, it produces mechanical vibration and cavitation occurs. Cavitation is the formation and collapse of vapor cavities in liquid. Thus, ultrasound can be directly used to produce emulsion [START_REF] Jaiswal | Nanoemulsion: An Advanced Mode of Drug Delivery System[END_REF].

It means, more exposure time to emulsification more energy that allows smaller droplet size. The stability tests showed in the range of 5 to 8 min, a size change around 30 nm from day 0 to day 77 (data not shown), being from 7 min where a homogeneous size distribution was maintained during this period. to 65 nm, respectively. T-80 concentration also played a major role in droplet size of nanoemulsion. Increasing surfactant concentration resulted in decrease in droplet diameter. Formulation with 6% surfactant concentration after sonication for 30 min was found to be 254 nm, whereas formulation with 12% surfactant was 96 nm and formulation with 18% surfactant has lowest droplet diameter of 65 nm after a sonication period of 30 min [START_REF] Ghosh | Cinnamon Oil Nanoemulsion Formulation by Ultrasonic Emulsification: Investigation of Its Bactericidal Activity[END_REF]. found this influence on size who prepared NE by aqueous phase titration method. Capryol 90 as oil, Tween 20 as surfactant and Transcutol P as cosurfactant. They maintained a constant percentage of surfactant (30%) and co-surfactant (10%) in the formulation and the percentage of oil was 10, 15 and 20% at the same time the percentage of water changed in 50, 45 and 40%. The size increased from 234.9 nm to 285.8 nm [START_REF] Mantena | Formulation, Optimization and in vitro Evaluation of Rifampicin Nanoemulsions[END_REF].

The size of the NE droplets supposes an increase, when increasing the oil ratio, the amount of phase is reduced, as a consequence the chains of the surfactant are reduced, increasing the interfacial tension [START_REF] Du | Optimization and Characterization of Biocompatible Oil-in-Water Nanoemulsion for Pesticide Delivery[END_REF]. The NE prepared for the evaluation of the influence of the preparation variables were stable up to 77 days, likewise, all the formulations showed a negative zeta potential. The negative value can be explained by the presence of negatively charged carboxyl groups of oleic acid [START_REF] Laouini | Membrane Emulsification: A Promising Alternative for Vitamin E Encapsulation within Nano-Emulsion[END_REF]. The negative value can be explained by the presence of negatively charged carboxyl groups of oleic acid [START_REF] Deruiter | Carboxylic Acid Structure and Chemistry: Part 2[END_REF]. The pKa of oleic acid is 5.02 (Pubchem). This explain when we compared at pH 3 the zeta potential is closer 0 Subsequently, an optimal NE was selected for the preparation of two formulations, for the encapsulation of RF1 and RF1. For the preparation of RF1-NE and RIF-NE the sonication time of 7 min, the concentration of T80 at 1% w/v and the ratio in the amount of oleic acid and aqueous phase of 3.5/96.5 g were selected. The obtained particle size with these variables was around 180 nm (Table I) and a homogeneous size distribution (Figure 4). Lately, the encapsulation of both active in NE was determined by HPLC. In Figure 5 the chromatogram with the RIF peak in an aqueous solution is observed. When the sample obtained from the centrifugation of the NE was analyzed, it was determined that the molecule is 99% encapsulated. Ahmed et al. prepared a NE with RIF using Sefsol 218 as oil and T80 as emulsifier and tween 85 as a co-emulsifier. They found an encapsulation efficiency of around 100% with stability for more than 19 months [START_REF] Ahmed | Potential of Nanoemulsions for Intravenous Delivery of Rifampicin[END_REF].

On the other hand, RF1 was dissolved in methanol in order to observe its chromatographic profile, it showed 15 peaks (Figure 6). The peaks 5, 9, 10, 14 and 15

were selected for their quantification within the NE, obtaining an encapsulation efficiency greater than 70%. Similar results were obtained by Ha et al. when determined the encapsulation of lycopene in a tomato extract formulated in NE, which was 51 to 65% [START_REF] Ha | Antioxidant Activity and Bioaccessibility of Size-Different Nanoemulsions for Lycopene-Enriched Tomato Extract[END_REF]. For both formulations, a negative zeta potential (Figure 7) and stability (without phase separation) were observed over 77 days (Figure 8). showed inhibition when the actives were at a concentration of 0.19 and 0.39 μg/mL, respectively, but OA and T80 were at a concentration of 68.10 and 18.75 μg/mL, respectively, as in blank NE. Choi proved an unsaturated acid called linoleic acid (α and γ form) against M. tuberculosis, in both cases fatty acid forms obtained a MIC of 75 μg/mL [START_REF] Choi | Evaluation of Anti-Tubercular Activity of Linolenic Acid and Conjugated-Linoleic Acid as Effective Inhibitors against Mycobacterium tuberculosis[END_REF]. Therefore, in our study, the inhibition of blank NE can be explained by the presence of oleic acid. It was not possible to observe the effect of the activity of RIF and RF1 when they were in NE due to the presence of the fatty acid.

CONCLUSION

Different parameters were evaluated for the obtaining of NE loaded with RF1 and RIF concluding:

-The optimal parameters for preparation of NE with RF1 and RIF were: sonication time of 7 min, concentration of T80 at 1% w/v and ratio in the amount of oleic acid and aqueous phase of 3.5/96.5 g, having a diameter around 180 nm, homogenous size distribution, negatively charged and, high encapsulation efficiency.

-The stability of NP was for 77 days.

-Both formulations showed high efficiency of encapsulation.

-The anti-M. tuberculosis activity showed inhibition in the same concentrations including blank NE, this behavior can be attributed due to the presence of oleic acid as oil phase.

-The formulations of NE with RF1 is promising as a co-adjuvant for the Tb treatment.

encapsulation of the fraction is achieved, its properties are preserved, and it is non-toxic at the active concentrations.

An important part of the characterization of nanoparticulate systems is the determination of the percentage drug loading and encapsulation efficiency, for this raison a method of quantification by HPLC was developed and validated using the peakscomponents of the plant as internal markers. Therefore, in this work we proposed a new strategy for the quantification of extracts or fractions of L. frutescens.

In the last part of the study, to make use of a sustained release system different of NP was proposed. Studies with NE were carried out testing the effect of sonication time, surfactant concentration and oil/water ratio on particle size, PDI, zeta potential and stability. The optimal formulation was selected for the encapsulation of RIF and the active fraction RF1 against M. tuberculosis. NE had a diameter around 180 nm, homogeneous size distribution, negatively charged and stable for 77 days. Both formulations showed high encapsulation efficiency. The anti-M. tuberculosis activity showed inhibition at the same concentrations including blank NE, this behavior can be attributed to the presence of oleic acid as oil phase. Thus, the optimal characterized and tested NE can be promising in the inhibition of M. tuberculosis.

With the results obtained in our work, the knowledge about the L. frutescens plant is extended, either by its activity against M. tuberculosis or by its antioxidant activity.

Likewise, it is revealed that NP or NE are a promising alternative to load extracts or fractions of the plant, converting them into a viable formulation for its administration.

Based on the results and conclusions obtained in this Doctoral Thesis, the perspectives are oriented in different directions.

In the Chapter 1, the results related to RIF, L. frutescens, NP and its activity against tuberculosis, encapsulation of the compounds in NP, the characterization of NP and studies of their effect on M. tuberculosis.

In the Chapter 2, the results related to L. frutescens, NP and its antioxidant activity were presented, due to the promising results obtained with the antioxidant effect of the plant, future investigations would be studies of in vitro release of the active encapsulated into formulations in order to know the time of release towards the environment in which they would be in the organism, also, to propose its release mechanisms and in vivo biodistribution studies.

4

  Size distribution of nanoemulsions by intensity percentage: (A) rifampicin loaded nanoemulsion; (B) hexane fraction from roots of Leucophyllum frutescens. 5 Chromatogram of rifampicin in water (9 μg/mL) obtained by HPLC: (A) water peak; (B) rifampicin peak, retention time = 3.2 min. 6 Chromatogram of the hexane fraction from roots of Leucophyllum frutescens (230 μg/mL) obtained by HPLC: (A) peaks of methanol. 7 Effect of the pH of the dispersion medium of the nanoemulsions on the zeta potential: blank nanoemulsions (NE), containing rifampicin (RIF-NE) and containing the hexane fraction from roots of Leucophyllum frutescens (RF1-NE) ( ±σ, n=3). 8 Stability of blank nanoemulsions (NE), containing rifampicin (RIF-NE) and containing the hexane fraction from roots of Leucophyllum frutescens (RF1-NE) ( ±σ, n=3).

Figure 1 .

 1 Figure 1. Structure of polymeric nanoparticles.

Figure 2 .

 2 Figure 2. Preparation of polymeric nanoparticles by nanoprecipitation.

o

  To obtain the methanol extracts of leaves and roots of L. frutescens by maceration and sonication and carry out their fractionation. o To develop a chromatographic method validated by HPLC in order to characterize the extracts and their fractions and to obtain their chromatographic profiles. o To encapsulate the extracts and active fractions by nanoprecipitation technique in NP and perform their physicochemical characterizations according to the size, polydispersity index (PDI), zeta potential, surface morphology, drug loading and encapsulation efficiency. o To encapsulate RIF in NP by nanoprecipitation technique and perform their physicochemical characterizations according to the size, PDI, zeta potential, surface morphology and incorporated compounds. o To evaluate the in vitro biological activity of the NP formulations on M. tuberculosis, as well as to determine the synergistic effect of the drug and the vegetable samples, free and encapsulated. o To evaluate the toxicity of NP formulations with better antimycobacterial activities. an emergency disease worldwide, caused by Mycobacterium tuberculosis. For its treatment four first-line drugs are administered; however, the emergence of resistant strains has led to the promising use of natural products as an alternative to combat the disease. Studies show that several plant extracts have action against M. tuberculosis, such as Leucophyllum frutescens. The disadvantage of the extracts is that they are recovered in vehicles as organic solvents, which makes difficult its application in vivo. The preparation of polymeric nanoparticles (NP) involves the elimination of the solvent in which the active is solubilized, it makes possible to use them as vehicles for the administration of extracts. While, RIF an antibiotic used in the treatment, is a model for the incorporation in NP. The objective of the present work was to formulate NP with the extract and fractions of L. frutescens and to evaluate its activity against M. tuberculosis in order to propose its use as a co-adjuvant of the antituberculosis drug RIF. In parallel, a formulation of RIF loaded NP was developed with the aim of improving the therapeutic performance of the drug. Firstly, chromatographic profile of methanol extracts of leaves and roots and their fractions of L. frutescens were obtained by HPLC. For leaves, four peaks-components were appreciated, for roots seven peakscomponents were appreciated. The screening of methanol extracts of leaves and roots and their fractions for anti-M. tuberculosis activity revealed that the best activities were shown with the extract of roots (EMR) and the hexane fractions (FHR and RF1) with a MIC=100, 40 and 40 μg/mL, respectively. Subsequently, EMR, FHR, RF1 and RIF were encapsulated. NP had sizes between 140 and 190 nm, with homogeneous distributions and negative zeta potential. Then, the formulations were tested on M. tuberculosis. The formulation of RIF with the best activity was PLGA-PVAL-NP with a MIC of 0.10 μg/mL compared with the free drug that showed a MIC of 0.20 μg/mL. While, among the vegetable samples, were the formulations of FHR-PLGA-NP and RF1-PLGA-NP which INTRODUCTION Tuberculosis, since 1993, is considered by the World Health Organization as an emergency disease worldwide. In 2016, 10.4 million people became ill with tuberculosis and 1.7 million died (OMS

tuberculosis

  H37Rv by the alamar blue assay in a microplate adapting the methodology used byMolina-Salinas et al. (Molina-Salinas et al. 2007). The strain was cultivated in Middlebrock 7H9 broth enriched with OADC (Becton Dickinson and Co., Sparks, MD, USA) at 37 °C for 14 days. After, the strain was adjusted according to the standard scale no. 1 of McFarland and diluted 1:20 for use in the assay. On the other hand, a stock solution in DMSO was prepared at a concentration of 20 mg/mL. Work solutions were prepared from the stock solution. On the other hand, in a 96-well microplate, 200 μL of water was added to the wells in the periphery. While, in the work wells, 100 μL of Middlebrock 7H9 broth enriched with OADC was added. Subsequently, in the first well of each row, 100 μL of each previously prepared work solution was added. Once all the samples were added, serial dilutions 1:2 of each sample were performed, taking 100 μL

  The ultrasound used during the extraction of EMH and EMR can facilitate the swelling and solvation causing the enlargement of the pores of the cell wall. The greater swelling will improve the rate of mass transfer and, occasionally, it will break the cell walls, which leads to an increase in extraction efficiency and/or reduction in extraction time[START_REF] Huie | A review of modern sample-preparation techniques for the extraction and analysis of medicinal plants[END_REF]. Soares-Melecchi et. al. optimized the technique of extraction by ultrasound to obtain the extract from flowers of Hibiscus tiliaceus L. They weighed 5 g of flowers and added 150 mL of methanol (1:30 ratio), reaching the highest yield (17.10%) in 5 h of extraction (Soares Melecchi

Figure 1 .

 1 Figure 1. Chromatographic profile of methanol extract from leaves of Leucophyllum frutescens (EMH) and its fractions (FHH, HF1, HF2, HF3, HF4 y HF5) at 400 μg/mL analyzed by HPLC.

Figure 2 .

 2 Figure 2. Chromatographic profile of methanol extract from roots of Leucophyllum frutescens (EMR) and its fractions (FHR, RF1, RF2, RF4 y RF5) at 400 μg/mL analyzed by HPLC.

Figure 3 .

 3 Figure 3. Rifampicin chromatogram (30 ppm) obtained by HPLC (retention time=2 min).

  example, in the Amorim et al. study, three flavonoids were identified in the hydroethanol extract from the aerial part of Tonina fluviatilis (6,7-dimethoxyquercetin-3-O-β-Dglucopyranoside, 6-hydroxy-7-methoxyquercetin-3-O-β-D-glucopyranoside and 6methoxyquercetin-3-O-β-D-glucopyranoside) and a chromatographic method was developed and validated to quantify these compounds in the plant. For the preparation of the calibration curve, solutions of the three flavonoids were prepared and the regression equation for each was determined. LOD and LOQ of the calibration curves were below 30 μg/mL (Amorim et al., 2014).For RF1 with the developed method, LOD and LOQ are superior because internal marker compounds of the fraction are used, it was possible preparing solutions of different concentrations of this hexane fraction for the preparation of the calibration curve, instead of standard solutions. The validation was carried out to ensure that the analytical procedure is accurate for the quantification of RF1 once it was loaded in NP (Martínez-[START_REF] Rivas | Nanoprecipitation Process: From Encapsulation to Drug Delivery[END_REF].

  medium change from pH 3 to pH 9[START_REF] Wiśniewska | Impact of Poly(vinyl Alcohol) Adsorption on the Surface Characteristics of Mixed Oxide Mn x O y -SiO2[END_REF]. Honary and Zahir prepared PLGA NP with two non-ionic surfactants, PVAL and Pluronic F68 (PF68). They obtained NP with negative zeta potential. The result obtained with PLGA-PVAL-NP was -5±1 mV and with PLGA-PF68-NP was -24±1 mV(Honary y Zahir, 2013), this formulation with PVAL presents a similar result compared with our work with this formulation (-5.57±1.35 mV).

  component in plant samples. The peak was encapsulated in all formulations, which indicates that the NP preparation method is favorable for the encapsulation of extracts or fractions extracted from L. frutescens plant. Some researchers have encapsulated plant compounds in NP such is the case of do Nascimento et al., who encapsulated the red propolis extract in five formulations of poly-ɛ-caprolactone (PCL) NP and quantified five flavonoids (liquiritigenin, pinobanksin, isoliquiritigenin, formononetin and biochanin A) by UPLC. %EE of the flavonoids in NP had an average value of 75%[START_REF] Do Nascimento | Polymeric Nanoparticles of Brazilian Red Propolis Extract: Preparation, Characterization, Antioxidant and Leishmanicidal Activity[END_REF]. However, in this work the chromatographic method was designed to detect the components of interest of the extracts and fractions obtained from L. frutescens and using them as internal markers for their quantification in NP.

Figure 4 .

 4 Figure 4. MEB image of PLGA nanoparticles prepared by nanoprecipitation. A and D blank nanoparticles; B and E: nanoparticles with rifampicin; C and F: nanoparticles with the hexane fraction of Leucophyllum frutescens roots (A, B, and C: scale bar represents 1 μm; D, E and F: scale bar represents 500 nm).

Figure 5 .

 5 Figure 5. Hemolytic activity of the vegetable samples from Leucophyllum frutescens: methanol extract and fractions ( ±σ, n=3).

  Figure 6. Hemolytic activity of the encapsulated hexane fraction from roots of Leucophyllum frutescens (RF1 NP) and non-encapsulated (RF1) ( ±σ, n=3).

  hemolysis can be avoided with the presence of antioxidant substances. The extracts and fractions that exhibit antioxidant activity can protect the cell against oxidative damage, as a result, the RBC lysis is avoided. Paiva-Martins et al., for example, made use of this method to determine the inhibition of the oxidative lysis of RBC. They obtained the compound called and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde (3,4-DHPEA-EDA) of olive oil and synthesized its metabolite 3,4-DHPEA-EDAH2. Its objective was to induce the oxidative stress of RBC by AAPH, and to add the compounds obtained to measure the capacity of them to protect the cells. Both compounds showed RBC protection from oxidative hemolysis at concentrations ranging from 10 to 80 μM. 4-DHPEA-EDA achieved 70% of protection at 80 μM[START_REF] Paiva-Martins | Effects of the Olive Oil Phenol Metabolite 3,4-DHPEA-EDAH2 on Human Erythrocyte Oxidative Damage[END_REF].

Figure 1 .

 1 Figure 1. Percentage of the antioxidant activity of the methanol extract from leaves of L. frutescens and its fractions ( ±σ, n=3).

Figure 2 .

 2 Figure 2. Percentage of the antioxidant activity of the methanol extract from roots of L. frutescens and its fractions ( ±σ, n=3).

Figure 4 .

 4 Figure 4. Calibration curve of the four peaks-components of interest present in the ethanol fraction from Leucophyllum frutescens roots ( ±σ, n=3).

Figure 5 .

 5 Figure 5. Antioxidant activity of the ethanol fraction from leaves of Leucophyllum frutescens (HF4) in its non-encapsulated and encapsulated form in biodegradable polymeric nanoparticles (NP). Ascorbic acid (AA) was taken as an antioxidant control ( ±σ, n=3).

CHAPTER 3 .

 3 RIFAMPICIN AND AN ACTIVE FRACTION OF Leucophyllum frutescens LOADED NANOEMULSIONS, CHARACTERIZATION AND POTENTIAL USE AGAINST Mycobacterium tuberculosisABSTRACTThe interest on the use of nanoemulsions (NE) is related to its application as drug delivery systems. NE have shown several advantages such as the incorporation of hydrophobic drugs into a hydrophilic dispersion medium, targeting, cellular uptake and increased bioavailability. In recent years, special interest has been placed on the encapsulation of natural products such as extracts and essential oils obtained from plants to improve their biological effects. Among the plants is included Leucophyllum frutescens commonly named "cenizo", which has been demonstrated an inhibition effect against Mycobacterium tuberculosis, causal agent of tuberculosis. For this reason, the aim of this work was to optimize and characterize a NE to encapsulate an active fraction from roots of L. frutescens (RF1), as well as, the antituberculosis drug rifampicin (RIF), and to evaluate their activity in vitro against M. tuberculosis. NE were prepared by ultrasonic emulsification and the influence of different preparation variables was tested. The results showed that at a longer time of sonication, the size and the polydispersity index (PDI) of NE globules decreased. The increase in the surfactant concentration, decreased the size and increased slightly the PDI. The increase in the amount of oil phase, increased the size and decreased slightly the PDI. The NE with a particle size around 180 nm and with homogeneous size distribution was used for the encapsulation of RF1 and RIF. The characterization of the loaded NE showed a particle size of 180 nm. For the determination of the percentage of the encapsulation efficiency of RF1, most abundant peaks were selected, being encapsulated at least 70%, while RIF was encapsulated at 99%. For the anti-M. tuberculosis activity were tested the blank NE, RF1-NE and RIF-NE, where, the blank NE showed inhibition at the same concentration as RF1-NE and RIF-NE, this behavior can be attributed to the presence of oleic acid as the oil phase. With this work the encapsulation and characterization of a vegetal sample (RF1) and RIF in NE are achieved. The optimal NEs characterized and tested are promising in the inhibition of M.

  elution 40:60 (A: B) for 15 min. The detection of the RIF peak was at λ=334 nm.frutescens and rifampicin loaded in the nanoemulsionsThe anti-M. tuberculosis activity was evaluated on the susceptible strain of M. tuberculosis H37Rv by the alamar blue assay in a microplate adapting the methodology used byMolina-Salinas et al. (Molina-Salinas et al., 2007). The strain was cultivated in Middlebrock 7H9 broth enriched with OADC (Becton Dickinson and Co., Sparks, MD, USA) at 37 °C for 14 days. After, the strain was adjusted according to the standard scale no. 1 of McFarland and diluted 1:20 for use in the assay. On the other hand, in a 96-well microplate, 200 μL of water was added to the wells in the periphery. While, in the work wells, 100 μL of Middlebrock 7H9 broth enriched with OADC was added. In the first well of each row, 100 μL of each sample (NE blank, NE-RF1 and NE-RIF) and control samples (RF1, RIF and tween 80 solution) were added. Once all the samples were added, serial dilutions 1:2 of each sample were performed, taking 100 μL of the first well and adding them to the second well of the row, then, of the second well, 100 μL was taken to add them to the third, this procedure was repeated until reaching the last well each row; the 100 μL taken from the last well was eliminated. Finally, 100 μL of the bacterial suspension was added to obtain a final volume in all wells of 200 μL. All samples were prepared in duplicate in the same day. The microplates were incubated at 37 °C for 5 days. At day 5, 20 μL of the blue alamar reagent and 12 μL of 10% v/v of tween 80 were added to all the work wells, and the microplates were reincubated at 37 °C for 24 h. The minimum inhibitory concentration (MIC) was determined from the color change of the blue to pink reagent. All tests were carried out at least in triplicate.

Figure 1 .

 1 Figure 1. Effect of the sonication time on the hydrodynamic diameter ( ±σ, n=3).

Figure 2 .

 2 Figure 2. Effect of the concentration of Tween 80 solution on the hydrodynamic diameter ( ±σ, n=3).

Figure 3 .

 3 Figure 3. Effect of the ratio on the amount of oleic acid (oil phase) and 1% w/v of Tween 80 solution (aqueous phase) on the hydrodynamic diameter ( ±σ, n=3).

  ) with pH 5 to pH 11 (-40 to -70 mV) a greatly increased in the negativity can be observed.Preparation and characterization of the hexanic fraction of Leucophyllum frutescens and rifampicin loaded in nanoemulsions

Figure 4 .

 4 Figure 4. Size distribution of nanoemulsions by intensity percentage: (A) rifampicin loaded nanoemulsion; (B) hexane fraction from roots of Leucophyllum frutescens.

Figure 5 .

 5 Figure 5. Chromatogram of rifampicin in water (9 μg/mL) obtained by HPLC: (A) water peak; (B) rifampicin peak, retention time = 3.2 min.

Figure 6 .

 6 Figure 6. Chromatogram of the hexane fraction from roots of Leucophyllum frutescens (230 μg/mL) obtained by HPLC: (A) peaks of methanol.

Figure 7 .

 7 Figure 7. Effect of the pH of the dispersion medium of the nanoemulsions on the zeta potential: blank nanoemulsions (NE), containing rifampicin (RIF-NE) and containing the hexane fraction from roots of Leucophyllum frutescens (RF1-NE) ( ±σ, n=3).

Figure

  Figure 8. Stability of blank nanoemulsions (NE), containing rifampicin (RIF-NE) and containing the hexane fraction from roots of Leucophyllum frutescens (RF1-NE) ( ±σ, n=3).

M

  . tuberculosis were shown. For this first section, future research would be about in vitro release studies of the active formulations obtained in order to know the time of release of the actives to the environment in which they would be in the body and, also, to propose their release mechanisms. Because the target organ of the formulations are macrophages, in vitro studies on macrophages would be promising. Likewise, from the favorable results obtained on the combination of the drug RIF and the formulation of NP-PLGA-RF1, we propose to work with the tests to determine the synergism effect. On the other hand, it would be interesting to know about the distribution of the active formulations in an organism, for which we suggest to carry out in vivo biodistribution studies of RIF and RF1 free and encapsulated into NP, individually and in combination. The final perspective to this chapter is to carry out the studies of isolation and identification of the compounds from the extracts and root fractions of L. frutescens that have the best activity against M.

Finally, in the Chapter 3 ,

 3 the results related to RIF, RF1, NE and their activity against M. tuberculosis were shown. Based on our research, it will be of great interest to 2013. In Vivo/in Vitro Pharmacokinetic and Pharmacodynamic Study of Spray-Dried Poly-(Dl-Lactic-Co-Glycolic) Acid Nanoparticles Encapsulating Rifampicin and Isoniazid. International Journal of Pharmaceutics 444 (1-2):10-17.

Table I . Percentage of yield of methanol extracts from leaves and roots of Leucophyllum frutescens and their fractions

 I

	Leaves	EMH	FHH	HF1	HF2	HF3	HF4	HF5
	Yield (%) 19.30±4.20 3.46±0.09 2.55±0.31	6.10±4.34 1.17±0.28 33.05±3.09 3.48±0.12
	Roots	EMR	FHR	RF1	RF2	RF3	RF4	RF5
	Yield (%)	7.92±0.38 9.62±5.04 10.46±0.99 7.19±0.36 0.40±0.05 13.99±4.06 16.27±0.56

  . EMH had a MIC value above 200 μg/mL while EMR had a MIC value of 100 μg/mL. In the study by Molina-Salinas et al. similar trends are reported, because in leaves the tested concentrations did not show activity, while in roots MIC was of 62.5 μg/mL(Molina-Salinas et al., 2007). Compared with our result, this variability in activity may be due to factors such as collection time or place of collection[START_REF] Nguyen Hoai | Development of HPLC fingerprints for Mallotus species extracts and evaluation of the peaks responsible for their antioxidant activity[END_REF].

Table II . Anti-M. tuberculosis activity H37Rv of the methanol extracts from leaves and roots of Leucophyllum frutescens and their fractions

 II MIC achieved by FHR and RF1 is comparable to MIC reported in studies with other plants.Gemechu et al. investigated five medicinal plants in Ethiopia: roots of Calpurnia aurea, seeds of Ocimum basilicum, leaves of Artemisia abyssinica, Croton macrostachyus, and Eucalyptus camaldulensis used locally to fight tuberculosis. Gemechu et al., 2013). On the other hand, Nguta et al. evaluated the antimycobacterial activity of the hydroethanol extract from leaves of Solanum torvum Aloe vera var.

	Methanol extracts of the plant materials were obtained by maceration and evaluated on M.
	tuberculosis strains such as: H37Rv, SIT73, SIT149, SIT149, SB1176 and SB1953, which
	were comparatively the most susceptible to the extracts with MIC of ≤50 μg/mL
	(
	Leaves	EMH	FHH	HF1	HF2	HF3	HF4	HF5
	MIC (μg/mL)	>200	>200	>200	>200	>200	>200	>200
	Roots	EMR	FHR	RF1	RF2	RF3	RF4	RF5
	MIC (μg/mL)	100	40	40	200	200	>200	>200
	However, an easy and rapid fractionation method was also developed (fractionation
	method 2), for the obtaining the fraction of interest preserving its antimycobacterial
	activity.

The best activity against M. tuberculosis was collected with the hexane fractions from roots (FHR and RF1) at a MIC of 40 μg/mL. Comparing the methods of fractionation 1 and 2, FHR and RF1, respectively, both demonstrate the same efficiency to the extract compounds related to hexane with antituberculosis activity. Previously, the isolation and identification of a compound extracted from roots with potent anti-M. tuberculosis activity was reported

(Molina-Salinas et al., 2011)

, this fraction of interest was obtained with hexane, with a similar methodology to the fractionation method 1 performed in this work.

barbadensis, Dissotis rotundifolia, Chenopodium ambrosioides and rizosimas of Zingiber officinale Roscoe on M. tuberculosis H37Ra and H37Rv. It was determined that the leaves of S. torvum were the best potential anti-M. tuberculosis, since, they showed a MIC of 156.3 and 1,250 μg/mL against M. tuberculosis H37Ra and H37Rv, respectively

[START_REF] Nguta | Antimycobacterial and cytotoxic activity of selected medicinal plant extracts[END_REF]

. Likewise,

Kahaliw et al. obtained

the chloroform extracts from roots of different plants, among them Pterolobium stellatum, which showed the highest MIC. The fractionation of this extract was carried out by solvent partition, in order to obtain the hexane and ethyl acetate fractions.

Table IV . Validation parameters of the chromatographic method for the quantification of the vegetable samples from Leucophyllum frutescens

 IV

	Regression equation	Correlation coefficient (r)	LOD (μg/mL)	LOQ (μg/mL)	Repeatability (RSD, %)	Reproducibility (RSD, %)
	y = 8.8983x -9.2698	0.99	0.71	2.14	5.97	6.79

(ND=not determined)

  TableVdescribes the characterization parameters of RIF loaded NP. For the four formulations developed to encapsulate RIF, a particle size in a range of 140 -180 nm was obtained, with homogeneous size distributions and negative zeta potential.

				Correlation
	Active	No. Peak	Regression equation	coefficient (r)	LOD (μg/mL)	LOQ (μg/mL)
	EMR	5	y = 1.712x -355.49	0.99	ND	ND
	FHR	5	y = 1.4231x -591.75	0.99	ND	ND
		5	y = 2.0497x -105.57	0.99	209.22	634.00
	RF1	6	y = 0.3646x -38.803	0.99	427.35	1295.00
		7	y = 1.3158 -224.39	0.99	103.98	315.10

Table V . Characterization parameters of biodegradable polymeric nanoparticles containing rifampicin prepared by nanoprecipitation

 V

(Lut: Lutrol F127 NF: PVAL: polyvinyl alcohol); ND=not determined

( ±σ, n=3)

  Due to the results shown in the studies against M. tuberculosis, EMR and its fractions FHR and RF1 were selected to be encapsulated in NP. Table VI describes the characterization parameters of NP with plant samples. For the two formulations that were developed to encapsulate the EMR, FHR or RF1, a particle size in a range of 160 -190 nm was obtained, with homogeneous size distributions and negative zeta potential.As already mentioned, NP from 150 to 200 nm with negative zeta potential have shown targeting towards the organs rich in macrophages such as the lungs(Nahar y Jain, 2009), NP with EMR, FHR or RF1 obtained in our work, are potential formulations to reach the lungs. Likewise, they have the characteristics for the internalization by the alveolar macrophages that contain the tuberculosis bacterium. Nicolete et al. observed that their blank PLGA NP with zeta potential of -17.2±6.1 mV were internalized by J774

	related to hydrophobic drugs such as RIF. NP preparation technique used in this work
	(nanoprecipitation) with the formulation parameters used, are favorable for formulating
	NP with RIF.
	Polymer Emulsifier agent	Size (nm)	PDI	Zeta Potential (mV)	%L	%EE
	PLA	Lut	142.8±15.4 0.210±0.042	ND	2.8±0.1 30.4±0.3
	PLGA	Lut	163.0±4.6 0.113±0.019	-15.93±3.10	0.7±0.1 6.0±1.0
	PLA	PVAL	178.5±4.1 0.168±0.045	-7.89±1.82	2.2±0.1 35.9±1.0
	PLGA	PVAL	176.3±9.4 0.139±0.007	-5.57±1.35	0.5±0.1 4.0±0.5

Table VI . Characterization parameters of biodegradable polymeric nanoparticles containing methanol extract and hexane fractions from Leucophyllum prepared by nanoprecipitation

 VI

( ±σ, n=3 and n=2)

  who incorporated 18-βglycyrrhetinic acid (GLA) in PLGA NP with a size around 200 nm and negative zeta potential to test them against: Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis. MIC of NP with GLA and free GLA for P. aeruginosa was around 75 and 20 μg/mL, respectively; for S. aureus was of 75 and 35 μg/mL, respectively;

Table VII . Minimal inhibitory concentration (MIC) of biodegradable polymeric nanoparticles containing rifampicin (n=3)

 VII

	Formulations	MIC total batch (μg/mL)	MIC encapsulated rifampicin (μg/mL)
	RIF-PLGA-Lut	0.20	0.30
	RIF-PLA-PVAL	0.40	0.90
	RIF-PLGA-PVAL	0.20	0.10
		(Total batch: encapsulated and non-encapsulated rifampicin)

Table VIII . Minimal inhibitory concentration (MIC) of biodegradable polymeric nanoparticles containing the vegetable actives (n=3)

 VIII

	Formulations	MIC total batch (μg/mL)
	EMR-PLA	400
	EMR-PLGA	400
	FHR-PLA	160
	FHR-PLGA	80
	RF1-PLA	160
	RF1-PLGA	80
		(Total batch: encapsulated and non-encapsulated active)

(MIC encapsulated active was not determined)

Table IX . Minimal inhibitory concentration (MIC) of rifampicin with methanol extract and hexane fractions from L. frutescens roots against M. tuberculosis

 IX

Table II . Polymeric nanoparticles characterization containing the ethanol fraction from Leucophyllum frutescens leaves

 II

		Regression equation		Correlation coefficient		LOD Quantification	LOQ
	Size (nm)	PDI	(r) Peak-Component	%L	(μg/mL)	(μg/mL) %EE
	1	y = 1.4826x + 1.8489	1	0.99	43.83 4.13±0.76	130.58 19.83±3.76
	2 206.4±3.3	y = 0.4121x + 2.5638 0.118±0.026	2	0.99	38.62 4.89±0.86	117.03 23.48±4.25
	3	y = 1.9841x -14.17	3	0.99	22.29 12.81±2.19	67.53 61.52±11.17
	4	y = 0.4178x -13.207	4	0.99	45.86 16.56±3.21	138.97 79.53±16.21
							( ±σ, n=3)

  S. cerevisiae and L. delbrueckii and at 30 •C for E. coli. After 2 h and 24 h, the surviving cells were evaluated by standard plate count method. The antimicrobial activity of formulations was evident over a longer time scale (24 h)[START_REF] Donsì | Design of Nanoemulsion-Based Delivery Systems of Natural Antimicrobials: Effect of the Emulsifier[END_REF]. Tsai y Some studies have focused on the use of plants against the microorganism M. tuberculosis, causal agent of tuberculosis, with the aim of reducing the large number of new cases and mortalities that occur per year. The plant known as "cenizo" L. frutescens has been studied for this purpose. Molina-Salinas et al. determined that the methanol extracts from leaves and roots showed activity against M. tuberculosis (Molina-Salinas et

	the activity of different essential oil components: carvacrol, limonene and cinnamaldehyde in the sunflower oil droplets of nanoemulsions. The antimicrobial activity was measured against three different microorganisms, such as Saccharomyces cerevisiae (ATCC 16664), Escherichia coli (ATCC 26) and Lactobacillus delbrueckii sp. Lactis (ATCC 4797). The microorganisms, centrifuged at 6500 rpm for 5 min at 4 •C, were resuspended in sterile distilled water to a final concentration of 10 4 CFU/mL in test tubes, where the nanoemulsions were added to the desired final antimicrobial concentrations. The test tubes were hence incubated at 32 catechin extract was incorporated in NE and tested in human prostate cancer cell PC-3 and human fibroblast cell CCD-986SK. After 72 h incubation catechin nanoemulsion exhibited a lower toxicity toward CCD-986SK cells than catechin extract. While, catechin nanoemulsion had a major inhibitory effect in prostate cancer cell PC-3 proliferation with the IC50 being 8.5 μg/mL than catechin extract with IC50 being 15.4 μg/mL (Tsai y Chen, •C for Chen extracted catechins from tea leaf waste of Camellia sinensis (L.) Kuntze. The 2016).

Table I . Characterization of nanoemulsions containing rifampicin and the hexane fraction from Leucophyllum frutescens roots

 I

	Active	Hydrodynamic diameter (nm)	PDI	Encapsulation efficiency (%)
	RIF	179.3±3.5	0.213±0.014		99.9±0.0
				Peak 5	75.8±3.5
				Peak 9	86.5±4.7
	RF1	179.1±1.4	0.217±0.002	Peak 10	72.8±0.4
				Peak 14	70.6±17.4
				Peak 15	84.7±5.3

( ±σ, n=3)

work on the formulation, determining the oil phase and aqueous phase that does not present activity in the microbiological studies.

For all the formulations obtained in this thesis work, other in vitro and in vivo methods should be carried out to expand knowledge about toxicity.

(acetone:methanol). The organic phase was added to 10 mL of an aqueous phase, containing polyvinyl alcohol (PVAL) (Clariant, Mexico) as a stabilizer agent at a concentration of 1% w/w. Then, the organic solvent was evaporated under reduced pressure. The NP characterization was carried out determining the particle size and polydispersity index (PDI) by dynamic light scattering (Zetasizer Nano ZS90, Malvern Instruments, UK). To determine the drug loading and encapsulation efficiency (%L and %EE), the NP formulations were centrifuged at 25,000 rpm (Allegra 64R, Beckman Coulter, USA), the supernatant was decanted, and the pellets were lyophilized (Freeze Dry System, LABCONCO, USA). The lyophilized NP were dissolved in acetonitrile and methanol. The obtained solutions were analyzed by HPLC to quantify the peaks encapsulated from the calibration curve of each one, the results obtained were substituted in the following equations: All the analyzes were carried out in triplicate. The experimental results were expressed as ±σ, n=3.

Determination of the antioxidant activity of the ethanol fraction from Leucophyllum frutescens leaves in polymeric nanoparticles

To evaluate the antioxidant activity of HF4 loaded NP, a suspension of RBC was prepared as previously described. For the preparation of the samples, solutions of AA and HF4 were prepared, the volume of the NP dispersion containing HF4 was taken to obtain the final concentrations of 25 to 200 μg/mL. 375 μL of the AAPH solution and 250 μL of the RBC suspension were added to all the samples. The antioxidant control was ascorbic acid (AA), which was prepared at the same concentrations of the plant samples. 375 μL of the AAPH solution and 250 μL of the RBC suspension were added to all the samples. The oxidant control was PBS, 375 μL of the AAPH solution and 250 μL of the RBC suspension. Two controls were added, one negative to the hemolysis (750 μL of PBS and 250 μL of RBC) and another positive to hemolysis (750 μL of milli-Q water and 250 μL of RBC). All test samples had a final volume of 1000 μL. Samples and controls were incubated at 37 ° C for 2.5 h with constant agitation. After this time, the samples were centrifuged at 10,000 rpm for 10 min, recovering the supernatant of all the samples and adding them to a 96-well microplate. Finally, the absorbance of the supernatants at λ=575nm was measured in a microplate reader. The results of the assay were determined by equation 1 and 2.

All analyzes were carried out at least in triplicate. The experimental results were expressed as ±σ, n=3.

Determination of the hemolytic activity of the ethanol fraction from Leucophyllum frutescens leaves in polymeric nanoparticles

To evaluate the hemolytic activity of the HF4 in NP, a suspension of RBC was prepared as previously described. For the preparation of the samples, the necessary volume of the dispersion of NP containing HF4. The samples were tested in a concentration range from 25 to 200 μg/mL. The negative control to the hemolysis was prepared with 975 μL of PBS and the positive control to the hemolysis was prepared with 975 μL of milli-Q water. 25 μL of the RBC suspension was added to all samples, including controls. The samples were incubated at 37 ° C for 1 h. After this time, the samples were centrifuged at 10,000 rpm for 10 min, recovering the supernatant of all the samples and adding them to a 96-well microplate. Finally, the absorbance of the supernatants was measure at λ=575 nm in the microplate reader. The hemolytic activity was expressed as a percentage according to equation 3. The experimental results were expressed as ±σ, n=3.

The test of the extracts and their fractions was carried out according to UNE-EN ISO 10993-4, which states that a percentage lower than 5% is considered non-hemolytic. TEMH, HF1, HF2, HF3, HF4 and HF5 did not show hemolysis at the analyzed concentrations (25-200 μg / mL), while the FHH was not hemolytic below 25 μg/mL.

Chromatographic analysis

Of all the plant samples with antioxidant activity evaluated in the present work, HF4 fraction was selected to be encapsulated in NP. Firstly, it was analyzed by a HPLC to observe its chromatographic fingerprint or its peak profile, which is a useful tool for quality control, as well as to determine the amount of peaks or components present in the vegetable sample [START_REF] Bian | Fingerprint Analysis and Simultaneous Determination of Phenolic Compounds in Extracts of Curculiginis rhizoma by HPLC-Diode Array Detector[END_REF].

The chromatographic method developed allowed the separation of four peaks or components of interest in HF4 (Figure 3). This method was validated in order to use it for the quantification of peaks 1-4, once the fraction in the NP was encapsulated.

VIII. GENERAL CONCLUSIONS

In this study some investigations with the extracts and fractions from L. frutescens were carried out in order to obtain a broader knowledge about the biological activity present in the plant. Likewise, the vegetable samples that showed activity were encapsulated in free systems of organic solvents. NP has shown to be a good alternative to load actives into nanoparticles. As good delivery systems, actives loaded into nanoparticles show stability, protection, controlled release and targeted. Different parameters during nanoprecipitation process can be modified to obtain a formulation with the desirable characteristics on the size, storage stability, active encapsulation and electrostatic charges.

Based on the antimycobacterial activity revealed by previous studies, the first part of this work was focused on testing the effect of L. frutescens against M. tuberculosis to propose it as a co-adjuvant of the drugs used for the tuberculosis treatment, such as RIF.

To obtain the methanol extract from leaves and roots of L. frutescens, an ultrasound method was developed, which allowed a good performance to be obtained in a short time (2 h). Two different fractionation methods were developed in order to obtain the hexane fraction of leaves and roots, the percentage of yield obtained with both methods was close. However, method 2 was selected to continue with the following partitions because it is faster and easier to execute. The chromatographic profiles of the extracts and fractions were obtained through HPLC, these results reveal that there is the same number of peaks between the extract (leaves or roots) and the fractions obtained from it; in roots there is higher number of peaks than leaves.

The evaluation of the activity against M. tuberculosis of the extracts and fractions of L. frutescens revealed that in roots are more activity than in leaves, specifically, EMR, FHR and RF1 (MIC = 100, 40 and 40 μg/mL, respectively). Biodegradable NP of RIF and vegetable samples (EMR, FHR and RF1) of L. frutescens were prepared by nanoprecipitation. Formulations of NP showed a size from 140 to 190 nm, with homogeneous distributions and negative zeta potential. RIF had a MIC of 0.20 μg/mL, but when RIF is encapsulated in NP-PLGA-PVAL, it enhanced its activity (0.10 μg/mL) against M. tuberculosis. On the other hand, the hexane fractions in NP had more activity than free. The most active formulation was NP-PLGA-FHR and NP-PLGA-RF1 with a MIC of 80 μg/mL for both.

The combination of FHR and RF1 with RIF decreases the MIC value in both cases, demonstrating a better effect. Finally, the toxicity of the best samples was proved, at the active concentrations against M. tuberculosis RIF and NP-RIF did not present hemolysis.

Whereas, RF1 and NP-RF1 showed hemolysis. However, when RF1 is combined with RIF, the concentrations decreased from 40 to 10 μg/mL for RF1 and from 80 to 20 μg/mL for RF1 loaded NP, and at these concentrations there is no presence of hemolysis. This suggested that the encapsulation of RF1 in NP favored the reduction of its toxicity.

Therefore, an alternative to make use of the hexane fraction from roots of L. frutescens with potential activity against M. tuberculosis, at concentrations below the hemolytic effect, is to combine it with conventional antituberculosis drugs such as RIF, and thus, to enhance the activity.

Because of L. frutescens has been less studied for its antioxidant capacity, the second part of this work was focused on the antioxidant effect of the previously obtained extracts and fractions. The extracts and fractions of the L. frutescens plant showed a certain degree of protection, avoiding the lysis of RBC caused by the induced oxidation of AAPH reagent. FHH, EMR, FHR, RF1, RF2 and RF4 presented their maximum antioxidant activity at low concentrations and, subsequently, decreased when they were tested at higher concentrations due to a hemolysis effect. The EMH, HF1, HF2, HF3, HF4, HF5 and RF5 were samples with antioxidant activity from 25 to 200 μg/mL and without hemolytic effect, being selected the fraction HF4 for the studies that proceeded.

Suspensions of HF4 loaded NP were obtained by the nanoprecipitation technique, NP had a particle size around 200 nm with a homogeneous distribution. A chromatographic method was partially validated to be used for the quantification of the peaks-components present in HF4, from which the encapsulation of four peaks in NP was determined, it revealed a favorable incorporation of the L. frutescens fraction. Finally, when HF4 was incorporated in NP the antioxidant activity was conserved. For this reason, the incorporation of HF4 loaded NP is promising as an antioxidant agent because the