Prithwiraj De

Florence Bedos-Belval

Corinne Vanucci-Bacqué

Michel Baltas

Cinnamic acid derivatives in tuberculosis, malaria and cardiovascular diseases-A Review

Keywords: Antituberculosis, antimalarial agents, cardiovascular diseases, cinnamic acid, cinnamide, cinnamoyl ester, cinnamic hydrazide

Cinnamic acid and its phenolic analogues are natural substances. Chemically, cinnamic acids or the 3-phenyl acrylic acids, offer three main reactive sites: substitution on the phenyl ring, addition on the α,β-unsaturation and reactions of the carboxylic acid. Owing to these chemical aspects, cinnamic acid derivatives received much attention in medicinal research as traditional as well as valuable scaffolds in recent synthetic bioactive agents. In the last two decades, there has been huge attention towards various cinnamoyl derivatives and their biological efficacy. This review provides a comprehensive literature compilation concerning the synthesis of various cinnamoyl acids, esters, amides, hydrazides and related derivatives and their biological activity evaluations against diseases such as tuberculosis and malaria, which are frequent in developing countries and cardiovascular diseases, which cause a high mortality rate worldwide. We envisage that our effort in this review contributes a much needed and timely addition to the literature of medicinal research.

Cinnamic acid (1a) has a long history of human use as a component of plant-derived scents and flavourings [START_REF] Hoskins | The occurrence, metabolism and toxicity of cinnamic acid and related compounds[END_REF].

Fig. 1: Cinnamic acid and its natural phenolic-analogues

It belongs to the class of auxin, which is recognized as plant hormones regulating cell growth and differentiation [START_REF] Thimann | The auxins[END_REF]. The cinnamoyl functionality is also present in a variety of secondary metabolites of phenylpropanoid biosynthetic origin. Those containing a sesquiterpenyl, monoterpenyl and isopentenyl chain attached to a 4-hydroxy group represent quite a rare group of natural products [START_REF] Epifano | Prenyloxyphenylpropanoids as novel lead compounds for the selective inhibition of geranylgeranyl transferase I[END_REF]. The hydroxyl cinnamic acids such as p-coumaric acid (1b), caffeic acid (1c), ferulic acid (1d), sinapic acid (1e) (Fig. 1) are natural products arising from the deamination of the phenyl alanine [START_REF] Thimann | The auxins[END_REF]; they are important constituents in the biochemical pathway in plants leading to the lignin (Scheme 1) [4], the second most abundant biopolymer after cellulose [5], resulting mainly from the oxidative polymerization [START_REF] Freudenberg | Biosynthesis and Constitution of Lignin[END_REF] of the three hydroxycinnamoyl alcohols, i.e., coumaryl (3a), coniferyl (3b), sinapyl alcohols (3c).

Scheme 1: Lignin biosynthesis pathway

Natural hydroxyl cinnamates are extremely potent antitumor agents [START_REF] Epifano | Prenyloxyphenylpropanoids as novel lead compounds for the selective inhibition of geranylgeranyl transferase I[END_REF]7]. Chemically, cinnamic acid is an aromatic fatty acid composed of a phenyl ring substituted with an acrylic acid group, commonly, in the trans-geometry and has low toxicity in human exposure.

Cinnamic acids possess an α,β-unsaturated carbonyl moiety, which can be considered as a Michael acceptor, an active moiety often employed in the design of drugs [8]. In recent years, trans-cinnamic acid derivatives have attracted much attention due to their antioxidative [START_REF] Chung | Characterization of antioxidant alkaloids and phenolic acids from anthocyanin-pigmented rice (Oryza sativa cv Heugjinjubyeo)[END_REF], antitumor [10a,b] and antimicrobial [11] properties. In this review, we will restrict our discussion on cinnamic type related derivatives, their synthesis and their reported biological activities in tuberculosis, malaria and cardiovascular diseases research.

CINNAMIC ACID DERIVATIVES AS ANTITUBERCULOSIS AGENTS

Introduction

Tuberculosis (TB) is a threat to worldwide public health. It is caused by Mycobacterium tuberculosis (M.tb.). Despite the availability of effective treatment, tuberculosis is responsible for more than three million deaths annually worldwide. The high susceptibility of human immunodeficiency virus-infected persons to the disease [START_REF] Nunn | Tuberculosis control in the era of HIV[END_REF], the emergence of multi-drugresistant (MDR-TB) strains [13a-c] and extensively drug-resistant (XDR-TB) ones have brought this infectious disease into the focus of urgent scientific interest. For this reason, there is a growing need and urgency to discover new class of chemical compounds acting with different mechanisms from those currently used. In spite of that fact that cinnamic acid (1a) and derivatives have a century-old history as antituberculosis agents, for example, in 1894, Warbasse et al. [START_REF] Warbasse | Cinnamic acid in the treatment of tuberculosis[END_REF] reported that gradual improvement was observed when the TB-patients were treated with cinnamic acid (1a) prepared from storax and in 1920s, ethyl cinnamate (4; Fig. 2) [15a], sodium cinnamate (5) [15b] and benzyl cinnamate [START_REF] Freudenberg | Biosynthesis and Constitution of Lignin[END_REF] [15c] were reported to be efficacious in the treatment of TB, we feel that this class of molecules remained underutilized until recent years.

Fig. 2: Ethyl cinnamate, sodium cinnamate and benzyl cinnamate

In an attempt to develop a new strategy to circumvent MDR-TB by augmenting the potential of the existing drugs, Rastogi et al. [START_REF] Rastogi | Potential drug targets for Mycobacterium avium defined by using radiometric drug-inhibitor combination techniques[END_REF] used trans-cinnamic acid (1) along with known antituberculous drugs (Fig. 3) such as isoniazid (7), rifampin (8), ofloxacine [START_REF] Chung | Characterization of antioxidant alkaloids and phenolic acids from anthocyanin-pigmented rice (Oryza sativa cv Heugjinjubyeo)[END_REF] or clofazimine [START_REF] Bezerra | In vivo growth-inhibition of Sarcoma 180 by piplartine and piperine, two alkaloid amides from Piper Braz[END_REF]. The synergistic increase in the activity of various drugs against Mycobacterium avium was observed. The same authors reported in 1998 [START_REF] Rastogi | Synergistic activities of antituberculous drugs with cerulenin and trans-cinnamic acid against Mycobacterium tuberculosis[END_REF] that the synergistic activity of trans-cinnamic acid with a variety of drugs was observed even with drug resistant isolates.

Fig. 3: Known antituberculous drugs

Although, trans-cinnamic acid (1a) was used to treat tuberculosis before antimycobacterial chemotherapy was used [START_REF] Ryan | The Forgotten Plague. Little[END_REF], this was the first example of MDR-TB activity in synergy with other drugs but the mechanism of action still remains unknown.

Natural Resources

Cinnamic ester derivatives

In another context, cinnamoyl ester was identified as an important frame in glycoside extracts of a native North American prairie plant named Ipomoea leptophylla. In fact, Manfredi et al.

reported recently [START_REF] Barnes | Characterization of an Anti-tuberculosis Resin Glycoside from the Prairie Medicinal Plant Ipomoea leptophylla[END_REF] that the organic soluble extracts from its leaves showed in vitro activity against M. tb. Through a bioassay-guided fractionation of these extracts the authors isolated leptophyllin A (11), a resin glycoside bearing a trans-cinnamic residue attached to one rhamnose moiety. This compound (Fig. 4) showed 13% inhibition at 6.25 µg/mL against M. tb. in the in vitro anti-tuberculosis assay. Furthermore, the bioassay results indicated that the cinnamic acid residue is required for the observed antimicrobial activity as an analogous compound leptophyllin B (12) also isolated from the same source without cinnamic acid residue showed no in vitro activity.

Fig. 4: Resin glycosides from I. leptophylla

Recently, Kanokmedhakul et al. [START_REF] Lekphrom | Bioactive styryllactones and alkaloid from flowers of Goniothalamus laoticus[END_REF] reported the identification of some bioactive styryllactones and alkaloids isolated from flowers of Goniothalamus laoticus. The authors isolated a styryllactone derivative, howiinin A (13; Fig. 5), by fractionation of the ethyl acetate and methanol extracts from the flowers of this species. This compound possessing a cinnamoyl ester moiety while inactive against Plasmodium falciparum, showed an interesting antituberculosis activity (MIC = 6.25 µg/mL) when tested against M.tb. strain H37Ra.

Synthetic compounds

Cinnamic hydroxamic acid derivatives

In 2002, Phanstiel and co-workers [START_REF] Guo | Synthesis and Biological Evaluation of New Citrate-Based Siderophores as Potential Probes for the Mechanism of Iron Uptake in Mycobacteria[END_REF] used siderophores (produced by mycobacteria itself) to target iron transport processes essential for the growth and survival of M. tb. Targeting the iron transport processes of M. tb. is challenging for several reasons. The complexity of the mycobactin architecture itself poses a daunting synthetic challenge, which hampers the generation of conjugates [START_REF] Xu | Total Syntheses of Mycobactin Analogues as Potent Antimycobacterial Agents Using a Minimal Protecting Group Strategy[END_REF]. Further, the iron transport mechanism involves an "ironhandoff" between two siderophore families, the exochelins and the mycobactins. In low iron environments, M. tuberculosis biosynthesizes and secretes hydrophilic exochelins (e.g., Mycobactin J (14); Scheme 2) to bind exogenous ferric ion. The iron-complex is then transferred to intracellular siderophores, i.e., the mycobactins, which are lipophilic chelators associated with the cytoplasmic membrane [START_REF] Roosenberg | Studies and Syntheses of Siderophores, Microbial Iron Chelators, and Analogues as Potential Drug Delivery Agents[END_REF]. The mycobactin associated iron either remains in the cell wall as an iron storage pool or is released into the cell by a mycobactin reductase [START_REF] Roosenberg | Studies and Syntheses of Siderophores, Microbial Iron Chelators, and Analogues as Potential Drug Delivery Agents[END_REF].

Therefore, the sequesteration of the available iron into a form, which cannot be processed by M.tb. may be an alternative therapeutic way. The success of this approach relies on understanding the molecular recognition events involved in mycobacterial iron transport. The authors synthesized different iron chelators containing α,β-unsaturated hydroxamic acid motifs appended to a citric acid platform such as Nannochelin A (19b) and compared its activities with the corresponding trans-octenoyl derivative.

Scheme 2: Synthesis of Nannochelin A

As shown in Scheme 2, the reaction of diamines (15a,b) with di-tert-butyl dicarbonate afforded the mono-Boc-protected diamines which were dissolved in a biphasic mixture containing carbonate buffer (pH 10.5) and benzoylperoxide dissolved in dichloromethane was added. After the oxidation step, the mixture was acylated with trans-cinnamoyl chloride to give the desired compounds 16a,b. They were then treated with a 10% NH4OH in methanol solution at 0 °C to deprotect hydroxamic acid and the resulting derivatives were treated with trifluoroacetic acid (TFA) at 0 °C to remove the Boc group and produce the TFA salts 17a,b. Notably, molecules that provided significantly higher growth index (GI) values than the native chelator mycobactin J [START_REF] Warbasse | Cinnamic acid in the treatment of tuberculosis[END_REF] were identified as superior growth stimulants and more efficacious iron delivery agents. The systems containing longer tethers gave higher GI values (e.g., GI= 0.76 for 19a vs 1.5 for 19b). It was envisaged by the authors that the longer tether allows for a more conformationally flexible ligand to properly coordinate to iron and provides an increase in hydrophobicity. However, the authors identified the derivative 19b as superior growth stimulants and more efficacious iron delivery agents. Such ligands, which offer regulation of the initial iron delivery step, provide the opportunity to compare the iron transport mechanisms of both native and genetically modified mycobacteria.

As shown in

Cinnamaldehyde Schiff's base derivatives

In 1997, Biava et al. [START_REF] Biava | New Toluidine Drivatives Antimycobacterial and Antifungal Activities[END_REF] reported the synthesis and antimycobacterial efficacy of a new class of styryl derivatives (Scheme 3). Ortho, meta or para-aminotoluidine compounds possessing an imidazole, pyrazine or morpholine frame (21a-c) were obtained after reduction of the corresponding nitro derivatives (20a-c). These compounds were coupled under reductive amination conditions (Scheme 3) with cinnamaldehyde [START_REF] Xu | Total Syntheses of Mycobactin Analogues as Potent Antimycobacterial Agents Using a Minimal Protecting Group Strategy[END_REF] affording the toluidine-styryl derivatives (24a-c).

Cinnamic oxadiazole derivatives

In 1997, Parekh et al. [START_REF] Joshi | Synthesis of Some Novel 1,3,4-Oxadiazoles and 5-Oxoimidazolines as Potent Biologically Active Agents[END_REF] reported the synthesis of some 1,3,4-oxadiazoles and oxoimidazolines compounds as potent biologically active agents. The synthetic routes are presented in Scheme 5. The starting common precursor 29 was obtained through condensation of 5-nitro-O-benzoylene-2,1-benzimidazole [START_REF] Copp | Natural product growth inhibitors of Mycobacterium tuberculosis[END_REF] with hydrazine hydrate. The cyclocondensation reaction of different aromatic acids with 29 in the presence of POCl3 afforded the 1,3,4-oxadiazoles 30a-e. Scheme 5: Synthesis of 1,3,4-oxadiazoles and 5-oxo-imidazolines Compounds 30a-d were found to be more active against M. tb. than the cinnamic derivative 30e (all activities were evaluated at 12.5g/mL against M. tb. H37Rv).

Modified drugs with Cinnamic-residues

Structural modifications of known drugs by introduction of cinnamoyl or substituted cinnamoyl groups have been also explored with some success.

Cinnamic ester derivatives

It is well known that triterpenes exhibit moderate to high in vitro antimycobacterial activity against M. tb. [START_REF] Cantrell | Antimycobacterial plant terpenoids[END_REF][START_REF] Copp | Natural product growth inhibitors of Mycobacterium tuberculosis[END_REF][START_REF] Okunade | Natural Antimycobacterial Metabolites: Current Status[END_REF]. In 2008, Suksamrarn et al. reported [START_REF] Tanachatchairatana | Antimycobacterial Activity of Cinnamate-Based Esters of the Triterpenes Betulinic, Oleanolic and Ursolic Acids[END_REF] the modification of natural triterpenes such as betulinic acid [START_REF] Reddy | Antimycobacterial Activity of New Rifamycin Derivative, 3-(4-Cinnamylpiperazinyl Iminomethyl)Rifamycin SV (T9)[END_REF], oleanolic acid (32) and ursolic acid [START_REF] Bairwa | Novel Molecular Hybrids of Cinnamic Acids and Guanylhydrazones as Potential Antitubercular Agents[END_REF] through introduction at the C-3 position of cinnamoyl frames (Scheme 6). Different cinnamoyl derivatives such as cinnamate, p-coumarate, ferulate, caffeate and p-chloro cinnamate esters of the above mentioned triterpenes were synthesized by reacting with the suitable cinnamoyl chlorides in the presence of 4-N,N-dimethylaminopyridine (DMAP) in benzene (Scheme 6).

All the hydroxyl cinnamic acids were acetylated as a protection to the phenolic group before generating the corresponding acid chlorides followed by coupling with the triterpenes. However, the hydroxycinnamate derivatives of the triterpenes ( 31d,f,h;32d,f,h;33d,f,h) were obtained by deacetylation of the acetylated derivatives (31c,e,g; 32c,e,g; 33c,e,g) using K2CO3 in methanol. The biological results indicated that the introduction of unsubstituted or p-chlorinated cinnamate ester functionality (31a,b; 32a,b; 33a,b) led to inactive compounds (MIC>200 µg/mL) or without any improvement in their antimycobacterial activity.

Interestingly, the results also indicated that introduction of the p-coumarate moiety at the C-3 position of the triterpenes (31d, 32d, 33d) resulted in an 8-fold increase in antimycobacterial activity of the parent triterpenes 31 (MIC = 50 µg/mL) and 32 (MIC = 50 µg/mL), and a 2fold increase in this activity of the triterpene 33 (MIC = 12.5 µg/mL). Introduction of a ferulate moiety (31h, 32h, 33h) resulted in a 4-fold increase in activity only in case of 33.

However, the p-hydroxyl group contributed to high antimycobacterial activity, while methylation and acetylation of the phenolic hydroxyl group, with the exception of the caffeate esters, decreased antimycobacterial activity. Scheme 6: Cinnamate-based triterpenes and their biological activities

Cinnamic amide derivatives

Rifampicin (RIF; 8) is one of the most important drugs in TB treatment. In search for new compounds with structural modifications of existing lead drugs, Dimova et al. [START_REF] Reddy | Antimycobacterial Activity of New Rifamycin Derivative, 3-(4-Cinnamylpiperazinyl Iminomethyl)Rifamycin SV (T9)[END_REF] reported in 1995 that the introduction of the cinnamoyl moiety on the piperazinyl frame of rifampicin that named rifamycin SV (T9) resulted in enhanced antimycobacterial activities. The antimycobacterial activities of 3-(4-cinnamylpiperazinyl-iminomethyl)rifamycin derivative (8a; Fig. 6) on 20 susceptible and MDR-strains of M. tb. and 20 Mycobacterium avium complex (MAC) strains were investigated by Reddy et al. [32]. The radiometric MICs of T9 for M.tb. were significantly lower than those of RIF. The MICs of T9 and RIF at which 90% of the RIF-susceptible strains were inhibited were <0.25 and <0.5 µg/mL, respectively. Interestingly, 8a had lower MICs against some RIF-resistant M. tb. strains. Compound 8a had better activity against MAC strains, and the MIC at which 90% of the MAC strains were inhibited was <0.125 µg/mL, and that of RIF was <2.0 µg/mL. Compound 8a also showed high in vitro bactericidal and intracellular activities which were significantly superior to those of RIF against both M.tb. and MAC strains. More importantly, 8a showed excellent in vivo activity against M.tb. H37Rv compared to RIF in both the lungs and spleens of C57BL/6 mice, indicating the potential therapeutic value of 8a in the treatment of mycobacterial infections.

Fig. 6: Structure of Rifamycin SV

In an attempt to find novel compounds active against TB, Degani and coworkers [START_REF] Bairwa | Novel Molecular Hybrids of Cinnamic Acids and Guanylhydrazones as Potential Antitubercular Agents[END_REF] synthesized and evaluated a series of phenylacrylamides designed by molecular hybridization of trans-cinnamic acids and guanylhydrazones (Scheme 7). While cinnamic acids are already known for their antituberculosis efficacy, guanylhydrazones have been shown to have antimicrobial activity including an interesting Gram-negative bacterial endotoxin lipopolysaccharide (LPS) sequestering activity owing to their cationic nature [START_REF] Gadad | Synthesis and antibacterial activity of some 5-guanylhydrazone/thiocyanato-6-arylimidazo[2,1-b]-1,3,4thiadiazole-2-sulfonamide derivatives[END_REF][START_REF] Khownium | Novel endotoxin-sequestering compounds with terephthalaldehyde-bis-guanylhydrazone scaffolds[END_REF][START_REF] Wu | Structure-activity relationships of lipopolysaccharide sequestration in guanylhydrazone-bearing lipopolyamines[END_REF]. M. tb. contains lipoarabinomannan (LAM), a complex lipid glycoprotein anchored to the cell membrane by phosphatidylinositol which has structural and functional similarity to LPS, including the presence of anionic phosphate groups [START_REF] Zhang | Activation of the interleukin 6 gene by Mycobacterium tuberculosis or lipopolysaccharide is mediated by nuclear factors NF-IL6 and NF-kappa B[END_REF]. Biosynthesis of LAM is known to be a target for several antitubercular agents, including the first line antitubercular agent, ethambutol [START_REF] Scherman | Biosynthetic origin of mycobacterial cell wall arabinosyl residues[END_REF][START_REF] Heijenoort | Formation of the glycan chains in the synthesis of bacterial peptidoglycan[END_REF]. For the synthesis of the most active phenylacrylamide derivative (37; Scheme 7), guanylhydrazone (34a), required as starting material, was prepared by the microwave assisted reaction of 3,4-dimethoxybenzaldehyde [START_REF] Gadad | Synthesis and antibacterial activity of some 5-guanylhydrazone/thiocyanato-6-arylimidazo[2,1-b]-1,3,4thiadiazole-2-sulfonamide derivatives[END_REF] with guanyl hydrazine hydrochloride [START_REF] Khownium | Novel endotoxin-sequestering compounds with terephthalaldehyde-bis-guanylhydrazone scaffolds[END_REF]. The phenyl 4-methoxycinnamate (36a) was prepared by treating phenol and thionyl chloride to 4-methoxycinnamic acid [START_REF] Wu | Structure-activity relationships of lipopolysaccharide sequestration in guanylhydrazone-bearing lipopolyamines[END_REF]. The reaction of equimolar quantities of guanylhydrazones (34a), with phenylcinnamates (36a), under microwave irradiation in the presence of triethylamine and ethanol as the solvent afforded the target derivative (E)-N-(((E)-2-(3,4-dimethoxybenzylidene)hydrazinyl)(imino)methyl)-3-(4-methoxyphenyl)acrylamide [START_REF] Zhang | Activation of the interleukin 6 gene by Mycobacterium tuberculosis or lipopolysaccharide is mediated by nuclear factors NF-IL6 and NF-kappa B[END_REF]. This principle of the design was applied to obtain other phenylacrylamide derivatives.

But compound 37 was found to be most active when tested on resazurin microtitre plate assay (REMA) against M. tb. H37Rv.

Scheme 7: Synthetic route for the synthesis of phenylacrylamide derivatives

Compound 37 showed MIC of 6.5 µM along with good safety profile (CC50 = 340 µM) in VERO cell line. Importantly, based on empirical structure-activity relationship data, it was observed that both steric and electronic parameters play major role in the activity of this series of compounds.

Cinnamic benzimidazole derivatives

In 2009, Hosamani et al. [START_REF] Shingalapur | Synthesis and evaluation of in vitro antimicrobial and anti-tubercular activity of 2-styryl benzimidazoles[END_REF] synthesized a new series of 5-(nitro/bromo)-styryl-2benzimidazoles (41a-f, 42a-f; Scheme 8) by condensation of 5-(nitro/bromo)-Ophenylenediamine [START_REF] Scherman | Biosynthetic origin of mycobacterial cell wall arabinosyl residues[END_REF][START_REF] Heijenoort | Formation of the glycan chains in the synthesis of bacterial peptidoglycan[END_REF] with trans-cinnamic acids (40a-f) in ethylene glycol for 6 h at around 200°C (Scheme 8). This work is based on the fact that benzimidazole and its derivatives were reported to be physiologically and pharmacologically active and find applications in the treatment of several diseases like epilepsy, diabetes, anti-fertility [START_REF] Orjales | New 2-Piperazinylbenzimidazole Derivatives as 5-HT3 Antagonists. Synthesis and Pharmacological Evaluation[END_REF][START_REF] Grimmett | Comprehensive Heterocyclic Chemistry II[END_REF]. It is an important pharmacophore and privileged structure in medicinal chemistry [START_REF] Khalafi-Nezhad | synthesis, antibacterial and QSAR studies of benzimidazole and imidazole chloroaryloxyalkyl derivatives[END_REF][START_REF] Evans | Methods for drug discovery: development of potent, selective, orally effective cholecystokinin antagonists[END_REF] encompassing a diverse range of biological activities. Screening for the in vitro anti-TB activities of these compounds (41a-f, 42a-f) on the M. tb. strain H37Rv was conducted at 7.25 µg/mL concentration and the inhibitory efficacies were determined. The benzimidazole derivatives wearing bromo-substituent (42a-f) exibited the best results with 63-83% inhibition. In our recent effort, we have synthesized some 4-alkoxycinnamic acid thio-ester, amides, hydrazides and triazolophthalazine derivatives [45a,b] and evaluated (MTT colorometric assay) their anti-TB efficacy. While 4-alkoxy substitutions were introduced to control the required lipophilicity following Lipinski's rules [START_REF] Lipinski | Experimental and computational approaches to estimate solubility and permeability in drug discovery and development settings[END_REF], their coupling partners were suitably chosen either to mimic biological intermediates or to modify any existing drug. appearance and spread of resistance around the world. By the early 1990s, malaria's percentage contribution to 'all-cause mortality' in African infants was climbing, in some areas accounting for nearly 50% of deaths. Currently, the only fully effective class of antimalarial drug is the artemisinins. As a result of the increasing prevalence of multidrug resistance of malaria parasites to standard chemotherapy, the discovery and use of nontraditional antimalarials with novel action mechanisms is becoming urgent [51a-c]. In this context, cinnamic derivatives from natural or synthetic sources form a class of drug candidates which we believe could be used as lead for the antimalarial drug discovery.

Natural Ressources

Cinnamic ester derivatives

In 1992, Nkunya and co-workers [START_REF] Achenbach | Antimalarial Compounds from Hoslundia opposita[END_REF]

8).

In vitro antiplasmodial effects of the compounds were also assessed.

Fig. 8: Andinermal A (57a) and flavononol glycosides isolated from Andira inermis

Andinermal A (57a) (Fig. 8) exhibited the strongest antiplasmodial activity with IC50 values of 2.3 mg/mL against poW and 3.9 mg/mL against Dd2 strains. Whereas the 3-O-rhamnosides 58a and 58b proved to be inactive, 3΄-O-trans-cinnamoyl-astilbin (58c) showed a 50% growth inhibition at 10.4 mg/mL (poW) and 4.2 mg/mL (Dd2). Obviously the trans-cinnamoyl residue could enhance the antiplasmodial activity of the unsubstituted rhamnoside 58a.

While screening a library of terrestrial plant and marine invertebrate extracts for their in vitro P. falciparum activity, Ovenden and co-workers [START_REF] Ovenden | Phenolic Glycosides with Antimalarial Activity from GreWillea "Poorinda Queen[END_REF] isolated an extract from the leaves and twigs of a Gre Villea "Poorinda Queen" displaying significant antimalarial activity.

Subsequent bioassay-guided fractionation of this methanol extract allowed for the identification of three new phenolic glycosides, robustasides E (59), F (60) and G (61) (Fig. 9). ). However, the mechanism of action of these compounds and the role of the hemiquinone in the observed differences in antimalarial activities remained unknown.

Cinnamic amide derivatives

In 2005, Ross and co-workers [START_REF] Ross | Alkamides from the Leaves of Zanthoxylum syncarpum[END_REF] isolated three alkamides (62-64; Fig. 10) from the leaves of Zanthoxylum syncarpum, commonly called "prickly ash", which is the largest genus in the family Rutaceae and comprises about 200 species of trees and shrubs, with a worldwide, but predominantly tropical, distribution. The antimalarial activity of the isolated racemic compounds (62-64) was evaluated against chloroquine-sensitive (D6, Sierra Leone) and resistant (W2, Indochina) strains of P. falciparum. Compounds 62 and 63 were inactive, whereas compound 64 showed moderate activity, with IC50 values of 4.2 and 6.1 µM against P. falciparum D6 clone, Sierra Leone, and P. falciparum W2 clone, Indochina, respectively.

Artemisinin and chloroquine showed IC50 values of 0.04 and 0.05 µM against P. falciparum D6 clone, respectively. Cytotoxicity was evaluated at an IC50 of 4.7µg/mL.

Cinnamic acid derivatives

Ginsburg et al. [START_REF] Kanaani | Effects of Cinnamic Acid Derivatives on In Vitro Growth of Plasmodium falciparum and on the Permeability of the Membrane of Malaria-Infected Erythrocytes[END_REF] reported that some cinnamic acid derivatives 65-68 (Fig. 11), obtained from commercial sources, inhibited the growth of intraerythrocytic P. falciparum in culture, which is in correlation with their hydrophobic character. It was found that all the derivatives also inhibit the translocation of carbohydrates and amino acids across the new permeability pathways induced in the host cell membrane by the parasite. This impediment correlated strictly with their effect on parasite growth. These drug-candidates caused a significant decline in ATP level in the parasite compartment, while they provoked only a small effect on ATP level in the intact cells and the host cell compartment. These observations suggest that these cinnamic derivatives (65-68) inhibit ATP production in the parasite and its utilization by the host cell. The authors studied the inhibition of P. falciparum growth and sorbitol uptake by α-fluorocinnamate (65), α-cyano-4-hydroxycinnamate (66), α-cyano-3-hydroxycinnamate (67) and α-Cyanop-(1-phenylindol-3-yl) acrylate [START_REF] Oh | Oxidative damages are critical in pathogenesis of reflux esophagitis implication of antioxidants in its treatment[END_REF]. The IC50 values for parasite growth inhibition (65; 0.612±0.084 mM, 66; 1.126±0.0005 mM, 67; 0.258±0.025 mM, 68; 0.064±0.006 mM) were found to be higher in comparison to their sorbitol uptake inhibition (65; 0.11 mM, 67; 0.16 mM, 68; 0.03 mM). These results indicated that the indolyl derivative [START_REF] Oh | Oxidative damages are critical in pathogenesis of reflux esophagitis implication of antioxidants in its treatment[END_REF] is the most efficient inhibitor. However, the fluorinated derivative (65) has a better sorbitol uptake inhibition profile than plasmodial growth inhibition.

Cinnamic amide derivatives

In 1975, Herrin and co-workers [START_REF] Hemin | Synthesis and Antimalarial Activity of 1-(4-Methoxycinnamoyl)-4-(5-phenyl-4-oxo-2-oxazolin-2yl)piperazine and Derivatives[END_REF] Pemoline (69a) was activated by acylation with acetic anhydride to yield a monoacetyl derivative which reacted smoothly with piperazine (71) to give the piperazine pemoline 69b.

Cinnamoyl groups were introduced by activating the corresponding cinnamic acid through mixed anhydride formation using ethylchloroformate and triethylamine followed by reacting with pemoline-piperazine derivative (69b) to afford 72a-g. All derivatives, tested against multidrug resistant P. falciparum strain Dd2, exibited activities in terms of IC50 from 0.2 to >100µM. Replacement of the 3-phenylpropionyl moiety of the lead structure 76 by a 4-propoxycinnamoyl residue (77j) resulted in a 10-fold improvement in anti-malarial activity (77j; IC50= 0.2µM vs 76; 2.7µM).

In 2006, Doerksen and co-workers [START_REF] Xie | 3D-QSAR Analysis of Antimalarial Farnesyltransferase Inhibitors Based on a 2,5-Diaminobenzophenone Scaffold[END_REF] used the class of antimalarials developed by Schlitzer et al. [START_REF] Wiesner | Structure-Activity Relationships of Novel Anti-Malarial Agents. Part 2: Cinnamic Acid Derivatives[END_REF][START_REF] Wiesner | Structure-Activity Relationships of Novel Anti-Malarial Agents. Part 3: N-(4-Acylamino-3-benzoylphenyl)-4-propoxycinnamic Acid Amides[END_REF][START_REF] Schlitzer | Synthesis and Early Structure-Activity Relationship of Farnesyltransferase Inhibitors which Mimic both the Peptidic and the Prenylic Substrate[END_REF] as plasmodial protein farnesyltransferase inhibitors. In order to investigate quantitatively the local physicochemical properties involved in the interaction between drug and biotarget, the 3D-QSAR methods CoMFA and CoMSIA were used to study some molecules of the series, including the screened lead compound 76 and cinnamic acid derivatives (77a-j). Steric, electrostatic, and hydrophobic properties of substituent groups were found to play key roles in the bioactivity of the series of compounds, while hydrogen

Cinnamic ester derivatives

In 2007, Baltas and co-workers [START_REF] Rakotondramanana | Synthesis of Ferulic Ester Dimers, Functionalisation and Biological Evaluation as Potential Antiatherogenic and Antiplasmodial Agents[END_REF] investigated ferulic dimers to identify new class of antimalarials. The feruloyl dimers were prepared by the oxidative coupling of the feruloyl methyl ester (81a), obtained by treating ferulic acid (1d) with refluxing methanol in the presence of sulfuric acid (Scheme 14). The biomimetic oxidative coupling of 81a was carried out using silver oxide Ag2O in toluene/acetone (2/1) mixture as solvent. Benzofuranic derivative 82 (sole diastereoisomer) was obtained as the major product along with some dimeric ferulic ester (83). The monoalcohol 86 was obtained by selective reduction of the benzofuranyl ester group of compound 82a with 6 equivalents of LiBH4 in THF at room temperature. Compound 86a, obtained after TBDMS deprotection of 86, was coupled with trisilylated gallic acid 85 in the presence of EDC/DMAP or DCC/DMAP to afford the gallate ester 87. Finally, silyl group deprotection was performed by using Et3N.3HF complex in THF.

Compound 83 possessing two allylic esters could not be reduced by lithium tetrahydroborate.

The treatment of 83a, the silylated derivative, with DIBAL-H afforded the diol 84. The reaction was quite sluggish when compound 83 was used. Compounds 82, 83, 86a, and 87a

were evaluated for their ability to inhibit in vitro P. falciparum, grown in asynchronous culture conditions. To this end, the chloroquine-resistant Plasmodium strain FCM29 was used. Compound 87a exhibited antiplasmodial activities with an IC50 value of 798 ± 12 nM.

The standard reference drug chloroquine had an IC50 value of 264 ± 11 nM. The remaining compounds 82, 83, and 86a did not show significant antiplasmodial activities.

Compound 82 showed cytotoxicity activities against P388 cell lines with IC50 of 772 ± 21 nM whereas the remaining compounds were devoid of such activities.

CINNAMIC ACID DERIVATIVES IN CARDIOVASCULAR DISEASES

Introduction

Heart diseases or cardiovascular diseases involve the heart or blood vessels (arteries and veins) [START_REF] Maton | Human Biology and Health[END_REF]. While the term technically refers to any disease that affects the cardiovascular system, it is usually used to refer to those related to atherosclerosis (arterial diseases). These diseases have similar causes, mechanisms, and treatments. Most countries face high and increasing rates of cardiovascular diseases. A large histological study showed vascular injury accumulates from adolescence, making primary prevention efforts necessary from childhood [65a,b]. By the time that heart problems are detected, the underlying cause (atherosclerosis) is usually quite advanced, having progressed for decades. There is therefore increased emphasis on preventing atherosclerosis by modifying risk factors, such as healthy eating, exercise and avoidance of smoking. In addition, low density lipoprotein (LDL) metabolism in human has a profound effect on atherosclerosis. Because LDL particles appear to be harmless until entering within the blood vessel walls and oxidized by free radicals [START_REF] Teissedre | Inhibition of in vitro human LDL oxidation by phenolic antioxidants from grapes and wines[END_REF], it is postulated that ingesting antioxidants and minimizing free radical exposure may reduce LDL's contribution to atherosclerosis, though results are not conclusive [START_REF] Esterbauer | Effect of antioxidants on oxidative modification of LDL[END_REF]. Naturally occurring polyphenolic cinnamic acid derivatives are known antioxidants and are traditional medicines for atherosclerosis-related diseases like hypertension. Our effort in this review is directed towards the understanding of natural and synthetic cinnamic derivatives in cardiovascular diseaserelated medicinal chemistry.

Natural sources

Cinnamic acid derivatives and analogues

Oxidative stress, the consequence of an imbalance of prooxidants and antioxidants in the organism, is gaining recognition as a key phenomenon in chronic illness like inflammatory and heart diseases, hypertension and some forms of cancer. Several gastrointestinal tract diseases seem to be induced by oxidative stress [START_REF] Oh | Oxidative damages are critical in pathogenesis of reflux esophagitis implication of antioxidants in its treatment[END_REF]. On the other hand, the traditional use of many Baccharis-species as hepatoprotective and digestive crude drugs have been reported [START_REF]270 Plantas medicinales iberoamericanas[END_REF]. Schmeda-Hirschmann et al. reported [START_REF] Tapia | Free radical scavangers and antioxidants from Baccharis grisebachii[END_REF] that the exudate and seriated extracts from the aerial parts of Baccharis grisebachii (Asteraceae) which is recommended as a digestive and to relieve gastric ulcers in Argentina, showed activities as free radical scavengers and inhibited lipoperoxidation in erythrocytes. Assay guided isolation led to p-coumaric acid derivatives and flavonoids as the main active constituents of the crude drug (Fig. 12). The activity towards the superoxide anion was mainly arising due to the flavonoid constituents. 5,7,4΄-

Trihydroxy

Cinnamic ester derivatives

Hypertension is a lifestyle-related disease which often leads to serious ailments such as heart diseases and cerebral hemorrhage. Angiotensin II (Ang II) plays an important role in regulating cardiovascular homeostasis. Uemura et al. [START_REF] Ohno | Inhibitory effect of benzyl benzoate and its derivatives on angiotensin II-induced hypertension[END_REF] found that EtOH extract from the resin of sweet gum Liquidambar styraciflua strongly inhibited Ang II signaling. The authors isolated benzyl benzoate and benzyl cinnamate (6) (Fig. 2) from this extract and found that these compounds inhibited the function of Ang II in a dose-dependent manner without cytotoxicity.

In 2006, Awang et al. [START_REF] Othman | Bioassay-guided isolation of a vasorelaxant active compound from Kaempferia galanga L[END_REF] isolated ethyl cinnamate (4) (Fig. 2) through bioassay guided fractionation from Kaempferia galanga L., a common Malaysian Zingiberaceae species. The species is locally used as a spice and commonly prescribed for the traditional treatment of hypertension, rheumatism and asthma. However, the authors reported that the active component, 4, has a vasorelaxant activity as it exhibited hypotensive activity by lowering the basal mean arterial pressure in anaesthetized rats.

Cinnamic amide derivatives and analogues

Thanh et al. reported [START_REF] Li | Isolation and identification of antiplatelet aggregatory principles from the leaves of Piper lolot[END_REF] in 2007 that the methanolic extract of Piper lolot, showed potent inhibitory activity on platelet aggregation induced by arachidonic acid (AA) and platelet activating factor (PAF). Members of the Piper genus, widely distributed throughout the tropical and subtropical regions, have commercial, economical, and medicinal importance.

Economically, the Piperaceae is employed for the production of pepper in worldwide spice markets. Plants from the Piper genus have been used for a number of practical applications, including remedies in many traditional medicinal systems, such as traditional Chinese medicine, the Indian Ayurvedic system, and folklore medicines of Latin America and the West Indies. Activity-guided isolation afforded amide alkaloids, piperlotine analogues, along with some known compounds (Fig. 13). The isolated compounds were tested for their The product thus obtained was subsequently deprotected by saponification to obtain the feruloyl amide (117). With a view that thioester derivatives are a masked form of thiol group, a well-known scavenger of oxygen radical, we planned to test some N-acetylcysteamine derivatives (119a-c) of p-coumaric acid, ferulic acid and related cinnamic acids for their antioxidant efficacy. However, the cinnamic-phosphonates (121a-c), bioisosteric varieties of cinnamic acid derivatives, were prepared by reacting suitable aldehydes (120a-c) with tetraethylmethylene diphosphonate in the presence of LDA. These compounds (121a-c) were then chlorinated in order to incorporate the N-acetylcysteamine residue to afford compounds 124a-c. But the protection of free phenolic functionality with silyl-group before chlorination became necessary due to messy reactions with oxalyl chloride, the chlorinating agent. The silyl-protection was then removed using the usual reagents at -25 °C to afford the cinnamicphosphonothioesters (125a-c). However, the same deprotection procedure at room temperature afforded the corresponding fluorinated derivatives (126a-c). Among the synthesized compounds, the amide (117), thioester (119c), phosphonothioester (125c) and the fluorophosphonocinnamic acid analogue (126c) exhibited potent inhibitory effects against LDL-oxidation and subsequent toxicities mediated by cultured human microvascular endothelial cells (HEMEC-1), with efficacies comparable to that observed with probucol (127), a known anti hyperlipidemic drug [START_REF] Yamamoto | A unique hyperantilipidemic drug-Probucol[END_REF]. Synthesized antioxidants could either share both radical scavenger and metal chelator activities, or show antioxidant activity only as metal chelator since LDL-oxidation in HMEC-1 was done in the presence of copper (1 μM).

However, electron donating substituents surrounding the 4-hydroxy group of the aromatic ring of these cinnamic derivatives seemed to play crucial role towards the observed antiatherogenic activity.

CONCLUSION AND PERSPECTIVES

Cinnamic acids are abundant in various natural resources. Cinnamic acid and its natural and synthetic analogues are unique as drug candidates in tuberculosis, malaria and cardiovascular diseases. Natural substances such as ethyl-(4) and benzyl-( 6) cinnamates not only have anti-TB activities, they are traditional medicines for hypertension as well. With α,β-unsaturated carboxyl functionality, cinnamic acids offer Michael-acceptor properties, particularly to the glutathione (GSH) and cystine residues. Although, mycobacteria, unlike E.coli, do not prefer the formation of Michael-adduct, at-least during cell wall biosynthesis, the presence of the cinnamoyl moiety certainly increased the antituberculosis efficacy in several occasions. For example, cinnamoyl-rifamycine (8a) has better in vitro anti-TB activity than rifamycine (8) itself and leptophyllin A (11) has better activity than its non-cinnamoylated analogue leptophyllin B [START_REF] Nunn | Tuberculosis control in the era of HIV[END_REF]. Similarly, the fact that naturally occurring cinnamoyl-hosloppone (56c) is a better antimalarial agent than hosloppone (56a) and its benzoyl-analogue (56b) reflects the importance of α,β-unsaturated carboxyl functionality. Importantly, the replacement of the double bond with an isosteric cyclopropyl ring decreased the anti-TB efficiency of the triazolophthalazines. On the other hand, introduction of cinnamoyl moiety to isoniazid, a frontline anti-TB drug, did not significantly alter the trend of biological activity or the mode of action. These observations indicate that the anti-TB activity depends not only on the α,βunsaturation but also on the functionalization of the carboxyl part of the cinnamoyl derivatives. Similarly, the introduction of 4-propyloxycinnamoyl residue to the N-(4-amino-2benzoylphenyl)-(4-methylphenyl)acetamide ( 77) resulted in a 10-fold enhancement of anti malarial activity compared to its phenethyl analogue (76). Notably, substituents at the benzene ring of the cinnamic acids also play a crucial role in the biological activities. While hydroxyl substitution in cinnamic acids and related derivatives confers antioxidative properties thereby making them useful in chronic illness such as inflammatory and heart diseases and hypertension, methoxy, isoprenyloxy and isoprenyl substituents also seem to play useful roles in tuberculosis, malaria and cardiovascular diseases. For example, 33h, 7b, and 37 are methoxyphenyl derivatives and they all have significant anti TB activities.

Syncarpamide [START_REF] Maton | Human Biology and Health[END_REF] and its analogues, ferulic acid dimers (86a, 87a) and 8-aminoquinoline derivatives such as 80b,c,d have significant anti malarial activities and piperlotin-analogues (90-92, 100) and tyramine derivative 103a,b are important anti-platelet aggregation agents.

Drupanin (89a) and its natural analogues (89b-e), with isoprenyl substitution on the aromatic ring, showed significant xanthine oxidase inhibitory effect and isoprenyloxy cinnamoyltriazolophthalazine derivative (54e) showed extremely potent anti-TB activity when tested against INH-resistant strains. In summary, cinnamic acid derivatives are potent anti-TB agents, active against P. falciparum even in nanomolar concentration range and they showed antioxidant properties as well as antiplatelet aggregation activities. In spite of all these multiactivities of cinnamic acid derivatives their mode of action and understanding of molecular mechanisms remains unclear. We express hope to learn more about this versatile molecule and its derivatives in addition to the synthesis of new useful biologically important compounds in near future.

Fig. 5 :

 5 Fig. 5: Structure of Howiinin A.

Scheme 2 ,

 2 the condensation of 17a,b with protected citric acid (18) in 1,4dioxane followed by TFA treatment gave the chelators 19a,b.

Scheme 3 :

 3 Scheme 3: Synthesis of toluidine derivatives

Scheme 8 :Scheme 9 :

 89 Scheme 8: Synthesis of styryl-2-benzimidazoles series

  4-Alkoxycinnamic acids were coupled with N-acetylcysteamine (48, Scheme 10) to afford the corresponding thio-esters 48a,e,f thereby mimicking the enoylacyl-ACP intermediate involved in the M.tb. fatty acid synthase II (FASII) cycle, an important step towards its cell wall biosynthesis. However, these thioesters showed poor anti-TB activities against M.tb. H37Rv possibly due to the weak C-S bond energy making these molecules labile under physiological conditions. In continuation, we introduced N-acetylethelenediamine 49 as coupling partner of cinnamic acids as a replacement of cysteamine moiety to afford compounds 49a,e,f (Scheme 10). In spite of our concern regarding proteolytic instability of the cinnamides, (E)-N-(2-acetamidoethyl)-3-(4-geranyloxyphenyl)acrylamide (49f) showed a very good anti-TB activity (MIC = 0.24 µM, vs INH; MIC = 0.6 µM). Unfortunately, poor cytotoxicity profile of this class of compounds forced us to think otherwise. No other amide derivatives (50a,b,d,f; 51 a,e,f) showed good biological activities. To alleviate the concern for the proteolytic instability we wanted to synthesize cinnamoyl hydrazides and thus, isoniazid became an immediate choice. To our delight, all six 4-alkoxycinnamoyl isonicotinyl hydrazides (52a-f) showed good anti-TB activities (MIC) and their cytotoxicity profile (IC50) were very much encouraging. At this point, it became absolutely necessary to test these molecules against INH-resistant strains (MYC5165, 1400) to find out if these molecules are pro-drug of INH. Two representative INH-derivatives 52a (same as 7b in Scheme 9) and 52e were tested on MYC5165, a M.tb. strain mutated in InhA and 1400 a M.tb. strain mutated in katG. The inhibitory activities of 52a (MIC = 16 µM: MYC5165; 320 µM: 1400) and 52e (MIC = 27 µM: MYC5165; 68 µM: 1400) were found to follow similar trends as that of INH (MIC = 18 µM: MYC5165; 729 µM: 1400) itself, thus not allowing at the moment to propose these compounds as isoniazid prodrugs or not. In order to explore the influence of other hydrazides, 1-hydrazinophthalazine hydrochloride 53, an antihypertensive drug [47] of moderate potency, was coupled with acids 46a-f in the presence of EDC.HCl, HOBt and triethylamine to afford (2E, N′E)-3-(4-alkoxyphenyl)-N'-[phthalazin-1-(2H)ylidiene]acrylohydrazides (53a-f). In a different experimental condition, coupling of 4-alkoxyphenyl-cyclopropyl acids (47a-f ) with 1-hydrazinophthalazine hydrochloride in acetonitrile under reflux for 48 h in presence of EDC.HCl, HOBt and triethylamine furnished the corresponding 3-(4-alkoxystyryl)-[1,2,4]triazolo[3,4-]phthalazines (54a-f). For the family of 1-phthalazino hydrazides (53a-f), MIC results were moderate but the trend of cytotoxic behaviour was not acceptable. Interestingly, the combination of isopentenyl-side chain as 4-alkoxy substituent with triazolophthalazine (54e), showed excellent antitubercular potency (MIC = 1.4 µM), in comparison with other derivatives in the series (54a-f), and more importantly, with good cytotoxicity (IC50 = 449 µM) and selectivity index (SI = 320). Finally, to our great delight, compound 54e showed 100-fold better in vitro activity against MYC5165 strain (54e; MIC= 0.2M) and 1800-fold better activity against 1400 strain (54e; MIC= 0.4 M) compared to INH (MIC= 18 and 729 µM respectively). The importance of the isopentenyl-side chain and triazolophthalazine part are evident from these biological results as none of the other triazolophthalazine derivatives (54a-d, 54f) are active enough. Further, the radio-thin-layer chromatography analysis revealed that compound 54e does not inhibit mycolic acid biosynthesis signifying a different mode of action than INH. In order to explore the importance of the enoyl-acyl backbone, with an approach to replace the double bond by isosteric cyclopropyl moiety, we also synthesized 3-[2-(4-alkoxyphenyl)cyclopropyl]-[1,2,4]triazolo[3,4-α]phthalazine (55a-f; racemates) and their in-vitro anti-TB potentiality were evaluated. Significantly, the MIC values of the compounds (55a-f) were found to be poor compared to their olefinic analogues (54a-f). In regard to the difference in activities between the enoyl and cyclopropyl series, a plausible explanation could be the respective Michael acceptor ability. Chew et al. [48a] have recently showed that cinnamaldehydes can act as Michael acceptors and inhibit thioredoxin reductase through nucleophilic addition of glutathione cystine -SH residues. In our case, from a chemical point of view, the compounds having electron withdrawing group in the para-position of the aromatic ring should be more active to Michael addition. It should be a clear structure activity relationship if this is the possible reason of their activity, i.e. 4-OCF3 derivatives are expected to show better inhibitory activities compared to their 4-OCH3 analogues. But this is not the case as compound 52a has a 4-fold better activity (MIC=0.3 µM) compared to 52b (MIC=1.1 µM) and similarly 54a (MIC=53 µM) exhibits approximately 15-fold better activity than 54b (702 µM). In view of these results, we can suggest that the Michael addition is not the mode of action of these compounds. This view was also supported by the fact that mycobacterial lip B prefers to form thioester intermediate with deca-2-enoic acid during mycolic acid biosynthesis unlike E.coli lipB which forms a thioether via Michael addition [48b].

  isolated two new hosloppone derivatives, 3-Obenzoylhosloppone (56b), 3-O-cinnamoylhosloppone (56c) (Fig.7), from the root bark of the antimalarial plant Hoslundia opposita Vahl. growing in East and West Africa. The crude nhexane extract of the root bark was found to have significant in vitro activity against Plasmodium falciparum (P. Falciparum) (IC50 = 5.6 µg/mL). In order to evaluate the active principles, different compounds were isolated and especially two esters (56b,c)of new abietane-type quinomethane alcohol named hosloppone (56a).

Fig. 7 :

 7 Fig. 7: Chemical structure of hosloppone derivatives

Fig. 9 :

 9 Fig. 9: Chemical structure of robustasides E (59), F (60), and G (61)

Fig. 10 :

 10 Fig. 10: Chemical structure of alkamides from leaves of Zanthoxylum syncarpum

Fig 11 :

 11 Fig 11: α-Substituted cinnamic acid derivatives.

  used (4-oxo-2-oxazolin-2-yl)piperazine scaffold to synthesize different potential antimalarial agents. The starting material for the compounds was 1-(5-phenyl-4-oxo-2-oxazolin-2-y1)piperazine (69b). Condensation of ester 69 with guanidine (70) gave 2-amino-5-phenyl-2-oxazolin-4-one (pemoline; 69a) (Scheme 12).

Scheme 11 :Scheme 12 :

 1112 Scheme 11: Synthesis of pemoline analogues

- 6 -

 6 methoxyflavone (88a) and quercetin (88b) presented high activity (64 and 79%) even at 12.5 µg/mL. The xanthine oxidase inhibitory effect of the extracts was related with the p-coumaric acid derivatives such as drupanin (89a), 4-acetyl-3,5-diprenylcinnamic acid (89b) and trans-ferulic acid O-hexan-3-onyl-ether (89c) which showed IC50 values in the range 28-40 µg/mL. Both p-coumaric acid derivatives and flavonoids inhibited lipoperoxidation in erythrocytes. The highest activity was found for the p-coumaric acid derivatives such as 4-acetyl-3-prenyl-ethoxycinnamate (89d), 3-prenyl-4-(4΄hydroxydihydrocinnamoyloxy)-cinnamate (89e) and compound 89c (69-82%), and for the flavonoids such as 88a, 88b, 5,7,4΄-trihydroxy-6,3΄-dimethoxyflavone (88c) and 5,7,4΄trihydroxy-6,8-dimethoxyflavone (88d) (64-84%) at 100 µg/mL. The most active free radical scavengers measured by the DPPH decoloration assay were the p-coumaric acid derivatives 89a and trans-ferulic acid O-hexan-3-onyl-ether (89c)(27-35% at 10 µg/mL) and the flavonoid quercetin (97 and 23% at 10 and 1 µg/mL, respectively). The results support the use of Baccharis grisebachii in Argentinian traditional medicine.

Fig. 12 :

 12 Fig. 12: Active components isolated from Baccharis grisebachii.

  inhibitory activity on the rabbit platelet aggregation. The compounds piperlotine A (90), piperlotine C (91), piperlotine D (92), piperlotine E (93), 3-phenyl-1-(2,4,6-trihydroxyphenyl) propan-1-one (94), 3-(4-methoxyphenyl)-1-(2,4,6-trihydroxyphenyl)propan-1-one (95), 1trans-cinnamoylpyrrolidine (96), sarmentine (97), pellitorine (98) and methyl 3phenylpropionate (99) showed potent antiplatelet aggregation activity (100% antiplatelet aggregation at 100 µg/mL). Importantly, platelet aggregation plays a central role in thrombosis (clot formation). The presence of a thrombus in an artery providing blood to the heart is the most common cause of acute coronary syndromes such as myocardial infarction and angina. Inhibitors of aggregation can provide protection against these diseases and lower vascular disease mortality and stroke incidence in patients with unstable ischemic heart disease [74a,b].

Fig. 13 :

 13 Fig. 13: Active compounds isolated from Piper lolot

Fig. 14 : 1 - 1 .

 1411 Fig. 14: 1-(3-Methoxycinnamoyl)pyrrolide

[ 79 ]Fig. 15 :Scheme 17 : 3 . 2 .

 79151732 Scheme 15: Synthesis of cinnamoyltyramine derivatives

ACKNOWLEDGEMENTS

We thank "Université Paul Sabatier" for postdoctoral grant (P.D.). Thanks are due to the European Community (integrated project "New Medicines for Tuberculosis: NM4TB 018923") and CNRS (France) for financial support.

Scheme 10: Synthetic route for the preparation of different cinnamoyl derivatives

CINNAMIC ACID DERIVATIVES AS ANTIMALARIAL AGENTS

Introduction

Malaria remains one of the most serious health threats in the world, affecting 300-400 million people and claiming approximately 3 million lives each year [49, 50a,b]. Malaria is generally caused by four species, including Plasmodium falciparum, P. Vivax, P. Ovle and P. Malariae, having the greatest toll in human health. For much of the twentieth century, malaria was treated with the fast-acting and inexpensive drugs chloroquine and pyrimethaminesulphadoxine. From the 1960s onwards, these drugs progressively succumbed to the bonding interactions show no obvious impact. The results provided insight for optimization of this class of antimalarials for better activity and might prove helpful for further lead optimization. In this study, the hydrophobic property seemed to be most significant factor that is correlated with activity.

Effective treatment and control of malaria continues to be challenged by parasite resistance to antimalarial drugs. To this aim, histone deacetylase enzymes (HDACs) in malaria parasites may represent potential new targets for antimalarial drug development. HDACs are Zndependent enzymes that play crucial roles in modulating mammalian cell chromatin structure, transcription, and gene expression. Fairlie and co-workers [START_REF] Wheatley | Antimalarial histone deacetylase inhibitors containing cinnamate or NSAID components[END_REF] found that compounds derived from L-2-aminosuberic acid (Asu), like 78 and 80a (Scheme 13), have potent antimalarial activity and also inhibited P. falciparum HDAC nuclear extracts in a dose-dependent manner (IC50= 78 nM and 87 nM, respectively). Compound 80a was a lead compound with a cinnamic acid residue. A series of synthetically accessible derivatives of cinnamic acids was synthesized (Scheme 13). 6-Bromohexanoic acid [START_REF] Woo | Synthesis of substituted cinnamoyl-tyramine derivatives and their platelet anti-aggregatory activities[END_REF] was protected as a methyl ester followed by iodide substitution forming methyl 6-iodohexanoate (79a). Alkylation of diethyl acetamidomalonate with 79a gave 6-acetamido-7-ethoxy-6-(ethoxycarbonyl)-7-oxoheptanoic acid (79b), which was hydrolyzed under acidic conditions followed by protection of the acid as the methyl ester, and conversion of the amine to the benzylcarbamate (79c). Chiral resolution of 79c was achieved using the cysteine protease, Carica papaya and stopped at 40% conversion to free acid 79d and ester 79c΄. The acid functionality of 79d was coupled with 8-aminoquinoline and terminal amine with cinnamoyl residues using standard coupling procedures to afford a series of inhibitors (80a-f).

The authors described a series of potent antimalarial cinnamates (80a-f) with IC50s <50 nM against a drug sensitive (3D7) strain of P. falciparum.

Scheme 13: Synthetic route to antimalarial HDAC inhibitors containing cinnamic rsidues

The inhibitors showed selectivity in killing the malarial parasite over normal cells and they caused hyperacetylation of P. falciparum histones. When docked in a P. falciparum HDAC (PfHDAC1) homology model, a preferred inhibitor binding mode revealed amide-NH Hbonding to PfHDAC1 Asp97. The inhibitors reported herein share a branch or fork at the chiral center, thereby enabling generation of compound libraries that can distinguish between HDAC surface contours at the entrance to the HDAC active sites, thereby enabling discrimination between different P. falciparum and human HDACs. This may be an important approach to enhancing selectivity over human HDAC enzymes. Together the data supports the case for targeting the PfHDAC1 enzyme to obtain novel antimalarial drugs.

Scheme 14: Synthetic route to ferulic esters dimers

Interestingly, the presence of the galloyl moiety in compound 87a led to the appearance of antiplasmodial effects with respect to the parent compound 86a. A decrease in cytotoxicity from compound 82 to compound 87a was noticed. Thus, gallate ester might be a good substitute to enhance the antimalarial activities of existing or potential drugs. Cytotoxicity activities of these compounds were also evaluated against the murine P388 leukaemia cells. Thus, thrombin activates many cell types such as vascular smooth muscle cells, leukocytes, endothelial cells, and platelets via activation of these receptors. In humans, thrombin-induced platelet aggregation is mediated by one subtype of these receptors, termed PAR1. Perez et al. [START_REF] Perez | Discovery of novel protease activated receptors 1 antagonists with potent antithrombotic activity in vivo[END_REF] reported the discovery of new antagonists of these receptors and more specifically two


Roger Erivan
email: rerivan@chu-clermontferrand.fr

Anne-Sophie Muller

Guillaume Villatte

Stéphane Millerioux

Aurélien Mulliez

Stéphane Boisgard

Stéphane Descamps

Short stems reproduce femoral offset better than standard stems in total hip arthroplasty. A case-control study

Keywords: femoral offset, short stem, total hip arthroplasty, case-control study femoral offset, short stem, total hip arthroplasty, case-control study

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

In total hip arthroplasty (THA), it is important to maintain femoral and acetabular offset in order to ensure good joint stability and restore hip abductor muscle function [1][2][3][4][5]. Consequently, preoperative acetabular offset should be maintained [6,7], and the same is true for the femoral side.

Altering the original offset can lead to poor outcome [8] or even complications or revision when the changes are too great [9,10]. Short stems were developed with the aim of conserving bone stock.

Although the first models are very old, long-term survival of the latest-generation stems is not yet known, although clinical results and 8-year survival are excellent [11].

Implant positioning usually spares the femoral neck, with the implant guided along the calcar. This anatomical landmark, with metaphyseal fixation, makes it possible to adapt to particular anatomical situations. Femoral offset with short stems has been rarely studied [12]. Kutzner [13,14], however, reported femoral offset using the same short stem as in the present study, with an increase in femoral offset of 5.8mm in one study and of 2.2mm in the other; however, he did not compare this to standard stems. Schmidutz compared another model of short stem to a standard stem, but with a modular neck [15].

The aim of the present study was to compare femoral offset between short and standard stems.

The hypothesis was that the short stem studied allows better control of postoperative femoral offset than a standard stem.

Material and methods

Patients

A case-control study retrospectively reviewed a continuous series of 200 THAs. All were performed with a monoblock cementless (press-fit) cup made of ultra-high molecular weight polyethylene coated with titanium with no metal shell (RM Pressfit™, Mathys, Bettlach, Switzerland).

Between 2013 and 2017, we included 100 consecutive THAs using an uncemented optimys™ short stem (Mathys, Bettlach, Switzerland). This short stem is available in standard or lateralized (+5 mm femoral offset) versions. These short stems were matched with 100 standard stems used during the same period. Two standard stem models were used: cemented CCA™ stem (Mathys, Bettlach, Switzerland) or uncemented twinsys™ (Mathys, Bettlach, Switzerland), according to femoral bone quality. Both were available in standard or lateralized (+5 to +8mm femoral offset, depending on size) versions. Our local review board approved the study (Comité de Protection des Personnes Sud Est 6, IRB 8526). Two senior surgeons performed THA.

Methods

Radiographic templates were used for preoperative planning. The femoral neck was cut as planned preoperatively to achieve the desired femoral offset. Either a standard or a lateralized stem was chosen, based on the preoperative plan. The femoral canal was prepared with rasps. A highviscosity antibiotic-loaded cement (Palacos™ Genta, Hereaus, Hanau, Germany) was injected retrogradely to fix cemented stems.

The surgical approach was anterolateral in most cases, without difference between the two groups. There were 105 left sides, without difference between groups. Cup size was 51.7+/-3.3 mm (range, 44-62), without difference between groups. 89 patients received a ceramic head in the shortstem group, and 67 in the standard group; the other patients received a chrome-cobalt alloy head.

Neck lengths in the short-stem group were short (-4mm) in 52 cases, medium in 35 and long (+4mm) in 16. In the standard group, neck lengths were short in 81 cases, medium in 14 and long in 5. The stem used in the short-stem group was lateralized in 80 cases and standard in 20; in the standard group, it was lateralized in 95 cases and standard in 5.

Assessment methods

All patients underwent standardized pre-and post-operative anteroposterior digital X-ray.

Orthoview© (Materialise, Belgium) software was used systematically for radiological evaluation of pre-and post-operative offset, and for preoperative planning, as shown in figure 1. In this example, although good pressfit is achieved intra-operatively it is not always reflected by the x-ray. A 30 mm diameter external marker was used for calibration. All measurements were made by two senior operators (other than the surgical operators).

Statistical methods

Findings were reported as counts and percentages for qualitative and categorical variables and as mean ± standard deviation and range for quantitative variables. Groups (short vs standard stem)

Results

Follow-up

Mean patient age was 67.1 +/-11.3 years (range, 17-90 years), without difference between groups. 92 patients were female. Mean follow-up was 1.5 years (range, 1-5 years). Pre-and postoperative radiographs were available for all patients. No THA revisions were performed and no patients showed complications or stem movement. Figure 2 and3 show two examples of patients who had a standard stem and a short stem with measurements of the prosthetic situation before, after surgery and the last follow-up.

Interobserver correlation

Interobserver correlation was good, with correlation coefficient r = 0.88 (p<0.001) for offset, r = 0.82 (p<0.001) for limb length, and r = 0.72 (p<0.001) for neck angle.

Offset results

Mean femoral offset increased by 6.0 +/-7.2 mm overall (p< 0.0001): 4.7 +/-6.7 mm in the shortstem group (p<0.0001), and 7.2 +/-7.5 mm in the standard-stem group (p<0.0001), with a significant inter-group difference (p=0.0152). Offset was increased by surgery overall, and more by standard than by short stems. Figure 42 shows the distribution of femoral offset variation.

Limb length

Mean limb length increased by 2.5 +/-5.5 mm overall (p< 0.0001): 2.4 +/-5.0 mm in the short-stem group (p<0.0001) and 2.5 +/-5.9 mm in the standard-stem group (p<0.0001), without significant inter-group difference (p=0.8425).

Cervico-diaphyseal angle

Mean cervico-diaphyseal angle increased by 4.5 +/-6.6° overall (p< 0.0001): 2.4 +/-6.3° in the shortstem group (p=0.0002) and 6.6 +/-6.4° in the standard-stem group (p<0.0001), with significant intergroup difference (p<0.001). Cervico-diaphyseal angle was increased by surgery overall, and more by standard than by short stems. Figure 53 shows the changes in cervico-diaphyseal angle.

Inter-group correlation

There were no correlations with gender or neck length except between femoral offset and neck length (Table 1).

Discussion

The study hypothesis was confirmed: short stems provided better control of femoral offset. The mean increase in femoral offset of 6.0 mm was significant and may lead to a loss of strength in abductor muscles [16]. The difference should be smaller with a short stem, in the light of the present results. The aim of short stems is to conserve bone stock and to restore anatomy more effectively [17]. Short stems were introduced as an option for restoring femoral offset and anatomy [13], but restoration of femoral offset compared to standard stems has not previously been studied. Kutzner found the same increase in femoral offset as in the present study, but without control group [13].

The present study shows the importance of preoperative planning. Schmidutz found results similar to those of the present study, but using a short stem with modular neck [15]. Wacha reviewed more than 1,200 short-stem procedures, but did not study femoral offset [18]. A new method for calculating femoral offset was described by Boese in 2016 [19], including rotation of the cervico- diaphyseal angle measured in the stem to enable femoral offset to be corrected. This method has not been validated for the stem used in the present study, and was therefore not applied here. Some authors recommended use of navigation for restoring offsets and length during surgery; however, this lengthens surgery time [20,21].

Analysis of the secondary endpoints showed no difference in limb-length between short and standard stem procedures. This parameter can affect clinical results after hip replacement.

Amenabar studied limb-length and femoral offset with a different short stem, but did not compare it to a standard stem [12]. The present study compared pre-and post-operative values. One remaining question is whether lower limb length needs to be restored to its value before onset of osteoarthritis or to its value before surgery. Length management is difficult even today [22], and can lead to revision in extreme cases [23]. The present series showed increased length, which is usually what is sought because of length loss induced by osteoarthritis.

Some biases may affect the present study. Offset measurement can be difficult, and some authors recommend CT. The present study did not control stem ante-or retro-version, which can influence offset. The study was retrospective, and a prospective randomized study would be necessary to confirm the present results. Boese showed that the position of the calibration marker is important for calibrating the templating [24]; this is why we corrected the enlargement of the X-ray, to take account of the size of the head in addition to the marker. We used several surgical different approaches, which could induce bias, although Schwarze, in a randomized controlled study, showed no effect of surgical approach on migration of a short-stem total hip prosthesis at 2 years' follow-up [25]. These new generation stems have 96% survival at 4.8 years' follow-up according to Wacha [18],

as confirmed by Hauer in a comparative analysis [26]. Short stems can lead to periprosthetic bone remodeling, studied by Yan [27], with onset mainly after 2 years. Short stems are often used with young patients, in order to conserve bone stock. Return to sport after short-stem THA is fast: usually within 6 months [28]. Short stems are also known to incur less blood loss and fewer transfusions [29]; we did not study these parameters.

Conclusion

It is critical to maintain offset in THA. The technique we use increases femoral offset, and we need to consider changing it. However, the present study showed that offset was less increased by short than standard stems. These findings must be taken into account so as to optimize clinical outcome.

Conflicts of interest: Stéphane Boisgard is an educational consultant for Zimmer-Biomet, outside of this study. The other authors have no conflicts of interest outside of this study. None of the authors have any conflicts of interest to declare relative to this study.

Introduction

In total hip arthroplasty (THA), it is important to maintain femoral and acetabular offset in order to ensure good joint stability and restore hip abductor muscle function [1][2][3][4][5]. Consequently, preoperative acetabular offset should be maintained [6,7], and the same is true for the femoral side.

Altering the original offset can lead to poor outcome [8] or even complications or revision when the changes are too great [9,10]. Short stems were developed with the aim of conserving bone stock.

Although the first models are very old, long-term survival of the latest-generation stems is not yet known, although clinical results and 8-year survival are excellent [11].

Implant positioning usually spares the femoral neck, with the implant guided along the calcar.

This anatomical landmark, with metaphyseal fixation, makes it possible to adapt to particular anatomical situations. Femoral offset with short stems has been rarely studied [12]. Kutzner [13,14],

however, reported femoral offset using the same short stem as in the present study, with an increase in femoral offset of 5.8mm in one study and of 2.2mm in the other; however, he did not compare this to standard stems. Schmidutz compared another model of short stem to a standard stem, but with a modular neck [15].

The aim of the present study was to compare femoral offset between short and standard stems.

The hypothesis was that the short stem studied allows better control of postoperative femoral offset than a standard stem.

Material and methods

Patients

A case-control study retrospectively reviewed a continuous series of 200 THAs. All were performed with a monoblock cementless (press-fit) cup made of ultra-high molecular weight polyethylene coated with titanium with no metal shell (RM Pressfit™, Mathys, Bettlach, Switzerland).

Between 2013 and 2017, we included 100 consecutive THAs using an uncemented optimys™ short stem (Mathys, Bettlach, Switzerland). This short stem is available in standard or lateralized (+5 mm femoral offset) versions. These short stems were matched with 100 standard stems used during the same period. Two standard stem models were used: cemented CCA™ stem (Mathys, Bettlach, Switzerland) or uncemented twinsys™ (Mathys, Bettlach, Switzerland), according to femoral bone quality. Both were available in standard or lateralized (+5 to +8mm femoral offset, depending on size) versions. Our local review board approved the study (Comité de Protection des Personnes Sud Est 6, IRB 8526). Two senior surgeons performed THA.

Methods

Radiographic templates were used for preoperative planning. The femoral neck was cut as planned preoperatively to achieve the desired femoral offset. Either a standard or a lateralized stem was chosen, based on the preoperative plan. The femoral canal was prepared with rasps. A highviscosity antibiotic-loaded cement (Palacos™ Genta, Hereaus, Hanau, Germany) was injected retrogradely to fix cemented stems.

The surgical approach was anterolateral in most cases, without difference between the two groups. There were 105 left sides, without difference between groups. Cup size was 51.7+/-3.3 mm (range, 44-62), without difference between groups. 89 patients received a ceramic head in the shortstem group, and 67 in the standard group; the other patients received a chrome-cobalt alloy head.

Neck lengths in the short-stem group were short (-4mm) in 52 cases, medium in 35 and long (+4mm) in 16. In the standard group, neck lengths were short in 81 cases, medium in 14 and long in 5. The stem used in the short-stem group was lateralized in 80 cases and standard in 20; in the standard group, it was lateralized in 95 cases and standard in 5.

Assessment methods

All patients underwent standardized pre-and post-operative anteroposterior digital X-ray.

Orthoview© (Materialise, Belgium) software was used systematically for radiological evaluation of pre-and post-operative offset, and for preoperative planning, as shown in figure 1. In this example, although good pressfit is achieved intra-operatively it is not always reflected by the x-ray. A 30 mm diameter external marker was used for calibration. All measurements were made by two senior operators (other than the surgical operators).

Statistical methods

Findings were reported as counts and percentages for qualitative and categorical variables and as mean ± standard deviation and range for quantitative variables. Groups (short vs standard stem)

Results

Follow-up

Mean patient age was 67.1 +/-11.3 years (range, 17-90 years), without difference between groups. 92 patients were female. Mean follow-up was 1.5 years (range, 1-5 years). Pre-and postoperative radiographs were available for all patients. No THA revisions were performed and no patients showed complications or stem movement. Figure 2 and3 show two examples of patients who had a standard stem and a short stem with measurements of the prosthetic situation before, after surgery and the last follow-up.

Interobserver correlation

Interobserver correlation was good, with correlation coefficient r = 0.88 (p<0.001) for offset, r = 0.82 (p<0.001) for limb length, and r = 0.72 (p<0.001) for neck angle.

Offset results

Mean femoral offset increased by 6.0 +/-7.2 mm overall (p< 0.0001): 4.7 +/-6.7 mm in the shortstem group (p<0.0001), and 7.2 +/-7.5 mm in the standard-stem group (p<0.0001), with a significant inter-group difference (p=0.0152). Offset was increased by surgery overall, and more by standard than by short stems. Figure 4 shows the distribution of femoral offset variation.

Limb length

Mean limb length increased by 2.5 +/-5.5 mm overall (p< 0.0001): 2.4 +/-5.0 mm in the short-stem group (p<0.0001) and 2.5 +/-5.9 mm in the standard-stem group (p<0.0001), without significant inter-group difference (p=0.8425).

Cervico-diaphyseal angle

Mean cervico-diaphyseal angle increased by 4.5 +/-6.6° overall (p< 0.0001): 2.4 +/-6.3° in the shortstem group (p=0.0002) and 6.6 +/-6.4° in the standard-stem group (p<0.0001), with significant intergroup difference (p<0.001). Cervico-diaphyseal angle was increased by surgery overall, and more by standard than by short stems. Figure 5 shows the changes in cervico-diaphyseal angle.

Inter-group correlation

There were no correlations with gender or neck length except between femoral offset and neck length (Table 1).

Discussion

The study hypothesis was confirmed: short stems provided better control of femoral offset. The mean increase in femoral offset of 6.0 mm was significant and may lead to a loss of strength in abductor muscles [16]. The difference should be smaller with a short stem, in the light of the present results. The aim of short stems is to conserve bone stock and to restore anatomy more effectively [17].

Short stems were introduced as an option for restoring femoral offset and anatomy [13], but restoration of femoral offset compared to standard stems has not previously been studied. Kutzner found the same increase in femoral offset as in the present study, but without control group [13].

The present study shows the importance of preoperative planning. Schmidutz found results similar to those of the present study, but using a short stem with modular neck [15]. Wacha reviewed more than 1,200 short-stem procedures, but did not study femoral offset [18]. A new method for calculating femoral offset was described by Boese in 2016 [19], including rotation of the cervico- diaphyseal angle measured in the stem to enable femoral offset to be corrected. This method has not been validated for the stem used in the present study, and was therefore not applied here. Some authors recommended use of navigation for restoring offsets and length during surgery; however, this lengthens surgery time [20,21].

Analysis of the secondary endpoints showed no difference in limb-length between short and standard stem procedures. This parameter can affect clinical results after hip replacement.

Amenabar studied limb-length and femoral offset with a different short stem, but did not compare it to a standard stem [12]. The present study compared pre-and post-operative values. One remaining question is whether lower limb length needs to be restored to its value before onset of osteoarthritis or to its value before surgery. Length management is difficult even today [22], and can lead to revision in extreme cases [23]. The present series showed increased length, which is usually what is sought because of length loss induced by osteoarthritis.

Some biases may affect the present study. Offset measurement can be difficult, and some authors recommend CT. The present study did not control stem ante-or retro-version, which can influence offset. The study was retrospective, and a prospective randomized study would be necessary to confirm the present results. Boese showed that the position of the calibration marker is important for calibrating the templating [24]; this is why we corrected the enlargement of the X-ray, to take account of the size of the head in addition to the marker. We used several surgical different approaches, which could induce bias, although Schwarze, in a randomized controlled study, showed no effect of surgical approach on migration of a short-stem total hip prosthesis at 2 years' follow-up [25]. These new generation stems have 96% survival at 4.8 years' follow-up according to Wacha [18],

as confirmed by Hauer in a comparative analysis [26]. Short stems can lead to periprosthetic bone remodeling, studied by Yan [27], with onset mainly after 2 years. Short stems are often used with young patients, in order to conserve bone stock. Return to sport after short-stem THA is fast: usually within 6 months [28]. Short stems are also known to incur less blood loss and fewer transfusions [29]; we did not study these parameters.

Conclusion

It is critical to maintain offset in THA. The technique we use increases femoral offset, and we need to consider changing it. However, the present study showed that offset was less increased by short than standard stems. These findings must be taken into account so as to optimize clinical outcome.

Conflicts of interest: Stéphane Boisgard is an educational consultant for Zimmer-Biomet, outside of this study. The other authors have no conflicts of interest outside of this study. None of the authors have any conflicts of interest to declare relative to this study.

Figure 1 :Figure 2 :Figure 3 :Figure 42 :

 12342 Figure 1: planning with Orthoview® Software Figure 2: example showing a patient who had a standard stem: A: preoperative X-ray with planification, B: early postoperative (3 months), C: late postoperative with measurement (2 years) Figure 3: example showing a patient who had a short stem: A: preoperative X-ray with planification, B: early postoperative (1.5 month), C: late postoperative with measurement (4 years)

Figure 1 :Figure 2 :Figure 3 :Figure 4 :Figure 5 :

 12345 Figure 1: planning with Orthoview® Software Figure 2: example showing a patient who had a standard stem: A: preoperative X-ray with planification, B: early postoperative (3 months), C: late postoperative with measurement (2 years) Figure 3: example showing a patient who had a short stem: A: preoperative X-ray with planification, B: early postoperative (1.5 month), C: late postoperative with measurement (4 years) Figure 4: Distribution of femoral offset variation

Figure 1 :

 1 Figure 1: planning with Orthoview®Software

Figure 1 Figure 2 :

 12 Figure 1 Click here to access/download;Figure;figure 1.docx

Figure 2 Figure 3 :

 23 Figure 2 Click here to access/download;Figure;figure 2.docx

Figure 3

 3 Figure 3 Click here to access/download;Figure;figure 3.docx

Figure 4 Figure 3 :

 43 Figure 4 Click here to access/download;Figure;figure 4.docx

Figure 5

 5 Figure 5 Click here to access/download;Figure;figure 5.docx

  were compared on chi-square test (or Fisher's exact test, as appropriate) for categorical data and Student t-test for continuous data (or Mann-Whitney test for non-normal distributions). Normal distribution was assessed on distribution plots and Shapiro-Wilk test. Relationships between continuous data were analyzed on Pearson's correlation coefficient (or Spearman's, for non-normal distributions) and scatter plots. Offset, angles and lower-limb length before versus after surgery were compared on paired Student t-test, for the whole sample and by group (short versus standard stem).

	Concordance between observers' measures (offset, angles and lower-limb length) was assessed on
	Pearson's (or Spearman's) correlation coefficient, scatter plots and Bland-Altman plots. All analyses
	used Stata software, version 12 (StataCorp, College Station, TX). All tests were two-sided and a p-
	value <5% was considered statistically significant.

Table 1 :

 1 Inter-group correlation

  were compared on chi-square test (or Fisher's exact test, as appropriate) for categorical data and Student t-test for continuous data (or Mann-Whitney test for non-normal distributions). Normal distribution was assessed on distribution plots and Shapiro-Wilk test. Relationships between continuous data were analyzed on Pearson's correlation coefficient (or Spearman's, for non-normal distributions) and scatter plots. Offset, angles and lower-limb length before versus after surgery were compared on paired Student t-test, for the whole sample and by group (short versus standard stem).

Concordance between observers' measures (offset, angles and lower-limb length) was assessed on Pearson's (or Spearman's) correlation coefficient, scatter plots and Bland-Altman plots. All analyses used Stata software, version 12 (StataCorp, College Station, TX). All tests were two-sided and a pvalue <5% was considered statistically significant.

Table 1 :

 1 Inter-group correlation

	Sub-groupeGroup	criterion		number	mean	standard deviation	minimum	maximum	p
	sexe W=woman M=mangender F = female M = male	femoral offset lower -limb length cervico -diaphyseal angle	F M 108 92 F 92 M 108 F 92 M 108	6.55 5.48 2.10 2.77 4.36 4.66	7.30 7.12 6.00 4.95 6.81 6.55	-9.34 -15.57 -17.40 -16.06 -16 -11	26.48 30.21 14.96 21.06 19 16	0.30 0.39 0.76
			S	133	6.96	6.63	-5.46	30.21
		femoral offset	M	46	4.17	8.27	-15.57	23.29	0.02
	neck length S=short M=medium L=long	lower -limb length	L S M L S	21 133 46 21 133	3.64 2.44 1.82 3.99 5.14	7.46 6.00 3.95 4.51 6.69	-6.53 -17.40 -7.18 -1.94 -16	20.89 21.06 10.77 13.97 19	0.32
		cervico -diaphyseal angle	M	46	3.37	6.92	-11	16	0.18
			L	21	3.12	5.49	-4.5	13.5

Table 1

 1 Click here to access/download;Table;modifications_table 1.docx

	Group	criterion		number	mean	standard deviation	minimum	maximum	p
	gender F = female M = male	femoral offset lower-limb length cervico-diaphyseal angle	F M 108 92 F 92 M 108 F 92 M 108	6.55 5.48 2.10 2.77 4.36 4.66	7.30 7.12 6.00 4.95 6.81 6.55	-9.34 -15.57 -17.40 -16.06 -16 -11	26.48 30.21 14.96 21.06 19 16	0.30 0.39 0.76
			S	133	6.96	6.63	-5.46	30.21
		femoral offset	M	46	4.17	8.27	-15.57	23.29	0.02
	neck length S=short M=medium L=long	lower-limb length	L S M L S	21 133 46 21 133	3.64 2.44 1.82 3.99 5.14	7.46 6.00 3.95 4.51 6.69	-6.53 -17.40 -7.18 -1.94 -16	20.89 21.06 10.77 13.97 19	0.32
		cervico-diaphyseal angle	M	46	3.37	6.92	-11	16	0.18
			L	21	3.12	5.49	-4.5	13.5

Table 1 clean

 1 Click here to access/download;Table;modifications_table 1 clean.docx


Pierre Milbeo

François Quintin

Laure Moulat

Claude Didierjean

Jean Martinez

Xavier Bantreil

Monique Calmès

Frédéric Lamaty

2]octane bridge

Keywords:

HAL is

Introduction

Metal-based anticancer drugs have received increasing attention since the discovery of cisplatin in the mid-1960s, a successful metallodrug still considered nowadays as part of a standard chemotherapy [1]. However, cisplatin and related platinum-based treatments have been associated with numerous side effects due to oxidative stress and high toxicity [2]. Therefore, the development of novel metal-based compounds with potential anticancer activity is of high importance. Several factors can affect the therapeutic activity of such compounds including the nature of the metal and the structure of the organic ligands.

Among those ligands, salen ligands bear particularly attractive features. Besides their widely known catalytic properties in organic synthesis [3,4], metal-salen complexes have been extensively studied in bioinorganic and medicinal chemistry [5]. The popularity of tetradentate N 2 O 2 bis-Schiff base ligands (salen) is mostly explained by their ease of synthesis and ability to coordinate a high diversity of transition metals in various oxidation states and geometries. Due to their catalytic properties and their rather amenable structural and photophysical characteristics, metal-salen complexes provide high ligating properties and have numerous applications as enzyme mimics [6,7], potential therapeutics [8] or biosensors for diagnostics [9,10]. Known to act as oxidation cata-lysts in synthesis [11], metallosalen species also display cytotoxic activities and have been proved to cause oxidative damage to DNA leading to apoptosis. DNA binding and cleavage were reported using diverse salen complexes with Ni [12], Cr [13], Mn [14], Cu [15], Co [16], or Fe [17] leading to potential application as anticancer and antimicrobial agents.

Recent work in our institute led to the development of the original chiral diamine 1 based on a bicyclo[2.2.2]octane scaffold (Fig. 1) [18]. Based on this diamine, diverse ligands and the corresponding copper complexes were synthesised and proved to be efficient catalysts in stereoselective metal-catalysed transformations [19].

We report herein the use of enantiopure diamine (R)-1,2diaminobicyclo[2.2.2]octane 1 in the synthesis of metal-salen complexes involving metals other than copper and their characterisation. The cytotoxicity of these new molecules in the proliferation of HCT116 cancer cells was then evaluated. A mechanosynthesis of the most promising ligand and metal complex was also developed.

Results and discussion

Synthesis of the ligand

The salen ligand used in this study was derived from the bicyclic diamine 1 obtained as an optically pure diacetate salt via Diels-Alder cycloaddition, chiral resolution and subsequent Hofmann https://doi.org/10.1016/j.tetlet.2020.152706 0040-4039/Ó 2020 Elsevier Ltd. All rights reserved.

⇑ Corresponding author.

E-mail address: frederic.lamaty@umontpellier.fr (F. Lamaty).

Tetrahedron Letters 63 (2021) 152706

Contents lists available at ScienceDirect Tetrahedron Letters j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / t e t l e t rearrangement of the corresponding bicyclic b-amino acid as described previously [18]. The condensation of diamine 1 and 3,5-di-tert-butylsalicylaldehyde at reflux in a mixture of ethanol and water allowed the formation of Schiff base 2 in very high yield (Scheme 1, Method A) [19].

In parallel to the solution synthesis, we also considered a solvent-free mechanochemical route [20,21] for the preparation of the metal complexes. Indeed, it was demonstrated in recent years that ligands and metallic complexes could be efficiently accessed by employing mechanochemistry [22][23][24]. In most cases, the synthetic procedures for the formation of metallic complexes are faster, simplified and easily scalable in comparison to the solution approach [25][26][27][28][29][30]. More specifically, it has been reported that salen ligands and the corresponding metal complexes could be mechanosynthesized [31][32][33].

First, we decided to test this approach for the preparation of ligand 2: 2 eq. of 3,5-di-tert-butylsalicylaldehyde, 1 eq. of diamine 1 and 1 eq. of K 2 CO 3 were mixed in a vibratory ball mill (vbm) at a frequency of 30 Hz for 1.5 h. The reaction mixture was recovered from the milling jar with water and washed with ethanol to provide the expected product with 90% isolated yield. It should be noted that no organic solvent was used to carry out the reaction and only water and EtOH were employed to recover pure product 2, with analytical data in agreement with those obtained from the solution synthesis of 2.

Synthesis of the metal-complexes

Metal-salen complexes 3 to 7 were synthesised in solution using different metal sources conditions (Table 1). The procedures and reagents used in these syntheses were inspired by previous work with other types of salen ligands [34]. These novel complexes were obtained as high-melting solids in good to very good yields. It is worth noting that the manganese complex spontaneously oxidizes into the Mn(III) complex upon exposure to air as previously reported with other ligands [34,35]. Treatment with brine, opened to air, allowed complete oxidation to the Mn(III) complex replacing the acetate counter ion with a chlorine anion. Complexes 3-7 were characterised using infrared analysis as well as high resolution mass spectrometry. Crystals of Pd(II), Cu(II), Co (II) and Ni(II) complexes (3 to 6) were grown by the slow addition of methanol into a solution of the complex in dichloromethane or acetonitrile. However, despite the efforts invested, no suitable crystals of Mn(III) complex 7 have been obtained.

The mechanosynthesis of the most promising (vide infra) Mnbased complex was also tested in the ball mill, by mixing ligand 2 with Mn(OAc) 2 Á4H 2 O for 1 h, followed by the addition of NaCl and further grinding for 1 h (Scheme 2). Gratifyingly, complex 7 was obtained in 83% yield. In sharp contrast to the synthesis in solution, which required an excess of the metallic salt, only an equimolar amount of the ligand and the Mn salt were needed in the case of the mechanochemical approach. Crystals could once again not be obtained for complex 7. Its existence was asserted by High Resolution Mass Spectrometry and its structure was confirmed by X-ray Photoelectron Spectroscopy (XPS) (see ESI). Complex 7 exhibits a Mn2p3 core level energy at 642.14 eV and a Cl2p at 198.50 eV. This is in agreement with the presence of a Mn(III) species stabilized as a salen complex and chloride ligand as reported previously in the literature [36].

Crystal structures

Compound 2 crystallized as yellow needles and its structure has been confirmed by X-ray diffraction (Fig. 2) [19]. The phenol rings were almost perpendicular and each hydroxyl group formed a strong intramolecular hydrogen bond with the adjacent nitrogen atom (see ESI). These 6-membered pseudo cycles stabilised the imine bonds, giving long term bench-top stability for ligand 2.

Crystals of M(II) complexes 3 to 6 were isomorphous with respect to each other (Fig. 3). The monoclinic asymmetric-unit contained a dimer of complexes and two molecules of solvent (dichloromethane or acetonitrile). The bond lengths and angles around the metal atoms were comparable to those observed in similar chiralmetal salen complexes (see ESI). The M(II) centers had a square planar geometry in a more or less distorted tetrahedral configuration (see ESI). In all cases, the distortion was more pronounced in one of the two independent molecules and the two phenol rings were nearly coplanar. The square planar geometry is of importance to allow a potential intercalation or minor groove binding to cancer cells DNA, a possible mode of biological action previously described for salen-metal complexes, together with redox proper-Scheme 1. Synthesis of salen ligand 2. ties [5]. Nevertheless, one can expect a modulation of these activities, including the mode of action, due to the presence of the bicyclic diamine as a bridge. Steric effects could indeed hamper an adequate intercalation.

Biological testing

The in vitro anticancer potential of 3-7 was established by evaluating their ability to inhibit the cell growth of a human carcinoma cell line, HCT116 (colorectal cancer) [37]. Cisplatin and doxorubicin were used as positive controls to assess the cytotoxicity of the tested compounds. Preliminary data for the primary screening was collected as a percentage of cell toxicity and reported in Table 2 for two different concentrations of each complex (10 À5 M and 10 À6 M). Of note, ligand 2 was tested in the same assay and did not display activity even at 10 mM. None of the M(II) complexes 3 to 6 exhibited any higher activity than 21% cell toxicity at 10 À5 M and the activity was completely lost after diluting the compounds ten times. Therefore, the IC 50 values of these compounds (>10 mM) were evaluated. However Mn(III) complex 7 induced full cellu-lar death at 10 À5 M and 97% cell toxicity was also maintained at 10 À6 M. These preliminary results proved promising and further investigation was carried out on the activity of compound 7.

The IC 50 value of Mn(III) complex 7 on the HCT116 cell line was determined by measuring the effect on the cell proliferation at different concentrations (see ESI). Compound 7 was found to possess high anti proliferative properties with an IC 50 of 336 (±10) nM relative to the HCT116 cell line. Under the same conditions, the extensively used chemotherapy drugs Doxorubicin and cisplatin possess an IC 50 value of 810 (±110) nM and 5370 (±150) nM, respectively. By comparison, the manganese-salen complex 7 is more active. It should be emphasized that comparison with cisplatin should be made with caution. Indeed, while cisplatin displayed cytotoxic properties on the HCT116 cell line, it was already shown to be ineffective, with side effects, in the treatment of colon cancer [38]. It remains difficult to perform a direct comparison with results obtained in previously reported work, but typically the manganese salen complexes are, at best, of the same order of magnitude as cisplatin for their cytotoxic activity [39][40][41]. The activity of the complexes reported herein is strongly dependent on the nature of the metal. Cu, Pd, Co and Ni complexes did not display relevant activities, in sharp contrast to the Mn complex. It is known that reported Mn(III) salen complexes are acting as mimetics of enzymes such as superoxide dismutase (SOD) or catalase [42,43]. Consequently, the higher activity displayed by complex 7, compared to other metals, suggests a mechanism of biological action involving the complex in an oxido-reduction reaction. It was also demonstrated that these types of complexes could present DNA binding/cleaving properties. However, an increase in the steric hindrance on the bridge of the ligand (such as phenyl groups for example) strongly decreased the possibility of an interaction/reaction with DNA [44]. Ligand 2 containing a bicyclic structure is more encumbered that a simple 1,2-ethane bridge, making it difficult to intercalate into DNA. Consequently, one hypothesis is that Mn(III) complex 7 is acting as a SOD mimetic, generating activated oxygen and triggering apoptosis of the cells [5].

Conclusion

A bridged bicyclic diamine was successfully used to synthesise a series of novel metal-salen complexes with different oxidation states. Mechanochemistry was applied to the synthesis of ligand 2 and one of the metal complexes (Mn-based, 7), highlighting that this strategy is efficient and could be used in further synthetic developments for application in medicinal mechanochemistry [45][46][47][48]. Mn(III)-salen complex 7 proved to be a potent cytotoxic agent (2.4 times more efficient than doxorubicin) on the proliferation of the human cancer cell line HCT116. The results obtained with the other metal salen complexes suggest that a SOD mimetic mode of action, rather than intercalation, might be involved.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Fig. 1 .

 1 Fig. 1. (R)-1,2-Diaminobicyclo[2.2.2]octane diacetate.

Table 1

 1 Reaction conditions for the synthesis of metal-salen complexes.

	Reagents	Solvents	T (°C)	Product	Yield (%)
	Pd(OAc) 2	MeOH	65	3 (M = Pd)	98
	Cu(OAc) 2	MeOH	65	4 (M = Cu)	90
	Co(OAc) 2	MeOH/CH 2 Cl 2	r.t.	5 (M = Co)	62
	Ni(OAc) 2 Á4H 2 O	MeOH	65	6 (M = Ni)	97
	Mn(OAc)

2 Á4H 2 O, then aq. NaCl MeOH/Toluene r.t. 7(M = Mn(Cl)) 82

Acknowledgements

The Université de Montpellier, Centre Nationale de la Recherche Scientifique (CNRS) and Agence Nationale de la Recherche (grant no. ANR-16-CE07-0009-01) are acknowledged for funding. We thank Jérôme Bignon from ICSN, UPR 2301, CNRS, (Gif sur Yvette, France) for helpful discussion.

Scheme 2. Mechanosynthesis of Mn(III) salen complex 7.

Table 2

Cytotoxicity of the new metal-salen complexes on the HCT116 cell line (data given as % of toxicity).

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.tetlet.2020.152706.