Lénaïc Madec
email: lenaic.madec@univ-pau.fr

Céline Tang

Jean-Bernard Ledeuil

Domitille Giaume

Liliane Guerlou- Demourgues

Hervé Martinez

Cross-section Auger analysis to study the bulk organization/structure of Mn-Co nanocomposites for hybrid supercapacitors

Developing new methods to prepare pseudocapacitive materials with high pseudocapacitance/electronic conductivity is of great interest for hybrid supercapacitors.

Recently, the exfoliation/restacking of manganese and cobalt layered transition metal oxides was proposed. Despite improved electrochemical performance of such Mn-Co composites, their bulk organization (i.e. the scale at which the stacking occurs) and structure (i.e. porosity…) remains to be elucidated so far. To tackle this issue, here, SEM and Auger analysis with a nanoscale resolution, coupled to cross-section preparation is proposed. A good correlation between the restacking method, the nanoscale organization/structure of composites and resulting electrochemical performance is obtained. Importantly, the combination of cross-section with Auger analysis allows revealing the nanoscale stacking of the Mn and Co phases. Also, the porosity of the nano-composites, revealed by the cross-section preparation, is correlated to the 2 speed of the restacking process. A fast flocculation step forms aggregates with a porous bulk structure while a slow flocculation step leads to a dense and closed bulk structure of the aggregates. These results highlight that a better control/understanding of the organization/structure of such nano-composites can lead to further improvement. Overall, the innovative cross-section Auger approach proposed in this study should also benefit to the understanding of other nano-composites.

Introduction

Electrochemical capacitors provide relatively high power density (10 kW/kg) at the expense of the energy (5 Wh/kg) as the charge storage reactions remain confined to the surface. [START_REF] Conway | Electrochemical Supercapacitors: Scientific Fundamentals and Technological Applications[END_REF] , 2 Thus, to increase the energy of commercially available carbon-based electrochemical double layer capacitors (EDLC, based on capacitive ion adsorption), the main approach is to optimize carbon/electrolyte interfaces, 3 i.e. to maximize the specific surface area while controlling the pore size. 4 Pseudocapacitive materials thus offer a promising alternative as they provide additional near surface redox reactions [START_REF] Conway | Electrochemical Supercapacitors: Scientific Fundamentals and Technological Applications[END_REF] that allow exceeding the energy density of EDLC with, however, lower power density. 5 , 6 Among them, manganese oxide (MnO2) 7 with its high theoretical capacity (1380 F/g, considering one electron exchanged per manganese) 8 combined to a good chemical stability and a low cost, is of great interest. 9 In practical conditions, capacitances in the range of 30 -110 F/g are often obtained, however, depending on the crystallographic structure. 10 One of the reason is the relatively poor electronic conductivity (10 -5 -10 -6 S/cm) of MnO2 8 that is also detrimental to the power density.

To tackle this issue, MnO2-based nano-composites materials or nano-composites electrodes containing conductive carbons, metals, metal oxides or polymers have been successfully proposed. 9 , 11 For instance, simple MnO2 electrodeposition on Ni foam allowed obtaining capacitances higher than 400 F/g at 1 A/g depending on the preparation conditions. 12,13,14 The drawback of this approach is, however, the relatively low MnO2 loading (about 1 mg/cm 2 ) of the obtained electrodes. Similarly, combining MnO2 (for its high pseudocapacity) with cobalt oxyhydroxides (for their high electronic conductivities) have been shown to significantly improve the electrochemical performance. 16 , 17 , 18 Indeed, Co3O4@MnO2 nanowire@nanosheetarray delivered ~400 F/g compared to ~100 F/g for Co3O4 nanowires at ~7.5 A/g, 16 cobalt doped (5%) MnO2 delivered ~200 F/g compared to ~100 F/g for MnO2 at 5 A/g, 17 and CoO@MnO2 nanowire@nanosheetarray delivered ~600 F/g compared to ~300 F/g for CoO nanowires at 30A/g. 18 However, such composite materials still lack from an optimal/controlled organization/homogeneity at the nanoscale which would further improve the electrochemical performance.

To address this challenge, an innovative synthesis approach, based on the exfoliation and restacking of manganese and cobalt layered transition metal oxides was recently proposed by some of us. 19 , 20 Exfoliation is achieved by weakening the interlayer bonds between metal slabs. Interestingly, as the isoelectric point (IEP) of exfoliated phases is of great importance to control and favor the nanostructuration during the restacking process, it was showed to be predictable from the metals mean oxidation state using the Multisite Complexation model (MUSIC). 19 Then, by tuning the restacking process, the microstructural homogeneity of the Mn-Co composites was improved so that superior electrochemical performance were obtained compared to the starting materials, 20 mostly due to the improvement of the electronic diffusion at the aggregate scale. [START_REF] Tang | niversité de Bordeaux[END_REF] The optimization of the Mn:Co ratio also led to further enhancement of the performance. [START_REF] Tang | niversité de Bordeaux[END_REF] These results were explained by a better organization/homogeneity of the Mn and Co phases for the exfoliated/restacked composites, as observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled to energy-dispersive X-Ray spectroscopy (EDS). 20 However, SEM-EDS only probes the micro-scale while TEM-EDS involves the composites dispersion in a solvent and focuses on individual nanostructures so that it is unlikely representative of the whole sample. Note also that commonly used chemical mapping with XPS (using parallel imaging mode) has a typical spatial resolution of about 3-5 μm, which is too high to study nanoscale assembly. Thus, these techniques are not suitable to observe the bulk organization (i.e. the scale at which the stacking occurs) and structure (i.e. porosity…) of nanocomposites when micrometer scale aggregates are considered. Overall, despite that these studies highlight that highly efficient pseudocapacitive materials can be obtained through this exfoliation/restacking approach, a better understanding of the bulk organization/structure of such composites at the nanoscale remains a challenge so far.

To tackle this issue, this study proposes Auger analysis with a nanoscale resolution coupled to a cross-section preparation as a powerful approach to elucidate the bulk organization/structure of Mn-Co composites. To the best of our knowledge, this approach has never been used for such composite materials. Results are discussed regarding both structural and electrochemical properties of the composites.

Material and methods

Synthesis -

The preparation of layered proton-inserted birnessite manganese oxide (H-MnO2) and layered β(III)-type cobalt oxyhydroxide (β3-CoOOH) are fully described elsewhere. 20 The exfoliation of H-MnO2 and β3-CoOOH was performed in tetrabutylammonium hydroxide (TBAOH) solutions for about 2 weeks at room temperature under vigorous stirring, allowing TBA + ions intercalation via proton exchange. For H-MnO2 and β3-CoOOH, the optimized molar ratio of TBA + / H + was fixed to 10 and 2, respectively. Resulting colloidal suspensions were then centrifugated at 6000 rpm for 15 min to remove any unexfoliated materials. Note that the stability of these colloidal suspensions (at pH=12, i.e. negatively charged) were up to few months. Then, based on the determined IEP, 19 the restacking of the as-prepared exfoliated Mnand Co-based nanosheets to form Mn-Co composites was then performed using two methods.

For better clarity, Figure 1 shows a schematic of the different approaches used to prepare the composites. Method 1: the two stable colloidal suspensions (i.e. at pH=12) were mixed then floculation was induced by the fast (1s) or slow (2 hours) addition into a nitric acid solution to lower the pH to 4.5 so that exfoliated/restacked composites RMC1a and RMC1b were obtained, respectively. Method 2: the pH of the two stable colloidal suspensions (i.e. pH=12) was lowered separetely to 4.5 by addition of a nitric acid solution. As this step can destabilize the suspensions to form aggregates due to the increase of the ionic strength, 3 centrifugation/ sonication cycles were performed to counteract this effect. Floculation was then induced by mixing the two suspensions with a control of the pH so that exfoliated/restacked composites RMC2 was obtained. Materials were then centrifugated and dried. For comparison, a reference sample was also prepared by mechanical grinding (MG), in a mortar, of the H-MnO2 and β3-CoOOH powders. Note that for all mixed Mn-Co composites, Mn:Co ratio was fixed to 1:1. Structural and electrochemical properties -The average coherent domain size (nm) along the slab stacking direction and the specific BET surface area (m 2 /g) of H-MnO2, β3-CoOOH and Mn-Co composites were determined following previously described X-ray diffraction/Scherrer method and N2 adsorption analysis conditions, respectively. 20 For clarity, diffraction patterns were recorded with a 0.0167° (2θ) step size and a 2.122° (2θ) active width in the detector using a Philips Panalytical X'Pert Pro diffractometer with a Bragg-Brentano θ-θ geometry. Copper Kα radiation (λKα2= 1.54439 Å, λKα1= 1.54056 Å) and cobalt Kα radiation (λKα2= 1.7928 Å, λKα1= 1.7889 Å) were used for manganese oxides and cobalt oxyhydroxides powders, respectively. Electrochemical performance were evaluated in a three-electrodes cell using 0.5M K2SO4 as electrolyte with platinum and Ag/AgCl as counter and reference electrodes. Working electrodes were prepared by mixing 80 wt.% of active material with 5 wt.% PTFE (Sigma-Aldrich, 60 wt.% water suspension) and 15 wt.% acetylene black (100% compressed, Alfa Aesar) with ethanol. 8 mm diameter discs were cut from the obtained self-supported film and pressed on stainless steel grid at 6 t/cm 2 . Cyclic voltammetry was performed using a VMP3 potentiostat (Biologic)/ECLab software between 0-0.8 V from 0.5 to 500 mV/s.

Mn-Co composites cross-section preparation and Scanning electron microscopy (SEM), Auger

electron spectroscopy (AES) and scanning Auger microscopy (SAM) analysis -Cross-section samples were prepared using a JEOL Cross-Polisher (JEOL Ltd, Tokyo, Japan) in a nitrogenfilled glove box. Powder samples were hand-mixed in a silver conducting epoxy resin then deposited on a silicon wafer. Resulting assemblies were then exposed (from the silicon wafer side and at normal angle) to an Ar + ion beam (6 keV, ∼120 µA) for 4h at 1.10 -4 Pa. More details about the technique can be found in previous works. [START_REF] Uhart | [END_REF] , 23 This allowed obtaining perfect planar surfaces with no Ar + ion implantation (Ar LMM Auger lines were never observed at the kinetic energies of 211 and 195 eV). Thus, possible sample damage would be limited to amorphization phenomenon with the same chemical composition. 24 , 25 , 26 For clarity, Figure S1 shows typical SEM images of a MnCo composite cross-section so that readers can appreciate the flatness of the cross-section as well as the resulting assembly using a silicon wafer and a silver epoxy resin. SEM, AES and SAM analysis were performed using a JEOL JAMP 9500 F Auger spectrometer (JEOL Ltd, Tokyo, Japan) equipped with a Schottky Field Emission gun and a hemi-spherical analyser coupled with a high dynamic multichannel detector following a previously described procedure. 23 , 27 For clarity, considering the beam energy/probe current used (10 keV/5 nA) for Auger analysis, the probe size for AES (i.e. to record an Auger spectrum) is about 20 nm leading to a spatial resolution for SAM (i.e. to record an Auger image) of about 30 nm. Also, the probing depth is about 3 nm. Thus, the simultaneous presence of Mn and Co transitions in an Auger spectrum means that the Mn and Co containing phases are located together at a 20 nm wide scale and for a 3 nm depth. The operating pressure was <2 x10 -7 Pa and analysis were performed at 30° tilt to prevent charging effect. AES survey spectra were recorded between 15 to 2000 eV with 1 eV step size using a focused probe (10 keV/5 nA, i.e. a probe size of about 20 nm) and a CRR mode (constant relative resolution, also called FRR mode) corresponding to a relative energy resolution (dE/E=constant) with dE/E = 0.5% (high sensitivity). Scanning Auger microscopy (SAM, elemental 2D distribution) images were recorded using a CAE mode (constant analyzer energy, also called FAT or CAR mode) corresponding to a fixed energy resolution (dE=constant). Images are represented using "peak minus background" (P-B) Auger intensity for a transition (dE/E=0.5%). The spatial resolution was about 30 nm (at 10 keV/5 nA). Also, for SAM analysis, an "auto probe tracking" correction was applied to control and compensate any potential drift.

Results and discussion

Previous XRD analysis 20 showed that both the mechanically grinded composite and the exfoliated/restacked composites showed no structural change in the layers, i.e. very close diffractograms compared to the initial H-MnO2 and β3-CoOOH phases. 20 Table 1 shows the average coherent domains size (nm) along the slab stacking direction and the specific BET surface area (m 2 /g) for all composites. The thickness of Mn-based domains similarly decreased regardless of the restack procedure, while the thickness of Co-based domains did not change except for RMC1a so that an increase of the specific BET surface area can be expected.

However, RMC1a and RMC2 gave intermediate BET surface area (between 90 to 100 m2/g) compared to the starting H-MnO2 (85 m 2 /g) and β3-CoOOH (110 m 2 /g) materials while a drastic decrease was observed for RMC1b (2 m 2 /g). Regarding the mechanically grinded (MG) composite, no significant change was observed compared to the starting materials so that the efficiency of the mixing step is expected to be rather poor. Overall, these results suggest: (i) an homogeneous organization with a porous structure for the RMC1a and RMC2 composites due to the fast flocculation step of oppositely charged Mn-and Co-nanosheets during the restacking process and (ii) a much denser structure for the RMC1b composite due to the slow flocculation step during the restacking process. At this point, however, the formation of nano-composites can not be proven by XRD and thus their bulk organization/structure still need to be investigated.

Table 1. Average coherent domain sizes (nm) along the slab stacking direction (i.e. thickness) of the Mn-and Cophases for the starting materials (H-MnO2 and β3-CoOOH), the mechanically grinded composite and the exfoliated/restacked Mn-Co composites as determined by the Scherrer method and their specific BET surface areas.

Size of coherent domain (nm)

Specific BET surface (m To tackle this issue, SEM, AES and SAM analysis were performed on cross-section of all composites. SEM and SAM (elemental 2D distribution, from Mn LMM and Co LMM transitions, in blue and green, respectively) images and Auger spectra are shown in Figure 2 for the mechanically grinded (MG) composite and in Figure 3 for the exfoliated/restacked Mn-Co (RMC1a, RMC1b and RMC2) composites. Overall, SEM images showed micrometer scale aggregates for all composites (Figures 2-3, S2-5). The bulk structure of the aggregates was clearly different, however, as function of the composite preparation method. SEM images taken at different magnification showed a porous bulk structure for both RMC1a and RMC2 while a much denser and closed bulk structure was observed for RMC1b (Figures 3, S3 andS5). This result explains the very low specific BET surface area of RMC1b (2 m 2 /g) compared to RMC1a

and RMC2 (about 95 m 2 /g). It also highlights that the flocculation step speed of oppositely charged Mn-and Co-nanosheets controls the porosity of the nano-composites. The fast decrease of the pH to induce the flocculation leads to a porous bulk structure of the aggregates (RMC1a and RMC2) while the slow decrease of the pH leads to a dense and closed bulk structure (RMC1b). Overall, SEM analysis coupled to cross-section preparation allowed revealing the bulk structure of Mn-Co composites, highlighting the interest of this approach compared to classical SEM. Now, considering that the average coherent domain sizes of both Mn and Co phases along the slab stacking direction (i.e. their thickness) is lower than 10 nm (Table 1), the aggregates are expected to be a stacking of Mn and Co phases. The bulk organization (i.e. the scale at which the stacking occurs) of the composites was then investigated. At this point, conventional approaches such as SEM-EDS only probes the micro-scale while TEM-EDS involves the composite dispersion in a solvent and the study of individual nanostructures, which is unlikely representative of the whole sample. Instead, cross-section Auger analysis was proposed as an alternative. It is reminded that the probing depth is about 3 nm, the probe size about 20 nm (to record an Auger spectrum) and the spatial resolution of about 30 nm (to record an Auger image).

In Auger spectra, transitions were observed at about 500 and 480 eV for the O KLL, at about 630, 580 and 530 eV (the latter overlapped with the O KLL at 500 eV) for the Mn LMM and at about 775, 710 and 645 eV (the latter overlapped with the Mn LMM at 630 eV) for the Co LMM. For the MG composite (Figure 2), Auger spectra taken at different positions of the aggregates showed either Mn LMM or Co LMM transitions. Results for additional aggregates shown in Figure S2 provides evidence that this result is representative of the whole sample.

Thus, the use of the mechanical grinding approach leads to a microscale segregated composite, as expected. At the opposite, aggregates of exfoliated/restacked composites showed the simultaneous presence of Mn and Co transitions in most Auger spectra (Figure 3) for a probe size of about 20 nm (with a 3 nm probing depth). This result supported by the analysis of additional aggregates (Figures S3-5) highlights that the stacking of Mn and Co phases occurred at the nanoscale. Therefore, these composites can be denoted as nano-composites, which could not be proven by XRD analysis. Moreover, some discrepancies were observed as function of the restacking method. In the case of RMC2 (prepared by method 2, Figure 1), some of the Auger spectra showed either Mn or Co transitions while for RMC1a and RMC1b (prepared by method 1, Figure 1), all Auger spectra showed both Mn and Co transitions (Figures 3, S3 compared to a more segregated distribution of the Mn and Co areas for RMC2. This is explained by the restacking method used. For RMC1a and RMC1b, colloidal suspensions of Mn and Co nanosheets were mixed together before flocculation (i.e. before the pH was lowered) so that a better nanoscale stacking is obtained. For RMC2, the pH of the separate colloidal suspensions were first lowered before mixing, favoring the formation of aggregates due to the destabilization of the solutions. Overall, Auger analysis coupled to cross-section preparation allowed elucidating the bulk organization (i.e. the scale at which the stacking occurs) of Mn-Co composites, which remained a challenge so far. Based on these results, the electrochemical performance of all composites (Figure 4) can be better understood. For comparison, the theoretical capacitance calculated on the basis of the starting H-MnO2 and β3-CoOOH capacitances (with the 1:1 ratio) is also shown in Figure 4 (dashed line). For the MG composite, slightly improved performance were observed compared to the theoretical capacitance, indicating the beneficial impact of the Co oxyhydroxide addition to the MnO2 birnessite. For the nano-composites RMC1a and RMC2, higher improvements were observed. In particular, RMC2 showed superior capacitances compared to MG, whatever the scan rate was. For RMC1a, higher capacitances than MG were observed but up to a scan rate of about 50 mV/s. These results can be explained by a better electronic conductivity due to the homogeneous stacking of MnO2 birnessite with highly electronic conductive Co oxyhydroxide at the nanoscale. This thus leads to a better use of the birnessite pseudocapacitance in the nanocomposites, in agreement with the more rectangular shapes of the CV curves previously observed compared to the starting H-MnO2. 20 Interestingly, despite a homogeneous nanoscale stacking, RMC1b showed poor performance due to its denser and closed bulk structure (i.e. low BET surface area) as observed by cross-section SEM.

Conclusions

In this study, the bulk organization (i.e. the scale at which the stacking occurs) and structure (i.e. porosity…) of Mn-Co composites formed by different exfoliation/restacking methods was investigated. XRD analysis as well as previous SEM-and TEM-EDS could not prove, however, the formation of nano-composites. To tackle this issue, SEM and Auger analysis coupled to cross-section preparation was proposed for the time to study such composites. Importantly, cross-section Auger analysis allowed revealing that the stacking of Mn and Co phases occurred at the nanoscale, which could not be proven so far. In addition, the porosity of the nanocomposites was revealed by the cross-section preparation and explained the low BET surface area of one of the sample. Interestingly, it highlighted that a fast flocculation step forms aggregates with a porous bulk structure while a slow flocculation step leads to a dense and closed bulk structure of the aggregates. Overall, a very good correlation between the restacking methods used, the nanoscale organization/structure of the composites and the resulting electrochemical

Figure 1 .

 1 Figure 1. Schematic of the different approaches used in this work to prepare the Mn-Co composites.

  -5). Therefore, RMC1a and RMC1b are more homogeneously stacked at the nanoscale compared to RMC2. This is further confirmed by SAM images (Figures3, S3-S5) that showed a more homogeneous distribution of the Mn and Co areas (in blue and green, respectively) for RMC1a and RMC1b

Figure 2 .

 2 Figure 2. SEM images for the mechanically grinded (MG) composite and Auger spectra taken at different positions as indicated.

Figure 3 .

 3 Figure 3. SEM and SAM images (elemental 2D distribution taken at the indicated areas, from Mn LMM and Co LMM transitions, in blue and green, respectively as well as Auger spectra taken at indicated positions for the

Figure 4 .

 4 Figure 4. Variation of specific capacitance (F/gactive-material) vs. scan rate (mV/s) obtained for the starting materials (H-MnO2 and β3-CoOOH), the mechanically grinded composite (MG) and the exfoliated/restacked Mn-Co nano-composites (RMC1a, b and RMC2). The dashed line corresponds to the theoretical average capacitance calculated on the basis of the capacitances of H-MnO2 and β3-CoOOH, for the 1:1 ratio.

Acknowledgment

This research was performed in the framework of "Réseau sur le Stockage Electrochimique de l'Energie" (RS2E) and the ANR program no. ANR-10-LABX-76-01.

performance was obtained. These results thus open new possibility to improve further the performance of such nano-composites for hybrid supercapacitors. Finally, the innovative crosssection Auger approach proposed in this study should also benefit to other researchers working on understanding and improving other nano-composites.


Paul León

S Mosset

E Benayache
email: fbenayache@yahoo.fr

I Marchioni

F Brouard

Benayache

Chahrazed Esseid

Francisco León

Paul Mosset

Samir Benayache

Eric Marchioni

Ignacio Brouard

Fadila Benayache

Coumarins and other constituents from Deverra battandieri

Keywords: Apiaceae, Deverra battandieri, coumarin, furanocoumarin, Saharan medicinal plants

Coumarins and other constituents from Deverra battandieri

Introduction

The members of the Apiaceae family are well-known producers of coumarins [START_REF] Caesar | A review of the medicinal uses and pharmacology of Ashitaba[END_REF][START_REF] Matos | Coumarins -An important class of phytochemicals[END_REF] and furanocoumarins [START_REF] Dueholm | Evolution of substrate recognition sites (SRSs) in cytochromes P450 from Apiaceae exemplified by the CYP71AJ subfamily[END_REF][START_REF] Sarker | Progress in the chemistry of naturally occurring coumarins[END_REF][START_REF] Bruni | Botanical sources, chemistry, analysis, and biological activity of furanocoumarins of pharmaceutical interest[END_REF]. Coumarins are recognized to exhibit valuable biological properties such as analgesic, anti-inflammatory, antibacterial, antiviral, antifungal, and antiprolifera tive [START_REF] Dehghan | Α Glucosidase inhibitory and antioxidant activity of furanocoumarins from Heracleum persicum[END_REF][START_REF] Hashita | Antioxidant and anti-inflammatory properties of marmelosin from Bael (Aegle marmelos L.); inhibition of TNF-α mediated inflammatory/tumor markers[END_REF][START_REF] Hassan | Therapeutic potential of coumarins as antiviral agents[END_REF][START_REF] Song | Evaluation of antifungal activities and structure-activity relationships of coumarin derivatives[END_REF][START_REF] Zhu | Pharmacological and nutritional effects of natural coumarins and their structure-activity relationships[END_REF], apart from their well-known photosensitizing properties [START_REF] Kasperkiewicz | Sunscrening and photosensitizing properties of coumarin and their derivatives[END_REF]. The genus Deverra D.C. (Apiaceae) is spread in the Mediterranean region includ ing the Arabic peninsula; it consists of seventeen species of which nine are accepted [START_REF] Dobignard | Index synonymique-Flore dʹAfrique du Nord[END_REF][START_REF] Downie | Major clades within Apiaceae subfamily Apioideae as inferred by phylogenetic analysis of nrDNA ITS sequences[END_REF]. Several members of the Deverra genus are used in folk medicine to treat asthma, rheumatism, digestive difficulties, urinary infections, and scorpion stings [START_REF] Attia | Chemical composition and acaricidal properties of Deverra scoparia essential oil (Araliales: Apiaceae) and blends of its major constituents against Tetranychus urticae (Acari: Tetranychidae)[END_REF][START_REF] Benchelah | Fleurs du Sahara. Voyage ethnobotanique avec les Touaregs du Tassili[END_REF][START_REF] Boukef | Les plantes dans la médecine traditionnelle tunisienne[END_REF][START_REF] Guetat | Phytochemical profile and biological activities of Deverra tortuosa (Desf.) DC.: a desert aromatic shrub widespread in Northern region of Saudi Arabia[END_REF][START_REF] Hammiche | Traditional medicine in Central Sahara: Pharmacopoeia of Tassili Nʹajjer[END_REF]. Deverra battandieri (Maire) Podlech [syn. Pituranthos battandieri (Maire)] is a traditional medicinal plant and a native species of the Sahara Desert of North Africa, particularly in Morocco and Algeria [START_REF] Quezel | Nouvelle flore de l'Algérie et des désertiques méridionales[END_REF][START_REF] El Oualidi | Checklist des endémiques et spécimens types de la flore vasculaire de l'Afrique du Nord[END_REF]. Previously, antioxidant properties and phytochemical study on the polar fractions of D. battandieri led to the isolation of coumarins: xanthotoxol, 8-(6′,7′-dihydroxygeranyloxy)psoralen, the flavonoid: isorhamnetin 3-O-ß-D-glucopyranoside, and mannitol [START_REF] Esseid | Chemical constituents and antioxidant activity of a polar extract from Pituranthos battandieri Maire[END_REF].

Following a systematic study of Saharan medicinal plants collected in Algeria [START_REF] Boumaraf | Exploring the bioactive terpene content of an Algerian plant of genus Pulicaria: first occurrence of the ent-series of asteriscunolides[END_REF][START_REF] Hammoud | Humulene derivatives from Saharian Asteriscus graveolens[END_REF], this report describes the isolation and structural elucidatio n of three previously undescribed coumarin derivatives (1-3) (Figure 1), nine known coumarins (4-12) (Figure S1), and additional ten known compounds from extracts of D. battandieri collected in Bechar region of southern Algeria.

A c c e p t e d m a n u s c r i p t

Results and discussion

Purification of the chloroform (CHCl3) and ethyl acetate (EtOAc) extracts of the hydroalcoholic (80:20) extract from the aerial parts of Deverra battandieri by column chromatography afforded three new furanocoumarin derivatives, pituranthosins A-C (1-3). The known furanocoumarins: 8-[(R)-6′,7′-dihydroxygeranyloxy]psoralen (4) [START_REF] Ito | Antimutage nic constituents of Casimiroa edulis with potential cancer chemopreventive activity[END_REF][START_REF] Row | Synthesis of 8geranyloxypsoralen analogues and their evaluation as inhibitors of CYP3A4[END_REF], xanthotoxol (5) [START_REF] He | Facile total synthesis of xanthotoxol[END_REF], xanthotoxin (6) [START_REF] Harkar | Steroids, chromone and coumarins from Angelica officinalis[END_REF], (R)-(+)heraclenin (7) [START_REF] Setzer | HPLC-NMR/HPLC-MS analysis of the bark extract of Stauranthus perforates[END_REF], (R)-(+)-byakangelicol (8) [START_REF] Setzer | HPLC-NMR/HPLC-MS analysis of the bark extract of Stauranthus perforates[END_REF], (R)-(+)byakangelicin (9) [START_REF] Ngwendson | Constituents of Peucedanum zenkeri seeds and their antimicrobial effects[END_REF], phellopterin (10) [START_REF] Kang | Chromatographic fingerprint analysis and characterization of furocoumarins in the roots of Angelica dahurica by HPLC/DAD/ESI-MS technique[END_REF]; and the coumarins (R)-(+)-marmin (11) [START_REF] Coates | Total synthesis of (+)-marmin and related coumarin monoterpenes[END_REF] and rutaretin (12) [START_REF] Lemmich | Coumarin sulphates of Seseli libanotis[END_REF] were also isolated. Several other known compounds such as vanillin [START_REF] Youssef | Constituents of the Egyptian Centaurea scoparia, III. Phenolic constituents of the aerial parts[END_REF], vanillic acid [START_REF] Kwon | Phytochemical constituents of Artemisia japonica ssp. littoricola[END_REF], β-hydroxypropiovanillone [START_REF] Karonen | Phenolic extractives from the Bark of Pinus sylvestris L. and their effects on inflammatory mediators nitric oxide and prostaglandin E2[END_REF], isorhamnetin [START_REF] Spinola | Phytochemical profile, chemotaxonomic studies, and in vitro antioxidant activities of two endemisms from Madeira archipelago: Melanoselium decipiens and Monizia edulis (Apiaceae)[END_REF], apigenin [START_REF] Kouichi | New iridoid diesters of glucopyranose from Linaria canadensis (L). Dum[END_REF], and biochanin A [START_REF] Agrawal | Isoflavonoids in carbon-13 NMR of flavonoids[END_REF] were isolated along with the mixtures: stigmaste ro l and β-sitosterol (50-50%) [START_REF] Hammoud | Humulene derivatives from Saharian Asteriscus graveolens[END_REF], daucosterol and stigmasterol 3-O-βglucopyranoside (72-28%) [START_REF] Voutquene | Cytotoxic polyisoprenes and glycosides of long chain fatty alcohols from Dimocarpus fumatus[END_REF]. The structures of these known compounds were confirmed by comparison of their spectroscopic data (MS and 1 H-and 13 C-NMR) with the literature.

Pituranthosin A (1) was isolated as a yellowish powder and its molecular formula was determined as C23H28O6 by its pseudo molecular peak on positive HRESIMS m/z 423.1773 1 and2) spectral data of compound 1 were close to those of 8-[(6′,7′-dihydroxy-3′,7′-dimethyl-2′-octenyl)oxy]psoralen [START_REF] Ito | Antimutage nic constituents of Casimiroa edulis with potential cancer chemopreventive activity[END_REF] with additional 1 H-NMR signals at H 3.40 (qd, J = 7.0, 1.7 Hz, 2H) and 1.12 (t, J = 7.0 Hz, 3H) ppm assignable to an ethoxyl group, which revealed that compound 1 was an O-ethyl derivative. To determine the position of the geranyl and ethoxyl groups, the HMBC (Figure 2) experiment was useful. Thus, connectivity observed between the protons of the signal at H Being well-known that the psoralen derivatives are known to be potential photosensitizers [START_REF] Kitamura | Molecular aspects of furocoumarin reactions: photophysics, photochemistry, photobiology and structural analysis[END_REF] this observation is extensive to the undescribed furanocoumarin derivatives isolated from D. battandieri (Figure 3b). This

Compound (1) was found optically active with

[] D 20 +8.8; [] 578 20 +9.7; [] 546 20 +10.3 (c 1.365
g/100 ml, MeOH). The positive value of the optical rotation agreed with the (R) configura tio n of the chiral center at C-6′ [START_REF] Edegger | Chemo-enzymatic enantioconvergent asymmetric synthesis of (R)-(+)-marmin[END_REF][START_REF] Wang | Divergent synthesis of four isomers of 6,7-dihydroxy-3,7-dimethyloct-2-enoic acid, ester and evaluation for the antifungal activity[END_REF]. Therefore, the structure of 1 was determined to be 8-[(R)-6ʹ-hydroxy-7ʹ-ethoxygeranyloxy]psoralen.

Compound (2) was obtained as a yellowish solid with a molecular formula of C24H28O6 1 and2) revealed that the signals due to ethoxy group at H 3.40 (qd, J = 7.0, 1.7 Hz, 2H) and 1.12 (t, Compound (3) differs in the side chain at C-8 from compounds 1 and 2. Its UV spectrum showed a maximum absorption at 312 nm due to the characteristic aromatic π-π* transition of furanocoumarins (Figure 3d) [START_REF] Kitamura | Molecular aspects of furocoumarin reactions: photophysics, photochemistry, photobiology and structural analysis[END_REF]. The positive HRESIMS spectrum of 3 showed a pseudomolecular ion [M+Na] + at m/z 411.1419 matching the molecular formula C21H24O7 (calcd for C21H24O7Na: 411.1420) and indicating a compound containing ten unsaturations. The NMR data of 3 (Tables 1 and2) was similar to those of citraurancouma r in B, a furanocoumarin, with the presence of a 2,6,7-trihydroxy-7-methyl-3(10)-methyleneocta n-1-oxy group at the C-5 position [START_REF] Xiong | A new phenolic glycoside and two new monoterpenoid furocoumarins from Aurantii fructus Immaturus[END_REF]. HMBC experiment of compound 3 allowed to identify the differences between compound 3 and citraurancoumarin B. 2 can be an artifact obtained from compound 4 and was generated with the use of acetone in the fractionation process. However, no harsh conditions were used in the isolation process of 2.

J = 7.0 Hz, 3H) ppm
The formation of 2 was not observed while incubating compound 4 with acetone for 24 h. These facts suggested that compounds 1 and 2 are indeed undescribed secondary metabolites. The number of coumarins reported from Deverra species are few; for example, D. triradiata reported the presence of pituranthoside, S-trans-marmin, xanthotoxol, umbellifero ne, isopimpinellin, and bergapten [START_REF] Halim | Pituranthoside from Pituranthos triradiatus[END_REF]; D. deanudata reported the coumarins :

bergapten, isoimperatorin, nodakenetin, osthol, and oxypeucedanin [START_REF] Aloui | Phytochemica l investigation, isolation and characterization of coumarins from aerial parts and roots of Tunisian Pituranthos chloranthus (Apiaceae)[END_REF], and the polar extracts of D. battandieri reported xanthotoxol and 8-(6′,7′-dihydroxygeranyloxy)psoralen [START_REF] Esseid | Chemical constituents and antioxidant activity of a polar extract from Pituranthos battandieri Maire[END_REF]. The high concentrations of coumarins found in this medicina l plant are potentially responsible for the wide variety of traditional benefits reported from this Saharan plant.

Experimental

General Procedure

Optical was generated by Millipore synergy System (Molsheim, France).

Plant material

The aerial parts from Deverra battandieri (Maire) Podlech [syn. Pituranthos battandieri Maire] [START_REF] Quezel | Nouvelle flore de l'Algérie et des désertiques méridionales[END_REF][START_REF] Ozenda | Flore du Sahara septentrional et central[END_REF][START_REF] El Oualidi | Checklist des endémiques et spécimens types de la flore vasculaire de l'Afrique du Nord[END_REF]

Extraction and isolation

Air-dried aerial parts (3350 g) of D. battandieri Maire (Apiaceae) were macerated three times (1000 ml/each) at room temperature with MeOH-H2O (80:20, v/v) for 48 h. After filtration, the filtrate was concentrated to reach a volume for around 1000 ml, then it was added additional H2O (1300 ml). The resulting solution was extracted successively with petroleum ether, CHCl3, EtOAc, and n-BuOH. The organic layers were dried with Na2SO4, filtered, and 1 and2; HRESIMS m/z: 435.1780 [M+Na] + (calcd for C24H28O6Na, 435.1784).

8-[2ʹ,6ʹ,7ʹ-trihydroxy-7ʹ-methyl-3ʹ(10ʹ)-octaenyloxy]psoralen (3): yellow powder; 1 H-NMR (400 MHz, MeOH-d4); 13 C-NMR (100 MHz, MeOH-d4) spectroscopic data, see Tables 1 and2; HRESIMS m/z: 411.1419 [M+Na] + (calcd for C21H24O7Na, 411.1420).

HPLC-UV profiling of the chloroform fraction of D. battandieri

The HPLC system included a Beckman HPLC system with Beckman 507E auto sampler, a 126 solvent delivery module, 166 single wavelength detector with the serial number: A c c e p t e d m a n u s c r i p t

  3.40 ppm (qd, J = 7.0, 1.7 Hz, 2H) and the quaternary carbon at C 78.32 helped us to situate the ethoxy group at C-7′. Besides, correlations between the protons in C-1′ at H 5.03 (d br, J = 7.6 Hz, 2H) and C-8 at C 132.29, and between the proton at H 7.57 (s, 1H, H-5) and the carbons C-4 (C 146.75) and C-10 (C 107.96) led us to link the geranyl group at C-8 position in the central core. The presence of the furanocoumarin nucleus was further supported by its ultraviolet (UV) spectrum which showed a typical absorption maximum at 310 nm due to aromatic π-π* transition.

  Thus, HMBC correlations between the proton at position C-5 (δH 7.59) with C-4 (δC 146.75), and C-10 (δC 107.98) and the HMBC correlation between C-8 (δC 132.97) and the protons of the oxygenated methylene C-1ʹ (δH 4.61 -4.54, 2H) confirmed the side chain at C-8. The stereochemistry was not determined due to the small amount of compound isolated. Therefore, compound 3 was characterized as 8-[2ʹ,6ʹ,7ʹ-trihydroxy-7ʹ-methyl-3ʹ(10ʹ)-octaenyloxy]psoralen and was named pituranthosin C. Initially, compound 1 seemed to be an artifact but during the isolation process and chromatographic separation, no ethanol solvent was used (see Experimental). Pituranthosin B A c c e p t e d m a n u s c r i p t

  , an endemic species of the Algerian-Moroccan Sahara, were harvested near the hydraulic dam of Djorf Torba in the Wilaya of Bechar in Southern Algeria (GPS coordinates 30°31ʹ0" N and 2°45ʹ0" W) during the flowering stage in April 2010. The plant material was authenticated by M. Mohamed Benabdelhakem, Director of the nature preservation agency, Bechar. A voucher specimen (PBA 54/04/10) was deposited at the Herbarium of the VARENBIOMOL Research Unit, Univers ity Frères Mentouri Constantine 1.

A

  up to 35°C to obtain the following partition extracts: petroleum ether (0.9 g), CHCl3 (17 g), EtOAc (12 g), and n-BuOH (70 g), respectively. The CHCl3 extract was fractionated by column chromatography (230-400 mesh silica gel; n-hexane-EtOAc step gradients, and then with increasing percentages of acetone) to give 31 fractions (F1-F31) which were obtained by combining the fractions based on TLC analysis. Following purification of fraction F3 (150.4 mg) (n-hexane/EtOAc 88:12) by crystallization in MeOH and a little amount of CHCl3, a mixture of -sitosterol and stigmasterol (50-50%) (27 mg) was isolated. Fraction F9 (276.8 mg) (n-hexane/EtOAc 80:20) was chromatographed on a silica gel column (nhexane/EtOAc 7:3) to yield 16 sub-fractions (subF1-subF16). SubF11 (50 mg) was chromatographed on preparative silica gel TLC (CHCl3 100%; two elutions) to afford xanthotoxin (6) (4 mg), phellopterin (10) (5 mg), and vanillin (8 mg). Fraction F11 (75.1 mg) (n-hexane/EtOAc 78:22) was chromatographed on preparative silica gel TLC (CHCl3/acetone 19:1) to afford xanthotoxol (5) (30.8 mg). Purification of fraction F13 (280 mg) (nhexane/EtOAc 70:30) on preparative plates of silica gel (CHCl3/acetone 19:1) yielded 8-[(R)-6ʹ-hydroxy-7ʹ-ethoxygeranyloxy] psoralen named pituranthosin A (1) (7 mg). Fraction F18 (1.5 g) (n-hexane/EtOAc 50:50) was chromatographed on a silica gel column (n-hexane/EtOAc) to yield 27 sub-fractions (subF1-subF27). SubF6 (62 mg) (n-hexane/EtOAc 85:15) was subjected to preparative plates of silica gel TLC (CHCl3/acetone 98:2) to afford 8-[6ʹ,7ʹdihydroxygeranyloxy]psoralen acetonide named pituranthosin B (2) (8 mg). SubF21 (45 mg) (nhexane/EtOAc 50:50) was chromatographed using preparative plates of silica gel TLC (CHCl3/acetone 9:1) and purified on a Sephadex LH-20 column to yield (R)-(+)-marmin (11) (9 mg), (R)-(+)-heraclenin (7) (11 mg), and rutaretin (12) (8 mg). SubF24 (32 mg) (nhexane/EtOAc 30:70) gave (R)-(+)-byakangelicol (8) (10 mg) after purification by crystallization in MeOH. Fraction F20 (766 mg) (n-hexane/EtOAc 45:55) yielded, (R)-(+)byakangelicin (9) (536.5 mg) after purification by crystallization in MeOH/CHCl3. Fraction F24 named pituranthosin C (3) (2 mg) after purification on preparative plates of silica gel (CHCl3/acetone 9:1 three elutions). The concentration of fraction F25 (543.8 mg) (n-hexane/EtOAc 15:85) yielded a yellowish precipitate which was washed with CHCl3/MeOH to give a mixture of daucosterol and stigmasterol 3-O--glucopyranoside at 72 and 28%, respectively (158 mg). The EtOAc extract (10 g) was chromatographed on a silica gel column (230-400 mesh silica gel; CHCl3-acetone step gradients and then with increasing percentages of MeOH) to yield 43 fractions (F1-F43) based on their TLC behavior. Fraction F9 (99 mg) (CHCl3/acetone 98:2) was subjected to preparative TLC on silica gel (CHCl3/acetone 9:1 two elutions) to give isorhamnetin (20 mg). Fraction F11 (173 mg) (CHCl3/acetone 93:7) was submitted to preparative silica gel TLC (CHCl3/acetone 9:1) and purified over Sephadex LH-20 column eluted with MeOH to afford vanillic acid (7 mg) and -hydroxypropiovanillone (4.5 mg). Fraction F14 (148 mg) (CHCl3/acetone 90:10) gave apigenin (10 mg) after purification on preparative plates of silica gel (CHCl3/acetone 9:1). Fraction F17 (71 mg) (CHCl3/acetone 88:12) was submitted to preparative plates of silica gel TLC (CHCl3/acetone 9:1) and purified on a Sephadex LH-20 column to afford 8-[(R)-6ʹ,7ʹ-dihydroxygeranyloxy]psoralen (4) (9 mg).Biochanin A (10 mg) was obtained from fraction F21 (124 mg) (CHCl3/acetone 85:15) following purification on preparative silica gel plates (CHCl3/acetone 8:2). 8-[(R)-6ʹ-hydroxy-7ʹ-ethoxygeranyloxy]psoralen (1): yellow powder; [] D 20 +8.8 (c 1.3, MeOH); 1 H-NMR (400 MHz, MeOH-d4) and 13 C-NMR (100 MHz, MeOH-d4) spectroscopic data, see Tables 1 and 2; HRESIMS m/z: 423.1773 [M+Na] + (calcd for C23H28NaO6, 423.17781), m/z: 439.1515 [M+K] + (calcd for C23H28KO6, 439.15175).

  -NMR (MeOH-d4, 500 MHz) and 13 C-NMR (MeOH-d4, 125 MHz) spectroscopic data, see Tables

  KA1B3VW. The detection was performed at 275 nm for UV active components. The analysis was carried on a C18 nucleosil column (5µm, 250 x 4.6 mm) which was protected by security guard cartridge and was maintained at a constant room temperature of 25 °C. The mobile phases consisted of eluent A: 0.1 % formic acid in water, and eluent B: MeOH. Gradient was applied (A:B, 10-70-70-10% MeOH) (0-10-20-21-33 min). The total run time was 55 min. The flow rate was kept at 1.0 mL/min and the injection volume was 20 L. Peak identity of the individ ua l peaks was assigned by retention time (RT) values based on comparison with the standards and spiked authentic standard to the sample.

Figure 2 .

 2 Figure 1. Undescribed furanocoumarins isolated from Deverra battandieri

Figure 3 .

 3 Figure 3. 3a) HPLC/UV (275 nm) chromatographic profile of the CHCl 3 extract of the aerial parts of D. battandieri. Column nucleosil HD-18 (5µm, 250 x 4.6 mm). Phase: 0.1% formic acid in milli-Q H 2 O-ACN. Gradient: % ACN) (0-5-30-43-55 min). Flow 1 mL. min -1 ; injection volume: 20 μL; 3b) UV spectrum of compound 1; 3c) UV spectrum of compound 2; 3d) UV spectrum of compound 3.

  was very similar to that of 1, suggesting that the two compounds were closely related in structure. The major difference is that 2 has two additional C-methyl resonances and lacked the ethyl group. A detailed comparison of the 1 H-and 13 C-NMR signals of 1 and 2 (Tables

deduced from the positive HRESIMS m/z 435.1780 [M+Na] + (calcd. for C24H28O6Na, 435.1784) and indicated eleven degrees of unsaturation in it. The 1 H-NMR data (Table 1) of 2,

A c c e p t e d m a n u s c r i p t

  of 1 have been replaced by signals due to an acetonide group seen at H

	1.36 (s, 3H), C 28.90; H 1.23 (s, 3H), C 27.15, and C 107.64. Thus, compound 2 was
	determined to be 8-[6ʹ,7ʹ-dihydroxygeranyloxy]psoralen acetonide and was named
	pituranthosin B.

  Rennes 1). Column chromatography (CC) were carried out with silica gel Fluka (cat. 60737, 40-63 μm), silica gel 60 (Merck 230-400 mesh) and Sephadex LH-20 (Sigma-Aldric h).

	Column fractions were monitored by TLC silica gel 60 F254 (Merck), 0.2 mm, Macherey Nagel
	(cat. 818-333) by detection with a spraying reagent CH3CO2H-H2O-H2SO4 (80:16:4) follo wed
	by heating at 100 °C. Preparative TLC was carried out on silica gel 60 PF254+366 (20 cm×20
	cm, 1 mm thickness, Analtech cat. 02014). Solvents such as CHCl3, toluene, EtOAc, and MeOH are reagent grade and were purchased from VWR (Fontenay-sous-bois, France); a n u s c r i p t acetonitrile is HPLC grade and was purchased from Fisher Scientific; Milli-Q water (18.2 MΩ)
	m
	standard pulse sequences operating at 400 and 500 MHz for 1 H and 100 and 125 MHz for 13 C, respectively. MeOH-d4, DMSO-d6, or CDCl3 were used as solvents with TMS as interna l standard. Chemical shifts (δ) are reported in ppm and coupling constants (J) are reported in Hz. High resolution mass spectra (HRESIMS) were performed on an Agilent 6520 Accurate Mass A c c e p t e d
	Q-TOF (Agilent Corporation, Santa Clara, CA, USA), a µ-QToF spectrometer (Bruker
	Daltonics, Wissembourg, France) with a LCT Premier XE Micromass Waters spectrometer in
	positive ionization mode (Waters Corporation) and a Bruker Maxis 4G (CRMPO Université de

rotations were measured using a Perkin Elmer model 341. UV spectra were recorded using a Shimadzu model (190-3200 nm, UV-3101PC) or Shimadzu model UV-1700 spectrophotometer. 1 H-and 13 C-NMR spectra were obtained by Bruker model Avance AMX-400 and AMX-500 MHz spectrometers (Bruker BioSpin, Rheinstetten, Germany) with

Table 1 :

 1 1 H NMR data of 1-3 (MeOH-d4). δ in ppm, J (Hz) in parentheses.

	Position	1 δH (J)	2 δH (J)	3 δH (J)
	2
	3	6.38, d (9.6)	6.36, d (9.6)	6.40, d (9.6)
	4	8.03, d (9.6)	8.05, d (9.6)	8.05, d (9.6)
	5	7.57, s	7.53, s	7.59, s
	9	7.90, d (2.2)	7.88, d (2.2)	7.91, d (2.2)
	10	6.96, d (2.2)	6.94, d (2.2)	6.97, d (2.2)
	1ʹ 2ʹ 4ʹ 5ʹ 6ʹ	5.03, d br (7.6) 5.65-5.55, m 2.24, ddd (14.2, 9.9, 4.7) 2.08 -1.95, m 1.58, dddd (13.7, 9.9, 6.9, 1.8) 1.27 -1.17, m 3.26 (dd, J = 10.5, 1.8)	5.01, dd (7.2, 1.6) 5.62 -5.53, m 2.18, ddd (11.4, 9.7, 5.3) 2.09 -1.97, m 1.52-1.45, m 1.45-1.30, m 3.58, dd (9.3, 3.6)	4.61 -4.54, m 4.46, ddd (11.0, 8.3, 5.7) 2.56-2.38, m 2.31-2.19, m 1.50, ddd (13.6, 6.8, 3.1) 1.89-1.78, m 3.25, m, overlapped
	8ʹ 9ʹ	1.10, s 1.05, s	1.16, s 1.03, s	1.18, s 1.16, s
	10ʹ	1.66, s	1.67, s	5.05, s
				5.27, s
	1ʹʹ 2ʹʹ 3ʹʹ	3.40, qd (7.0, 1.7) 1.12, t (7.0)	1.36, s 1.23, s

Acknowledgments

This work was carried out with the support of PCI program (Spain-Algeria Cooperation Project A1/035449/11) and Tassili program (France-Algeria Cooperation, project 12-MDU856).

A c c e p t e d m a n u s c r i p t