Search

The Breast Cancer Resistance Protein (BCRP/ABCG2) belongs to the G class of ABC (ATP-Binding Cassette) proteins, which is known as one of the main transporters involved in the multidrug resistance (MDR) phenotype that confer resistance to anticancer drugs. The aim of this study was to design, synthesize and develop new potent and selective inhibitors of BCRP that can be used to abolish MDR and potentialize clinically used anticancer agents. In previous reports, we showed the importance of chromone scaffold and hydrophobicity for the inhibition of ABC transporters. In the present study we report the design and development of chromones linked to one or two amino acids residues that are either hydrophobic or found in the structure of FTC, one of most potent (but highly toxic) inhibitors of BCRP. Herewith, we report the synthesis and evaluation of 13 compounds. The studied molecules were found to be not toxic and showed strong inhibition activity as well as high selectivity toward BCRP. The highest activity was obtained with the chromone bearing a valine residue (9c) which showed an inhibition activity against BCRP of 50 nM. The rationalization of the inhibition potential of the most active derivatives was performed through docking studies. Taken together, the ease of synthesis and the biological profile of these compounds render them as promising candidates for further development in the field of anticancer therapy.

The transporter Multidrug Resistance Protein 1 (MRP1, ABCC1) is implicated in multidrug resistant (MDR) phenotype of cancer cells. Glutathione (GSH) plays a key role in MRP1 transport activities. In addition, a ligand-stimulated GSH transport which triggers the death of cells overexpressing MRP1, by collateral sensitivity (CS), has been described. This CS could be a way to overcome the poor prognosis for patients suffering from a chemoresistant cancer. The molecular mechanism of such massive GSH transport and its connection to the other transport activities of MRP1 are unknown. In this context, we generated MRP1/MRP2 chimeras covering different regions, MRP2 being a close homolog that does not trigger CS. The one encompassing helices 16 and 17 led to the loss of CS and MDR phenotype without altering basal GSH transport. Within this region, the sole restoration of the original G1228 (D1236 in MRP2) close to the extracellular loop between the two helices fully rescued the CS (massive GSH efflux and cell death) but not the MDR phenotype. The flexibility of that loop and the binding of a CS agent like verapamil could favor a particular conformation for the massive transport of GSH, not related to other transport activities of MRP1.

The membrane transporter BCRP/ABCG2 has emerged as a privileged biological target for the development of small compounds capable of abolishing multidrug resistance. In this context, the chromone skeleton was found as an excellent scaffold for the design of ABCG2 inhibitors. With the aims of optimizing and developing more potent modulators of the transporter, we herewith propose a multidisciplinary medicinal chemistry approach performed on this promising scaffold. A quantitative structure-activity relationship (QSAR) study on a series of chromone derivatives was first carried out, giving a robust model that was next applied to the design of 13 novel compounds derived from this nucleus. Two of the most active according to the model’s prediction, namely compounds 22 (5-((3,5-dibromobenzyl)oxy)-N-(2-(5-methoxy-1H-indol-3-yl)ethyl)-4-oxo-4H-chromene-2-carboxamide) and 31 (5-((2,4-dibromobenzyl)oxy)-N-(2-(5-methoxy-1H-indol-3-yl)ethyl)-4-oxo-4H-chromene-2-carboxamide), were synthesized and had their biological potency evaluated by experimental assays, confirming their high inhibitory activity against ABCG2 (experimental EC50 below 0.10 μM). A supplementary docking study was then conducted on the newly designed derivatives, proposing possible binding modes of these novel molecules in the putative ligand-binding site of the transporter and explaining why the two aforementioned compounds exerted the best activity according to biological data. Results from this study are recommended as references for further research in hopes of discovering new potent inhibitors of ABCG2.

Toxoplasma gondii is an intracellular protozoan parasite widely distributed in animals and humans. Infection of host cells and parasite proliferation are essential steps in Toxoplasma pathology. The objective of this study was to develop and validate a novel automatic High Content Imaging (HCI) assay to study T. gondii infection and proliferation. We tested various fluorescent markers and strategies of image analysis to obtain an automated method providing results comparable to those from gold standard infection and proliferation assays. No significant difference was observed between the results obtained from the HCI assay and the standard assays (manual fluorescence microscopy and incorporation of [3H]-uracil). We developed here a robust and time-saving assay. This automated technology was then used to screen a library of compounds belonging to four classes of either natural compounds or synthetic derivatives. Inhibition of parasite proliferation and host cell toxicity were measured in the same assay and led to the identification of one hit, a thiosemicarbazone that allows important inhibition of Toxoplasma proliferation while being relatively safe for the host cells.

To tackle the problems associated with membrane protein (MP) instability in detergent solutions, we designed a series of glycosyl-substituted dicarboxylate detergents (DCODs) in which we optimized the polar head to clamp the membrane domain by including, on one side, two carboxyl groups that form salt bridges with basic residues abundant at the membrane-cytoplasm interface of MPs and, on the other side, a sugar to form hydrogen bonds. Upon extraction, the DCODs 8 b, 8 c, and 9 b preserved the ATPase function of BmrA, an ATP-binding cassette pump, much more efficiently than reference or recently designed detergents. The DCODs 8 a, 8 b, 8 f, 9 a, and 9 b induced thermal shifts of 20 to 29 °C for BmrA and of 13 to 21 °C for the native version of the G-protein-coupled adenosine receptor A2A R. Compounds 8 f and 8 g improved the diffraction resolution of BmrA crystals from 6 to 4 A. DCODs are therefore considered to be promising and powerful tools for the structural biology of MPs.

International audience; Aim: Cisplatin resistance in ovarian cancer remains a complex problem as tumors frequently develop resistance against drugs, a mechanism sometimes mediated by ATP-Binding Cassette transporters. Our goal was to find compounds restricting their inhibition capacity to the cisplatin efflux mediated by ABCC2 pump, among previously identified inhibitors, derived from the 2-indolylmethylenebenzofuranones. Methodology & results: An original method setup allows direct quantitation of platinum by employing cyTOF mass cytometry. Among tested derivatives, some led to a full platinum accumulation and efficiently resensitized cisplatin-resistant A2780 cells to cisplatin while preserving most of the calcein efflux activity. Conclusion: CyTOF is therefore a powerful and promising method to quantify cisplatin accumulation that may be used in the clinical setting to improve and personalize cancer treatment.

Cancer cells are permanently being selected for survival and proliferation. During this process, tumor cells often co-opt basic physiological mechanisms to protect themselves from toxic chemotherapy. One of these mechanisms is the overexpression of ATP-binding cassette (ABC) drug efflux pumps leading to multidrug resistance (MDR) of cancer cells through an increase of drug efflux. In the past 20 years, many efforts were done to circumvent MDR through the inhibition of ABC transporters. A number of inhibitors of these transporters were found but are rarely specific or rationally developed. Beside this approach, a new therapeutic strategy towards eradicating drug resistant tumor cells has recently emerged from the observation that cancer cells expressing a high level of these pumps show an unexpected hypersensitivity, called collateral sensitivity (CS) to a selected subset of chemical compounds. In this review, we target the multidrug resistance protein 1 (MRP1) and after a non-exhaustively highlighting of some of the most exemplary inhibitors of MRP1 and modulators of its expression, we focus on CS agents specifically targeting MRP1 which becomes, when overexpressed, the so calledquot;Achilles#039; heelquot; of multidrug resistant cancer cells. We discuss the link between the prominent role of glutathione translocation and related redox balance of the cell and the CS induced by certain types of compounds. The latter are discussed according to their chemical class, and perspectives in their development for successful eradication of resistant cancer are proposed.

ABC-transporters play a vital role in drugs bioavailability. They prevent intracellular accumulation of toxic compounds, rendering them a major defense mechanism against harmful substances. In this large family, ABCC2 is an apical efflux pump representing about 10% of all membrane proteins in liver and small intestine, and up to 25% in colon. In these tissues, ABCC2 plays a major role in the pharmacokinetics and pharmacodynamics of endo- and xenobiotics. To gain insight in the function of this crucial protein, we have investigated and developed the first effective inhibitors of this pump. Firstly, we set up a cellular flow cytometry assay for monitoring the drug efflux carried out by ABCC2, and used it for the screening of chemical libraries derived from several chemical classes. We found that 2-indolylmethylenebenzofuranone derivatives as promising candidates. Optimization of the hits provided new compounds that inhibit ABCC2 in the micromolar range, making them the first potent ABCC2 inhibitors reported so far. Such compounds would constitute valuable tools to further investigate the role of ABCC2 in the pharmacokinetics and pharmacodynamics of drugs.

Among the human copper-containing monooxygenases, Tyrosinase (Ty) is an important enzyme involved in the determinant step of the biosynthetic pathway of melanin pigment. In this pathway, Ty catalyzes the tyrosine monooxygenation into L-DOPA-quinone, which is the precursor of the skin pigment melanin. Ty inhibitors/activators are a well-established approach for controlling in vivo melanin production, so their development has a huge economical and industrial impact. Moreover, recent publications highlight that targeting tyrosinase with inhibitors/activators to treat melanogenesis disorders is one of many possible approaches, due to the complex biochemical reaction involved in the melanin synthesis.

Covering up to 2016, Nauclea latifolia (syn. Sarcocephalus latifolius, Rubiaceae), commonly called the African pincushion tree, is a plant widely used in folk medicine in different regions of Africa for treating a variety of illnesses, including malaria, epilepsy and pain. N. latifolia has not only drawn the interest of traditional healers but also of phytochemists, who have identified a range of bioactive indole alkaloids in its tissue. More recently, following up on the traditional use of extracts in pain management, a bio-guided purification from the roots of the tree led to the identification of the active ingredient as tramadol, available as a synthetic analgesic since the 1970s. The discovery of this compound as a natural phytochemical was highlighted worldwide. This review focuses on the correlation between extracted compounds and pharmacological activities, paying special attention to infectious diseases and neurologically-related disorders. A critical analysis of the data reported so far on the natural origin of tramadol and its proposed biosynthesis is also presented.

International audience; We previously identified 1-(2,4-dimethoxyphenyl)-3-(1-methylindolyl) propenone (IPP51), a new chalcone derivative that is capable of inducing prometaphase arrest and subsequent apoptosis of bladder cancer cells. Here, we demonstrate that IPP51 selectively inhibits proliferation of tumor-derived cells versus normal non-tumor cells. IPP51 interfered with spindle formation and mitotic chromosome alignment. Accumulation of cyclin B1 and mitotic checkpoint proteins Bub1 and BubR1 on chromosomes in IPP51 treated cells indicated the activation of spindle-assembly checkpoint, which is consistent with the mitotic arrest. The antimitotic actions of other chalcones are often associated with microtubule disruption. Indeed, IPP51 inhibited tubulin polymerization in an in vitro assay with purified tubulin. In cells, IPP51 induced an increase in soluble tubulin. Furthermore, IPP51 inhibited in vitro capillary-like tube formation by endothelial cells, indicating that it has anti-angiogenic activity. Molecular docking showed that the indol group of IPP51 can be accommodated in the colchicine binding site of tubulin. This characteristic was confirmed by an in vitro competition assay demonstrating that IPP51 can compete for colchicine binding to soluble tubulin. Finally, in a human bladder xenograft mouse model, IPP51 inhibited tumor growth without signs of toxicity. Altogether, these findings suggest that IPP51 is an attractive new microtubule-targeting agent with potential chemotherapeutic value.

Tyrosinase is a copper-containing enzyme found in plants and bacteria, as well as in humans, where it is involved in the biosynthesis of melanin-type pigments. Tyrosinase inhibitors have attracted remarkable research interest as whitening agents in cosmetology, antibrowning agents in food chemistry, and as therapeutics. In this context, commercially available tyrosinase from mushroom (TyM) is frequently used for the identification of inhibitors. This and bacterial tyrosinase (TyB) have been the subjects of intense biochemical and structural studies, including X-ray diffraction analysis, and this has led to the identification of structural homology and divergence among enzymes from different sources. To better understand the behavior of potential inhibitors of TyM and TyB, we selected the aurone family-previously identified as potential inhibitors of melanin biosynthesis in human melanocytes. In this study, a series of 24 aurones with different hydroxylation patterns at the A- and B-rings were evaluated on TyM and TyB. The results show that, depending on the hydroxylation pattern of A- and B-rings, aurones can behave as inhibitors, substrates, and activators of both enzymes. Computational analysis was performed to identify residues surrounding the aurones in the active sites of both enzymes and to rationalize the interactions. Our results highlight similarities and divergence in the behavior of TyM and TyB toward the same set of molecules.

International audience; Following our recent report showing the potential of naturally occurring aurones (2benzylidenebenzofuran-3(2H)-ones) as anti-hepatitis C virus (HCV) agents, efforts were continued in order to refine the structural requirements for the inhibitory effect on HCV RNA-dependent RNA polymerase (RdRp). In this study, we targeted the Bring moiety of aurones with the aim to improve structural features associated with higher inhibition of the targeted polymerase. In vitro evaluation of the RdRp inhibitory activity of the 37 newly synthesized compounds pointed out that the replacement of the Bring with a N-substituted indole moiety induced the highest inhibitory effect. Of these, compounds 31, 40 and 41 were found to be the most active (IC50 = 2.3-2.4 µM). Docking experiments performed with the most active compounds revealed that the allosteric thumb pocket I of RdRp is the binding pocket for aurone analogues.

International audience; ETHNOPHARMACOLOGICAL RELEVANCE: The roots of Nauclea latifolia Smith (Rubiaceae) popularly known as "koumkouma" is used in traditional Cameroonian medicine as neuropathic pain remedy and for the treatment of headache, inflammatory pain and convulsion. This study was conducted to evaluate the antinociceptive effects of the alkaloid fraction isolated from Nauclea latifolia in neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve in rat. MATERIALS AND METHODS: Bioactive-guided fractionation of the root extracts of Nauclea latifolia using the Von Frey in a rat model of neuropathic pain (Benett model), afforded a potent anti-hyperalgesic fraction IV. Further fractionation of this fraction was performed by high-performance liquid chromatography (HPLC), yielded eight sub-fractions (F1-F8) which were tested for antinociceptive effects. The alkaloid fraction (F3) collected by HPLC, exhibited potent antinociceptive effects, and the anti-allodynic and anti-hyperalgesic effects of this fraction (8, 16, 40 and 80 mg/kg) were determined using the von Frey and acetone tests respectively in a rat model of neuropathic pain. Rota-rod performance and catalepsy tests were used for the assessment of motor coordination. RESULTS: The alkaloid fraction (80 mg/kg) administered intraperitoneally induced a completely decreased hyperalgesia 90 min post-dosing. In the acetone test, the Nauclea latifolia fraction at 80mg/kg showed its maximal anti-allodynic effects 120 min post-injection. The areas under the curve (AUC) of the anti-allodynic or anti-hyperalgesic effects produced by the alkaloid fraction at 80 mg/kg were significantly (p

International audience; Chalcones are naturally occurring compounds with diverse pharmacological activities. Chalcones derive from the common structure: 1,3-diphenylpropenone. The present study aims to better understand the mechanistic pathways triggering chalcones anticancer effects and providing evidences that minor structural difference could lead to important difference in mechanistic effect. We selected two recently investigated chalcones (A and B) and investigated them on glioblastoma cell lines. It was found that chalcone A induced an apoptotic process (type I PCD), via the activation of caspase-3, -8 and -9. Chalcone A also increased CDK1/cyclin B ratios and decreased the mitochondrial transmembrane potential (ΔΨm). Chalcone B induced an autophagic cell death process (type II PCD), ROS-related but independent of both caspases and protein synthesis. Both chalcones increased Bax/Bcl2 ratios and decreased Ki67 and CD71 antigen expressions. The present investigation reveals that despite the close structure of chalcones A and B, significant differences in mechanism of effect were found.

The NorA efflux pump lowers intracellular fluoroquinolone concentrations by expelling antibiotics through the membrane of Staphylococcus aureus. We identified 3-aryl-4-methyl-2-quinolin-2-ones as compounds able to restore the activity of the NorA substrate, ciprofloxacin, against resistant S. aureus strains, and acting as efflux pump inhibitors (EPI). In particular, 5-hydroxy-7-methoxy-4-methyl-3-phenylquinolin-2-one (6 c) presents both an EPI and an antimicrobial effect. Its efficacy and safety make it a potential candidate for further investigations.

moderate to severe pain without any known side effects. [8, 9] It was designed by a simplification of the structure of morphine that kept the pharmacophoric elements responsible for the analgesic effect. Herein, we describe the isolation of tramadol from the root bark of N. latifolia, and the different methods used to prove the authenticity of its natural origin. The

International audience; The breast cancer resistance protein ABCG2 confers cellular resistance to irinotecan (CPT-11) and its active metabolite SN-38. We utilised ABCG2-expressing xenografts as a model to evaluate the ability of a non-toxic ABCG2 inhibitor to increase intracellular drug accumulation. We assessed the activity of irinotecan in vivo in SCID mice: irinotecan completely inhibited the development of control pcDNA3.1 xenografts, whilst only delaying the growth of ABCG2-expressing xenografts. Addition of MBLI-87, an acridone derivative inhibitor, significantly increased the irinotecan effect against the growth of ABCG2-expressing xenografts. In vitro, MBLI-87 was as potent as GF120918 against ABCG2-mediated irinotecan efflux, and additionally was specific for ABCG2. A significant sensitisation to irinotecan was achieved despite the fact that doses remained well below the maximum tolerated dose (due to the rather limited solubility of MBLI-87). This suggested that MBLI-87 is an excellent candidate to prevent drug efflux by ABCG2, without altering plasma concentrations of irinotecan and SN-38 after IP (intra-peritoneal) injections. This could constitute a useful strategy to improve drug pharmacology, to facilitate drug penetration into normal tissue compartments protected by ABCG2, and potentially to reverse drug resistance in cancer cells.

International audience; We have identified naturally occurring 2-benzylidenebenzofuran-3-ones (aurones) as new templates for non-nucleoside hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) inhibitors. The aurone target site, identified by site-directed mutagenesis, is located in thumb pocket I of HCV RdRp. The RdRp inhibitory activity of 42 aurones was rationally explored in an enzyme assay. Molecular docking studies were used to determine how aurones bind to HCV RdRp and to predict their range of inhibitory activity. Seven aurone derivatives were found to have potent inhibitory effects on HCV RdRp, with IC(50) below 5 μM and excellent selectivity index (inhibition activity versus cellular cytotoxicity). The most active aurone analogue was (Z)-2-((1-butyl-1H-indol-3-yl)methylene)-4,6-dihydroxybenzofuran-3(2H)-one (compound 51), with an IC(50) of 2.2 μM. Their potent RdRp inhibitory activity and their low toxicity make these molecules attractive candidates as direct-acting anti-HCV agents.

In addition to its critical role is controlling drug availability and protecting sensitive organs and stem cells through cellular detoxification, breast cancer resistance protein (BCRP/ABCG2) plays an important role in cancer cell resistance to chemotherapy, together with P-glycoprotein/ABCB1. A main approach to abolish multidrug resistance is to find out specific inhibitors of the drug-efflux activity, able to chemosensitize cancer cell proliferation. Many efforts have been primarily focused on ABCB1, discovered thirty years ago, whereas very few studies have concerned ABCG2, identified much more recently. This review describes the main types of inhibitors presently known for ABCG2, and how quantitative structure-activity relationship analysis among series of compounds may lead to build up molecular models and pharmacophores allowing to design lead inhibitors as future candidates for clinical trials. A special attention is drawn on flavonoids which constitute a structurally-diverse class of compounds, well suited to identify potent ABCG2-specific inhibitors.

International audience; A series of compounds derived from naturally occurring flavonoids and synthetic analogs have been evaluated on cell lines overexpressing the wild-type breast cancer resistance protein (BCRP/ABCG2) halftransporter. Human ABCG2-transfected cells were used for screening their inhibitory activity. Five new natural compounds obtained from Morus mesozygia Stapf and one synthetic chromone, comprising a flavonoidic scaffold, were also evaluated. Based on the results obtained with a total of 34 compounds, a 3D linear solvation energy QSAR was investigated by VolSurf descriptors of molecular-interaction fields (MIFs) related to hydrophobic-interaction forces, polarisability and hydrogen-bonding capacity. Accuracy of the constructed 3D-QSAR model was attested by a correlation coefficient r2 of 0.77. Shape parameters and hydrophobicitywere revealed to bemajor physicochemical parameters responsible for the inhibition activity of flavonoid derivatives and synthetic analogs towards ABCG2, whereas hydrogen-bond donor capacity appeared highly unfavorable.

1-(2,4-dimethoxyphenyl)-3-(1-methylindolyl) propenone, namely IPP51, was identified by screening a library of 3-indolyl-1-phenylpropenones. IPP51 was investigated for its ability to inhibit proliferation and/or to induce apoptosis of human bladder cancer cell lines and to assess its potential use in bladder carcinoma treatment. After treating the cells with IPP51 for 24 h, the title compound induced a predominant and reversible G2+M accumulation at the prometaphase stage of mitosis. However, when used for a longer period, it leads to cell apoptosis. These results suggest that the compound has potential anticancer activities, which could be useful in bladder cancer treatment.

This study investigated the effect of naturally occurring flavonoids and synthetic aurone derivatives on the formation of cardiotoxic doxorubicinol and transport of doxorubicin in breast cancer cells. Quercetin significantly inhibited the formation of doxorubicinol. Quercetin and aurones did not significantly affect transport of [14C]doxorubicin in human resistant breast cancer cells. In conclusion, quercetin should be further tested for its potency to decrease doxorubicin-mediated toxicity.

The breast cancer resistance protein (BCRP, ABCG2) is among the latest discovered ABC proteins to be involved in MDR phenotype and for which only few inhibitors are known. In continuing our program aimed at discovering efficient multidrug resistance modulators, we conceived and synthesized new acridones as ABCG2 inhibitors. The design of target molecules was based on earlier results dealing with ABCG2 inhibition with flavone and chromone derivatives. The human wild-type (R482) ABCG2-transfected cells were used for rational screening of inhibitory acridones. The synthesis of target compounds, the inhibitory activity against ABCG2, and structure-activity relationships are described. One of the acridones was even more potent than the reference inhibitor, GF120918, as shown by its ability to inhibit mitoxantrone efflux.

2-Alkyl-5-hydroxychromones (2-alkyl-5-hydroxy-4-oxo-4H-1-benzopyran) and 3-alkoyl-2-alkyl-5-hydroxychromones (3-alkoyl-2-alkyl-5-hydroxy-4-oxo-4H-1-benzopyran) were prepared in one-step and one pot reaction by condensation of 2',6'-dihydroxyacetophenone with an alkoyl chloride in the presence of K2CO3.

In targeting molecules, destinated for treatment of skin ageing, we synthesized esters of hesperitin (4′-methoxy-5,7,3′-trihydroxyflavanone). Esterification with lauric acid was used with the aim to overcome the flavonoid instability and to improve the therapeutic usefulness. Stability, free radical scavenging activity and anti-elastase potency of the prepared compounds were studied and compared to those of hesperitin (natural compound). Compounds obtained are more stable than hesperitin and display similar or higher anti-elastolytic and free radical scavenging activities.

This PhD. Thesis was carried out in the field of phytochemistry and pharmacognosy, including two major parts. The first part is dedicated to the phytochemical investigation of the roots of Nauclea latifolia, an African shrub largely used in traditional medicine. In 2013, tramadol, a fully synthetic drug was isolated from the roots of Nauclea latifolia. This unpreceded discovery was largely covered by media worldwide As it can be expected, the natural origin of tramadol was inevitably the subject to some discrepancies. The main goal of this project is to isolate tramadol from new samples of N. latifolia in order to perform isotopic 14C analyses to determine the natural origin of compound.The purification of the root extracts by using semi-preparative HPLC led to the isolation of two tramadol. The isotopic 14C analyses of the samples tend to show a natural origin. However, the analysis of a new sample of tramadol from a third batch is necessary to confirm/affirm its origin.The second part of this thesis was dedicated to the phytochemical study of two alpine plants in order to valorize the local flora as a source of bioactive molecules. The first plant was Helianthemum nummularium, which is a specie very present in the alimentary diet of ungulates. In order to explain the preference of ungulates for this species over-consumption, two hypotheses were evoked: 1) nutritional values of the plant, 2) consumption of the plant for self-medication. In this context, we were interested by the second hypothesis by performing a phytochemical analysis of the aerial parts of the plant. The purification of the ethanolic extract allowed to obtain 8 compounds among which some were reported as potential anthelmintic agents.The second plant is Chenopodium bonus-henricus, an alpine specie popular in the local alimentary diet. The phytochemical study of the dichloromethane and ethanolic extracts of the aerial parts led to the isolation of six molecules among which one was never described in any natural resources.Furthermore, the plants of altitude grow in drastic environmental conditions and must develop some defense mechanisms. In this context, the alpine plants extract and the pure molecules were tested on their effect on the activation pathway of Nuclear Factor Erythroid-2-related Factor 2 (Nrf2)., Cette thèse s’inscrit dans le domaine de la phytochimie et de la pharmacognosie, et comprend deux parties majeures. La première porte sur l’investigation phytochimique des racines de Nauclea latifolia, un arbuste utilisé en médecine traditionnelle pour ses propriétés thérapeutiques. En 2013, la découverte du tramadol, un médicament de synthèse dans les racines de Nauclea latifolia a été exposée à une couverture médiatique inédite. De ce fait, l’origine naturelle du tramadol a été remise en question. L’objectif principal de ce projet est d’isoler du tramadol à partir de nouveaux lots de racines de Nauclea latifolia dans le but de réaliser des analyses isotopiques 14C pour déterminer l’origine naturelle (ou non) du composé.La purification d’extraits de ces racines par HPLC semi-préparative a permis l’isolement de deux échantillons de tramadol. Les analyses isotopiques en carbone 14 des échantillons ont montré des résultats qui tendent à montrer une origine naturelle. Cependant, l’analyse d’un nouvel échantillon de tramadol issu d’un troisième lot est nécessaire pour confirmer/affirmer son origine.Le deuxième volet de cette thèse a porté sur l’étude phytochimique de deux plantes alpines dans le but de valoriser la flore locale en tant que sources de molécules bioactives. La première plante est l’Helianthemum nummularium, une espèce que l’on retrouve en surprésentation dans le régime alimentaire des ongulés montagnards. Afin d’expliquer cette surconsommation, deux hypothèses étaient possibles : 1) valeurs nutritionnelles importantes et 2) consommation de la plante dans un but d’automédication. Dans ce contexte, nous nous sommes principalement intéressés à la deuxième hypothèse en réalisant une analyse phytochimique des parties aériennes de plante. La purification de l’extrait éthanolique des parties aériennes ont permis l’isolement de 8 dérivés polyphénoliques dont certains ont été rapportés comme de potentiels agents antiparasitaires et pourraient présenter un intérêt pour les ongulés. La deuxième plante est le Chenopodium bonus-henricus, une espèce alpine très utilisée dans le secteur alimentaire local. L’étude phytochimique des extraits dichlorométhane et éthanolique des parties aériennes a permis l’isolement de 6 molécules dont une est nouvelle.La valorisation thérapeutique des extraits et molécules issus des plantes alpine, nous a conduit à conduire des tests biologiques. Dans ce contexte, nous nous sommes penchés sur l’induction d’activation du facteur de transcription Nrf2 par les extraits et les molécules isolées.

Understanding of tridimensional structure of membrane proteins (MPs) is crucial in medicinal chemistry and biochemistry. To maintain them in solution and consequently to prevent them from aggregation for structural and functional studies, utilization of detergents is indispensable. However, the conformation of MPs in complex with detergents could be very different from its membrane-embedded one. We synthetized new family of detergents, in which the incorporated carboxylates could generate a network of salt-bridges with basic-residue-enriched region of MPs, confer tighter interactions which could preserve their structural integrity. The detergents in which the glycoconjugation was achieved by Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction showed remarkable capacity to extract, stabilize and crystallize studied PMs. On the other hand, novel inhibitors of ABCC2, a non-crystallized MP to date, were identified by screening: the 2-indolylmethylenebenzofuranones. Such compounds could be considered as useful tools to further investigate the role of ABCC2 in the pharmacokinetics of drugs.; L’obtention de la structure tridimensionnelle des protéines membranaires (PMs) est cruciale pour la chimie médicinale et la biochimie. Afin de maintenir les PMs en solution, et donc d’éviter leur agrégation, pour les études structurales et fonctionnelles, l’utilisation de détergents est indispensable. Cependant, la conformation des PMs en complexe avec les détergents pourrait être très différente de celle dans la membrane. Nous avons synthétisé une nouvelle famille de détergents, dans lesquels des carboxylates incorporés pourraient générer un réseau de ponts salins avec les acides aminés basiques des PMs, entraînant des interactions plus étroites qui pourraient préserver leur structure native. Les détergents dans lesquels la glycoconjugation a été réalisée par la réaction de cycloaddition d'azide-alkyne (CuAAC) catalysée par le Cu (I) ont montré une capacité remarquable à extraire, à stabiliser et à cristalliser les PMs étudiées. D'autre part, de nouveaux inhibiteurs efficaces d’ABCC2, une PM non cristallisée à ce jour, ont été identifiés par criblage : les 2-indolylméthylènebenzofuranones. De tels composés pourraient être considérés comme des outils pour étudier le rôle d’ABCC2 dans la pharmacocinétique des médicaments.

Rising incidence of cancers and ever-growing microbial infections are the main concerns of modern medicine, coevolving with the respective drug targeting resistances. This “growing health crisis”, as defined by the World Health Organization in 2014, prompts researchers to find new resources of drug leads. Despite the large number of terrestrial natural products derivatives approved as pharmaceutics, industry has reduced its reliance on it, mostly due to the high rate of rediscovery of known compounds. Therefore, academicians and private industry have turned their efforts toward exploring the marine world as new sources of bioactive molecules. We contributed to this effort in participating in a research project named PharmaSea, based on the bio discovery, identification and development of new substances from marine organisms. The key step to successful drug bio discovery from marine sources is the rapid identification of the known compounds before isolating them. Called dereplication, this approach is essential to assess chemical novelty of crude extracts and their fractions. The profusion of data sets and the lack of confirmatory data make this task arduous. Different strategies of dereplication procedures involving Liquid chromatography coupled with High Resolution Mass Spectrometry are thus emerging. In this regard, we investigated the PharmaSea dereplication method on 21 tunicates extracts. This method combines the ACDLabs IntelliXtract software with the MarinLit database from the Royal Society of Chemistry to dereplicate mass data. Nuclear Magnetic Resonance was also used to streamline the prioritization of samples to study to validate the method. The most interesting sample according to these strategies was selected for further purification leading to the isolation of seven compounds of which five are new as evidence of the success of the method.; L’émergence de résistance aux antibiotiques et aux anticancéreux est aujourd’hui définie par l’Organisation Mondiale de la Santé comme une crise de santé mondiale, incitant les chercheurs à développer des agents thérapeutiques innovants et plus spécifiques. L’industrie a restreint son recours aux substances naturelles végétales, notamment en raison de la fréquente redécouverte de composés connus. Les scientifiques tournent alors désormais leurs efforts vers le milieu marin, encore très peu exploité. Nous avons contribué à cet effort en participant au projet de recherche Européen PharmaSea axé sur la découverte, la caractérisation, et le développement de nouvelles substances pharmaceutiques tirées d'organismes marins. Une étape clé pour réussir dans la découverte de « médicaments de la mer » est la déréplication : l'identification rapide de composés déjà connus avant l’isolement. L’abondance de données et le manque d’informations confirmatives compliquent cette tâche. Différentes stratégies de déréplication comme la Chromatographie Liquide couplée à la Spectrométrie de Masse Haute Résolution émergent actuellement. Nous avons investigué la méthode de déréplication des données de masse de PharmaSea sur 21 extraits de tuniciers. Cette méthode est basée sur une combinaison du logiciel ACDLabs IntelliXtract et de la base de données MarinLit de la Royal Society of Chemistry. Grâce à l’ajout d’une analyse par Résonnance Magnétique Nucléaire, nous avons pu classer les extraits à étudier pour valider la méthode. Les plus prometteurs de nouveauté ont été purifiés, conduisant à l'isolement de sept composés dont cinq nouveaux, preuve de l'efficacité du mode de déréplication utilisé.

Understanding of tridimensional structure of membrane proteins (MPs) is crucial in medicinal chemistry and biochemistry. To maintain them in solution and consequently to prevent them from aggregation for structural and functional studies, utilization of detergents is indispensable. However, the conformation of MPs in complex with detergents could be very different from its membrane-embedded one. We synthetized new family of detergents, in which the incorporated carboxylates could generate a network of salt-bridges with basic-residue-enriched region of MPs, confer tighter interactions which could preserve their structural integrity. The detergents in which the glycoconjugation was achieved by Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction showed remarkable capacity to extract, stabilize and crystallize studied PMs. On the other hand, novel inhibitors of ABCC2, a non-crystallized MP to date, were identified by screening: the 2-indolylmethylenebenzofuranones. Such compounds could be considered as useful tools to further investigate the role of ABCC2 in the pharmacokinetics of drugs., L’obtention de la structure tridimensionnelle des protéines membranaires (PMs) est cruciale pour la chimie médicinale et la biochimie. Afin de maintenir les PMs en solution, et donc d’éviter leur agrégation, pour les études structurales et fonctionnelles, l’utilisation de détergents est indispensable. Cependant, la conformation des PMs en complexe avec les détergents pourrait être très différente de celle dans la membrane. Nous avons synthétisé une nouvelle famille de détergents, dans lesquels des carboxylates incorporés pourraient générer un réseau de ponts salins avec les acides aminés basiques des PMs, entraînant des interactions plus étroites qui pourraient préserver leur structure native. Les détergents dans lesquels la glycoconjugation a été réalisée par la réaction de cycloaddition d'azide-alkyne (CuAAC) catalysée par le Cu (I) ont montré une capacité remarquable à extraire, à stabiliser et à cristalliser les PMs étudiées. D'autre part, de nouveaux inhibiteurs efficaces d’ABCC2, une PM non cristallisée à ce jour, ont été identifiés par criblage : les 2-indolylméthylènebenzofuranones. De tels composés pourraient être considérés comme des outils pour étudier le rôle d’ABCC2 dans la pharmacocinétique des médicaments.

Systemic Sclerosis (SSc) is a serious disease affecting the skin microcirculation and characterized by fibrosis. Digital ulcers (DU) are the principal manifestation of this microvascular dysfunction in the extremities. DUs are frequent, painful, can cause functional impairment and have a major negative impact on the quality of life. Wound healing of DU is delayed and this can result in gangrene and amputation. To date, intravenous prostacyclin analogues (iloprost) are the only approved treatment for active SSc-related DU but their use is limited by serious vasodilation-induced side effects and usually requires hospitalization. Treprostinil is a prostacyclin receptor agonist that induces vascular relaxation and is used to treat advanced digital ischemia. Treprostinil is a very interesting candidate to enhance wound healing of ulcers in fibrotic skin. Scleroderma is a complex pathology and there is none existing animal model that can encompass all aspects of the disease related to fibrosis and vasculopathy. Among existing models, we selected two murin models (HOCL and uPAR-/-) that were recently described as promising tool to study SSc-related vasculopathy and fibrosis such as digital ulcers.The main objective of this study was to evaluate the therapeutic effect of topical administration of treprostinil on wound healing in two different preclinical models of SSc. Briefly, cutaneous excisional wounds were induced on mice. Animals were randomized into 3 sub-groups according the treatment to be administered: “sham”, “control” and “treprostinil” and wound process was followed until full recovery.Treprostinil iontophoretically-administered induced a significant acceleration in wound healing process in both models of SSc. The most significant effect was observed during the early phase of the healing process.This study demonstrated that iontophoresis of treprostinil could be proposed as a local therapeutic strategy to SSc patients with digital ulcers. Further pre-clinical studies should be realized to explore the underlying pharmacological and electrical mechanisms involved and clinical study should be started soon to assess the potential effect on SSc-related ulcers.; La sclérodermie (SSc) est une pathologie grave caractérisée par une atteinte microvasculaire combinée à une fibrose cutanée. Au niveau des extrémités, ce phénomène provoque des ulcères digitaux (UD) particulièrement douloureux et qui contribuent à diminuer la qualité de vie des patients atteints. La cicatrisation des UD est difficile et souvent de mauvais pronostic avec d’importants risques d’infection voire d’amputation. A ce jour, les injections intraveineuses d’iloprost, un analogue de la prostacycline, sont le seul traitement reconnu mais leur utilisation entraîne des effets secondaires et requiert une hospitalisation. Le treprostinil, un autre analogue de la prostacycline, est susceptible d’induire une importante vasorelaxation ce qui en fait une molécule d’intérêt majeur dans la prise en charge des UD. La sclérodermie est une pathologie complexe et aucun modèle animal ne présente l’ensemble de ses caractéristiques physiopathologiques. Parmi les modèles existants nous avons sélectionnés deux modèles murins (HOCL et uPAR-/-) récemment décrits comme étant prometteurs pour développer de nouvelles approches thérapeutiques dans la prise en charge des symptômes de la SSc.L’objectif de cette étude est d’évaluer l’iontophorèse de treprostinil comme stratégie locale pour induire une accélération de la cicatrisation d’ulcères provoqués sur modèles de SSc. Brièvement, une lésion a été réalisée par excision de peau au niveau du dos de souris. Les animaux ont été répartis aléatoirement dans trois groupes : « témoin », « contrôle » et « treprostinil » et les plaies ont été suivies jusqu’à cicatrisation complète.Les animaux traités par iontophorèse de treprostinil présentent une cicatrisation accélérée. Ces résultats ont été observés pour les deux modèles de SSc. L’effet le plus important a été mesuré au cours de la phase précoce de la cicatrisation.Cette étude est la première a démontré que la iontophorèse de treprostinil s’avère être une piste prometteuse dans la prise en charge thérapeutique des UD chez les patients atteints de SSc. D’autres études précliniques devront être menées pour mieux comprendre les mécanismes et une étude clinique devra confirmer ce résultat sur des patients.

The fibrillation of the tau protein occurs in many neurodegenerative diseases, including Alzheimer’s disease, and leads to the formation of amyloid fibres called neurofibrillary tangles. Using organic molecules able to mark these fibres or inhibit their formation provides an interest both in diagnosis and therapy in Alzheimer’s disease. A series of aurones was synthesized and their ability to interfere with the fibrillation process was evaluated in vitro on models of tau fibres developed in this project. This work shows that polyhydroxylated aurones are able to act both as probes and as inhibitors of the fibrillation process. The ligation of these aurones with biomolecules or their radiolabelling has also been investigated., La fibrillation anormale de la protéine tau est un phénomène présent dans de nombreuses maladies neurodégénératives, dont la maladie d’Alzheimer, et conduit à la formation de fibres amyloïdes appelées dégénérescences neurofibrillaires. L’utilisation de molécules organiques capables de marquer ces fibres ou d’inhiber leur formation revêt un intérêt à la fois diagnostic et thérapeutique dans la maladie d’Alzheimer. Une série d’aurones a été synthétisée et leur capacité à interagir et interférer avec le processus de fibrillation a été évaluée in vitro sur des modèles de fibres de tau développés ou optimisés lors de ce projet. Ce travail a permis de montrer que des aurones polyhydroxylées sont capables d’agir comme sonde et/ou comme inhibiteur du processus de fibrillation. Afin d’élargir les applications possibles des aurones, la ligation d’aurones avec des biomolécules ou encore leur radiomarquage a également été évaluée.

Resistance to chemotherapeutic agents (Multidrug Resistance or MDR) is a major hurdle for anticancer chemotherapy. Among different mechanisms involved in MDR, the overexpression of membrane proteins belonging to ABC family is the most relevant one. Among such proteins, ABCG2 and MRP1 are considered to play an important role. These transporters are able to induce a massive efflux of anticancer agents out of the cancer cells, reducing their intracellular concentration and their therapeutic potency. In order to overcome this resistance, novel modulators of ABCG2 and MRP1 were designed, synthetized and tested biologically. In this context, new derivatives of chromones as inhibitors of ABCG2 were developed in order to restore sensitivity of cancer cells to chemotherapeutic agents. In addition, molecular modelling of new pharmacophores allowed us to gather new data exploring ABCG2-ligand interactions. New modulators of MRP1, derivatives of flavonoids, are able to induce a massive efflux of intracellular glutathione that is mediated by the protein, without being transported and causing selective apoptosis of cancer cells overexpressing MRP1., La résistance à de multiples drogues anticancéreuses (Multidrug Resistance ou MDR) est actuellement un problème majeur dans le cas de nombreuses chimiothérapies. Parmi les mécanismes à l'origine de la MDR, la surexpression de protéines membranaires de type ABC est le plus étudié. Les deux protéines ABCG2 et MRP1 sont parmi les protéines membranaires impliquées. Ces transporteurs sont capables d'induire un efflux massif des agents anticancéreux hors des cellules cancéreuses, réduisant ainsi leur concentration intracellulaire et donc leur efficacité thérapeutique. Afin de contrecarrer cette chimiorésistance, notre objectif s'est concentré sur le développement de nouveaux modulateurs d'ABCG2 et de MRP1. Dans ce cadre, de nouveaux inhibiteurs d'ABCG2, dérivés de chromones, ont été conçus afin de restaurer la sensibilité des cellules cancéreuses aux agents anticancéreux. De plus, la modélisation de modèles pharmacophores nous a permis d'obtenir de nouvelles informations quant aux interactions ABCG2-ligands. Les nouveaux modulateurs de MRP1, dérivés de flavonoïdes, sont capables quant à eux d'induire un efflux massif de glutathion cellulaire via MRP1, sans être transportés eux même, entraînant l'apoptose sélective des cellules cancéreuses surexprimant le transporteur.

Used in traditional medicine for centuries, copaiba oleoresin, is a resinous fluid directly extracted by drilling the Copaifera tree trunk, which grows in all tropical areas of Latin America and West Africa. It has many pharmacological properties such as being anti-inflammatory, immunomodulating, wound healing, cancer, gastroprotective. This oleoresin is chemically composed mainly of sesquiterpenes such as β-caryophyllene which is the dominant compound, and some diterpenes. After GC-MS characterization of commercial copaiba oleoresin from Brazil, the oleoresin was tested free, micro-encapsulated or incorporated in plastic films. Antibacterial tests on solid and liquid media showed antibacterial properties of copaiba oleoresin on gram-positive bacterium, Bacillus subtilis. These properties were retained when the oleoresin is microencapsulated, incorporated or coated on plastic films. Because of its pharmacological properties, Copaiba oleoresin could be used in different areas as therapeutic (e.g. to treat leishmaniasis, psoriasis) or as preservative in cosmetics or active packaging.; Utilisée dans la médecine traditionnelle depuis plusieurs siècles, l’oléorésine de copaïba, est un fluide résineux directement extrait par forage du tronc de l’arbre Copaifera qui pousse dans l’ensemble des zones tropicales d'Amérique Latine et d’Afrique de l'Ouest. Elle présente de nombreuses propriétés pharmacologiques comme anti-inflammatoires, immunomodulatrices, cicatrisantes, anticancéreuses, gastroprotectrices. Cette oléorésine est chimiquement composée en majorité de sesquiterpènes comme le β-caryophyllène qui est le composé dominant, et de quelques diterpènes. Après la caractérisation par GC-MS d’une oléorésine de copaïba commerciale venant du Brésil, l’oléorésine a été étudiée sous forme libre ou micro-encapsulée sur des films plastiques. Des tests antibactériens sur gélose et en milieu liquide ont mis en évidence des propriétés antibactériennes de l’oléorésine de copaïba sur une bactérie gram positif Bacillus subtilis. Ses propriétés sont bien conservées lorsqu’elle est micro-encapsulée, incorporée ou enduite sur des films plastiques. L’oléorésine de copaïba pourrait donc être utilisée dans des nombreux domaines, aussi bien thérapeutiques (pour traiter par exemple la leishmaniose et le psoriasis), qu’en tant que conservateur dans les cosmétiques ou les emballages actifs.

Aurones, a subclass of flavonoids, present a favorable pharmacological profile and a wide, promising spectrum of biological activites. During this work, we used this potential for the modulation of two major therapeutic targets. Firstly, since several hepatitis C virus protease NS3/4A inhibitors were recently marketed, the inhibition of the polymerase NS5B is now the focus of research efforts in the fight against HCV. The use of aurones against the HCV polymerase is here reported for the first time. Four generations of compounds were synthesized and evaluated, and several bioactive derivatives were found, including some natural products, with an IC50 below 5 μM. Furthermore, additional investigations regarding inhibitor – receptor interactions allowed to identify the aurones binding site, which is Thumb Site I. Secondly, although the modulation of tyrosinase in a therapeutic aim remains a matter of discussion, a number of studies considers this enzyme as a potential target for future treatments against some hardly curable diseases, such as cancer or Parkinson's disease. During this work, aurones showed a great versatility toward tyrosinase. According to their substitution pattern, the compounds embraced very different behaviours, i.e. alternative substrate, hyperbolic activator or mixed inhibitor behaviour. However a consistent model was proposed, which gathers and explains all of these behaviours. During this study, a large number of widely substituted or modified aurone derivatives were prepared, according to structure-dependant adaptative synthetic methods.; Les aurones, qui constituent une sous-classe des flavonoïdes, présentent un profil pharmacologique et un spectre d'activités biologiques prometteurs. Au cours de ce travail, nous avons mis à profit ce potentiel pour la modulation de deux cibles thérapeutiques majeures. En premier lieu, depuis la mise sur le marché d'inhibiteurs de la protéase NS3/4A, l'inhibition de la polymérase NS5B du virus de l'hépatite C représente un enjeu primordial dans la lutte contre cette maladie. L'utilisation des aurones contre cette polymérase trouve ici ses premiers développements. L'évaluation de quatre générations de composés a mené à l'identification de plusieurs dérivés actifs, dont certains produits naturels, présentant un IC50 inférieur à 5 μM. L'étude des interactions ligand – récepteur a en outre permis de déterminer que les aurones se fixent probablement sur le site « Thumb I ». En second lieu, si la modulation de la tyrosinase dans un cadre thérapeutique reste actuellement hypothétique, de nombreuses études voient en cette enzyme une cible pour le traitement futur de pathologies difficilement curables, comme le cancer ou la maladie de Parkinson. Les aurones ont fait preuve lors de ce travail d'une grande versatilité face à la tyrosinase, adoptant au gré des substitutions des comportements très différents de substrat alternatif, d'activateur hyperbolique ou d'inhibiteur mixte. Un modèle cohérent a cependant été proposé, qui regroupe et explique ces comportements. Au cours de ce travail, de nombreux dérivés d'aurone diversement substitués ou modifiés ont été préparés, par le biais de méthodes de synthèse adaptées à la structure de chaque produit formé.

Aurones, a subclass of flavonoids, present a favorable pharmacological profile and a wide, promising spectrum of biological activites. During this work, we used this potential for the modulation of two major therapeutic targets. Firstly, since several hepatitis C virus protease NS3/4A inhibitors were recently marketed, the inhibition of the polymerase NS5B is now the focus of research efforts in the fight against HCV. The use of aurones against the HCV polymerase is here reported for the first time. Four generations of compounds were synthesized and evaluated, and several bioactive derivatives were found, including some natural products, with an IC50 below 5 μM. Furthermore, additional investigations regarding inhibitor – receptor interactions allowed to identify the aurones binding site, which is Thumb Site I. Secondly, although the modulation of tyrosinase in a therapeutic aim remains a matter of discussion, a number of studies considers this enzyme as a potential target for future treatments against some hardly curable diseases, such as cancer or Parkinson's disease. During this work, aurones showed a great versatility toward tyrosinase. According to their substitution pattern, the compounds embraced very different behaviours, i.e. alternative substrate, hyperbolic activator or mixed inhibitor behaviour. However a consistent model was proposed, which gathers and explains all of these behaviours. During this study, a large number of widely substituted or modified aurone derivatives were prepared, according to structure-dependant adaptative synthetic methods., Les aurones, qui constituent une sous-classe des flavonoïdes, présentent un profil pharmacologique et un spectre d'activités biologiques prometteurs. Au cours de ce travail, nous avons mis à profit ce potentiel pour la modulation de deux cibles thérapeutiques majeures. En premier lieu, depuis la mise sur le marché d'inhibiteurs de la protéase NS3/4A, l'inhibition de la polymérase NS5B du virus de l'hépatite C représente un enjeu primordial dans la lutte contre cette maladie. L'utilisation des aurones contre cette polymérase trouve ici ses premiers développements. L'évaluation de quatre générations de composés a mené à l'identification de plusieurs dérivés actifs, dont certains produits naturels, présentant un IC50 inférieur à 5 μM. L'étude des interactions ligand – récepteur a en outre permis de déterminer que les aurones se fixent probablement sur le site « Thumb I ». En second lieu, si la modulation de la tyrosinase dans un cadre thérapeutique reste actuellement hypothétique, de nombreuses études voient en cette enzyme une cible pour le traitement futur de pathologies difficilement curables, comme le cancer ou la maladie de Parkinson. Les aurones ont fait preuve lors de ce travail d'une grande versatilité face à la tyrosinase, adoptant au gré des substitutions des comportements très différents de substrat alternatif, d'activateur hyperbolique ou d'inhibiteur mixte. Un modèle cohérent a cependant été proposé, qui regroupe et explique ces comportements. Au cours de ce travail, de nombreux dérivés d'aurone diversement substitués ou modifiés ont été préparés, par le biais de méthodes de synthèse adaptées à la structure de chaque produit formé.

Resistance to chemotherapeutic agents (Multidrug Resistance or MDR) is characterized by the overexpression of membrane ABC proteins, such as MRP1 and ABCG2. These transporters decrease intracellular concentrations of chemotherapeutic agents by increasing their efflux from the cancer cell. In order to find effective modulators of drug resistance, we have designed, synthesized and investigated MRP1 activators and ABCG2 inhibitors. We designed and synthesized new derivatives of flavonoids and verapamil as activators of MRP1. These activators are capable of inducing a rapid and massive efflux of intracellular glutathione via MRP1 and causing cells death by apoptosis. We have also designed and synthesized new compounds, derivatives of chromone, as selective inhibitors of ABCG2, to restore sensitivity of cancer cells to chemotherapeutic agents. The biological evaluation of investigated compounds enabled us to identify new activators of MRP1 as well as potent and selective inhibitors of ABCG2. Keywords: MRP1, ABCG2, flavonoids, verapamil analogs, chromone, inhibitors, activators, La résistance aux agents chimiothérapeutiques (Multidrug Resistance ou MDR) est caractérisée par la surexpression de différentes protéines membranaires de type ABC, parmi lesquelles, MRP1 et ABCG2 sont largement impliquées. Ces transporteurs diminuent les concentrations intracellulaires des agents chimiothérapeutiques en augmentant leur efflux de la cellule cancéreuse. Dans le but de contrecarrer cette chimiorésistance, nous avons conçu, synthétisé et étudié des activateurs de MRP1 et des inhibiteurs d'ABCG2. Les activateurs de MRP1 sont des dérivés de flavonoïdes et de vérapamil. Ces activateurs sont capables d'induire un efflux rapide et massif de glutathion cellulaire via MRP1 qui entraîne l'apoptose des cellules cancéreuses. Nous avons également conçu et synthétisé de nouveaux composés, dérivés de chromone, inhibiteurs sélectifs d'ABCG2, afin de restaurer la sensibilité des cellules cancéreuses aux agents chimiothérapeutiques. Mots clés : MRP1, ABCG2, flavonoïdes, analogues de vérapamil, chromones, inhibiteurs, activateurs

The aim of this work is to present molecular modeling methods applied to molecular recognition analysis and new drug design by two approaches: structure base design or ligand based design.In the first part, knowledge-based homology modeling of protein structure by Blundell, implemented in Sybyl-Composer, and docking method by Morris, implemented in Autodock3, are described and applied to study molecular recognition mechanisms of a polysaccharidic antigen of Shigella flexneri 5a and peptides mimics by human protective antibody : IgA I3.In the second part, statistical analysis of CoMSIA molecular interaction field descriptors and validation methods of resulting models are described and used to build three dimensional quantitative structure activity relationship models of 27 flavonoïd compounds modulators of ABCG2 transporter (BCRP), a protein involved in multidrug resistance capability developed by tumour cells. Designing new bioactive drugs was possible using the most statistically reliable and performing models built., L'objet de ce travail est de présenter de facon détaillée des méthodes de modélisation appliquées à l'analyse des mécanismes de reconnaissance moléculaire et à la conception de nouveaux composés bioactifs selon deux approches : la conception basée sur la structure des récepteurs et la conception basée sur la structure des ligands.Dans le cadre du premier axe, la méthode de construction de protéines par homologie de Blundell, implémentée dans le module COMPOSER de SYBYL et la méthode d'amarrage de Morris, implémentée dans le logiciel AUTODOCK3, sont décrites et appliquées à la modélisation et à l'étude des mécanismes de reconnaissance moléculaire d'un antigène polysaccharidique de la bactérie Shigella flexneri 5a et de mimes peptidiques immunogènes par un anticorps humain protecteur : IgA I3.Dans le cadre du second axe, l'analyse statistique de descripteurs de champs d'interaction moléculaire de type CoMSIA et les méthodes de validation des modèles qu'elle génère sont présentées et appliquées à l'étude des relations structure activité en trois dimensions d'une série de 27 analogues de flavonoïdes modulateurs du transporteur ABCG2 (BCRP), impliqué dans le mécanisme de résistance multiple aux anticancéreux que développent les cellules tumorales. La production de modèles statistiquement fiables et performants a permis de concevoir de nouveaux composés biologiquement actifs.