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Aim: The synthesis of a novel class of compounds bearing a coumarin entity was targeted. They are either iminocoumarins or characterized by the presence of a pyridone ring fused within the iminocoumarin scaffold. Methods & results: The targeted compounds were synthesized through a short method, thanks to microwave activation. The study evaluated the antifungal activity of 13 newly synthesized compounds against a new fungal strain of Aspergillus niger. The most active compound showed activity comparable to the widely used reference drug, amphotericin B. Conclusion: The conditions and the ease of synthesis warrant high potential of the method for diversity-oriented synthesis, very useful within the drug discovery area.

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Purpose: Tamoxifen (Tam) is the most prescribed hormonal agent for treatment of estrogen receptor α (ERα)-positive breast cancer patients. Using microarray analysis, we observed that metastatic breast tumors resistant to Tam therapy had elevated levels of Dicer.Experimental Design: We overexpressed Dicer in ERα-positive MCF-7 human breast cancer cells and observed a concomitant increase in expression of the breast cancer resistance protein (BCRP). We thus hypothesized that Tam resistance associated with Dicer overexpression in ERα-positive breast cancer cells may involve BCRP. We analyzed BCRP function in Dicer-overexpressing cells using growth in soft agar and mammosphere formation and evaluated intracellular Tam efflux.Results: In the presence of Tam, Dicer-overexpressing cells formed resistant colonies in soft agar, and treatment with BCRP inhibitors restored Tam sensitivity. Tumor xenograft studies confirmed that Dicer-overexpressing cells were resistant to Tam in vivo. Tumors and distant metastases could be initiated with as few as five mammosphere cells from both vector and Dicer-overexpressing cells, indicating that the mammosphere assay selected for cells with enhanced tumor-initiating and metastatic capacity. Dicer-overexpressing cells with elevated levels of BCRP effluxed Tam more efficiently than control cells, and BCRP inhibitors were able to inhibit efflux.Conclusion: Dicer-overexpressing breast cancer cells enriched for cells with enhanced BCRP function. We hypothesize that it is this population which may be involved in the emergence of Tam-resistant growth. BCRP may be a novel clinical target to restore Tam sensitivity. Clin Cancer Res; 17(20); 6510–21. ©2011 AACR.

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International audience; In human, Tyrosinase enzyme (TyH) is involved in the key steps of protective pigments biosynthesis (in skin, eyes and hair). The use of molecules targeting its binuclear copper active site represents a relevant strategy to regulate TyH activities. In this work, we targeted 2-Hydroxypyridine-N-oxide analogs (HOPNO, an established chelating group for the tyrosinase dicopper active site) with the aim to combine effects induced by combination with a reference inhibitor (kojic acid) or natural substrate (tyrosine). The HOPNO-MeOH (3) and the racemic amino acid HOPNO-AA compounds (11) were tested on purified tyrosinases from different sources (fungal, bacterial and human) for comparison purposes. Both 2 compounds have more potent inhibitory activities than the parent HOPNO moiety and display strictly competitive inhibition constant, in particular with human tyrosinase. Furthermore, 11 appears to be the most active on the B16-F1 mammal melanoma cells. The investigations were completed by stereospecificity analysis. Racemic mixture of the fully protected amino acid 10 was separated by chiral HPLC into the corresponding enantiomers. Assignment of the absolute configuration of the deprotected compounds was completed, based on X-ray crystallography. The inhibition activities on melanin production were tested on lysates and whole human melanoma MNT-1 cells. Results showed significant enhancement of the inhibitory effects for the (S) enantiomer compared to the (R) enantiomer. Computational studies led to an explanation of this difference of activity based for both enantiomers on the respective position of the amino acid group versus the HOPNO plane.

Helianthemum nummularium is a European shrub growing at high altitude where it copes with a high level of stress. It was found to be overexpressed in ungulates diets compared to more abundant surrounding plants. These elements combined with the fact that H. nummularium from the Alps has never been investigated prompted us to study the phytochemical composition of its aerial parts. The analysis of the polar extract allowed for the isolation of eight compounds: p-hydroxybenzoic acid, tiliroside, kaempferol, astragalin, quercetin, plantainoside B, quercetin-3-O-glucoside, and quercetin-3-O-glucuronide. We investigated the effect of the polar extract and isolated compounds on nuclear factor erythroid 2-related factor 2 transcription factor, which regulates the expression of a wide variety of cytoprotective genes. We found that the ethanolic extract activates the expression of nuclear factor erythroid 2-related factor 2 in a dose-dependent manner, whereas the pure compounds were much less active. The activation of the nuclear factor erythroid 2-related factor 2 pathway by the plant extract could pave the way for studies to promote healthy aging through protection of cells against oxidative stress. Moreover, the isolated compounds could be investigated alone or in combination in the perspective of making the link between the ungulateʼs preference for this plant and possible use of it for self-medication.

Multidrug ABC transporters translocate drugs across membranes by a mechanism for which the molecular features of drug release are so far unknown. Here, we resolved three ATP-Mg 2+ –bound outward-facing conformations of the Bacillus subtilis (homodimeric) BmrA by x-ray crystallography and single-particle cryo–electron microscopy (EM) in detergent solution, one of them with rhodamine 6G (R6G), a substrate exported by BmrA when overexpressed in B. subtilis . Two R6G molecules bind to the drug-binding cavity at the level of the outer leaflet, between transmembrane (TM) helices 1–2 of one monomer and TM5′–6′ of the other. They induce a rearrangement of TM1–2, highlighting a local flexibility that we confirmed by hydrogen/deuterium exchange and molecular dynamics simulations. In the absence of R6G, simulations show a fast postrelease occlusion of the cavity driven by hydrophobicity, while when present, R6G can move within the cavity, maintaining it open.

Diversity-Oriented Synthesis (DOS) represents a strategy to obtain molecule libraries with diverse structural features starting from one common compound in limited steps of synthesis. During the last two decades, DOS has become an unmissable strategy in organic synthesis and is fully integrated in various drug discovery processes. On the other hand, natural products with multiple relevant pharmacological properties have been extensively investigated as scaffolds for ligand-based drug design. In this article, we report the amino dimethoxyacetophenones that can be easily synthesized and scaled up from the commercially available 3,5-dimethoxyaniline as valuable starting blocks for the DOS of natural product analogs. More focus is placed on the synthesis of analogs of flavones, coumarins, azocanes, chalcones, and aurones, which are frequently studied as lead compounds in drug discovery.

The iron-dependent, non-apoptotic cell death, known as ferroptosis is an emerging strategy for the development of anticancer drugs. RSL3 was identified as an activator of ferroptosis through the inhibition of the glutathione peroxidase 4 (GPX4) which plays a crucial role in the cellular lipid oxidative stress. RSL3 is characterized by the presence of an electrophilic chloroacetyl moiety, namely warhead which covalently bonds to the catalytic and nucleophilic selenocysteine residue (Sec46) of GPX4. Like the major ferroptosis inducers, RSL3 suffers from lack of selectivity toward tumor cells. In this study, we report the first synthesis of an antibody-drug conjugate (ADC) containing RSL3 fragment and trastuzumab with the aim to deliver the agent selectively to tumors. The synthesis uses a judiciously chosen strategy to preserve the vital but fragile warhead. Full characterization of the ADC was accomplished, demonstrating the generation of a homogeneous DAR 8 conjugate. The robustness of the synthesis was successfully applied to another ADC associating the anti-CD74 mAb milatuzumab. The ADC induces ferroptotic cell death through reactive oxygen species accumulation and increases the activity of doxorubicin. The ADC associating trastuzumab and RSL3 may therefore offer potential applications in vectorized therapy alone or in combination with conventional chemotherapies.

Seeds of Crotalaria cleomifolia (Fabaceae) are consumed in Madagascar in preparation of popular beverages. The investigation of extracts from the seeds of this species revealed the presence of high amounts of alkaloids from which two pyrrolizidine-derived alkaloids were isolated. One of them was fully characterized by spectroscopic and spectrometric methods, which was found to be usaramine. Owing to the high toxicity of these alkaloids, issuing a strong warning among populations consuming the seeds of Crotalaria cleomifolia must be considered.

Tauopathies, such as Alzheimer's disease, have been the subject of several hypotheses regarding the way to treat them. Hyperphosphorylation of tau protein leading to its aggregation is widely recognized as a key step in the development of these diseases resulting in neuronal dysfunction. The AcPHF6 model of tau that includes the shorter critical fragment involved in the protein aggregation was used in vitro to identify new potential inhibitors. Following a previous study on aurone derivatives, we herein compare this polyphenol family to a very close one, the benzylidene-2,3-dihydro-1H-inden-1-one (also named indanone). The structure activity relationship studies bring to light the importance of the hydroxylation pattern in both series: the more hydroxylated, the more active. In addition, the three-dimensional shape of the molecules is involved in their interaction mode with their target, thus defining their role either as inhibitors of fiber elongation or as fiber-binding molecules. Indanone 13a was identified as a promising inhibitor: its activity was confirmed by circular dichroism and atomic force microscopy studies.

International audience; Tyrosinase enzymes (Tys) are involved in the key steps of melanin (protective pigments) biosynthesis and molecules targeting the binuclear copper active site on tyrosinases represent a relevant strategy to regulate enzyme activities. In this work, we studied the possible synergic effect generated by combination of known inhibitors. For this, derivatives containing kojic acid (KA) and 2-Hydroxypyridine-N-oxide (HOPNO) combined with a thiosemicarbazone (TSC) moiety were synthetized. Their inhibition activities were evaluated on purified tyrosinases from different sources (mushroom, bacterial and human) as well as on melanin production by lysates from human melanoma MNT-1 cell line. Results showed significant enhancement of the inhibitory effects compared to the parent compounds, in particular for HOPNO-TSC. In order to elucidate the interaction mode with the dicopper(II) active site, we investigated the binding studies towards a tyrosinase bio-inspired model of the dicopper(II) center. The structure of the isolated adduct between one ditopic inhibitor (KA-TSC) and the model complex reveals that the binding to a dicopper center can occur with both chelating sites. Computational studies on model complexes and docking studies on enzymes led to the identification of KA and HOPNO moieties as interacting groups with the dicopper active site.

Background: The aim of the present work was to set-up compounds that are able to act simultaneously as antimalarial and antioxidants. Trolox, a known antioxidant was chosen as a core structure to ensure the antioxidant activity and contribute to antiplasmodial effect. Results: Ten compounds were prepared in one step and evaluated on chloroquino-sensitive (3D7) and chloroquino-resistant (FcB1) strains of Plasmodium falciparum. The most active compound (3d) shows antiplasmodial activity in the range of chloroquine against chloroquino-sensitive and chloroquino-resistant P. falciparum strain. The antioxidant activity of (3d) was conducted through four tests and was found to be more potent than trolox itself and L-ascorbic acid. Conclusion: Compound (3d) can be considered as an excellent lead molecule for further in vivo studies. This study paves the way for building large chemical libraries to be investigated in the field of malaria., info:eu-repo/semantics/published

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 resistance of tumors against anticancer drugs is a major impediment for chemotherapy. Tumors often develop multidrug resistance as a result of the cellular efflux of chemotherapeutic agents by ABC transporters such as P-glycoprotein (ABCB1/P-gp), Multidrug Resistance Protein 1 (ABCC1/MRP1), or Breast Cancer Resistance Protein (ABCG2/BCRP). By screening a chemolibrary comprising 140 compounds, we identified a set of naturally occurring aurones inducing higher cytotoxicity against P-gp-overexpressing multidrug-resistant (MDR) cells versus sensitive (parental, non-P-gp-overexpressing) cells. Follow-up studies conducted with the P-gp inhibitor tariquidar indicated that the MDR-selective toxicity of azaaurones is not mediated by P-gp. Azaaurone analogs possessing pronounced effects were then designed and synthesized. The knowledge gained from structure&ndash, activity relationships will pave the way for the design of a new class of anticancer drugs selectively targeting multidrug-resistant cancer cells.

International audience; Aim: Resistance against antifungals used for Candida albicans (Ca) treatment is mediated by two multidrug transporters, Mdr1p and Cdr1p, which are of enormous interest to the development of modulators combined with antifungals.Experimental: A set of chalcones was synthesized by condensation reactions in laboratory and was then subject to biological assays to evaluate the effects on different yeast strains.Results: The obtained chalcones were screened using the checkerboard liquid chemosensitization assays. Compounds 4, 10, 12 and 18, when combined with fluconazole, triggered strong sensitization on yeast strains overexpressing CaMdr1p and CaCdr1p, whereas displaying no cytotoxicity by themselves towards control strains and transporter-expressing yeast cells. In the Nile Red transport assay, the two most active compounds, 12 and 18 showed moderate-to-high accumulation of Nile Red with different behaviors towards the two transporters.Conclusion: Chalcones are promising drug candidates for further development to make azole antifungals active again.

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.

Recent years have witnessed a considerable renewed interest for the uncommon flavonoid class of aurones. The characterization of two major biosynthetic machineries involved in their biosynthesis in flowers has encouraged the revival of phytochemical studies and identification of original structures, a process started almost seventy-five years ago. This review draws up an exhaustive map of natural occurrences of aurones their biosynthetic pathways and roles, with the aim to link their original structural properties among flavonoids to their place in evolution and the selective advantages they bring to some of the most advanced taxa in the plant kingdom.

International audience; A set of variously substituted aurones was synthesized and evaluated against Methicillin-Resistant S. aureus (MRSA) and P. aeruginosa. Several analogues were found active against MRSA, but no effect was recorded against P. aeruginosa. Compounds 27, 30 and 33 showed low cytotoxicity, and were tested against a full range of bacterial (Gram-positive and Gram-negative) and fungal species, including resistant strains. These aurones displayed a selective inhibition of Gram-positive bacteria with excellent Therapeutic Index values, while showing no significant action on several Gram-negative strains, H. pylori and V. alginolyticus being the only susceptible strains among the Gram-negative bacteria tested. A per-meabilization assay showed that the antibacterial activity of at least some of the aurones could be linked to alterations of the bacterial membrane. Overall, this study endorses the use of the aurone scaffold for the development of new potent and selective antibacterial agents.

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.

International audience; Phosphatidylinositide 3-kinases (PI3Ks) are widely expressed enzymes involved in membrane signalization pathways. Attempts to administer inhibitors with broad activity against different isoforms have failed due to toxicity. Conversely the PI3K delta isoform is much more selectively expressed, enabling therapeutic targeting of this isoform. Of particular interest PI3K delta is expressed in human basophils and its inhibition has been shown to reduce anti-IgE induced basophil degranulation, suggesting that PI3K delta inhibitors could be useful as anti-allergy drugs. Herein, we report for the first time the activity of compounds derived from chalcone scaffolds as inhibitors of normal human basophil degranulation and identified the most active compound with anti-PI3K delta properties that was investigated in preclinical models. Compound 18, namely 1-[2-hydroxy-4,6-dimethoxy-3-(N-methylpiperidin-4-yl)pheny1]-3(2,4,6-trimethoxypheny1)-prop-2-en-1-one, was found to inhibit normal human basophil degranulation in a dose-dependent manner. In a murine model of ovalbumin-induced asthma, compound 18 was shown to reduce expiratory pressure while its impact on the inflammatory infiltrate in alveolar lavage and total lung was dependent on the route of administration. In a DNFB-induced model of atopic dermatitis compound 18 administered systemically proved to be as potent as topical betamethasone. These results support the anti-atopic and allergic properties of the title compound and warrant further clinical development. (C) 2018 Elsevier Masson SAS

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.

Tramadol, previously only known as a synthetic analgesic, has now been found in the bark and wood of roots of the African medicinal tree Nauclea latifolia . At present, no direct evidence is available as to the biosynthetic pathway of its unusual skeleton. To provide guidance as to possible biosynthetic precursors, we have adopted a novel approach of retro-biosynthesis based on the position-specific distribution of isotopes in the extracted compound. Relatively recent developments in isotope ratio monitoring by 13 C NMR spectrometry make possible the measurement of the nonstatistical position-specific natural abundance distribution of 13 C (δ 13 C i ) within the molecule with better than 1‰ precision. Very substantial variation in the 13 C positional distribution is found: between δ 13 C i = −11 and −53‰. Distribution is not random and it is argued that the pattern observed can substantially be interpreted in relation to known causes of isotope fractionation in natural products. Thus, a plausible biosynthetic scheme based on sound biosynthetic principals of precursor–substrate relationships can be proposed. In addition, data obtained from the 18 O/ 16 O ratios in the oxygen atoms of the compound add support to the deductions made from the carbon isotope analysis. This paper shows how the use of 13 C NMR at natural abundance can help with proposing a biosynthetic route to compounds newly found in nature or those difficult to tackle by conventional means.

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.

Two new series of ring-opened analogues of cromakalim bearing sulfonylurea moieties (series A: with N-unmethylated sulfonylureas, series B: with N-methylated sulfonylureas) were synthesized and tested as relaxants of vascular and respiratory smooth muscles (rat aorta and trachea, respectively). Ex vivo biological evaluations indicated that the most active compounds, belonging to series B, displayed a marked vasorelaxant activity on endothelium-intact aortic rings and the trachea. A majority of series B compounds exhibited a higher vasorelaxant activity (EC50 57 μM for all, and EC50 > 200 μM for a majority of them), but some of them showed an interesting relaxing effect on trachea (i.e. A15 and A33, EC50 = 30 μM). The most potent compounds of both series, i.e. A15, A33 and B16, tested on aortic rings in the presence of glibenclamide or 80 mM KCl, suggested that they acted as voltage-gated Ca2+ channel blockers, like verapamil, instead of being ATP-potassium channel activators, as is cromakalim, the parent molecule. Further investigations on cultured vascular smooth muscle cells showed a strong stimulating effect on elastin synthesis, especially compound B16, which was more active at 20 μM than diazoxide, a reference ATP-sensitive potassium channel activator. Taken together, our results show that the N-methylation of the sulfonylurea moieties of ring-opened cromakalim analogues led to new compounds blocking calcium-gated channels, which had a major impact on the arterial and tracheal activities as well as selectivity.

Background The multicomponent primary active ATP-binding cassette transporter Cdr1p in the structure of the pathogenic yeast Candida albicans is among the culprits of antifungal agent resistance reported in recent decades. So far, various potential novel inhibitors/ modulators of this protein have been purified, synthesized, and biologically tested, with results showing their ability to effectively reverse CaCdr1p-mediated drug resistance phenomenon. These compounds are of diverse origins, possess non-identical structural features and adopt different mechanisms of action. Method A structured search of chemical features and mechanisms of studied modulators of CaCdr1p was carried out using both original research publications and review articles. The nature of possible inhibitory mechanisms against the pump was analyzed in relation to the structure and the activity of the transporter. A process of summarizing modulatory spectra of the listed compounds against 2 other efflux pumps of Candida albicans namely Cdr2p and Mdr1p was also conducted, during which selective inhibitors of Cdr1p were revealed. Results In this article, 6 possible mechanisms with which a molecule can manifest their activity against the efflux pump are described, and a list of nearly 50 CaCdr1p modulators found in literatures along with their respective mechanism(s) (if already identified) is provided, summarizing the results obtained so far in the search of new inhibitors of the drug extrusion transporter that can enhance the potency of commonly used antifungal agents. A table of inhibitory spectra of the listed compounds against Cdr1p, Cdr2p and Mdr1p is also given, with several selective modulators of Cdr1p finally indicated. Conclusion The findings of this review contribute to future studies regarding CaCdr1p and its modulators by summarizing the results obtained so far on this emerging issue of health sciences. Further research concerning novel compounds capable of inhibiting Cdr1p needs to be carried out in hopes of completing the lists provided in this article.

Ethnopharmacoalogical relevance The genus Nauclea in Africa comprises seven species. Among them, N. latifolia , N. diderrichii and N. pobeguinii are widely used by the local population in traditional remedies. Preparation from various parts of plants (e.g. roots, bark, leaves) are indicated by traditional healers for a wide range of diseases including malaria, pain, digestive ailments or metabolic diseases. Materials and methods A literature search was conducted on African species of the genus Nauclea using scientific databases such as Google Scholar, Pubmed or SciFinder. Every document of ethnopharmacological, phytochemical or pharmacological relevance and written in English or French were analyzed. Results and discussion The Nauclea genus is used as ethnomedicine all along sub-Saharan Africa. Several local populations consider Nauclea species as a major source of remedies for malaria. In this regard, two improved traditional medicines are currently under development using extracts from N. latifolia and N. pobeguinii . Concerning the chemical composition of the Nauclea genus, indoloquinolizidines alkaloids could be considered as the major class of compounds as they are reported in every analyzed Nauclea species, with numerous structures identified. Based on traditional indications a considerable amount of pharmacological studies were conducted to ensure activity and attempt to link them to the presence of particular compounds in plant extracts. Conclusion Many experimental studies using plant extracts of the African species of the genus Nauclea validate traditional indications (e.g. malaria and pain). However, bioactive compounds are rarely identified and therefore, there is a clear need for further evaluations as well as for toxicity experiments. The sustainability of these plants, especially of N. diderrichii , a threatened species, should be kept in mind to adapt local uses and preparation modes of traditional remedies.

With the aim to develop effective and selective human tyrosinase inhibitors, we investigated aurone derivatives whose B-ring was replaced by a non-oxidizable 2-hydroxypyridine-N-oxide (HOPNO) moiety. These aurones were synthesized and evaluated as inhibitors of purified human tyrosinase. Excellent inhibition activity was revealed and rationalized by theoretical calculations. The aurone backbone was especially found to play a crucial role, as the HOPNO moiety alone provided very modest activity on human tyrosinase. Furthermore, the in vitro activity was confirmed by measuring the melanogenesis suppression ability of the compounds in melanoma cell lysates and whole cells. Our study reveals that HOPNO-embedded 6-hydroxyaurone is to date the most effective inhibitor of isolated human tyrosinase. Owing to its low toxicity and its high inhibition activity, it could represent a milestone on the path toward new valuable agents in dermocosmetics, as well as in medical fields where it was recently suggested that ty...

The multidrug resistance protein 1 (MRP1) is involved in multidrug resistance of cancer cells by mediating drug efflux out of cells, often in co-transport with glutathione (GSH). GSH efflux mediated by MRP1 can be stimulated by verapamil. In cells overexpressing MRP1, we have previously shown that verapamil induced a huge intracellular GSH depletion which triggered apoptosis of the cells. That phenomenon takes place in the more global anticancer strategy called "collateral sensitivity" and could be exploited to eradicate some chemoresistant cancer cells. Seeking alternative compounds to verapamil, we screened a library of natural flavonoids and synthetic derivatives. A large number of these compounds stimulate MRP1-mediated GSH efflux and the most active ones have been evaluated for their cytotoxic effect on MRP1-overexpressing cells versus parental cells. Interestingly, some are highly and selectively cytotoxic for MRP1-cells, leading them to apoptosis. However, some others do not exhibit any cytotoxicity while promoting a strong GSH efflux, indicating that GSH efflux is necessary but not sufficient for MRP1-cells apoptosis. In support to this hypothesis, structure activity relationships show that the absence of a hydroxyl group at position 3 of the flavonoid C ring is an absolute requirement for induction of MRP1-cells death, but is not for GSH efflux stimulation. Chrysin (compound 8) and its derivatives, compounds 11 and 22, exhibit a high selectivity toward MRP1-cells with a IC₅₀ value of 4.1 μM for compound 11 and 4.9 μM for chrysin and compound 22, making them among the best described selective killer compounds of multidrug ABC transporter-overexpressing cells.

With the aim to develop anticancer agents acting selectively against resistant tumor cells, we investigated ferrocene embedded into chalcone, aurone and flavone skeletons. These compounds were conceived and then investigated based on the concept of collateral sensitivity, where the target is the Achilles Heel of cancer cells overexpressing the multidrug ABC transporter MRP1. The 14 synthesized compounds were evaluated for their ability to induce efflux of glutathione (GSH) from tumor cells overexpressing MRP1. When tested at 5 and 20 μM, at least one compound from each series was found to be a highly inducer of GSH efflux. The different compounds inducing a high efflux of GSH were evaluated on both sensitive and resistant cell lines, and two of them, belonging to the flavones class were found to be more cytotoxic on resistant cancer cells, with the best selectivity ratio >9.1. Our results bring chemical and biological bases for further optimization.

Waltheria indica is used in traditional pharmacopeia in Burkina Faso for the treatment of asthma and conditions of inflammation. To evaluate its pharmacological properties and isolate the active compounds, a study through a bioguided phytochemical approach was conducted. This search was guided by a two-level investigation. First, we evaluated the impact of various fractions on the activity of enzymes involved in smooth muscle contraction (PDE4A1α) and inflammatory processes (PLA2 , 5-LOX). Second, we investigated the inhibitory effect of fractions on isolated rat trachea. The initial hydroalcoholic extract from roots of W. indica (HA), n-hexane fraction (F1 ), dichloromethane fraction (F2 ), ethyl acetate fraction (F3 ), residuary fraction (F4 ) reduced enzyme activity of PDE4A1α (inhibition of 22-42% at 50 μg/mL), 5-LOX (60-80% at 10 μg/mL), and PLA2 (42-94% at 100 μg/mL). On isolated rat trachea, only HA, F3 , and fractions obtained from F3 by chromatography on silica gel column, using dichloromethane/methanol, dose dependently inhibited contraction induced by acetylcholine. IC50 was 1051 μg/mL for HA and comprised between 181 and 477 μg/mL for F3 and its fractions. The most active fractions were purified and led to the identification of (-)-epicatechin. (-)-epicatechin from W. indica dose dependently inhibited PLA2 (IC50 = 154.7 μm) and 5-LOX (IC50 = 15.8 μm). In conclusion, both inhibition of PDE4A1α, 5-LOX, and PLA2 activities and rat trachea relaxation by W. indica validate its use in traditional management of asthma and other conditions of inflammation. These effects should be, at least in part, attributed to the presence of (-)-epicatechin in roots of W. indica.

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.

With the aim to develop effective and selective human tyrosinase inhibitors, we investigated aurone derivatives whose B-ring was replaced by a non-oxidizable 2-hydroxypyridine