Search

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.

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.

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.

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.

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.

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.

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.

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.

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.

Cancer cell resistance to chemotherapy is often mediated by overexpression of P-glycoprotein, a plasma membrane ABC (ATP-binding cassette) transporter which extrudes cytotoxic drugs at the expense of ATP hydrolysis. P-glycoprotein (ABCB1, according to the human gene nomenclature committee) consists of two homologous halves each containing a transmembrane domain (TMD) involved in drug binding and efflux, and a cytosolic nucleotide-binding domain (NBD) involved in ATP binding and hydrolysis, with an overall (TMD-NBD)2 domain topology. Homologous ABC multidrug transporters, from the same ABCB family, are found in many species such as Plasmodiumfalciparum and Leishmania spp. protozoa, where they induce resistance to antiparasitic drugs. In yeasts, some ABC transporters involved in resistance to fungicides, such as Saccharomyces cerevisiae Pdr5p and Snq2p, display a different (NBD-TMD)2 domain topology and are classified in another family, ABCG. Much effort has been spent to modulate multidrug resistance in the different species by using specific inhibitors, but generally with little success due to additional cellular targets and/or extrusion of the potential inhibitors. This review shows that due to similarities in function and maybe in three-dimensional organization of the different transporters, common potential modulators have been found. An in vitro 'rational screening' was performed among the large flavonoid family using a four-step procedure: (i) direct binding to purified recombinant cytosolic NBD and/or full-length transporter, (ii) inhibition of ATP hydrolysis and energy-dependent drug interaction with transporter-enriched membranes, (iii) inhibition of cell transporter activity monitored by flow cytometry and (iv) chemosensitization of cell growth. The results indicate that prenylated flavonoids bind with high affinity, and strongly inhibit drug interaction and nucleotide hydrolysis. As such, they constitute promising potential modulators of multidrug resistance.Cancer cell resistance to chemotherapy is often mediated by overexpression of P-glycoprotein, a plasma membrane ABC (ATP-binding cassette) transporter which extrudes cytotoxic drugs at the expense of ATP hydrolysis. P-glycoprotein (ABCB1, according to the human gene nomenclature committee) consists of two homologous halves each containing a transmembrane domain (TMD) involved in drug binding and efflux, and a cytosolic nucleotide-binding domain (NBD) involved in ATP binding and hydrolysis, with an overall (TMD-NBD)2 domain topology. Homologous ABC multidrug transporters, from the same ABCB family, are found in many species such as Plasmodiumfalciparum and Leishmania spp. protozoa, where they induce resistance to antiparasitic drugs. In yeasts, some ABC transporters involved in resistance to fungicides, such as Saccharomyces cerevisiae Pdr5p and Snq2p, display a different (NBD-TMD)2 domain topology and are classified in another family, ABCG. Much effort has been spent to modulate multidrug resistance in the different species by using specific inhibitors, but generally with little success due to additional cellular targets and/or extrusion of the potential inhibitors. This review shows that due to similarities in function and maybe in three-dimensional organization of the different transporters, common potential modulators have been found. An in vitro 'rational screening' was performed among the large flavonoid family using a four-step procedure: (i) direct binding to purified recombinant cytosolic NBD and/or full-length transporter, (ii) inhibition of ATP hydrolysis and energy-dependent drug interaction with transporter-enriched membranes, (iii) inhibition of cell transporter activity monitored by flow cytometry and (iv) chemosensitization of cell growth. The results indicate that prenylated flavonoids bind with high affinity, and strongly inhibit drug interaction and nucleotide hydrolysis. As such, they constitute promising potential modulators of multidrug resistance.

Breast cancer resistance protein (BCRP/ABCG2) is one of the major transporters involved in the efflux of anticancer compounds, contributing to multidrug resistance (MDR). Inhibition of ABCG2-mediated transport is then considered a promising strategy for overcoming MDR in tumors. We recently identified a chromone derivative, namely MBL-II-141 as a selective ABCG2 inhibitor, with relevant in vivo activity. Here, we report the pharmacomodulation of MBL-II-141, with the aim of identifying key pharmacophoric elements to design more potent selective and non-toxic inhibitors. Through rational structural modifications of MBL-II-141, using simple and affordable chemistry, we obtained highly active and easily-made inhibitors of ABCG2. Among the investigated compounds, derivative 4a, was found to be 3-fold more potent than MBL-II-141. It was similarly efficient as the reference inhibitor Ko143 but with the advantage of a lower intrinsic cytotoxicity, and therefore constitutes the best ABCG2 inhibitor ever reported displaying a very high therapeutic ratio.

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.

Hepatitis C is a viral liver infection considered as the major cause of cirrhosis and hepatocellular carcinoma (HCC). Hepatitis C virus (HCV) possesses a single positive strand RNA genome encoding a polyprotein composed of approximatively 3000 amino acids. The polyprotein is cleaved at multiple sites by cellular and viral proteases to liberate structural and nonstructural (NS) proteins. NS5B, the RNA-dependent RNA polymerase (RdRp), which catalyzes the HCV RNA replication has emerged as an attractive target for the development of specifically targeted antiviral therapy for HCV (DAA, for direct-acting antivirals). In the last 10 years, a growing number of non-nucleoside compounds have been reported as RdRp inhibitors and few are undergoing clinical trials. Over the past 5 years, several reviews were published all describing potentially active molecules. To the best of our knowledge, only one review covers the structure-activity relationships.(1) In this review, we will discuss the reported non-nucleoside molecules acting as RdRp inhibitors according to their chemical class especially focusing on structure-activity relationship aspects among each class of compounds. Thereafter, we will attempt to address the global structural requirements needed for the design of specific inhibitors of RdRp.

ABCG2 plays a major role in anticancer-drug efflux and related tumor multidrug resistance. Potent and selective ABCG2 inhibitors with low cytotoxicity were investigated among a series of 44 chalcones and analogues (1,3-diarylpropenones), by evaluating their inhibitory effect on the transport of mitoxantrone, a known ABCG2 substrate. Six compounds producing complete inhibition with IC(50) values below 0.5 μM and high selectivity for ABCG2 were identified. The number and position of methoxy substituents appeared to be critical for both inhibition and cytotoxicity. The best compounds, with potent inhibition and low toxicity, contained an N-methyl-1-indolyl (compound 38) or a 6'-hydroxyl-2',4'-dimethoxy-1-phenyl (compound 27) moiety (A-ring) and two methoxy groups at positions 2 and 6 of the 3-phenyl moiety (B-ring). Methoxy substitution contributed to inhibition at positions 3 and 5, but had a negative effect at position 4. Finally, methoxy groups at positions 3, 4, and 5 of the B-ring markedly increased cytotoxicity and, therefore, should be avoided.

A series of 13 disubstituted chromones was synthesized. Two types of substituents, on each side of the scaffold, contributed to both the potency of ABCG2 inhibition and the cytotoxicity. The best compound, 5-(4-bromobenzyloxy)-2-(2-(5-methoxyindolyl)ethyl-1-carbonyl)-4H-chromen-4-one (6g), displayed high-affinity inhibition and low cytotoxicity, giving a markedly high therapeutic index. The chromone derivative specifically inhibited ABCG2 versus other multidrug ABC transporters and was not transported. It constitutes a highly promising candidate for in vivo chemosensitization of ABCG2-expressing tumors.

Multidrug-resistance protein 1 (MRP1) belongs to the ATP-binding cassette (ABC) transporter family. MRP1 mediates MDR (multidrug resistance) by causing drug efflux either by conjugation to glutathione (GSH) or by co-transport with free GSH (without covalent bonding between the drug and GSH). We recently reported that the calcium channel blocker verapamil can activate massive GSH efflux in MRP1-overexpressing cells, leading to cell death through apoptosis. However, clinical use of verapamil is hampered by its cardiotoxicity. Then, in the search for compounds that act similarly to verapamil, but without major side effects, we investigated xanthones. Herein we show that xanthones induce apoptosis among resistant cells overexpressing MRP1 similarly to the verapamil effect. Among the xanthones studied, 1,3-dihydroxy-6-methoxyxanthone was identified as the most active derivative, able to specifically kill cells transfected with human MRP1 with even greater potency than verapamil. Under the same conditions, the active xanthones have no toxic effect on control (sensitive) cells. Xanthones could therefore be considered as new potential anticancer agents for the selective treatment of MRP1-positive tumors.

Tyrosine kinase receptors (RTKs) play a crucial role in the regulation of the cell division cycle. Currently more than 50 RTKs divided into several subfamilies have been described. The inhibition of these enzymes has emerged as an important research-area. Compounds able to inhibit the activity of these enzymes are expected to display antiproliferative properties. Flavonoids are representative of various small molecules acting as RTK inhibitors. These naturally occurring compounds are able to bind to the ATP-binding site of several kinases. The most plausible current hypothesis explaining the action of these substances on kinases is that the chromenone moiety of the flavonoid acts as a mimetic of the adenine moiety of ATP, the receptor co-factor. In this review, we report recent results on the activity of natural and synthetic derivatives of flavonoids as inhibitors of RTKs. Mechanistic aspects, the therapeutic usefulness, and the potential clinical use are discussed.

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.

In this study, we report for the first time the presence of alkaloids belonging to β-carboline type in the pods of the endemic Albizia polyphylla from Madagascar. Three major alkaloids were isolated and structurally identified as: 1-methyl-β-carboline, (+)-(R)-1-methyl-1,2,3,4-tetrahydro-β-carboline and (–)-(S)-1,2-dimethyl-1,2,3,4-tetrahydro-β-carboline.

Tramadol has recently been isolated from the roots and bark of Nauclea latifolia. A plausible biosynthetic pathway has been proposed and the product-precursor relationship has been probed by (13)C position-specific isotope analysis. By further exploring this pathway, we demonstrate that a key step of the proposed pathway can be achieved using mild conditions that mimic in vivo catalysis.

We have investigated the effect of 13 flavonoid derivatives on [ 14 C]paclitaxel transport in two human breast cancer cell lines, the adriamycin-resistant NCI/ADR-RES and sensitive MDA-MB-435. For this study, we selected representatives of aurones, chalcones, flavones, flavonols, chromones, and isoflavones with known binding affinity toward nucleotide-binding domain (NBD2) of P-glycoprotein and for which no reported work is available regarding paclitaxel transport. Aurones CB - 284 , CB - 285 , CB - 287 , and ML - 50 most effectively inhibited P-gp related transport in the resistant line in comparison with chalcones, flavones, flavonols, chromones, and isoflavone derivatives and accordingly increased the accumulation of [ 14 C]paclitaxel and decreased its efflux. Those agents efficiently modulated paclitaxel transport in P-gp highly expressing resistant human breast cancer cells and they could increase the efficiency of chemotherapy in paclitaxel-resistant tumors. In contrast, the sensitive cell line responded reversely in that CB - 284 , CB - 285 , CB - 287 , and ML - 50 significantly inhibited accumulation of [ 14 C]paclitaxel and especially CB - 287 , which significantly stimulated its efflux. Some, but not all, of the data correlated with the binding of flavonoid derivatives to P-gp, and indicated that even in the P-gp highly expressing NCI/ADR-RES cells, the binding was not the only factor influencing the transport of [ 14 C]paclitaxel. Opposite effects of flavonoid derivatives on the P-gp highly expressing and MDA-MB-435 non-expressing cell lines indicate that paclitaxel is not only transported by P-gp and let us assume that Mrp2 or ABCC5 seem to be good transport-candidates in these cells. The inhibition of paclitaxel accumulation and stimulation of its efflux are potentially unfavorable for drug therapy and since they could be due to modulation of drug transporters other than P-gp, their expression in tumors is of great significance for efficient chemotherapy.

Melanin play a major role in human skin protection and their biosynthesis is vital. Due to their color, they contribute to the skin pigmentation. Tyrosinase is a key enzyme involved in the first stage of melanin synthesis, catalyzing the transformation of tyrosine to l-dopaquinone. The aim of the present study was to study molecules able to inhibit melanin synthesis through inhibition of tyrosinase and their potential use in treating pigmentation-related disorders. We targeted amides obtained from coupling p-hydroxycinnamic acid derivatives with phenylalkylamines. The biological activity was evaluated on human melanocytes by an assay which measures tyrosine-catalyzed L-Dopa oxidation. The most active amides were: trans-N-caffeoyltyramine, N-dihydrocaffeoyltyramine, and trans-N-dihydro-p-hydroxycinnamoyltyramine which induce complete inhibition at 0.1mM. At the latter concentration, kojic acid, which was used as the reference inhibitor, was inactive.

Tyrosinase (Ty) is a copper-containing enzyme widely present in plants, bacteria, and humans, where it is involved in biosynthesis of melanin-type pigments. Development of Ty inhibitors is an important approach to control the production and the accumulation of pigments in living systems. In this paper, we focused our interest in phenylthiourea (PTU) and phenylmethylene thiosemicarbazone (PTSC) recognized as inhibitors of tyrosinase by combining enzymatic studies and coordination chemistry methods. Both are efficient inhibitors of mushroom tyrosinase and they can be considered mainly as competitive inhibitors. Computational studies verify that PTSC and PTU inhibitors interact with the metal center of the active site. The KIC value of 0.93 μM confirms that PTSC is a much more efficient inhibitor than PTU, for which a KIC value of 58 μM was determined. The estimation of the binding free energies inhibitors/Ty confirms the high inhibitor efficiency of PTSC. Binding studies of PTSC along with PTU to a dinuclear copper(II) complex ([Cu2(μ-BPMP)(μ-OH)](ClO4)2 (1); H-BPMP = 2,6-bis-[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol) known to be a structural and functional model for the tyrosinase catecholase activity, have been performed. Interactions of the compounds with the dicopper model complex 1 were followed by spectrophotometry and electrospray ionization (ESI). The molecular structure of 1-PTSC and 1-PTU adducts were determined by single-crystal X-ray diffraction analysis showing for both an unusual bridging binding mode on the dicopper center. These results reflect their adaptable binding mode in relation to the geometry and chelate size of the dicopper center.

Tyrosinase is a copper-dependent enzyme which converts l- tyrosine to dopaquinone and is involved in different biological processes such as melanogenesis and skin hyperpigmentation. The purpose of this study was to investigate naturally occurring aurones (Z-benzylidenebenzofuran-3(2H)-one) and analogues as human tyrosinase inhibitors. Several aurones bearing hydroxyl groups on A-ring and different substituents on B-ring were synthesized and evaluated as inhibitors of human melanocyte-tyrosinase by an assay which measures tyrosinase-catalyzed l-Dopa oxidation. We found that unsubstituted aurones were weak inhibitors; however, derivatives with two or three hydroxyl groups preferably at 4,6 and 4' positions are able to induce significant tyrosinase inhibition. The most potent aurone was found to be the naturally occurring 4,6,4'-trihydroxyaurone which induces 75% inhibition at 0.1 mM concentration and is highly effective when compared to kojic acid, one of the best tyrosinase inhibitors known so far (the latter is completely inactive at such concentrations). Active aurones are devoid of toxic effects as shown by in vivo studies.

International audience; In continuing research that led us to identify chromanone derivatives (J. Med. Chem. 2003, 46, 2125) as P-glycoprotein inhibitors, we obtained analogues able to modulate multidrug resistance (MDR) mediated by the breast cancer resistance protein (BCRP). The linkage of 5-hydroxybenzopyran-4-one to piperazines or phenalkylamines affords highly potent inhibitors of BCRP. By using sensitive (HCT116) and resistant colon cancer cells expressing BCRP, we evaluated the effect of 14 benzopyranone (chromone) derivatives on the accumulation and the cytotoxic effect of the anticancer drug, mitoxantrone. At 10 microM, three compounds increased both intracellular accumulation and cytotoxicity of mitoxantrone in HCT116/R cells with a comparable rate as fumitremorgin C and Gleevec used as reference inhibitors. The most potent molecules 5b and 5c are still active at 1 microM, whereas FTC shows weak inhibition. These molecules do not induce cell death as shown by the cell cycle distribution study, which makes them potential candidates for in vivo studies.

Aurones [2-benzylidenebenzofuran-3(2H)-ones] are the secondary metabolites natural compounds belong to the flavonoids family, and structurally are the isomers of flavones, widely present in fruits and flowers where they play significant role in the pigmentation of the part of plant in which they occur. Literature survey clearly indicates that flavones, chalcones, flavonols and isoflavones have been studied largely for their therapeutical potential. Somehow, aurones still are less studied and it is only recently that these compounds have begun to be investigated. In this review, we report the recent advances made on the therapeutical potential of aurones in different biological areas. Their synthesis, structure-activity relationships, the importance of the substitution pattern will also be discussed. Finally, some aspects regarding the possible development of aurones will be highlighted briefly.

Flavonoid derivatives were synthesized and tested for their ability to modulate P-glycoprotein (Pgp)-mediated multidrug resistance (MDR) in vitro. These compounds belong to various flavonoid subclasses, namely: chromones, azaisoflavones, and aurones. Among the investigated compounds, three showed potent reversing activity. 2-(4-methylpiperazin-1-ylcarbonyl)-5-hydroxychromone (4a), 5,7-dimethoxy-3-phenyl-4-quinolone (5), and 4,6-dimethoxyaurone (6) potentiated daunorubicin cytotoxicity on resistant K562 cells. They were also able to increase the intracellular accumulation of rhodamine-123, a fluorescent molecule which acts as a probe of P-glycoprotein-mediated MDR. This suggests that these compounds act, at least in part, by inhibiting P-glycoprotein activity. The most active compound, 5-hydroxy-2-(4-methylpiperazin-1-ylcarbonyl)chromone (4a) was found to be a powerful reversal agent, more potent than cyclosporin A, used as the reference molecule. No effect was observed on MRP transport nor on cell proliferation. Little apoptosis was induced on K562S cells with 4a compared to K562R, probably due to the extrusion of the compound by Pgp.

P-glycoprotein (P-gp) is a plasma membrane glycoprotein that confers multidrug resistance on cells by virtue of its ability to exclude cytotoxic drugs in an ATP-dependent manner. The most commonly considered hypothesis is that P-gp acts as an ATP-driven drug-export pump, the mechanism of which is not understood in detail. Therefore, a tremendous effort is being made to find out modulator molecules to inhibit P-gp. We have been developing flavonoid derivatives as a new class of promising modulators using a new in vitro rational-screening assay based on measurements of the binding-affinity toward the C-terminal nucleotide-binding domain (NBD2) of P-gp. This review is focused on our results obtained with a variety of flavonoids. Structure-activity relationships of flavonoids as potential MDR modulators are reported.P-glycoprotein (P-gp) is a plasma membrane glycoprotein that confers multidrug resistance on cells by virtue of its ability to exclude cytotoxic drugs in an ATP-dependent manner. The most commonly considered hypothesis is that P-gp acts as an ATP-driven drug-export pump, the mechanism of which is not understood in detail. Therefore, a tremendous effort is being made to find out modulator molecules to inhibit P-gp. We have been developing flavonoid derivatives as a new class of promising modulators using a new in vitro rational-screening assay based on measurements of the binding-affinity toward the C-terminal nucleotide-binding domain (NBD2) of P-gp. This review is focused on our results obtained with a variety of flavonoids. Structure-activity relationships of flavonoids as potential MDR modulators are reported.

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

We recently identified a chromone derivative, 5-(4-bromobenzyloxy)-2-(2-(5-methoxyindolyl)ethyl-1-carbonyl)-4H-chromen-4-one, named here as chromone 1, as a potent, selective, nontoxic, and nontransported inhibitor of ABCG2-mediated drug efflux (Valdameri et al. J. Med. Chem. 2012, 55, 966). We have now synthesized a series of 14 derivatives to study the structure-activity relationships controlling both drug efflux and ATPase activity of ABCG2 and to elucidate their molecular mechanism of interaction and inhibition. It was found that the 4-bromobenzyloxy substituent at position 5 and the methoxyindole are important for both inhibition of mitoxantrone efflux and inhibition of basal ATPase activity. Quite interestingly, methylation of the central amide nitrogen strongly altered the high affinity for ABCG2 and the complete inhibition of mitoxantrone efflux and coupled ATPase activity. These results allowed the identification of a critical central inhibitory moiety of chromones that has never been investigated previously in any series of inhibitors.

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.

Heat stress (HS) is known to confer protection against ischemia-reperfusion injury, including mechanical dysfunction and myocardial necrosis. However, the mechanisms involved in this cardioprotection are yet to be elucidated. Mitogen-activated protein (MAP) kinase cascades have been demonstrated to be involved in cellular response to different stresses. In particular, p38 MAP kinase is known to be activated by HS. Therefore, we investigated the implication of this kinase in HS-induced resistance to myocardial infarction, in the isolated rat heart model, using SB 203580 (SB) to selectively inhibit p38 MAP kinase. Rats were treated with SB (2.83 mg/kg, i.p.) or vehicle (1% DMSO in saline, i.p.) before they were either heat stressed (42 degrees C for 15 minutes) or sham anesthetized. Their hearts were isolated 24 hours later, retrogradely perfused, and subjected to a 35-minute occlusion of the left coronary artery followed by 120 minutes of reperfusion. The infarct-to-risk ratio was significantly reduced in HS (16.9 +/- 2.0%) compared with sham (41.6 +/- 2.5%) hearts. This reduction in infarct size was abolished in the SB 203580-treated group (37.8 +/- 1.9% in HS + SB vs. 42.0 +/- 1.9% in sham + SB). Risk zones were similar between experimental groups. Western blot analysis of the myocardial HSP72 showed an HS-induced increase of this protein, which was not modified by the p38 MAP kinase inhibitor, SB 203580. We conclude that activation of p38 MAP kinase appears to play a role in the functional cardioprotection associated with the heat stress response, which seems to be unrelated to the HSP72 level. Further investigations are required to elucidate the precise role of the p38 MAP kinase and heat stress proteins in this adaptative response.

A series of 4-alkoxy-2',4',6'-trihydroxychalcones have been synthesized and evaluated for their ability to inhibit P-glycoprotein-mediated multidrug resistance (MDR) by direct binding to a purified protein domain containing an ATP-binding site and a modulator-interacting region. The introduction of hydrophobic alkoxy groups at position 4 led to much more active compounds as compared to the parent chalcone. The binding affinity increased as a function of the chain length, up to the octyloxy derivative for which a K(D) of 20 nM was obtained.

Previous studies have shown that flavonoids are modulators of the transmembrane P-glycoprotein (P-gp) which mediates cell multidrug resistance. Some structural elements have been identified which seem to contribute to these compounds' activity. In the present study, a series of halogenated chalcones was prepared to further explore the structural requirements for the P-gp modulation. Four halogenated chalcones have been synthesized and evaluated as potential modulators of P-gp-mediated multidrug resistance of cancer cells by in vitro assays using a purified recombinant domain of the transporter containing the modulator binding site. Halogenated chalcones exhibited high-affinity binding, the 2',4', 6'-trihydroxy-4-iodochalcone behaving as the most potent compound with a KD value in the nanomolar range.

ABCG2 impacts oral availability, tissue distribution and excretion of its substrates, including anticancer and anti-infectious drugs. Highly expressed at physiological barriers, its secretion level significantly controls drug distribution. Furthermore, its increased content into many types of cancer may lead to cell chemoresistance. Owing to the clinical relevance of ABCG2 in the multidrug resistance phenomenon, ABCG2 constitutes an appealing therapeutic target to increase drug distribution. Development of ABCG2 inhibitors can be used in combination with anticancer drugs to block the drug secretion from cancer cells. Very recently, an alternative use of ABCG2 inhibitors in enhancing the bioavailability of ABCG2 substrates has emerged. Hence, it is important to investigate ABCG2 inhibitors with high selectivity, high potency and safety. New inhibitors discovered during the last 5 years will be presented and discussed.

Ethnopharmacological relevance Waltheria indica L. ( syn. Waltheria americana ) is commonly used in traditional medicine in Africa, South America and Hawaii, mainly against pain, inflammation, conditions of inflammation, diarrhea, dysentery, conjunctivitis, wounds, abscess, epilepsy, convulsions, anemia, erectile dysfunctions, bladder ailments and asthma. Aim of the review to provide an up-to-date overview of the botany, phytochemistry, traditional uses, pharmacological activities and toxicity data of Waltheria indica . Additionally, studies providing an evidence for local and traditional uses of Waltheria indica are discussed. Further phytochemical and pharmacological potential of this species are suggested for future investigations. Materials and methods The information was collected from scientific journals, books, theses and reports via academic libraries and electronic search. These sources include Pubmed, Web of Science, Portal de Portales-Latindex, Science Research.com and Google scholar. These studies about the medical botanical, traditional uses, chemical, pharmacological and toxicological data on Waltheria indica were published in English, Portuguese, Spanish, German and French. Results Crude extracts and isolated compounds from Waltheria indica were investigated and showed analgesic, anti-inflammatory, antibacterial, antifungal, antimalarial, anti-anemic, anti-oxidant, sedative and anticonvulsant activities. The phytochemical investigations showed the presence of cyclopeptid alkaloids, flavonoids ( e.g. , (–)-epicatechin, quercetin, kaempferol, kaempferol-3- O -β- d -(6″- E - p -coumaryl)-glucopyranoside), tannins, sterols, terpenes, saponins, anthraquinones. Studies of acute toxicity in animal indicated that Waltheria indica can be toxic. Conclusion Waltheria indica possess therapeutic potential in the treatment of inflammation, malaria, infectious diseases ( e.g. , lungs infection due to Klebsiella pneumoniae , diarrhea due to Candida albicans or Escherichia coli ) and prevention of oxidative stress. Further studies are necessary to explore pure compounds responsible for the pharmacological effects and the mechanisms of action. Further investigations are also needed to provide an evidence base for traditional uses of this species against pain, anemia, convulsions and epilepsy. In addition, there is a pressing need to investigate the other traditional uses such as dysentery, syphilis, erectile dysfunctions and asthma.

ATP-Binding Cassette transporters such as ABCG2 confer resistance to various anticancer drugs including irinotecan and its active metabolite, SN38. Early quantitative evaluation of efflux transporter inhibitors-cytotoxic combination requires quantitative drug-disease models. A proof-of-concept study has been carried out for studying the effect of a new ABCG2 transporter inhibitor, MBLI87 combined to irinotecan in mice xenografted with cells overexpressing ABCG2. Mice were treated with irinotecan alone or combined to MBLI87, and tumour size was periodically measured. To model those data, a tumour growth inhibition model was developed. Unperturbed tumour growth was modelled using Simeoni's model. Drug effect kinetics was accounted for by a Kinetic-Pharmacodynamic approach. Effect of inhibitor was described with a pharmacodynamic interaction model where inhibitor enhances activity of cytotoxic. This model correctly predicted tumour growth dynamics from our study. MBLI87 increased irinotecan potency by 20% per μmol of MBLI87. This model retains enough complexity to simultaneously describe tumour growth and effect of this type of drug combination. It can thus be used as a template to early evaluate efflux transporter inhibitors in-vivo.

Efflux transporters play an important role in drug absorption and also in multidrug resistance. ABCG2 (BCRP) is an efflux transporter conferring cross-resistance to mitoxantrone (Mit), irinotecan (CPT11), and its active metabolite SN38. MBLI87, a new ABCG2 inhibitor has proven its efficacy against ABCG2-mediated efflux in vitro and in vivo. This work aimed at modeling and quantifying the cellular interaction between MBLI87 and different substrates using a mechanistic template model. An in vitro competition experiment study was carried out with HEK293 cells overexpressing ABCG2 exposed to fixed concentrations of substrates (Mit, CPT11, SN38) and to MBLI87 at several concentration levels. A nonlinear mixed-effects transport inhibition model was developed to fit intracellular drug concentrations. In this model, drugs cross the cell membrane through passive diffusion, active drug efflux is ABCG2 mediated, interaction between substrates and inhibitor occurs within the transporter. The interaction was found to be noncompetitive. The MBLI87 Ki was estimated to 141 nm for Mit, 289 nm for CPT11, and 1160 nm for SN38. The ratio of intrinsic transport clearance divided by diffusion clearance was estimated to 2.5 for Mit, 1.01 for CPT11, and 5.4 for SN38. The maximal increase in the intracellular substrate concentration that is possible to achieve by inhibition of the transporter was estimated to 1.5 for Mit, 0.1 for CPT11, and 4.4 for SN38. This mechanistic template model describes both drug accumulation and cellular transport, and the mixed-effects approach allows an estimation of intra- and interassay variability. This model is of great interest to study cytotoxic cellular pharmacokinetics.

A series of 4-hydroxy-6-methoxyaurones and 4,6-dimethoxyaurones has been synthesised and tested for their binding affinity toward the nucleotide-binding domain of P-glycoprotein, an ABC (ATP-Binding Cassette) transporter which mediates the resistance of cancer cells to chemotherapy. These compounds differ from each other by the nature of the substituent on the aurone B-ring. The binding affinity seems to be linked to the nature of the substituent, as well as to the presence or the absence of a hydroxy group at position 4. The most active compounds were 4'-bromo-4-hydroxy-6-methoxyaurone and 4-hydroxy-4'-iodo-6-methoxyaurone.A series of 4-hydroxy-6-methoxyaurones and 4,6-dimethoxyaurones has been synthesised and tested for their binding affinity toward the nucleotide-binding domain of P-glycoprotein, an ABC (ATP-Binding Cassette) transporter which mediates the resistance of cancer cells to chemotherapy. These compounds differ from each other by the nature of the substituent on the aurone B-ring. The binding affinity seems to be linked to the nature of the substituent, as well as to the presence or the absence of a hydroxy group at position 4. The most active compounds were 4'-bromo-4-hydroxy-6-methoxyaurone and 4-hydroxy-4'-iodo-6-methoxyaurone.

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.