Elisabeth Mouray

New ferrocenic pyrrolo[1,2-a]quinoxaline derivatives: synthesis, and in vitro antimalarial activity.

Following our search for antimalarial compounds, novel series of ferrocenic pyrrolo[1,2-a]quinoxaline derivatives 1-2 were synthesized from various substituted nitroanilines and tested for in vitro activity upon the erythrocytic development of Plasmodiumfalciparum strains with different chloroquine-resistance status. The pyrrolo[1,2-a]quinoxalines 1 were prepared in 6-8 steps through a regioselective palladium-catalyzed monoamination by coupling 4-chloropyrrolo[1,2-a]quinoxalines with 1,3-bis(aminopropyl)piperazine or -methylamine using Xantphos as the ligand. The ferrocenic bispyrrolo[1,2-a]quinoxalines 2 were prepared by reductive amination of previously described bispyrrolo[1,2-a]quinoxalines 9 with ferrocene-carboxaldehyde, by treatment with NaHB(OAc)(3). The best results were observed with ferrocenic pyrrolo[1,2-a]quinoxalines linked by a bis(3-aminopropyl)piperazine. Moreover, it was observed that a methoxy group on the pyrrolo[1,2-a]quinoxaline nucleus and no substitution on the terminal N-ferrocenylmethylamine function enhanced the pharmacological activity. Selected compounds 1b, 1f-h, 1l and 2a were tested for their ability to inhibit beta-haematin formation, the synthetic equivalent of hemozoin, by using the HPIA (heme polymerization inhibitory activity) assay. Of the tested compounds, only 2a showed a beta-haematin formation inhibition, but no inhibition of haem polymerization was observed with the other selected ferrocenic monopyrrolo[1,2-a]quinoxaline derivatives 1b, 1f-h and 1l, as the IC(50) values were superior to 10 equivalents.

New ferrocenic pyrrolo[1,2-a]quinoxaline derivatives: Synthesis, and in vitro antimalarial activity – Part II

Following our search for antimalarial compounds, novel series of ferrocenyl-substituted pyrrolo[1,2-a]quinoxalines 1-2 were synthesized from ferrocene-carboxaldehyde and tested for their in vitro activity upon the erythrocytic development of Plasmodium falciparum strains with different chloroquine-resistance status. The ferrocenic pyrrolo[1,2-a]quinoxalines 1-2 were prepared in 6 or 9 steps through a Barton-Zard reaction. Promising pharmacological results against FcB1, K1 and F32 strains were obtained with ferrocenyl pyrrolo[1,2-a]quinoxalines 1j-l linked by a bis-(3-aminopropyl)piperazine linker substituted by a nitrobenzyl moiety.

Plasmodium telomeric sequences: structure, stability and quadruplex targeting by small compounds.

The increasing resistance of Plasmodium falciparum to the most commonly used antimalarial drugs makes it necessary to identify new therapeutic targets. The telomeres of the parasite could constitute an attractive target. They are composed of repetitions of a degenerate motif (5′GGGTTYA3′, where Y is T or C), different from the human one (5′GGGTTA3′). In this report we investigate the possibility of targeting Plasmodium telomeres with G‐quadruplex ligands. Through solution hybridisation assays we provide evidence of the existence of a telomeric 3′ G‐overhang in P. falciparum genomic DNA. Through UV spectroscopy studies we demonstrate that stable G‐quadruplex structures are formed at physiological temperature by sequences composed of the degenerate Plasmodium telomeric motif. Through a FRET melting assay we show stabilisation of Plasmodium telomeric G‐quadruplexes by a variety of ligands. Many of the tested ligands display strong quadruplex versus duplex selectivity, but show little discrimination between human and Plasmodium telomeric quadruplexes.

Antiplasmodial phenolic compounds from Piptadenia pervillei.

Piptadenia pervillei Vatke (Fabaceae) was selected from a screening programme devoted to the search of naturally-occuring antimalarial compounds from plants of Madagascar. Bioassay-guided fractionation of the ethyl acetate extract of the leaves led to the isolation of four phenolic compounds, (+)-catechin ( 1), (+)-catechin 5-gallate ( 2), (+)-catechin 3-gallate ( 3) and ethyl gallate ( 4). Structures were determined by NMR and mass spectroscopy. Compounds 2 and 3 displayed the highest in vitro activity against the chloroquine-resistant strain FcB1 of Plasmodium falciparum with IC (50) values of 1.2 microM and 1.0 microM, respectively, and no significant cytotoxicity against the human embryonic lung cells MRC-5 was measured (IC (50) values > 75 microM). Five analogues ( 5 - 9) of (+)-catechin 5-gallate ( 2) were synthesized and evaluated for their antiplasmodial activity.

Sesquiterpene lactones from the endemic Cape Verdean Artemisia gorgonum.

Leaves and flowers of Artemisia gorgonum (Asteraceae) collected in Fogo, Cape Verde islands, were phytochemically investigated and resulted in isolation and characterization of three guaianolides 1, 2, 5, and a secoguainolide 4, in addition to eight known guaianolides 6-11 and two known germacranolides 12, 13. Structures were elucidated by 1D and 2D NMR experiments. Careful examination of the (13)C NMR spectrum led to revision of the structure of a previously described guaianolide from 2 to 3. Most compounds exhibited mild antiplasmodial activities, ridentin (13) being the most interesting with an IC(50) of 3.8+/-0.7microgml(-1) against Plasmodium falciparum FcB1 and weak cytotoxicity in a vero cell line (IC(50) 71.0+/-3.9microgml(-1)).

Parallel synthesis and anti-malarial activity of a sulfonamide library.

Solution-phase synthesis and evaluation of a library of 31 sulfonamides as inhibitors of a chloroquine-resistant strain of Plasmodium falciparum are described. The most potent compound displayed an activity 100-fold better than chloroquine. Experiments using a fluorescent sulfonamide derivative suggest that their site of action inside the parasite is different to that of chloroquine.

Cloning of Plasmodium falciparum protein disulfide isomerase homologue by affinity purification using the antiplasmodial inhibitor 1,4-bis{3-[N-(cyclohexyl methyl)amino]propyl}piperazine 1

A series of 10 1,4‐bis(3‐aminopropyl)piperazine compounds was found to display antiplasmodial activity with 50% growth inhibition between 30 and 250 nM, on three Plasmodium falciparum strains differently sensitive to chloroquine. By affinity chromatography using one of these compounds, a 52‐kDa protein was isolated from P. falciparum, microsequenced and cloned. It corresponded to a single copy gene encoding a 453 amino acid protein displaying the typical features of protein disulfide isomerases, a thiol metabolizing enzyme belonging to the thiol: disulfide oxidoreductase superfamily, which was not previously described in malarial species.

The Traditional Medicine Spilanthes acmella, and the Alkylamides Spilanthol and Undeca‐2E‐ene‐8,10‐diynoic Acid Isobutylamide, Demonstrate In Vitro and In Vivo Antimalarial Activity

Spilanthes spp. are used as traditional herbal medicines in Africa and India to treat malaria. Yet, to date, there are no data on the active constituents or the most effective extraction methods for this indication. The isolated alkylamides, spilanthol and undeca‐2E‐ene‐8,10‐diynoic acid isobutylamide, found in S. acmella Murr., were shown to have IC50s of 16.5 μg/mL and 41.4 μg/mL on Plasmodium falciparum strain PFB and IC50s of 5.8 μg/mL and 16.3 μg/mL for the chloroquine resistant P. falciparum K1 strain, respectively. Further investigations revealed that at relatively low concentrations, spilanthol and the water extract of S. acmella reduced the parasitemia 59% and 53% in mice infected with P. yoelii yoelii 17XNL at 5 mg/kg and 50 mg/kg, respectively. Unexpectedly, the 95% ethanol extract of S. acmella was less effective (36% reduction in parasitemia) at 50 mg/kg. These results provide the first evidence supporting S. acmella against malaria and demonstrating active constituents in S. acmella against P. falciparum. Copyright

Involvement of calyculin A-sensitive phosphatase(s) in the differentiation of Trypanosoma cruzi trypomastigotes to amastigotes.

Differentiation of the non-dividing trypomastigote form of Trypanosoma cruzi, the causative agent of Chagas disease, to the dividing amastigote form normally occurs in cytoplasm of infected cells. Here we show that calyculin A. a potent inhibitor of protein phosphatases 1 and 2A, induces at pH 7.5 extracellular transformation of long slender trypomastigotes to round amastigote-like forms which acquire characteristic features observed after the normal differentiation process: repositioning and structural changes of the kinetoplast, release of surface neuraminidase, and expression of amastigote-specific epitopes. Calyculin A inhibits parasite phosphatases and changes in the phosphorylation of specific proteins occur during the transformation process. As an exposure of trypomastigotes to calyculin A concentrations as low as 1 nM and for only 1-2 h is sufficient to induce transformation, the inhibition of calyculin A-sensitive phosphatase(s) appears to play a major role in initiating the trypomastigote differentiation.

Antiplasmodial and cytotoxic activities of medicinal plants traditionally used in the village of Kiohima, Uganda.

AIM OF THE STUDY In Uganda, malaria is the most common disease and Ugandan people largely rely on traditional medicine. In this context, we carried out an ethnobotanical study on the Kiohima village, located close to the Kibale National Park in South-Western Uganda and investigated in vitro the antiplasmodial and cytotoxic activities of selected medicinal plants. MATERIALS AND METHODS Seventy-five plants-using adults (men and women) were interviewed to find out their plant use. From these information, 48 plants used in traditional medicine were identified and according to their reported uses and to bibliographic data, several parts of 28 plants (leaves, barks, roots), were selected and collected for biological evaluations. These samples were dried, extracted with ethyl acetate and the crude extracts were assayed for in vitro antiplasmodial and cytotoxic activities at 10 μg/mL. RESULTS One third of the screened plants showed a significant antiplasmodial activity with inhibition greater than 50% at 10 μg/mL. CONCLUSION These results may indicate a possible explanation of the use of some medicinal plant against malaria in the village of Kiohima and have also allowed to highlight a plant with potent antimalarial activity: Citropsis articulata root barks.