Evaluation de l'activité antiparasitaire de plantes utilisées en médecine traditionnelle au Bénin et identification de principes actifs

Content Provider	Semantic Scholar
Author	Bero, Joanne
Copyright Year	2012
Abstract	Parasitic diseases are still responsible for many health problems. Among them, African trypanosomiasis or sleeping sickness caused by Trypanosoma brucei, malaria transmitted by Plasmodium species of which the most dangerous is Plasmodium falciparum and leishmaniasis. Plant biodiversity and knowledge of traditional healing allow, as it was the case for artemisinin, to open new ways in the field of therapeutic. In this work, we analyzed the activity of several plants from Benin selected by ethnobotanical and bibliographical studies. These plants are used in traditional medicine as antimalarials. Crude extracts from powders of leaves, twigs, roots or aerial parts were prepared by maceration. These extracts were studied for their antiparasitic activities by in vitro tests on Plasmodium falciparum, Trypanosoma brucei brucei and Leishmania mexicana mexicana. In addition, cytotoxicities were analysed to determine the selectivity of crude extracts. The dichloromethane extracts of Keetia leucantha were selected and known antiparasitc compounds were identified and quantified by LC-MS. As they could not account for the total activity observed, we isolated by bioguided fractionation several triterpenic esters, vanillin derivatives, a sterol and a coumarin. The structure determination of isolated compounds was performed by NMR studies and high resolution mass spectrometry. We also identified and quantified by GC-MS the major volatile constituents from the essential oil of leaves. The isolated compounds were studied in vitro for their antiplasmodial, antitrypanosomal and antileishmanial activities. Several of them showed a sub-micromolar antiplasmodial activity, including some triterpenic esters which are 10 to 100 times more active than ursolic acid. In addition, we tested the in vivo antimalarial activity of some extracts: the dichloromethane extract of twigs of Keetia leucantha showed 40.7 % inhibition in mice infected by Plasmodium berghei at 100 mg/kg/day and the total aqueous extract a 30.8% inhibition at 200 mg/kg/day. Furthermore, some compounds with good antitrypanosomal activity were studied to understand their mode of action by in vitro tests on the bloodstream and procyclic forms of trypanosomes, by studies of parasite motility and by inhibitory tests on a glycolytic enzyme. The results showed an inhibition of the activity of glyceraldehyde-3-phosphate dehydrogenase trypanosomale (GAPDH) at low concentration for some of them, the most active being oleanolic acid.
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Resource Type	Article