Antiprotozoal activities of Millettia richardiana (Fabaceae) from Madagascar.
Résumé
With at least 60% of the Millettia species (Fabaceae) being in medicinal use, we found it relevant to assess the potential antiprotozoal and antifungal activities of Millettia richardiana. Water and methanol crude extracts of the stem barks from M. richardiana and the six fractions resulting from the fractionation of the methanol extract were tested. The dichloromethane extracted fraction showed the best in vitro antiprotozoal activities (IC50=5.8 μg/mL against Plasmodium falciparum, 11.8 μg/mL against Leishmania donovani and 12.8 μg/mL against Trypanosoma brucei brucei) as well as low cytotoxicity on several cell lines. The phytochemical analysis showed this selected fraction to be rich in terpenoids and alkaloids, which could explain its antiparasitic activity. A phytochemical study revealed the presence of lonchocarpenin, betulinic acid, β-amyrin, lupeol, palmitic acid, linoleic acid and stearic acid, among which betulinic acid and lupeol could be the compounds responsible of these antiprotozoal activities. By contrast, neither the crude extracts nor the fractions showed antifungal activity against Candida. These results confirm the importance of the genus Millettia in Malagasy ethnomedicine, its potential use in antiparasitic therapy, and the interest of developing a sustainable exploitation of this plant. Moreover, both molecules betulinic acid and lupeol appeared as very relevant molecules for their antiprotozoal properties.