Leishmanicidal activity of onopordopicrin isolated from the leaves of Brachylaena discolor

Abstract

Brachylaena discolor (Asteraceae) is a medicinal plant used in Mozambique to treat stomachache, tuberculosis, and diabetes. To discover new lead compounds with leishmanicidal activity, a methanolic extract of the leaves of this plant was investigated. Through fractionation, employing several chromatographic methods, two sesquiterpene lactones onopordopicrin (1) and its germacronolide epoxide derivative (2), together with other ten know phenolic compounds derivatives (3-12) were isolated. The structures of the isolated compounds were determined by spectroscopic methods, mainly 1D and 2D NMR experiments, as well as by comparing their spectroscopic data as reported in the literature. Compounds 1 and 2 were evaluated for their leishmanicidal activity using the Colorimetric method-XXT. Compound 1 showed a significant leishmanicidal activity against Leishmania amazonensis and L. braziliensis (IC50 values 39.6 and 27.9 μM, respectively) as compared to miltefosine (12.5 and 12.0 μM, respectively), a currently used agent to treat leishmaniosis. While compound 2 was inactive against both stains tested with IC50 values >50μM compared with the same agent. Compounds 3-12 were not assayed for leishmanicidal activity. This is the first study reporting the above-mentioned activity of onopordopicrin (1). The results could suggest that compound 1 is a promising lead structure to treat leishmaniosis.