Phytochemical and Antimicrobial Studies of Maprounea membranacea Pax & K. Hoffm (Euphorbiaceae)

Abstract

The aim of the present study was to carry out the isolation, purification and structural identification of  secondary metabolites from methanolic extract of stem bark of Maprounea membranacea and further to evaluate the antimicrobial activity of its fractions. According to the literature and due to their use in traditional medicine, plants of the genus Maprounea may be good candidate for new antimicrobial drugs. In this study, the air-dried and powdered stem bark (6.3 kg) of M. membranacea was extracted 02 times by percolation with methanol (MeOH) for 48 h. A part of this residue (350 g) was suspended in distilled water and partitioned successively between hexane and ethyl acetate (EtOAc) to obtain hexane, ethyl acetate and water soluble fractions. The two first fractions were then subjected to repeated column chromatographic separation. The structures of the isolates were established by means of spectroscopic methods. The crude extract and its fractions were also screened in vitro for their activity against bacteria and fungi. Eight known compounds including friedelin, betulinic acid, lupeol, epigallocatechin, β-sitosterol, β-sitosterol glucoside, stigmasterol and stigmasterol glucoside were isolated from hexane and ethyl acetate fractions of methanolic extract of stem bark. The structures of these compounds were determined by comprehensive spectroscopic analyses (1D, 2D NMR) and by comparison of their data with those reported in the literature. The agar diffusion test resulted in low to missing antibacterial activities. In addition, all fractions and crude extract displayed significant antifungal activities with MIC value ranging from 1.25-40.0 µg/µl.