Sesquiterpenoids with antiplasmodial activities from Warburgia stuhlmanii Engl. root bark

Abstract

Phytochemical investigation of Warburgia stuhlmannii ethyl acetate root extract led to isolation of ten known compounds identified as polygodial (1), cinnamolide (2), warburganal (3), bemadienolide (4), ugandensidial (5), muzigadial (6), mukaadial (7), 6α-hydroxymuzigadial (8), ugandensolide (9) and deacetylugandensolide (10). Structures of the isolated compounds were determined by spectroscopic methods; NMR, IR, UV-Vis and spectrometric method, EI-MS, as well as comparison with literature data. In their antiplasmodial activities, the compounds had moderate activities against the chloroquin sensitive (D10) and chloroquin resistant (W2) strains of Plasmodium falciparum. Among the compounds, mukaadial (7) had the highest activities against both D10 and W2 strains of P. falciparum, with IC50 values of 5.2 µM and 5.8 µM, respectively, while muzigadial (6) though effective on D10 strain (IC50 = 5.6 µM) was less effective against W2 strain (IC50 = 16.4 µM).