Endodesmiadiol, a friedelane triterpenoid, and other antiplasmodial compounds from Endodesmia calophylloides

From the ethyl acetate extract of the stem bark of Endodesmia calophylloides (Guttiferae), a novel friedelane triterpenoid named endodesmiadiol (1), as well as the known compounds friedelin (2), canophyllol (3), canophyllal (4), cerin (5), morelloflavone (6), volkensiflavone (7), 8-deoxygartanin (8), 3 beta-acetoxyoleanolic acid (9) and 1,8-dihydroxy-3-isoprenyloxy-6-methylxanthone (10) have been isolated. The structures of these compounds were established by spectroscopic analysis, and the relative configuration of endodesmiadiol (1) was confirmed by X-ray diffraction. The antiplasmodial activity of the isolated compounds was evaluated against the W2 strain of Plasmodium falciparum which is resistant to chloroquine and other antimalarial drugs. All the compounds were found to be active with IC50 values ranging from 7.2 to 23.6 microM. The IC50 of endodesmiadiol was found to be 11.8 microM.