New Bioactive Lupane Triterpene Coumaroyl Esters Isolated from Buxus cochinchinensis

Five new lupane triterpene coumaroyl esters (1-5), together with betulin (6) and a known Buxus alkaloid, N-3-benzoyldihydrocyclomicrophylline F (7), were isolated from a CHCl3-soluble partition of a methanol extract of Buxus cochinchinensis Pierre ex Gagnep. (Buxaceae) collected in Vietnam. Isolation work was monitored using human colon cancer cells (HT-29). The structures of the new compounds (1-5) were determined on the basis of spectroscopic data interpretation. In addition to their cytotoxicity against HT-29 cells and nuclear factor-kappa B (p65) inhibitory activity in an enzyme-linked immunosorbent assay, all isolates as well as two semisynthetic compounds derived from betulin and 5, respectively, were also evaluated for their in vitro antiplasmodial activities against the drug-resistant Dd2 strain of Plasmodium falciparum and antifungal effects on the growth of the pathogenic yeast Candida albicans. The new lupane triterpene coumaroyl esters (1-5), along with a betulin derivative and the known Buxus alkaloid, were found to show significant in vitro antimalarial activities, with IC50 values ranging from 0.26 to 2.07 µM.