The crude ethanol extract from the leaves of Dendroponax cf. querceti
(Araliaceae) from Monteverde, Costa Rica, exhibits cytotoxic activity
against Hep-GZ, A-431, and H-411E tumor cell lines. The active compone
nt has been isolated by activity-directed separation and identified by
H-1-and C-13-NMR spectroscopy as the triterpene lupeol. The mechanism
of cytotoxic activity of lupeol has been determined to be inhibition
of topoisomerase II.