Of the five quassinoids isolated from the root bark of Hannoa klaineana, only 15-desacetylundulatone was found active against P388 mouse lymphocytic leukemia cells and colon 38 adenocarcinoma. Undulatone and especially 15-O-beta-D-glucopyranosyl-21-hydroxy-glaucarubolone were found to be more toxic