Abstract A bioassay study of Pasak bumi (Eurycoma longifolia) led to the isolation of four quassinoids, pasakbumin-A (1),-B (2),-C (4), and-D (7). Both pasakbumin-A (= eurycomanone) 1 and pasakbumin-B 2 exhibited potent antiulcer activity. This prompted us to test some modified quassinoids to reveal that ailanthone (8), the main quassinoid of Ailanthus altissima, and its α-epoxide (9) have potent activity and less toxicity. Thus, ...
