Quassinoids from Eurycoma longifolia

Ten new structurally diverse quassinoids (1-10) and 14 known compounds were isolated from the stems of Eurycoma longifolia. The new compounds were two eurycomanone-type C₂₀ quassinoids (1, 2), one klaineanone-type C ₂₀ quassinoid (3), one C₁₉ quassinoid (4) with a 1,2-seco-1-nor-6(5⇀10)-abeo-picrasan-2,5-olide skeleton, and six eurycomalactone-type C₁₉ quassinoids (5-10). Compounds 5 and 6 both possessed a 3,4-epoxy group observed for the first time in eurycomalactones. Compound 1 had an R-oriented OH group at C-14 that had not been reported previously in eurycomanone-type quassinoids. All of the isolates were evaluated for cytotoxicity toward the highly metastatic HT-1080 human fibrosarcoma cell line, and compounds 11, 23, and 24 showed potent cytotoxicity (IC₅₀ values 0.93-1.1 μM).