Quassinoids and Alkaloids From the Roots of Eurycoma longifolia

Five quassinoids and 2 alkaloids were isolated from the roots of Eurycoma longifolia. The structures of 3 new quassinoids, eurycomalide F, G, and H (1-3), were elucidated using a variety of spectroscopic methods. The known compounds were identified as eurycomalide A (4), laurycolactone B (5), 5-methoxycanthin-6-one (6), and canthin-6-one (7). Among the isolated compounds, canthin-6-one (7) exhibited the strongest inhibitory effect on nitric oxide production (IC50 = 16.9 μM). 5-Methoxycanthin-6-one (6) and eurycomalide F (1) exhibited weak inhibition with IC50 values of 23.4 and 32.7 μM, respectively