Four new quassinoids from the roots of Eurycoma longifolia Jack.

Seven compounds were isolated from the roots of Eurycoma longifolia, and characterized by comprehensive analysis of 1D and 2D NMR experiments along with single crystal X-ray diffraction. Among them, four new quassinoids were identified and three of them were diastereomers for each other. Compounds 1-7 were evaluated for cytotoxicities against HT-29, MCF-7, LOVO, BGC-823, MGC-803, HepG2, HeLa, and A549 cancer cell lines. Compounds 2 and 5 exhibited the lowest IC50 values of 24.9 μM, 11.8 μM, and 44.1 μM, 14.1 μM towards MCF-7, MGC-803 cancer cell lines, respectively, while compound 6 exhibited moderate cytotoxicity towards all the selected cancer cell lines.