Biologists have isolated 17 secondary metabolites, including three novel compounds from the valuable endangered tropical plant species Alangium longiflorum. A newly isolated compound, 8-hydroxytubulosine, showed growth inhibitory effects at submicromolar levels against several human tumor cell lines except for drug transporter-overexpressing cells. Compound 1 caused accumulation of sub-G1 cells with no effect on cell cycle progression, suggesting that this substance is an apoptosis inducer.