Abstract
Alangium longiflorum is currently in extinction crisis, which will likely severely hamper further phytochemical investigation of this plant species from new collections. A crude extract of leaves of A. longiflorum (N33539), collected for the U.S. National Cancer Institute in 1989, showed potent cancer cell line antiproliferative activity. A phytochemical study resulted in the isolation of 17 secondary metabolites, including two new tetrahydroisoquinoline alkaloids, 8-hydroxytubulosine (1) and 2'- O- trans-sinapoylisoalangiside (2), as well as a new sinapolyloxylupene derivative (3). Using in-house assays and NCI-60 panel screening, compound 1 displayed broad-spectrum inhibitory activity at submicromolar levels against most tested 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.