A molecular modeling study of two alkaloids, tubulosine and psychotrine, isolated from the sap of Pogonopus speciosus, and other related ipecac alkaloids, showed that these flexible alkaloids favor a nonplanar structure. The biologically active compounds had conformations with a similar angle
Bioassay-guided phytochemical investigation of the stems of Pogonopus speciosus, using human oral epidermoid carcinoma (KB) cells as a monitor, led to the isolation of a novel alkaloid, 1',2', 3',4'-tetradehydrotubulosine (1), along with tubulosine (2) and psychotrine (3) as bioactive constituents.