Cytotoxic aspidosperma-type alkaloids from Melodinus axillaris.

One new aspidosperma-type alkaloid, melotenine A (1), together with five known ones (2-6), was isolated from the leaves of Melodinus axillaris. Their structures were elucidated by detailed spectroscopic analysis and quantum chemical ECD calculation. The isolated aspidosperma-type alkaloids were evaluated for their cytotoxicity against four human cancer cell lines and melotenine A showed significant cytotoxicity against all cells with IC₅₀ values ranging from 0.6 to 1.5 μM.