Cytotoxic Indole Alkaloids from Melodinus tenuicaudatus

Four new bisindole alkaloids, melodinines H−K (1−4), a new monomer, melodinine L (5), and 11 known alkaloids were isolated from Melodinus tenuicaudatus. The structures of 1−5 were elucidated by extensive spectroscopic methods, and the known compounds were identified by comparison with data in the literature. All of the compounds were evaluated for their cytotoxicity against five human cancer cell lines. Alkaloids 1, 3, and 4 and the known compound 11-methoxytabersonine (8) exhibited inhibitory effects, with IC50 values comparable to those of cisplatin and vinorelbine.