Isolation and structure characterization of cytotoxic alkaloids from Micromelum integerrimum

Ten undescribed alkaloids, named integerrines A-J, including one racemic heterodimer of carbazole and indole, two racemic, two scalemic, and one enantiomerically enriched biscarbazoles, two aldoximes, and one racemic pyrrolone, were isolated from the dried leaves and stems of Micromelum integerrimum. The racemic or scalemic compounds were resolved using chiral-phase HPLC and their configurations were determined by comparison of experimental and calculated ECD data. Four compounds exhibited moderate to weak cytotoxicities against HepG2, HTC-116, HeLa, and PANC-1 cell lines, with IC₅₀ values of 14.1-67.5 μM.