Two new β-carboline alkaloids from the stems of Picrasma quassioides.

Two new β-carboline alkaloids, 1-acetyl-4-methoxy-8-hydroxy-β-carboline (1) and 1-acetyl-4,8-dimethoxy-β-carboline (2), together with 10 known compounds; seven β-carboline alkaloids (3-9), two canthin-6-one alkaloids (10 and 11), and one quassinoid (12) were isolated from the stems of Picrasma quassioides. The structure of the new compounds 1 and 2 were determined by spectroscopic analyses including 1D- and 2D-NMR and HRMS interpretation. All the isolates (1-12) were evaluated for their cytotoxicity against human ovarian carcinoma A2780 and SKOV3 cell lines using MTT assays. Of the isolates, compounds 5-7 exhibited the most potent cytotoxicity on both A2780 and SKOV3 cell lines in vitro.