Isolation and cytotoxic activity of selaginellin derivatives and biflavonoids from Selaginella tamariscina

Five selaginellin derivatives, including two new selaginellins termed selaginellins M (1) and N (2), and three previously identified compounds, selaginellin (3), selaginellin A (4), and selaginellin C (5), were isolated from the Selaginella tamariscina (Beauv.) Spring plant. In addition, four known biflavonoids, namely neocryptomerin ( 6), hinokiflavone (7), pulvinatabiflavone (8), and 7'- O-methylamentoflavone (9), were also isolated. The structures of new compounds 1 and 2 were elucidated by spectroscopic analysis. The cytotoxic activity of compounds 1- 9 was evaluated against a small panel of human cancer cell lines, including U251 (human glioma cells), HeLa (human cervical carcinoma cells), and MCF-7 (human breast cancer cells). The two new selaginellins, selaginellins M (1) and N (2), showed medium activity against the human cancer cell lines.