New cytotoxic biflavones from Selaginella doederleinii.

Three new biflavones, apigenin-(3',8″)-chrysin (1), (2S)-2,3-Dihydroametoflavone 5,4'-dimethyl ether (2), and (2S)-5″,7″-Dihydroxy-2″-phenoxychromonyl-(4'″,3')-naringenin (3), together with seven known biflavones (4-10) were isolated from the 75% EtOH extract of Selaginella doederleinii. The structures of new compounds were established by application of spectroscopic methods, including 1D and 2D NMR, HRMS, and CD measurements. In addition, all new compounds were evaluated for their cytotoxic potential against three human cancer cell lines A549, MCF-7, and SMMC-7721 in vitro. Compound 2 exhibited potent cytotoxic activity with IC₅₀ values ranging from 6.35 to 10.18 μM.