A New Optical Biflavonoid, (2″ R )-2″,3″-Dihydrorobustaflavone 7,4′-Dimethyl Ether, and Other Constituents from Selaginella trichoclada Alsto

A new optical biflavonoid, (2” R)-2″,3″-dihydrorobustaflavone 7,4′-dimethyl ether (1), and 6 known compounds (2-7) were isolated for the first time from the 70% ethanol extract of Selaginella trichoclada Alsto. The structures of the compounds were confirmed by extensive spectroscopic data analyses. Racemic compound 1 was separated by chiral-phase high-performance liquid chromatography, and the absolute configurations of (±)-1 were defined by circular dichroism spectroscopic data. Compound 1 exhibited moderate cytotoxicity against MCF-7, A549, and HepG2 human cancer cell lines.