Isolation of lignans and biological activity studies of Ephedra viridis.

Phytochemical investigation of Ephedra viridis (whole plant) led to the isolation of four lignans including (+)-9-acetoxyisolariciresinol, which is a new lignan, lariciresinol, 9-acetoxylariciresinol and isolariciresinol. All the isolates were tested for their antioxidant activity and cytotoxicity against a panel of solid tumor and human leukemia cells. They were also screened for estrogenic activity using a recombinant yeast estrogen screening (YES) assay. Most of the lignans exhibited moderate antioxidant activity without any cytotoxicity. None of them were estrogenic in the YES assay.