Bioassay-guided isolation, identification, and quantification of the estrogen-like constituent from PCSPES

The herbal mixture PC SPES, a dietary supplement for patients with prostate cancer, has been proved to have estrogenic activity in clinical trials. To determine the active components in PC SPES for estrogenic activity; a bioassay-guided fractionation of PC SPES using a functional estrogen receptor (ER) assay led to the isolation and identification of the most active constituent, ethinyl estrodiol, together with two flavonones, neobaicalein and tenaxin I. The isolation, identification and quantification of ethinyl estrodiol are discussed.