S: In vitro estrogenic potency of phytoestrogen-glycosides and some plant flavanoids

Many plants produce chemicals that mimic or interact with hormonal signals in animals. Their presence in human diet is the object of many studies concerned with prevention of breast and prostate cancer, osteoporosis and other hormone-dependent diseases. Isoflavones, daidzein and genistein occurring either free or bound in glycosides are the main phytoestrogens in soya. The present study investigated the estrogenic activities of two isoflavones, two glucosylated isoflavones, one isoflavandiol, two flavanoids and some other plant-derived phenolic compounds. The bioassay used in this study was an estrogen responsive cell line Ishikawa Var-1. Besides, this study also used the recombinant yeast cells bearing the human estrogen receptor for confirming the actual estrogenic nature of the plant chemicals. There was a marked stimulation of alkaline phosphatase activity in Ishikawa cells and β-galactosidase activity in yeast cells by glucosylated isoflavones, genistin and daidzin. Considering the potency of body’s endogenous estrogen (17β-estradiol) as 100, in the Ishikawa assay the relative estrogenic potency of these compounds were found to be genistein (0.11), genistin (0.06), daidzein (0.08) and daidzin (0.07). In the yeast cell assay, the relative estrogenic potencies were genistein (0.1), genistin (0.01), daidzein (0.02) and daidzin (0.002). Estrogenic potency of equol was almost equal (0.18 & 0.16) in both Ishikawa and yeast cell assays, respectively. While kaempferol and resveratro