(-)-Equol

S-equol is a metabolite of soy isoflavonoid phytoestrogen daidzein, produced by human intestinal bacteria. S-equol has a high affinity for estrogen receptor beta (ERβ) than estrogen receptor (ERα) with Ki values of 0.73 and 6.4 nM respectively. It inhibits the growth of LnCaP, DU145 and PC3 human prostate cancer cell lines. It has significant anti-prostate cancer activities in vitro and in vivo. The anticancer effects are associated with the activation of FOXO3a via an Akt-specific pathway and inhibitory effects on MDM2 expression.