(±) -Equol

(±) -Equol ((R, S) -Equol) is a non-steroidal estrogen produced from the metabolism of the isoflavonoid phytoestrogen daidzen by human intestinal microflora. The estrogen receptor (ER) agonist activity of the naturally occurring (S) -enantiomer (EC50 = 85 and 65 nM for human ER? and ER?, respectively) is similar to that of genistein but exceeds that of daidzein. (±) -Equol preferentially binds ER? (Ki = 0.73 nM) and demonstrates approximately 9-fold lower affinity for ER? (Ki = 6.41 nM) . (±) -Equol is also a potent antagonist of dihydrotestosterone, which has important implications for prostate cancer and other androgen-mediated pathologies.