(R)-Equol is a non-steroidal estrogen produced from the metabolism of the isoflavonoid phytoestrogen daidzein by human intestinal microflora. It is a chiral molecule that exists in two enantiomeric forms. In contrast to the estrogen receptor selectivity of (S)-equol , (R)-equol is a weaker ER agonist that binds to ERα and ERβ with Ki values of 27.4 and 15.4 nM, respectively. The (R)-enantiomer demonstrates higher ER agonist activity at ERα compared to ERβ.
