Equol (4′,7-isoflavandiol) is an isoflavandiol metabolized from daidzein, a type of isoflavone found in soybeans and other plant sources, by bacterial flora in the intestines.While endogenous estrogenic hormones such as estradiol are steroids, equol is a nonsteroidal estrogen. However, only about 30-50% of people have intestinal bacteria that make equol. Equol can exist in two enantiomeric forms, (S)-equol and (R)-equol.(S)-Equol preferentially binds estrogen receptor beta.
(S)-equol is under development for the treatment of menopausal symptoms such as hot flashes and benign prostatic hyperplasia.