Equol
Equol (4',7-isoflavandiol) is an isoflavandiol metabolized from daidzein, a type of isoflavone, by bacterial flora in the intestines. While endogenous estrogenic hormones such as estradiol are steroids, equol is a non-steroidal 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.
History
(S)-Equol was first isolated from horse urine in 1932, and the name was suggested by this equine connection. Since then, equol has been found in the urine or plasma of many other animal species, although these animals have significant differences in their effectiveness in metabolizing the soy isoflavone daidzein into equol. In 1980, scientists reporting the discovery of equol in humans. The ability of (S)-equol to play a role in the treatment of estrogen- or androgen-mediated diseases or disorders was first proposed in 1984.
