Equol: pharmacokinetics and biological actions

J Nutr. 2010 Jul;140(7):1363S-8S. doi: 10.3945/jn.109.119784. Epub 2010 Jun 2.


Equol [7-hydroxy-3-(4'-hydroxyphenyl)-chroman], an isoflavan produced by intestinal bacteria in response to soy isoflavone intake in some but not all humans, exhibits a wide range of biological properties. It exists as the diastereoisomers S-(-)equol and R-(+)equol. Intestinal bacteria produce exclusively S-(-)equol, which has selective affinity for estrogen receptor (ER)-beta. The evidence is conflicting on whether there is an advantage to producing S-(-)equol in response to soy isoflavone intakes, but the ability to now synthesize these diastereoisomers opens the way for future clinical trials to directly examine their potential in a number of hormone-dependent conditions. In this review, the plasma and urinary pharmacokinetics of S-(-)equol and R-(+)equol are reviewed and summarized, and some of the more recent evidence supporting potential biological effects of S-(-)equol is considered.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Animals
  • Bacteria / metabolism
  • Biotransformation
  • Equol
  • Humans
  • Intestines / microbiology
  • Isoflavones / chemistry
  • Isoflavones / pharmacokinetics*
  • Isoflavones / pharmacology*
  • Stereoisomerism


  • 4',7-dihydroxy-3,4-dihydroisoflavone
  • Isoflavones
  • Equol