X-ray single-crystal analysis of (-)-(S)-Equol isolated from rat's feces

The biological effects of soy isoflavones have attracted considerable interest in recent years, leading to numerous studies on dietary intake and epidemiology. (-)-(S)-Equol (3) is a metabolite produced in vivo from the isoflavone daidzein, a kind of soy phytoestrogen, by the action of gut microflora. It has higher biological activity than its precursor. Here, we wish to report the isolation and first X-ray crystal structure of 3 from the feces of rats fed a soy-isoflavone-containing diet.