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Metabolites 2015, 5(1), 56-73; doi:10.3390/metabo5010056

The Role of Colonic Bacteria in the Metabolism of the Natural Isoflavone Daidzin to Equol

Division of Microbiology, National Center for Toxicological Research, FDA, Jefferson, AR 72079, USA
Academic Editor: Wendy Roslyn Russell
Received: 7 November 2014 / Accepted: 7 January 2015 / Published: 14 January 2015
(This article belongs to the Special Issue Metabolomic Studies of the Human Gut Microbiome)
View Full-Text   |   Download PDF [538 KB, uploaded 15 January 2015]   |  


Isoflavones are found in leguminous plants, especially soybeans. They have a structural similarity to natural estrogens, which enables them to bind to estrogen receptors and elicit biological activities similar to natural estrogens. They have been suggested to be beneficial for the prevention and therapy of hormone-dependent diseases. After soy products are consumed, the bacteria of the intestinal microflora metabolize isoflavones to metabolites with altered absorption, bioavailability, and estrogenic characteristics. Variations in the effect of soy products have been correlated with the isoflavone metabolites found in plasma and urine samples of the individuals consuming soy products. The beneficial effects of the soy isoflavone daidzin, the glycoside of daidzein, have been reported in individuals producing equol, a reduction product of daidzein produced by specific colonic bacteria in individuals called equol producers. These individuals comprise 30% and 60% of populations consuming Western and soy-rich Asian diets, respectively. Since the higher percentage of equol producers in populations consuming soy-rich diets is correlated with a lower incidence of hormone-dependent diseases, considerable efforts have been made to detect the specific colonic bacteria involved in the metabolism of daidzein to the more estrogenic compound, equol, which should facilitate the investigation of the metabolic activities related to this compound. View Full-Text
Keywords: metabolites; metabolism; intestinal bacteria; phytoestrogen; isoflavone; daidzin; daidzein; equol metabolites; metabolism; intestinal bacteria; phytoestrogen; isoflavone; daidzin; daidzein; equol

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Rafii, F. The Role of Colonic Bacteria in the Metabolism of the Natural Isoflavone Daidzin to Equol. Metabolites 2015, 5, 56-73.

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