Abstract
Isoflavones are transformed in the gut into more estrogen-like compounds or into inactive molecules. However, neither the intestinal microbes nor the pathways leading to the synthesis of isoflavone-derived metabolites are fully known. In the present work, 73 fecal isolates from three women with an equol-producing phenotype were considered to harbor equol-related genes by qPCR. After typing, 57 different strains of different taxa were tested for their ability to act on the isoflavones daidzein and genistein. Strains producing small to moderate amounts of dihydrodaidzein and/or O-desmethylangolensin (O-DMA) from daidzein and dihydrogenistein from genistein were recorded. However, either alone or in several strain combinations, equol producers were not found, even though one of the strains, W18.34a (also known as IPLA37004), was identified as Adlercreutzia equolifaciens, a well-described equol-producing species. Analysis and comparison of A. equolifaciens W18.34a and A. equolifaciens DSM19450T (an equol producer bacterium) genome sequences suggested a deletion in the former involving a large part of the equol operon. Furthermore, genome comparison of A. equolifaciens and Asaccharobacter celatus (other equol-producing species) strains from databases indicated many of these also showed deletions within the equol operon. The present results contribute to our knowledge to the activity of gut bacteria on soy isoflavones.
Highlights
The consumption of soy and soy-derived products correlates with better intestinal health, reduced menopause symptoms, and a smaller prevalence of hormone-mediated syndromes, cardiovascular disease, and cancer
More than 500 colonies from the dilutions of the fecal samples were screened by quantitative PCR (qPCR) targeting the tdr gene
No association was seen between the formation of dihydrodaidzein from daidzein and that of dihydrogenistein from genistein, some strains produced both isoflavone derivatives
Summary
The consumption of soy and soy-derived products correlates with better intestinal health, reduced menopause symptoms, and a smaller prevalence of hormone-mediated syndromes, cardiovascular disease, and cancer (for a recent review, see Zaheer et al [1]). Soy has many biologically active compounds [2], but its beneficial health effects have been repeatedly attributed to its isoflavone content [3]. As recorded for other polyphenols, isoflavones have antioxidant [6] and enzyme-inhibitory [7] properties. All of these features may contribute to their supposed health benefits. While 80–90% of people can produce O-DMA, only 25–50% of humans produce equol [10,11,12] Both O-DMA and equol are produced from the isoflavone daidzein via the exclusive action of intestinal bacteria [9]
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