The dietary intervention of synbiotic preparation promotes the bioconversion of soy isoflavones to equol and its metabolic mechanism

Soy isoflavones (SI) undergo biotransformation into equol (EQ) by gut microbiota and equol exhibits higher bioactivity than soy isoflavones. As a result, the endogenous equol concentration becomes a crucial indicator for assessing the bioavailability of soy isoflavones. This study screened prebiotics and probiotics capable of promoting equol production and constructed a human flora-associated (HFA) mice model with both high- and lowequol-producing levels to investigate the effects of synbiotic preparation on soy isoflavones transformation by gut microbiota. In vitro fermentation revealed that lactulose and Lactobacillus rhamnosus ATCC 7469 significantly enhanced equol production. Furthermore, synbiotic preparation intervention substantially increased plasma equol concentration in low-producing HFA mice. Through the integration of metagenomics and metatranscriptomics analyses, we identified EC 2.7.1.40 in the ko00010 pathway as a crucial auxiliary factor facilitating equol production. In conclusion, this study presents a novel model for enhancing endogenous equol levels through synbiotic preparation intervention.