Biotransformation analysis of daidzin in vitro based on fecal bacteria and probiotics

Daidzin, as one of isoflavone glycosides, has been reported to have multiple activities with few absorbed into body. However, the metabolic behavior of daidzin by intestinal flora has not been researched, that this defect severely constrains its applications. In this study, daidzin and its metabolites were qualitatively and quantitatively analyzed by HPLC and ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) in the fermentation system for daidzin and fecal bacteria. Meanwhile, the alterations of intestinal flora with daidzin were detected by 16S rRNA sequencing technology. Based on the results of intestinal flora, the daidzin and its metabolites transformed by the screened probiotics were quantified and qualified, which the results would corroborate the transformation of daidzin and fecal bacteria. Eventually, daidzin was decreased from 0.30158 mg/mL at 0 h to 0.01176 mg/mL at 48 h, daidzein, as the aglycone of daidzin, was increased from 0.02963 mg/mL at 0 h to 0.04682 mg/mL at 48 h, suggesting the presence of other metabolites. Next, 31 metabolites including the products of ketone removal, Retro-Diels-Alder (RDA) fragmentation, hydroxylation, methylation, C ring cracking and sulfation were identified. The results of 16S rRNA sequencing showed that the intestinal flora, especially Bifidobacterium, was dramatically altered after incubation with daidzin (p < 0.05). Hereby, the fermentation systems of five probiotics (Lactobacillus 3044, Bifidobacterium adolescentis 1.2190, Bifidobacterium longum 25033, Lactobacillus plantarum F1 and Lactobacillus plantarum B2) and daidzin were approved, and these results showed that most metabolites of daidzin were able to be identified with the identical transformation reactions. The study revealed the rationality of daidzin biotransformation at the new perspective, and constructs a new model for fecal metabolites of compounds. These results will also broaden the continued research on daidzin.