Analysis of interaction property of calycosin-7-O-β-d-glucoside with human gut microbiota

Calycosin-7-O-β-d-glucoside as the major isoflavonoids in Astragali Radix has been investigated intensively and has been reported to possess a wide range of pharmacological properties. However, the route and metabolites of calycosin-7-O-β-d-glucoside by human intestinal bacteria are not well understood and its metabolites may accumulate to exert physiological effects. Therefore, the objective of this study was to screen the ability of the bacteria to metabolize calycosin-7-O-β-d-glucoside and assess the effect of this compound on the intestinal bacteria. Finally, five strains including Bacteroides sp.13, and sp.58, Clostridium sp.21-2, Veillonella sp.43-1, and Bacillus sp.46 were isolated from human intestinal bacteria and were studied their abilities to convert calycosin-7-O-β-d-glucoside. A total of six metabolites were identified in human incubated solution by ultra performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC–Q-TOF-MS). The results indicated that hydrolysis, demethylation, dehydroxylation and acetylation were the major metabolism of calycosin-7-O-β-d-glucoside. On the other hand, different strains of intestinal bacteria have varying degrees of growth sensitivity to calycosin-7-O-β-d-glucoside. Growth of certain pathogenic bacteria such as Enterobacter, Enterococcus, Clostridium and Bacteroides was significantly repressed by calycosin-7-O-β-d-glucoside, while commensal probiotics such as Lactobacillus, Bifidobacterium were less severely affected. This indicates that calycosin-7-O-β-d-glucoside exert significant effects on the intestinal environment by modulation of the intestinal bacterial population. Our observation provided further evidence for the importance of intestinal bacteria in the metabolism, absorption and potential activity of calycosin-7-O-β-d-glucoside in human health and diseases.