The two-way phenolic–microbiota interaction: In vitro investigations on the phenolic compound metabolism and microbiota composition with complex apigenin C- and kaempferol O-derivatives

Colonic metabolism appears to be an important role in the biotransformation of flavonoid glycosides in the human body. Conversion can result in bioactivated compounds. However, information about the microbial conversion of complex, highly glycosylated flavonoids and the impact on the gut microbiota are still limited. In this study, the ability of the human intestinal microbiota to convert selected flavonoid O- and C-glycosides was evaluated by performing different in vitro fermentations. Substrate depletion and metabolite formation were determined with a targeted HPLC-ESI-MS/MS method. Changes in the main bacterial groups were estimated with qPCR analyses and 454 sequencing. Short chain fatty acids (SCFA), as important degradation products of the carbohydrate substituent, were investigated with GC. The results showed that all flavonoid glycosides were metabolized yielding smaller molecular substances. Differences in the metabolite formation and time courses between the donors and substances were determined. However, significant changes in the microbiota composition and in the SCFA production were not detected. Therefore, a prebiotic effect of phenolic compounds seems to be not achievable with flavonoid glycosides concentrations in typical diets