Impact of polyphenols from black tea and red wine/grape juice on a gut model microbiome

Abstract

Food and beverage products derived from fruit and vegetables contain polyphenols, which have been associated with various health benefits. Polyphenols may influence health through direct uptake in the intestine but also upon interaction with the gut microbiota for example by modification of the microbial composition or by conversion of the polyphenols to further bioactive compounds. So far, there are limited studies of complex polyphenols on the human gut microbiota especially using modern molecular technologies. Most studies investigating effects of dietary polyphenols have focused on single molecules or bacterial strains. In the current study, an in vitro gut microbial ecosystem, namely simulator of the intestinal microbial ecosystem (SHIME), was challenged with either a black tea or a red wine grape extract (RWGE), both containing complex dietary polyphenol mixtures. Within the context of the model system, the effects of these interventions on both microbial numbers and composition as well as metabolite levels were assessed. Antimicrobial effects, largely confined to unculturable members of the ecosystem, were revealed by complementary microbiological techniques. Pyrosequencing analysis showed a shift in the Firmicutes:Bacteroidetes ratio for both interventions. Black tea stimulated Klebsiella, enterococci and Akkermansia and reduced bifidobacteria, B. coccoides, Anaeroglobus and Victivallis. RWGE promoted growth of Klebsiella, Alistipes, Cloacibacillus, Victivallis and Akkermansia while bifidobacteria, B. coccoides, Anaeroglobus, Subdoligranulum and Bacteroides were decreased.The study shows that these complex polyphenols in the context of a model system can modulate select members of the human gut microbiota. These members represent novel targets of polyphenol degrading or resistant microbes to be validated under physiological conditions in vivo and further investigated for polyphenol metabolism or resistance mechanisms.