Effects of in vitro fecal fermentation on the metabolism and antioxidant properties of cyanidin-3-O-glucoside

Anthocyanins' potential health benefits have garnered significant interest. However, due to low bioavailability, the gut microbiota-associated metabolites are suspected to mediate their bioactivity. In this study, cyanidin-3-glucoside (C3G) was fermented with fecal inoculum to simulate colonic microbiota interaction in vitro. The metabolites and antioxidant properties of pre- (P-C3G) and post-fermentation (F-C3G) were determined. Fermentation significantly increased contents of five metabolites (cyanidin, protocatechuic acid, phloroglucinaldehyde, 4-hydroxybenzoic acid and 4-hydroxyphenylacetic acid). Additionally, F-C3G demonstrated superior radicals scavenging than P-C3G, as well as to alleviate H2O2-induced damage in HepG2 cell via increasing superoxide dismutase by 43.26% and catalase by 39.83%, reducing malonaldehyde by 16.40% and cellular ROS production, and activating Nrf2 pathway. Moreover, F-C3G significantly extended the survival rate by 20.67% of Caenorhabditis elegans under heat stress by antioxidation in vivo. This study suggested that anthocyanins metabolism by gut microbiota produce specific metabolites, which potentially exerts protection.