Effect of free and bound polyphenols from Rosa roxburghii Tratt distiller's grains on moderating fecal microbiota

Rosa roxburghii Tratt distiller's grains (R. roxburghii DGs), the main by-product of wine processing, showed functional value and potential for high-value usage which benefited from their rich polyphenols. In this study, the free and bound polyphenols from R. roxburghii DGs were extracted and their potential effect on modulating fecal microbiota was investigated using in vitro fecal fermentation. The free polyphenols (26.32-26.45 mg GAE/g) showed higher antioxidant activity compared to the bound polyphenols (8.76-9.01 mg GAE/g). The free and bound polyphenols significantly improved the fecal microbiota community structure and enhanced short chain fatty acids concentrations after the stimulated colonic fermentation for 24 h. Furthermore, the effect of R. roxburghii DGs polyphenols on modulating fecal microbiota was primarily attributed to quercetin, catechin, kaempferol, cyanidin and baicalin. This research suggests that R. roxburghii DGs are a promising source of natural antioxidants and prebiotic foods.