Bound polyphenols contribute to the microbiota-linked metabolic effects of Rosa roxburghii dietary fiber in rats

Bound polyphenols (BPs) are important non-extractable phytochemicals that remain associated with dietary fiber (DF) matrices and may contribute to the biological activity of plant-derived foods. However, their specific in vivo contribution to the functionality of fruit-derived DF remains insufficiently understood. In this study, BPs-retained DF from Rosa roxburghii Tratt. pomace (RRT-DF) and its dephenolized counterpart (DF-F) were compared in rats to evaluate the potential contribution of BPs to differences in gut microbiota, short-chain fatty acids (SCFAs) production, and host metabolic responses. Compared with DF-F, RRT-DF was associated with more favorable serum lipid-related parameters and hepatic antioxidant capacity. Gut microbiota analysis showed that BPs-retained RRT-DF was associated with higher relative abundances of genera related to fiber fermentation and SCFAs metabolism, including Oscillospira and Ruminococcus , together with higher fecal butyrate levels. Serum metabolomics further revealed distinct metabolic profiles between the RRT-DF and DF-F groups, with major differences related to lipid-related metabolism, bile acid-associated metabolites, porphyrin/cofactor metabolism, and ether lipid metabolism. In addition, microbiome–metabolome correlation analysis identified specific associations between DF-enriched genera and serum metabolites related to bile acid and amino acid derivative metabolism. These findings suggest that retention of naturally associated BPs may contribute to the distinct in vivo bioactivity associated with RRT-DF, potentially in relation to differences in gut microbiota and microbiota-linked metabolic signatures. Overall, this study supports the potential functional significance of preserving BPs in fruit by-product-derived DF and provides new evidence linking BPs retention with antioxidant-related and metabolic responses in vivo .