Structural evolution and prebiotic-like potential of insoluble dietary fiber-polyphenol complexes from Rosa roxburghii Tratt during in vitro digestion and colonic fermentation

Rosa roxburghi Tratt. (RRT) pomace is rich in insoluble dietary fiber (IDF) and polyphenols, but free polyphenols are susceptible to premature loss during digestion. This study constructed an IDF–polyphenol complex (IDF-PP) from RRT pomace via non-covalent adsorption and evaluated its gastrointestinal fate and in vitro colonic fermentation behavior. IDF-PP reduced premature phenolic loss during simulated upper gastrointestinal digestion and enabled a more gradual release during fermentation. Structural analyses showed fermentation-induced remodeling, generating a porous residual matrix while retaining part of the polysaccharide framework. Compared with free polyphenols and IDF, IDF-PP increased short-chain fatty acid production, especially butyrate, and was associated with higher relative abundance of Prevotella -centered Bacteroidetes taxa and Faecalibacterium , together with lower relative abundance of Proteobacteria . Fermentation products also showed enhanced antioxidant and α-glucosidase inhibitory activities. These findings suggest that RRT pomace-derived IDF-PP is a promising fermentation-responsive functional ingredient with potential to modulate gut microbial fermentation.