Pectin-Type Polysaccharides from Raspberry (Rubus Idaeus L.): Structure Characterization and Anti-Colitis Activity

This study explored the structural properties and therapeutic potential of RAP-3A, a novel pectin-type polysaccharide extracted from raspberry (Rubus idaeus L.), in DSS-induced colitis. Structural analysis revealed that RAP-3A, with a molecular weight of 51.03 kDa, is primarily composed of a backbone of 1, 4-galacturonic acid glycan, incorporating a 1, 4-linked α-GalpA and 1, 2-linked α-Rhap disaccharide repeating unit, with branches at C-4 of the Rhap residue comprising 1, 6-linked β-Galp, 1, 4-linked β-Galp or 1, 5-linked α-Araf. Remarkably, RAP-3A significantly alleviated colitis symptoms in mice, including weight loss, disease activity index (DAI), and histopathological damage. Mechanistically, RAP-3A inhibited the TLR4/NF-κB pathway, enhanced intestinal barrier function by upregulating ZO-1 and occludin, and reduced goblet cell depletion. Furthermore, RAP-3A promoted a favorable shift in gut microbiota composition, increasing the abundance of beneficial SCFA-producing bacteria such as Bacteroidales_S24-7, Rikenellaceae, Clostridiales, Oscillospira, and Lachnospiraceae, while suppressing pathogenic bacteria, notably Escherichia. GC-MS analysis further confirmed that RAP-3A significantly increased fecal SCFAs levels. Collectively, these findings suggested that RAP-3A holds considerable potential for development as a functional food aimed at the treatment of colitis.