Structural Characterization and Protective Effects of Camellia oleifera Fruit Shell Polysaccharides against DSS-Induced Ulcerative Colitis in Mice

Plant polysaccharides have been reported to possess multiple pharmacological effects that can inhibit the progression of inflammatory diseases. The shell of Camellia oleifera fruits is a byproduct of the C. oleifera industry that is insufficiently utilized. Herein, a novel polysaccharide (CFP-A) was purified from C. oleifera fruit shells, and its structure elucidation and anti-inflammatory activity against dextran sulfate sodium (DSS)-induced ulcerative colitis were investigated. Structural analysis revealed that CFP-A is a neutral heteropolysaccharide with a molecular weight of 5643 Da, primarily comprising arabinose (Ara), galactose (Gal), and glucose (Glc). The main chain of CFP-A was →3,6)-α-d-Galp-(1→3,6)-α-d-Galp-(1→3,6)-α-d-Galp-(1→3)-α-d-Galp-(1→. The branch chains α-d-Galp-(1→6)-α-d-Galp-(1→, α-l-Araf-(1→[5)-α-l-Araf-(1]₇→3,5)-α-l-Araf-(1→, and α-l-Araf-(1→[4)-α-d-Glcp-(1]₂→ were respectively connected at the C6 position of →3,6)-α-d-Galp-(1→. CFP-A reduced the expression levels of interleukin-6 and interleukin-1β and the production of nitric oxide in lipopolysaccharide-induced Raw264.7 macrophages; it also downregulated inflammatory factor levels in the colon and alleviated splenic hypertrophy, colonic tissue damage, and apoptosis in DSS-induced colitis. Mechanistically, CFP-A attenuated DSS-induced colonic inflammation in mice by activating the Keap1/Nrf2/HO-1 pathway. Collectively, these findings highlight the potential of CPF-A as a complementary therapy for ulcerative colitis.