Optimization, Structural Characterization, and Bioactivities of Polysaccharides from Rosa roxburghii Tratt Fruit Using Enzyme-Assisted Extraction

This study aimed to optimize the enzyme-assisted extraction of polysaccharides (RTFPs) fromRosa roxburghiifruit using response surface methodology. Under the optimal extraction conditions, the yield of RTFPs reached 14.02%, which was close to the predicted value of 13.96%. The primary structural characteristics and the antioxidative and immunomodulatory activities of RTFPs were also examined. Structural characterization revealed that RTFPs comprise 36.38% neutral sugar, 48.83% uronic acid, and 7.29% protein. Their heteropolysaccharide structure features two distinct molecular weight fractions (1.87 × 105Da and 4.75 × 103Da) and a monosaccharide composition dominated by glucose (38.93%), arabinose (20.66%), galactose (20.58%), galacturonic acid (10.94%), and xylose (6.52%). Antioxidant assays demonstrated potent radical scavenging activity, with IC50values of 11 μg/mL (DPPH) and 150 μg/mL (ABTS), comparable to conventional antioxidants. Immunomodulatory studies on RAW264.7 macrophages revealed that RTFPs (100–400 μg/mL) significantly enhanced phagocytosis by 12.61–76.63% and stimulated the secretion of nitric oxide (NO) and tumor necrosis factor-α (TNF-α). These bioactivities are attributed to RTFPs’ high uronic acid content, moderate molecular weight distribution, unique monosaccharide profile, and highly branched conformation.