Abstract:This study aimed to understand the total sugar and reducing sugar content in the products of in vitro simulated gastric and small intestinal digestion of Rosa roxburghii Tratt polysaccharides （RRTP）,the types and content of short-chain fatty acids （SCFAs） from colonic anaerobic fermentation products,and the antioxidant function of digestion products. The total sugar content was determined by the phenol-sulfuric acid method,and the reducing sugar content was determined by the 3,5-dinitrosalicylic acid （DNS） method. The types and content of SCFAs were determined by gas chromatography. The scavenging rates of hydroxyl free radical （·OH）,1,1-diphenyl-2-picrylhydrazyl free radical,and 2,2′-azino-bis（3-ethylbenzothiazoline-6-sulfonic acid）+ free radical were determined by colorimetry. The results showed that the content of total sugar and reducing sugar in RRTP did not change after simulated gastric digestion in vitro. After simulated small intestinal digestion in vitro,the total sugar content decreased. After digestion for 2 h,the reducing sugar content increased and then leveled off. After simulated colonic anaerobic fermentation in vitro,the total sugar content decreased significantly（P<0.05）,and the reducing sugar content decreased significantly within 12 h（P<0.05） and then leveled off,with SCFAs such as acetic acid,propionic acid,and n-butyric acid produced. In the simulated gastric digestion stage in vitro,the ·OH scavenging rate of RRTP products changed most,showing a trend of first increasing and then decreasing. At the stage of small intestinal digestion,the scavenging rates of ·OH and ABTS+free radicals by RRTP products increased at 6 h（P<0.05）. In the anaerobic fermentation stage of colon,the scavenging rate of DPPH free radical by RRTP products changed most and also showed a trend of first increasing and then decreasing. In summary,the in vitro simulated gastric digestion of RRTP was limited,but they can be fermented and decomposed in the colon to produce SCFAs such as acetic acid,propionic acid,and n-butyric acid. Their in vitro digestion products had strong antioxidant function,and this function changed with the progress of digestion.