Effects of simulated gastrointestinal digestion in vitro on the chemical properties, antioxidant activity, α-amylase and α-glucosidase inhibitory activity of polysaccharides from Inonotus obliquus

This study was aimed to investigate the impacts of gastrointestinal digestion in vitro on the physicochemical properties and the biological activities of polysaccharides from Inonotus obliquus (UIOPS-1). Results showed that the monosaccharides composition, structure and conformation of polysaccharides were remarkably altered, and the molecular weight (Mw) of UIOPS-1 was steadily decreased from 105.02 kDa to 88.97 kDa and 36.74 kDa after simulated digestion. The reducing ends were increased and the free monosaccharides including d-glucose, d-galactose and d-xylose were released suggested that the degradation of UIOPS-1 was caused by disrupting the aggregates and glycosidic bonds. The antioxidant activities of UIOPS-1 were significantly increased after gastric digestion (P < 0.05), however, they were decreased after intestinal digestion. The α-amylase and α-glucosidase inhibitory activities of UIOPS-1 were significantly increased after digestion indicating a good control of postprandial hyperglycemia (P < 0.001). The results indicated that UIOPS-1 still exhibited antioxidant and antihyperglycemic potential after gastrointestinal digestion, which could be considered as a promising candidate for functional foods.