Preparation of the controlled acid hydrolysates from pumpkin polysaccharides and their antioxidant and antidiabetic evaluation

Pumpkin polysaccharides (PPe) have various biological activities. This research was to optimize the acid hydrolysis process of PPe with OH scavenging ability based on central composite design (CCD), and to explore the antioxidant and antidiabetic activities of the acid hydrolysates (PPe-H). A rat model of type 2 diabetes mellitus (T2DM) using high-fat diet and low-dose streptozotocin were established to assess the bioactivities. Both PPe and PPe-H could distinctly reduce fasting blood glucose level, prevent the weight loss in T2DM rats, and exhibited the remarkable ability to enhance the activities of the antioxidant enzymes (CAT and GR, p < 0.01, p < 0.01) and the level of GSH (p < 0.05, p < 0.01). Besides, PPe-H could significantly decrease the level of MDA (p < 0.05). Furthermore, PPe-H could cause an evident improvement to glucose stimulated GLP-1 secretion from 0 min to 30 min (p < 0.05). PPe and PPe-H were both the heteropolysaccharide and composed of rhamnose, arabinose, glucose and galactose, their molecular weight were 104.27 kDa and 37.58 kDa, respectively. The potential antidiabetic mechanism of PPe-H might be related to stimulating the secretion of endogenous GLP-1, decreasing oxidative damages, and then slowing down the process of diabetes.