Bioactivities and physicochemical properties of crude polysaccharides from mulberry twigs, agricultural by-products

Jialing 20 is an excellent artificial triploid mulberry variety and the main mulberry cultivar in China, which has a very high biological yield. Its twigs are agricultural by-products that need to be exploited urgently. There are many studies on small-molecule metabolites of its twigs but no studies on polysaccharides. To realize the comprehensive utilization of its twigs in non-food biologics, this study extracted Jialing 20 mulberry twigs polysaccharides (MTPs) by hot water and precipitated them by 30%、60%、90% ethanol into three fractions (MTP30、MTP60、MTP90). Then their contents, monosaccharide compositions, physicochemical properties, and antioxidant and hypoglycemic activities were evaluated. The results showed that they all had good scavenging activities of DPPH free radicals, ABTS free radicals, OH free radicals, and α-glucosidase inhibition. In addition, MTPs all could protect against H2O2-induced Caco-2 cell damage, and their activities were MTP90 > MTP60 > MTP30. These differences might be closely related to different physical and chemical properties. Although they had similar functional groups, the molecular weight distribution showed a decreasing trend with the increasing ethanol concentration. What’s more, MTPs were made up of comparable types of monosaccharides in varying quantities. Polysaccharides with diverse structures have different solubilities in graded ethanol, which may lead to differences in physicochemical properties and biological activities of MTPs. These data suggest MTPs of Jialing 20 could be developed into industrially produced non-food biologics with health benefits, especially to avoid oxidative damage and control blood sugar. At the same time, the different physicochemical properties of the segments precipitated by different ethanol concentrations could be helpful to develop products with different morphologies and types.