Sulfated modification, characterization, antioxidant and hypoglycemic activities of polysaccharides from Sargassum pallidum

The aim of this study was to investigate the effect of sulfated modification on the in vitro antioxidant and hypoglycemic activities of Sargassum pallidum polysaccharides (SPP). Three sulfated derivatives (S-SPP1-4, S-SPP1-6 and S-SPP1-8) were prepared using chlorosulfonic acid-pyridine method under different reaction conditions. Physicochemical characterization indicated that sulfated modification had successfully occurred. The degrees of substitution (DS) of S-SPP1-4, S-SPP1-6 and S-SPP1-8 were determined to be ranging from 0.85 to 1.19. Sulfated modification resulted in some changes in chemical component, molecular weight and monosaccharide composition of SPP. Among these sulfated polysaccharides, S-SPP1-4 exhibited the best DPPH and ABTS radical scavenging activities, while S-SPP1-8 exhibited the best alpha-glucosidase inhibitory activity and promoting-effect on glucose consumption in insulin resistant (IR)-HepG2 cells. Furthermore, all the sulfated derivatives exhibited better hypoglycemic ability than native SPP. These results suggest that appropriately sulfated modification could enhance the antioxidant and hypoglycemic activities of S. pallidum polysaccharides, which might be used as an alternative derivative of natural antioxidant and hypoglycemic agent. (C) 2018 Elsevier B.V. All rights reserved.