Abstract: This study employed ultrasonic-assisted water extraction followed by ethanol precipitation to prepare sea buckthorn residue polysaccharide (SBRP). Molecular modification of SBRP was performed via free radical degradation reaction mediated by the hydrogen peroxide-ascorbic acid (H2O2-VC) system, yielding degraded polysaccharides. The primary structure, in vitro antioxidant activities, and hypoglycemic activities of the native and degraded polysaccharides were investigated. The results indicated that after degradation, the total sugar content of SBRP increased, while the protein content decreased significantly. The major monosaccharide composition and functional groups remained largely unchanged. Scanning electron microscopy (SEM) revealed morphological changes in the degraded polysaccharides. The in vitro antioxidant and hypoglycemic activities of the polysaccharides significantly enhanced after degradation. The half-maximal inhibitory concentration (IC50) value for 1,1-diphenyl-2-picrylhydrazyl radical scavenging decreased from 0.37 to 0.13 mg/mL, and that for 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) cation radical scavenging decreased from 0.31 to 0.10 mg/mL. The IC50 value for α-amylase inhibition decreased from 12.61 to 8.77 mg/mL, and that for α-glucosidase inhibition from 0.87 to 9.73 μg/mL. This study provides theoretical support for the comprehensive utilization of SBRP and its application in the development of functional foods.

Key words: polysaccharides; degradation; antioxidant; hypoglycemic activity