Extraction and structural features of water chestnut peel polysaccharides with antioxidant and hypoglycemic potential

To explore the high-value utilization of water chestnut peel, this study focused on the preparation, structural characterization, and in vitro biological activities of its polysaccharides. Polysaccharides were extracted by hot water, purified via water-soluble alcohol precipitation, deproteinization, and dialysis to obtain refined water chestnut peel polysaccharide (WCPP). The crude polysaccharide yield was 12.2%, with the purified product achieving a maximum purity of 90.1%. Structural characterization showed WCPP had a weight-average molecular weight (Mw) of 47.4 kDa and number-average molecular weight (Mn) of 32.1 kDa, with glucose (86.59%) as the dominant monosaccharide, accompanied by small amounts of galactose (4.15%), arabinose (2.40%), xylose (1.18%), rhamnose (0.56%), mannose (0.46%), and acidic monosaccharides (galacturonic acid: 3.74%; glucuronic acid: 0.91%), belonging to a low-pectin-like substance. In vitro antioxidant assays indicated deproteinized WCPP exhibited potent radical scavenging (DPPH: 94%, hydroxyl: 92%, superoxide anion: 93%) and reducing ability (0.91) at 3.2 mg/mL, approaching vitamin C (Vc) levels. Using the RAW264.7 cell model, WCPP dose-dependently inhibited hydrogen peroxide-induced damage by downregulating malondialdehyde (MDA) production and enhancing catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activities to alleviate oxidative stress. In vitro hypoglycemic studies showed WCPP blocked starch digestion and glucose absorption via inhibiting α -amylase and α -glucosidase activities (dose-dependent), while medium and high concentrations significantly increased glucose consumption in insulin-resistant HepG2 cells. This study provides an efficient technical route for water chestnut peel waste recycling and theoretical/experimental support for developing natural antioxidant and hypoglycemic functional foods or health products.