Characterization of a polysaccharide from Ipomoea batatas and its in vitro hypoglycemic activity

A medium-molecular-weight (18.04 kDa) polysaccharide named PSPP1 was isolated and purified from Ipomoea batatas (sweet potato). PSPP1 was found to be primarily composed of fructose, glucose, and arabinose. Further structural analysis revealed that its backbone comprised mainly β-D-Fruf residues, with a minor proportion of α-D-Glcp units, and side chains predominantly attached to the O-6 position of →1,6)-β-D-Fruf-(2 → residues. In vitro, PSPP1 significantly inhibited α-glucosidase activity and restored glucose metabolism parameters in an insulin-resistant HepG2 cell model. Transcriptomic and metabolomic analyses indicated that PSPP1 enhanced insulin sensitivity through regulation of oxidative-stress-related metabolic processes, including glutathione (GSH) metabolism, cysteine and methionine metabolism, and porphyrin metabolism, thereby maintaining cellular redox homeostasis and modulating the PI3K/AKT signaling pathway. Further validation by real-time quantitative PCR and Western blotting showed that PSPP1 modulated the expression of key genes (IRS1, PI3K, and AKT) in this pathway and altered phosphorylation levels of IRS1 and AKT, thereby improving insulin signaling. Taken together, these findings identify PSPP1 as a hypoglycemic polysaccharide with potential applications as a functional food ingredient or as a candidate for nutraceutical development.