Structural Characterization and Hypoglycemic Effects of a Purified Polysaccharide From Cinnamomum cassia

A purified polysaccharide, designated CCP1A, was extracted and isolated from Cinnamomum cassia bark using ultrasonic-assisted composite enzymatic extraction followed by DEAE-52 and Sephadex G-100 column chromatography. CCP1A had a molecular weight of 8.161 kDa and was primarily composed of glucose and galacturonic acid, with minor amounts of rhamnose, arabinose, galactose, xylose, and mannose. Spectroscopic analyses (FT-IR and ¹H NMR) confirmed the coexistence of α- and β-glycosidic linkages and a pyranose ring structure. The Congo red assay indicated a stable helical conformation, and transmission electron microscopy revealed dendritic, coiled aggregates. In a mouse model of type 2 diabetes induced by a high-fat diet combined with low-dose streptozotocin, oral administration of CCP1A (100, 200, and 300 mg/kg/day for 4 weeks) dose-dependently reduced fasting blood glucose, improved glucose tolerance and lipid profiles (TG, TC, LDL-C, and HDL-C), and alleviated polydipsia, polyphagia, weight loss, as well as pancreatic pathological damage. Mechanistically, CCP1A suppressed intestinal α-amylase and α-glucosidase activities, promoted hepatic and muscle glycogen synthesis, upregulated the hepatic mRNA expression of GCK, GLUT2, PI3K, AKT, and Nrf2, downregulated PEPCK mRNA expression, increased serum levels of T-SOD, GSH-Px, CAT, and T-AOC, and decreased MDA and GSP levels. These findings suggest that CCP1A exerts multi-target hypoglycemic effects potentially involving inhibition of intestinal glucose absorption, modulation of insulin signaling-related genes, promotion of glycogen synthesis, suppression of gluconeogenesis, and upregulation of Nrf2 mRNA. Hence, CCP1A represents a promising natural candidate for functional food development against type 2 diabetes.