Structure identification and activity evaluation of polysaccharide from Codonopsis pilosula ( C. pilosula nannf. Var. modesta (nannf.) L. T. Shen) )

Codonopsis pilosula is a medicinal plant with properties related to food, and the antioxidant and hypoglycemic components of its natural polysaccharides, as well as their related mechanisms, have not been fully understood. This study examined the physicochemical properties and structure of C. pilosula polysaccharide (WCP) using an orthogonal extraction method involving hot water-alcohol precipitation, high-resolution spectroscopy, and microscopic imaging technology. The antioxidant and hypoglycemic activities of the polysaccharides were assessed. Six fractions (WCP1, WCP2, WCP3, WCP4, WCP5, and WCP6) were identified through purification using a DEAE-cellulose column and Sephadex G-100 gel column. Mannose, glucose, and arabinose were identified as the primary monosaccharide components of WCPs through Gas Chromatography (GC). The polysaccharide exhibited a crystal structure composed of irregularly entangled pyranose particles of WCPs as revealed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The polysaccharide decomposed into smoother triple-helix fibrous flocs as indicated by Congo red analysis and circular dichroism analysis (CD). The antioxidant capacity of the polysaccharides against various free radicals was evaluated, with WCP4 demonstrating a significant reducing capacity. Moreover, WCP3 and WCP5 displayed notable inhibition rates of alpha-amylase and alpha-glucosidase, respectively. Molecular docking studies indicated the interaction of WCP5 with two enzymes, forming multiple hydrogen bonds through specific amino acids. In the gromacs simulation, both composite systems maintained a steady state in terms of root mean square deviation (RMSD), root mean square fluctuation (RMSF), and radius of gyration, providing strong support for their potential as a reference for the developing novel therapeutic approaches to diabetes.