Isolation, Purification, and Structural Characterization of Antioxidant Polysaccharides Isolated from the Fruiting Bodies of Cordyceps militaris

In the present study, the fruiting bodies of Cordyceps militaris were used as raw materials to extract the crude polysaccharides Y-1, Y-2, Y-3, Y-4, Y-5, Y-6 and Y-7, which fractional precipitation using the ethanol with different volume fractions of 30%, 40%, 50%, 60%, 70%, 80% and 90%. The graded crude polysaccharide with the strongest antioxidant activity was selected to separate and purify the homogeneous polysaccharide with the strongest by DEAE-52 cellulose ion exchange chromatography and Sephadex G-150 gel chromatography. High performance gel chromatography, gas chromatography and infrared spectroscopy were used to identify the molecular weight, monosaccharide composition and functional groups of the homogeneous polysaccharide, and evaluate its antioxidant activity in vivo. The results showed that the graded polysaccharide Y-4 with the strongest antioxidant activity was isolated and purified by DEAE-52 cellulose ion exchange chromatography and Sephadex G-150 gel chromatography, and obtained a homogeneous polysaccharide STP-4 with the strongest antioxidant activity. STP-4 was an α-type configuration oligosaccharide composed of arabinose, mannose, and glucose, with a molecular weight of approximately 1434 Da. It had the functional groups such as O-H, C-H, COOH, C=O, and C-O-C. In addition, STP-4 could significantly reduce the malondialdehyde (MDA) content (P<0.01), increase the superoxide dismutase (SOD) activity (P<0.5), and the glutathione peroxidase (GSH-Px) activity (P<0.01) in the serum of mice with oxidative damage. This study provides a theoretical basis for the in-depth development and antioxidant activity research of Cordyceps militaris resources.