Structural elucidation and immunostimulatory activity of polysaccharide isolated by subcritical water extraction from Cordyceps militaris.

Water-soluble polysaccharides were obtained from Cordyceps militaris (C. militaris) (CMP) by subcritical water extraction (SWE). Two polysaccharides fractions, CMP-W1 and CMP-S1, were isolated from CMP using DEAE-52 cellulose and Sephadex G-150 column chromatography. The structural characteristics of CMP-W1 and CMP-S1 were investigated. The results showed that the molecular weight of CMP-W1 and CMP-S1 are 3.66×105Da and 4.60×105Da, respectively, and both of them were heteropolysaccharides composed of d-mannose, d-glucose, d-galactose with the molar ratios of 2.84:1:1.29 and 2.05:1:1.09, respectively. FT-IR spectra analysis suggested that CMP-W1 and CMP-S1 belonged to pyranose form sugar and protein free. For immunostimulatory activity assay in vitro, CMP-W1 and CMP-S1 significantly promoted lymphatic spleen cell proliferation of mice. Therefore, the polysaccharides obtained from C. militaris by SWE can be used as potential natural immunostimulant in functional foods or medicine.