Extraction, structure characterization, carboxymethylation and antioxidant activity of acidic polysaccharides from Craterellus cornucopioides

Herein, we isolated and purified polysaccharides from Craterellus cornucopioides. Chemical composition analysis revealed that both polysaccharides (CCPs-1 amd CCPs-2) were composed of different molar ratios of rhamnose, fucose, arabinose, xylose, mannose, glucose, and galactose. The structure of polysaccharides was determined using FT-IR, periodate oxidation, smith degradation, methylation analysis, and NMR, which demonstrated that the two polysaccharides were primarily connected by mannose with (1→3)-linked. Notably, the configuration of the two polysaccharides exhibited random coil with pyranoid polysaccharide containing α or β glycosidic bond. Furthermore, to increase the antioxidant activity of polysaccharides (CCPs-1 amd CCPs-2), two carboxymethylated polysaccharides were obtained as cmCCPs-1 and cmCCPs-2 with the degree of substitution values of 0.34 and 0.52, respectively. Structural analysis elucidated that nonselective carboxymethylation occurred in cmCCPs-1 and cmCCPs-2, where C-2, C-4 or C-6 were partially substituted. Of note, cmCCPs-2 exhibited the most significant antioxidant activity.