Separation, Purification, Structural Characterization and Antioxidation Effects of a Polysaccharide from Nervilia fordii

The crude polysaccharide from Nervilia fordii obtained by water extraction and ethanol precipitation was separated and purified, and the components of the polysaccharide were analyzed and characterized, and the antioxidant activity in vitro was evaluated. Results showed that: A polysaccharide, NFP-2 was purified by DEAE-52 cellulose and Sephadex G-100 column chromatography from the crude polysaccharides of Nervilia fordii obtained by water extraction and ethanol precipitation. The molecular weight of NFP-2 was determined to be 1150 kDa, and the total sugar content, the uronic acid content and the protein content of NFP-2 were measured to be 82.64%, 16.65% and 6.38%, seperately. It was measured that the NFP-2 was composed of galactose, arabinose, mannose, glucose, rhamnose, and galacturonic acid with their molar ratio of 21.27:13.21:5.26:3.02:2.82:1. And NFP-2 was an acidic polysaccharide without triple helix structure, its glycosidic bond configuration was β-configuration. Its antioxidation effects were tested by several assays in vitro, and it showed that the NFP-2 could scavenge hydroxyl radicals with IC₅₀ 7.95 mg/mL, the scavenging ability of the NFP-2 of 0.5 μg/mL on superoxide anion radicals was 60%, the scavenging ability of the NFP-2 of 10 mg/mL on ABTS cation free radicals was 35.44%, and the scavenging ability of the NFP-2 of 120 μg/mL on DPPH free radicals was 17%.