Antioxidant and immunomodulatory activities of polysaccharides from the rhizome of Dryopteris crassirhizoma Nakai.

Rhizome of the fern Dryopteris crassirhizoma Nakai is used as an antiviral drug in China. The objective was to characterize physicochemical properties, structural features and antioxidant and immunological activities of D. crassirhizoma polysaccharides. An acidic polysaccharide fraction (DCP-3) was obtained from Dryopteris crassirhizoma Nakai by purification with DEAE-52 and Sephadex G-100. DCP-3 was a novel triple-helical polysaccharide with an average MW of 273.2 kDa. This fraction was mainly composed of galactose (36.65%), xylose (34.75%), arabinose (17.07%) and mannose (9.22%). DCP-3 had strong activity for scavenging DPPH radical (IC50: 2.04 mg/mL), hydroxyl radical (IC50: 1.70 mg/mL), and superoxide anions (IC50: 4.20 mg/mL) and also was capable of reducing ferric ions. In addition, nitric oxide production was enhanced in RAW264.7 macrophages stimulated by DCP-3. Based on these bioactivities, we inferred that DCP-3 was a functional component of D. crassirhizoma and may confer antivirus activity, with potential applications in functional food and drug industries.