Abstract: In this study, water-soluble polysaccharide from Osmunda japonica (WOJP), obtained by sequential water extraction and ethanol precipitation, was purified and fractionated by chromatography on diethylaminoethyl (DEAE)-cellulose columns into two major fractions: neutral WOJP (WOJP-N) and acidic WOJP (WOJP-A). As determined by high performance liquid chromatography (HPLC), the molecular mass of WOJP-N was 31.8 kDa, composed of rhamnose, galacturonic acid, glucose, galactose, xylose and arabinose, with a molar ratio of 9.1:5.7:13.3:37.6:5.6:11.8; WOJP-A had a molecular mass of 15.7 kDa, composed of rhamnose, galacturonic acid, galactose, and arabinose, with a molar ratio of 7.0:56.4:26.1:5.2. Fourier transform infrared spectroscopic (FTIR) analysis showed that WOJP-N was mainly composed of β-galactose; WOJP-A was mainly composed of galactopyranouronic acid with partial esterification modification. The antioxidant experiments showed that the Fe3+ reducing power, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, and superoxide anion radical scavenging capacity of WOJP were similar to those of vitamin C (VC), indicating that WOJP had good antioxidant activity. WOJP-N and WOJP-A played synergistic roles in antioxidant activity, and both of them were active components of WOJP. These results will provide a basis for further studies on the structure-activity relationship of polysaccharides from Osmunda oleracea and the development of potential functional foods, and also provide a reference for the application of Osmunda oleracea.

Key words: Osmunda japonica; polysaccharide; isolation and purification; antioxidant activity