Abstract: In this study, polysaccharide was prepared from Cornus officinalis seeds by subcritical water extraction, 30% (V/V) H2O2 decolorization, and Sevag deproteinization. Using DEAE-52 cellulose chromatography, the polysaccharide was fractionated into five fractions, namely COSP-1, COSP-2, COSP-3, COSP-4 and COSP-5. Sephadex G-100 gel chromatography was used to further purify the main fracion COSP-4. Gel chromatography and monosaccharide composition analysis showed that COSP-4 had a molecular mass of 2.03 × 104 Da as an acidic homogeneous polysaccharide composed of rhamnose, glucuronic acid, galacturonic acid, glucose, galactose and xylose, with a molar ratio of 0.96 : 0.18 : 5.48 : 0.28 : 1 : 10.70. The methylation reaction and nuclear magnetic resonance (NMR) showed that COSP-4 contained 14 kinds of methylated sugars, as well as α- and β-glycosyl residues. The most abundant monosaccharide in the polysaccharide was 1,4,5-tri-O-acetyl-2,3-di-O-methyl xylitol. Scanning electron microscopy (SEM) showed that COSP-4 had an irregular, fragmentary, loose and spongy structure. The antioxidant experiments showed that COSP-4 had strong scavenging capacity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radicals with half maximal inhibitory concentrations (IC50) of (1.72 ± 0.14), (1.48 ± 0.17), and (2.87 ± 0.27) mg/mL, respectively. These results will provide the basis for further research on the structure-activity relationship of Cornus officinalis seed polysaccharides and will promote their application.

Key words: Cornus officinalis seed polysaccharides; purification; structural characterization; antioxidant activity