Structural identification of ginseng polysaccharides and testing of their antioxidant activities

A large number of polysaccharides were presented in boiling-water extraction of ginseng. A DEAE-Sepharose CL-6B column chromatography was used to isolate the major polysaccharides from ginseng. Two fractions were obtained, named GPII and GPIII. Both GPII and GPIII were a neutral polysaccharide and a single peak in HPLC with Sugar KS-804 column, with a molecular weight of 3 × 105 and 4 × 105, respectively, comprised mainly of glucose. Analysis by Periodate oxidation–Smith degradation indicated that GP was composed of 60.06% (1→)- or (1 → 6)-glycosidic linkages and 39.94% (1 → 3)-glycosidic linkages, and GPIII 16.23% (1→)- or (1 → 6)-glycosidic linkages, 25.98% (1 → 2)-glycosidic linkages, and 57.79% (1 → 3)-glycosidic linkages. On the basis of superoxide radical assay, hydroxyl radical assay and self-oxidation of 1,2,3-phentriol assay, their antioxidant activities were investigated. GPII exhibited equivalent inhibiting power for self-oxidation of 1,2,3-phentriol to Vc, a little higher scavenging activity of superoxide radical and hydroxyl radical than Vc, and should be explored as a novel potential antioxidant.