Abstract: This paper studied the effects of different processing methods on the antioxidant activity of polysaccharide from Nitraria sibirica Pall. In this experiment, polysaccharide was obtained through hot-drying,freeze-drying and decolorization. By different processing methods,the superoxide free radical (O₂^-·) and DPPH free radical (·DPPH),hydroxyl free radical (·OH) scavenging effects and reducing power of the extracted sample were measured to study the antioxidant ability of polysaccharide from N. sibirica. The results showed that the EC₅₀ values of polysaccharide samples processed by hot-drying,freeze-drying and decolorization were all less than 0.1 mg/mL. Compared with the polysaccharide samples obtained by freeze-drying,the antioxidant ability of the samples obtained by hot-drying decreased because of high temperature resulting in the partial loss of antioxidant activity during the hot-drying process. In addition,experimental results also showed that the capability of scavenging hydroxyl free radical (·OH) in decolorization sample increased. Meanwhile,the superoxide free radical (O₂^-·) scavenging and reducing power decreased. Conversely,in the non-decolorization samples,the scavenging ability of hydroxyl free radical (·OH) and DPPH free radical (·DPPH) declined,the scavenging capacity of superoxide free radical (O₂^-·) and reducing power increased. These results indicated that the polysaccharides from N. sibirica with different processing methods showed different antioxidant activitites. It can be used as a potential antioxidant agent in food industry.

Key words: polysaccharide, Nitraria sibirica Pall;antioxidant;free radicals