Abstract: In this study,the experimental condition for decolorization of polysaccharide from Isatidis indigotica was optimized.Based on single factor experiments,orthogonal experiment was performed to select the optimal condition for the decolorization of polysaccharide using the decolorization rate and polysaccharide retention rate as indexes.The optimal technological process of decolorization was adding 1.0%(m/v)active carbon to polysaccharide solution at 70 ℃,with pH at 7.0 and decoloring the solution for 80 min.The decolorization rate was 92.97%,and the retention rate of polysaccharide was 92.45%.DPPH lone electron conjugate method was used to detect scavenging effect of DPPH radical;pyrogallol autoxidation method was used to detect scavenging effect of superoxide anion radical.The results indicated I.indigotica polysaccharides had certain ability of scavenging free radicals,but the scavenging ability was decreased after decolorization.

Key words: Isatidis indigotica, polysaccharide;decoloration;active carbon;antioxidation