Carboxymethylation and antioxidant activity of rhodiola polysaccharide

Objective To study the changes in antioxidant activity of rhodiola polysaccharide due to carboxymethylated modification.Methods Extraction of rhodiola polysaccharide was prepared with water extract-alcohol precipitation method.The conditions of carboxymethylated modification was optimized with orthogonal experiment.The elimination of 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate (ABTS)-related free radicals and superoxide anion free radicals were detected before and after the modification of rhodiola polysaccharide to evaluate its antioxidant activity.Results The optimal reaction temperature was 60 ℃ for the carboxymethylated modification of rhodiola polysaccharide under the chloroacetic acid dosage of 15 mg,the etherification reaction time of 3.5 hours,and the carboxymethyl substitution degree of 10.73.At the concentration of 5 mg/mL,the carboxymethylated rhodiola polysaccharide-induced scavenging of superoxide anion radical and ABTS-related free radicals were was 53.16% and 45.64%,which were obviously higher than the scavenging activities of rhodiola polysaccharide.Conclusion Rhodiola polysaccharide is of strong antioxidant activity after being carboxymethylated.