Abstract: Objective: To separate and purify an antioxidant polysaccharide fraction from Apostichopus japonicus longitudinal muscle and to measure the abilities of the fraction and its sulfated counterpart to scavenge hydroxyl and superoxide anion free radicals. Methods: The separation and purification procedure was made up of papain hydrolysis, deprotenization with trichloroacetic acid, and Sephacryl S-400 gel filtration chromatography. The resulting fraction with higher free radical scavenging activity was selected for further studies including infrared spectral analysis and determination of molecular weight and sulfate content. Meanwhile, the fraction was sulfated, and its free radical scavenging activity was compared with that of its sulfated counterpart. Results: The obtained polysaccharide revealed an acidic glycosaminoglycan structure, whose relative molecular weight, sulfate content and substitution degree were 676 kD, 10.98% and 0.285, respectively. Its sulfated counterpart had a sulfate content of 17.43% and a substitution degree of 0.360. Both of them had certain antioxidant activity to scavenge hydroxyl and superoxide anion free radicals, and the antioxidant activity of the sulfated polysaccharide was stronger. Conclusion: Sulfation can result in an increase in the sulfate content, substitution degree and antioxidant activity of the polysaccharide fraction with higher from Apostichopus japonicus longitudinal muscle.

Key words: longitudinal muscle polysaccharide, Apostichopus japonicus, purification, antioxidant activity