Abstract: Carboxymethy chitosan was oxidatively degraded with H2O2. The effects of reaction time and concentration of H2O2 on the degradation were studied. Viscosity determination and modified Schales’ procedure were applied to assay the molecular weights of degraded carboxymethyl chitosan. Antioxidant activity of degraded carboxymethy chitosan was evaluated as hy- droxyl radical scavenger by flow injection chemoluminescence technology. The results showed that the molecular weights of degraded products would be a relative constant value with the increase of H2O2 concentration. Carboxymethyl chitosan with molecular weight of about 1100 would be obtained when the H2O2 concentration is higher than 1.3mol/L and reaction time is longer than 16h. All degraded carboxymethyl chitosans show certain hydroxyl radical scavenging activity, but the antioxidant activity is stronger at lower molecular weight.

Key words: carboxymethy chitosan, H2O2 oxidative degradation, hydroxide radical, antioxidant activity