Antioxidative activities of water-soluble disaccharide chitosan derivatives

Water-soluble chitosan derivatives, having various degrees of substitution with disaccharide (DS 20-30%, 40-50%, 60-70%), were prepared by reductive alkylation of alpha-chitosan with lactose, maltose or cellobiose. Antioxidative activities were determined in the present study, including radical scavenging effect for alpha,alpha-diphenyl-beta-picryl-hydrazyl (DPPH) radicals, superoxide anion radicals, hydrogen peroxide and copper ion chelating ability of these chitosan derivatives. It was found that the tested chitosan derivatives exhibited multiple antioxidative activities that varied with the concentration, DS with disaccharides and the kind of disaccharide present in the derivative molecule. In general, the antioxidative activities increased as the concentration of these chitosan derivatives increased up to a certain extent. A stronger scavenging effects for superoxide anion radicals, DPPH radicals and H2O2 was noted with the chitosan derivatives having lower DS with disaccharide than those with higher DS. Among the various antioxidative activities tested, the disaccharide chitosan derivatives were found to show the highest excellent hydrogen peroxide scavenging activity. At a concentration of 400 mug/ml, all the chitosan derivatives tested exhibited 60% or greater scavenging activity for hydrogen peroxide. (C) 2004 Elsevier Ltd. All rights reserved.