Significantly enhanced antioxidant activity of chitosan through chemical modification with coumarins†
A new class of chitosan derivatives possessing coumarins was synthesized to improve the antioxidant activity of chitosan. Their antioxidant properties were tested, including the inhibition of lipid peroxidation activity, metal ion chelating ability, and free radical-scavenging activity. Base on the value of IC50, the inhibitory property of the synthesized chitosan derivatives exhibited a remarkable improvement over chitosan. The IC50 of the inhibition of lipid peroxidation, iron-chelation, and hydroxyl (˙OH) radical-scavenging was 0.11–0.13, 0.02–0.04, and 0.09–0.14 mg mL−1, respectively. The chelation of iron and the scavenging of superoxide radicals could affect the scavenging of ˙OH, which in turn affects the inhibition of lipid peroxidation. In the cytotoxicity assay, no cytotoxicity was observed for the 3T3-L1 and HHL-5 cells incubated with chitosan and its derivatives at all the testing concentrations. Meanwhile, the synthesized chitosan derivatives could prompt the 3T3-L1 cell growth, which should be related to their high antioxidant activity. These results demonstrated that the combination of chitosan and coumarins improved the antioxidant activity of chitosan obviously, and the antioxidants or free radical scavengers based on natural polymers and coumarins showed potential applications.