Phenolic-containing chitosan quaternary ammonium derivatives and their significantly enhanced antioxidant and antitumor properties

A class of phenolic-chitosan quaternary ammonium derivatives have been designed and synthesized. Three chitosan derivatives possess effective structure of hydroxycinnamic acid have been obtained through chemical modification to get chitosan derivatives owning high antioxidant activity and antitumor activity. In this study, the scavenging ability of DPPH, hydroxyl (•OH), and superoxide (O2•−) free radical and reducing power have been tested to evaluate the antioxidant activity of the synthesized chitosan derivatives. Base on the value of IC50, the chitosan derivatives have the best inhibitory property of 0.019 mg/mL (DPPH), 0.016 mg/mL (•OH), and 0.008 (O2•−), respectively; and the chitosan derivatives with conjugate structure of ferulic acid and sinapic acid (4b and 4c) show promising antitumor activity toward A549 cells with the IC50 of 0.046 and 0.052 mg/mL. These data indicate that the chitosan derivatives with phenolic group give much stronger antioxidant activity and antitumor activity. On the other hand, the synthesized chitosan derivatives show no cytotoxicity for L929 cells at the testing concentrations. These results demonstrate that the introduction of phenol group improves the antioxidant activity of chitosan obviously, and the antioxidant or free radical scavenger based on nature polymers and phenol shows potentials application.