Synthesis and characterization of α-lipoic acid grafted chitosan derivatives with antioxidant activity

Here, α-lipoic acid (LA) was grafted onto chitosan via EDC/NHS to improve the antioxidant effect. Chitosan acetate was innovatively used as precursor replaced pristine chitosan to synthesize α-lipoic acid grafted chitosan derivatives with different grafting ratios. The grafting ratio of LA-g-CS conjugates could be controlled by adjusting the reaction temperature, reaction time, and feed ratio of α-lipoic acid to anhydroglucose unit, and the feed ratio is the main factor on the grafting efficiency. The antioxidant results (superoxide anion, hydroxyl, and DPPH radicals scavenging activities, and reducing power) indicated that LA-g-CS displayed significantly enhanced antioxidant activity over pristine chitosan. Moreover, antioxidant efficiency of LA-g-CS showed an ascending tendency with the increasing of the grafting degree. The present study provided a novel synthesis strategy for preparation of α-lipoic acid grafted chitosan derivatives that could be a potential antioxidant biomaterial in food and biomedical industries.