Comparative Assessment of the Antioxidant and Antibacterial Properties of Various Phenolic Acid-Chitosan Grafted Polymers

The augmentation of chitosan's (CS) antioxidative and antibacterial properties via grafting with phenolic acids constitutes a significant method for expanding the utility of chitosan. In this investigation, four phenolic acids (gallic acid, GA; protocatechuic acid, PCA; hydroxybenzoic acid, HA; and salicylic acid, SA) were conjugated with CS utilizing carbodiimide (EDC)-mediated grafting. The resultant phenolic acid-CS graft copolymers underwent characterization employing infrared spectroscopy, x-ray diffraction, and thermogravimetric analysis. Furthermore, ex vivo antioxidative and antibacterial assays were performed. Findings revealed that among the synthesized phenolic acid-chitosan graft copolymers, gallic acid-chitosan (GA-CS) demonstrated the highest antioxidative and antibacterial efficacy, primarily attributed to its elevated grafting ratio and abundance of hydroxyl groups. The antioxidative and antibacterial performances of the remaining three graft copolymers followed this order: CS-PCA > CS-HA > CS-SA, aligning with the trend in grafting ratios. This correlation arises from the higher grafting ratios of copolymers yielding more active  OH groups, thereby exhibiting enhanced antioxidative and antibacterial properties. Phenolic acid-chitosan graft polymers exhibit promising antioxidative and antibacterial attributes, making them suitable additives for application in the food preservation packaging industry.