Synthesis of chitosan–phenolic acid copolymer: exploration of structural and physicochemical properties

Abstract

SummaryChitosan and phenolic acid were catalysed by 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride (EDC)/1‐hydroxybenzotriazole (HOBt) to produce graft copolymer with high performance. The grafting ratios of gallic acid‐grafted chitosan copolymer (GA‐CS, 16.58%) and protocatechuic acid‐grafted chitosan copolymer (PCA‐CS, 14.36%) were determined by ultraviolet–visible spectrometer. The characterisation of products was analysed by Fourier transform infrared spectrometer, proton nuclear magnetic resonance and X‐ray photoelectron spectroscopy. The water solubility of natural chitosan (NA‐CS, 5.63%), GA‐CS (45.05%) and PCA‐CS (85.96%) confirmed that the water solubility of the modified chitosan enhanced after the existence of phenolic acid. 1,1‐diphenyl‐2‐picryl hydrazine (DPPH) scavenging test, β‐carotene rinsing experiment, total reducing power determination and standard agar well diffusion assay method were used to evaluate the antioxidant capacity and antibacterial ability of copolymer. Notably, the antibacterial ability of PCA‐CS and GA‐CS remained relatively consistent, but GA‐CS has the highest antioxidant capacity. This study shows that the EDC/HOBt reaction system can successfully graft phenolic acids onto chitosan without affecting the bioactivity of phenolic acids. In addition, the preparation of food preservation coatings by phenolic acid–chitosan copolymers with high antibacterial and antioxidant properties will have great development potential in the field of food technology.