Synthesis, Characterization, and Antimicrobial Activity of Kojic Acid Grafted Chitosan Oligosaccharide

A novel water-soluble chitosan oligosaccharide (COS) derivative, chitosan oligosaccharide/kojic acid grafts assigned as COS/KA, was prepared by using the selective partial alkylation of N-benzylidene COS and chlorokojic acid in the presence of dimethyl sulfoxide (DMSO) and pyridine (Py). The derivative was characterized by UV-vis spectroscopy, FTIR, H-1 NMR, TGA, SEM, and XRD techniques, which showed that the alkylation reaction took place at the C-6 and C-3 positions of COS. The results showed that the degree of substitution (DS) for COS/KA was from 0.38 to 1.21, and the product exhibited an excellent solubility in organic solvents and distilled water. The antibacterial results indicated that the antibacterial activity of COS/KA was strengthened relative to COS with the increase of DS for Staphylococcus aureus, Escherichia coli, Aspergillus niger and Saccharomyces cerevisiae. These findings provide important supports for developing new antibacterial agents and expand the scope of application of COS in the food industry.