The Antioxidant and Antibacterial Activities of the Pyridine‐4‐Aldehyde Schiff Bases Grafted Chloracetyl Chitosan Oligosaccharide Derivatives

Abstract As a reactive intermediate, chloracetyl chitosan oligosaccharide (CACS) can be nucleophilic substituted by some bioactive groups to give novel derivatives of chitosan oligosaccharide (COS). The Schiff bases of pyridine‐4‐aldehyde are grafted onto CACS to give four COS derivatives in this paper. Specific structural characterization is implemented by fourier‐transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The degree of substitution (DS) of COS derivatives is quantitatively calculated by ratio of hydrogen proton integral. Their antioxidant property is evaluated using free radical scavenging assay towards 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and superoxide anion radicals, and the antibacterial activity against Staphylococcus aureus ( S. aureus ) and Escherichia coli ( E. coli ) is also investigated. The results revealed that the pyridine‐4‐aldehyde Schiff bases grafted chloracetyl chitosan oligosaccharide derivatives showed better antioxidant activity as well as antibacterial activity than COS and CACS, which may be related to the positive charge of these derivatives. Among all final products, derivative BPCACS with the highest DS has the best bioactivity with scavenging rate of 91.49% for the DPPH assay and inhibition diameter of 39.25 mm for S. aureus inhibitory assay, respectively. These results indicated that COS derivatives with enhanced biological activities could serve as potential biomaterial for antioxidant and antibacterial applications.