A novel chitosan oligosaccharide derivative: Synthesis, antioxidant and antibacterial properties

A novel thioether chitosan oligosaccharide (COS-All-Tio) was prepared by the reaction of chitosan oligosaccharide (COS) with 3-bromopropene, followed by the coupling with tiopronin (Tio) using a thiol-ene reaction. The degree of substitution of COS-All-Tio reached 1.48. The structure of COS-All-Tio was identified by IR, NMR spectra. It was found that COS-All-Tio possessed more potent antioxidant activities than COS. The IC₅₀ values of COS-All-Tio for scavenging DPPH, ABTS⁺ and OH were 0.31, 0.39 and 0.73 mg/mL, respectively, while the corresponding values for COS were 0.66, 2.89 and 1.41 mg/mL, respectively. COS-All-Tio was also found to possess much stronger antibacterial effect than COS against five bacteria strains (Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes, Escherichia coli and Pseudomonas aeruginosa). Further, COS-All-Tio was found to be non-toxic to RAW264.7 macrophages and MRC-5 human lung cells. This work provides a convenient way to improve the antioxidant and antibacterial activities of COS.