Preparation, antioxidant and tyrosinase inhibitory activities of chitosan oligosaccharide-hydroxypyridinone conjugates

[Display omitted] •Two chitosan oligosaccharide (COS)-hydroxypyridone (HPO) conjugates were prepared.•The structure of COS conjugates was confirmed by FT-IR, XRD and NMR spectra.•The thermal stability of COS-HPOs were improved when compared to COS.•The two conjugates possessed enhanced antioxidant and anti-tyrosinase activities.•COS-HPOs were found to be non-toxic at cell level. Two novel chitosan oligosaccharide (COS)-hydroxypyridone (HPO) conjugates were prepared by reacting chitosan oligosaccharide with 2-chloromethyl-5-hydroxypyridone (HPO), which was synthesized by a series of reactions starting from kojic acid. The degree of substitution of COS-HPO2 reached 1.2, with a yield of 74.9%. The structure of the two conjugates (COS-HPO1 and COS-HPO2) was identified by NMR and FT-IR analysis. The two conjugates showed significantly higher free radical (DPPH•, ABTS+• and •OH) scavenging activity and reducing power than those of COS and HPO (p