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Keywords:

  • Antioxidant;
  • chitosan;
  • inhibition;
  • phloroglucinol;
  • tyrosinase

Summary

A novel chitosan–phloroglucinol conjugate was developed by conjugating phloroglucinol onto a chitosan backbone. The chitosan–phloroglucinol conjugate was characterised by 1H nuclear magnetic resonance (NMR), and the NMR spectra confirmed the conjugation. Antioxidant and tyrosinase inhibitory activities of the chitosan–phloroglucinol conjugate were investigated. The chitosan–phloroglucinol conjugate showed strong 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide and ABTS+ radical scavenging activities as well as reducing power compared with those of the unmodified chitosan (P < 0.05). The formation of malondiadehyde (MDA) as an indicator of lipid peroxidation in a linoleic acid emulsion was 30.56 μM in the absence of the chitosan–phloroglucinol conjugate after 4 days incubation, whereas MDA was 4.14 μM in the presence of the chitosan–phloroglucinol conjugate (P < 0.05). The activity was higher than that of ascorbic acid, which is currently used as a food preservative. Moreover, the chitosan–phloroglucinol conjugate inhibited 56.30% tyrosinase activity, which is responsible for browning of foods, and acted as non-competitive inhibitor. Taken together, the chitosan–phloroglucinol conjugate may have potential for application in functional foods and/or as a food preservative.