The study of inhibitory effects and mechanism of carboxylate chitooligomer on melanin, prepared by laccase/TEMPO system

Schematic illustration of reaction mechanism of C-COS and tyrosinase. [Display omitted] •Carboxylate chitooligomer (C-COS) skin-whitening material was prepared by laccase/TEMPO oxidation system.•Chitooligomer (COS) and C-COS were used to assess their inhibitory effects on melanin pigmentation.•C-COS improved melanin inhibition compared with COS.•C-COS chelates Cu ions in tyrosinase (TYR), inhibits TYR activity and reduces melanin production. A carboxylate chitooligomer (C-COS) containing carboxyl groups attached to chitooligomer (COS) molecules has been prepared by laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) system, which is a green-chemistry method. Several experiments were designed to evaluate inhibition effects on melanin and mechanisms of C-COS. The results indicated that C-COS exhibited more distinct anti-melanogenic effects compared to COS. C-COS inhibits melanin production with tyrosine (Tyr) and DOPA as the substrate of melanin formation, and the inhibition rates are, respectively, 89.07% and 84.45%, which reach 1.4–2 times those of COS. UV–vis spectroscopy was used to elucidate the interaction mechanism between C-COS and tyrosinase (TYR). It is C-COS chelating with metal Cu ions in tyrosinase (TYR) that decreases the enzyme activity. Half-maximal inhibitory concentrations (IC50) of C-COS were calculated as 13.49 and 4.07 mg/mL for monophenolase (cresolase) and diphenolase (catecholase), respectively.