Inhibitory effects of α-Na8SiW11CoO40 on tyrosinase and its application in controlling browning of fresh-cut apples

Visual appearance of fresh-cut apples with (a) or without (b) short-term SiW11Co treatment after 2h. α-Na8SiW11CoO40 (SiW11Co) was synthesized and characterized. The Native-PAGE and the spectrophotometry assay showed that SiW11Co had a significant inhibitory effect on tyrosinase dose-dependently (IC50=0.239mM, KI=0.164mM). In addition, the assay on the browning of apple slices indicated that SiW11Co treatment could significantly decrease the browning degree of apples slices and the activity of polyphenol oxidase (PPO), and controlled the oxidation of fresh-cut fruits and vegetables. As shown in figure, visual appearance of apple slices in treatment group was apparently lighter than that of the control group, which also suggested that SiW11Co could inhibit the browning process of apple slices distinctly. [Display omitted] •A novel tyrosinase inhibitor from polyoxometalates is studied.•Apply α-Na8SiW11CoO40 decreased the browning degree and polyphenol oxidase activity of apple slices.•High contents of phenolic compounds and ascorbic acid are maintained by α-Na8SiW11CoO40 treatment.•Provided a promising anti-browning agent for controlling the browning of fresh-cut apples. α-Na8SiW11CoO40 was synthesized and characterized. The inhibitory effects of α-Na8SiW11CoO40 on the activity of mushroom tyrosinase and the effects of α-Na8SiW11CoO40 on the browning of fresh-cut apples were studied. The Native-PAGE result showed that α-Na8SiW11CoO40 had a significant inhibitory effect on tyrosinase. Kinetic analyses showed that α-Na8SiW11CoO40 was an irreversible and competitive inhibitor. The inhibitor concentration leading to a 50% reduction in activity (IC50) was estimated to be 0.239mM. Additionally, the results also showed that α-Na8SiW11CoO40 treatment could significantly decrease the browning process of apple slices and inhibit the polyphenol oxidase (PPO) activity. Moreover, application of α-Na8SiW11CoO40 resulted in higher peroxidase activity and promoted high amounts of phenolic compounds and ascorbic acid. This study may provide a promising method for the use of polyoxometalates to inhibit tyrosinase activity and control the browning of fresh-cut apples.