Studies on the inhibitory effect of Graptopetalum paraguayense E. Walther extracts on mushroom tyrosinase

This study was aimed to evaluate the kinetic properties and capacities of 95% ethanolic (GE95), 50% ethanolic (GE50) and water (GWE) extracts from Graptopetalum paraguayense for their potential to inhibit mushroom tyrosinase activity. The results showed that GE95, GE50 and GWE showed potent inhibitory effects on l-3,4-dihydroxyphenylalanine (l-Dopa) oxidation catalyzed by tyrosinase. It was found that the tyrosinase inhibitory activities of all the extracts increased with the increase of their concentrations. The inhibition kinetics, analyzed by Lineweaver–Burk plots, revealed that G. paraguayense extracts showed a mixed-type inhibition for mushroom tyrosinase when l-Dopa was used as substrate. A comparison of the IC50 and Ki values showed that GE95 exhibited the most effective inhibition of tyrosinase among the extracts.