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.