Objective: To study the inhibition of extracts from Synotis erythropappa on tyrosinase.
Methods: The 70% ethanol extracts were extracted by petroleum benzine, ethyl acetate and n-butanol, and the inhibitory activities against tyrosinase of every fraction were determined in vitro and the inhibitory kinetics of ethyl acetate and n-butanol fractions were investigated.
Results: The four fractions extracted all had inhibitory activities on tyrosinase, inhibitory activities of ethyl acetate and n-butanol fraction were higher. Their IC50 were 57.8, 140 microg/ml for monophenol oxidase activity and 41.2, 59.6 microg/ml for diphenol oxidase activity, respectively. The inhibition kinetics analyzed by Hnewaver-Burk plots showed that ethyl acetate fraction was a competitive type inhibitor, and its Ki was determined to be 19.7 microg/ml. n-butanol fraction was an uncompetitive type inhibitor, and its Ki was determined to be 60.7 microg/ml.
Conclusion: Ethyl acetate and n-butanol fractions of extracts from Synotis erythropappa show potential inhibitory activity on tyrosinase.