Screening tyrosinase inhibitors from traditional chinese medicine by capillary electrophoresis with electrophoretically mediated microanalysis

Electrophoretically mediated microanalysis (EMMA) is an analytical method using on-column assays. In the setup, substrate and enzyme were individually introduced into the capillary as distinct plugs. The electrophoretic conditions for the enzyme reaction and separation of substrate and product were optimized in this study. The inhibition constant and type of kojic acid (a reference tyrosinase inhibitor) were obtained by this method, which agreed with the literature data. Furthermore, the inhibitory ratios of enzymatic activity (IRE) of 21 traditional Chinese drugs were determined. The EMMA method has superiority over traditional assay methods, in not only minimizing the false-positive results but also simplifying the experimental procedure. Therefore, it could be employed to screen inhibitors from natural sources.