Kinetic study of mushroom tyrosinase inhibition using naturally occurring bromophenols and comparison with related phenolic compounds

Abstract

Naturally occurring bromophenols and commercially available halogenated phenols were investigated kinetic inhibition study and a comparison of inhibitory activity against mushroom tyrosinase. All four bromophenols investigated showed noncompetitive inhibition from the results of Lineweaver-Burk plots. The inhibitors may bind another site of the active site and combine with either free enzyme or enzyme-substrate complex. Among them, inhibition constants of symmetric bromophenol dimers, bis(2,3-dibromo-4,5-dihydroxyphenyl)methane and bis(2,3-dibromo-4,5-dihydroxybenzyl)ether, exhibited low values compared to ones of asymmetric dimers. Additionally, 2,3-dibromo-6-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl methyl ether showed the most potent inhibition among the compounds investigated. Chlorinated phenols, 2,4-dichlorophenol and 2,2’-methylenebis-(4-chlorophenol), exhibited moderate inhibition against mushroom tyrosinase among commercially available phenols. These results suggest that inhibition of halogenated phenols against mushroom tyrosinase requires a catechol moiety and/or halogen substitution in the one ortho-position of phenolic hydroxy group and vacant substitution in the other ortho-position.