Nineteen dialkylphosphorylhydrazones with different substituents at the aromatic ring were evaluated as potential tyrosinase inhibitors, which could then be used as efficient agents in the control of pigmentation disorders. The inhibition activity was measured by a modified Patil and Zucker UV-Vis method. Briefly, the assays were carried out with solutions containing phosphate buffer, L-3,4-dihidroxyphenylalanine (L-DOPA), (EDTA), tyrosinase and varying concentrations of organophosphorus compounds. The formation of dopachromone was determined by monitoring the absorbance at 475 nm. Three compounds were found to be the most active compounds of the series (IC50 = 105 ± 20 µmol L-1), (IC50 = 127 ± 16 µmol L-1) and (IC50 = 188 ± 27 µmol L-1), being three to seven times more active than ascorbic acid (IC50 = 730 µmol L-1), used as a standard. The most active compound is only 1.5 times less potent than the commercial kojic acid (IC50 = 69.4 µmol L-1). This study may lead to the discovery of potent agents against very important pigmentation disorders including hyperpigmentation.
dialkylphosphorylhydrazones; tyrosinase inhibitor; organophosphorus compounds
