Synergic and Additive Effects of the Combined Effect of Tyrosinase Inhibitors

Abstract

Background. Excessive melanin accumulation in the skin can lead to various diseases and cosmetic issues. While tyrosinase inhibitors are commonly used to reduce pigment biosynthesis, many of them are associated with significant side effects. When multiple drugs are used in combination, it can result in synergism, additive effects, or antagonism. Combining multiple tyrosinase inhibitors is considered a promising approach to minimize side effects and enhance therapeutic efficacy. Objective. This study aims to investigate the combined use of tyrosinase inhibitors to determine the nature of their interaction, whether it's synergistic or additive. Methods. We utilized tyrosinase isolated from Agaricus bisporus mushrooms. Enzyme inhibition by test compounds was assessed by measuring tyrosinase activity using tyrosine (30 min in 0.05 M Na-phosphate buffer solution, pH 6.5, 25 °C). To explore joint inhibition, compound solutions were mixed in pairs at various concentrations. The interaction was quantified using the combination index and isobolograms. Results. To determine the effect of the combined action of agents on tyrosinase activity, we examined standard inhibitors of the enzyme (kojic acid, arbutin, phenylthiourea) and our discovered compound, 3-(2-hydroxyphenylamino)-1,3-dihydro-indol-2-one. Calculations of the combination index and isobolograms for all studied combinations of standard tyrosinase inhibitors revealed additive effects in all studied cases. Simultaneous use of kojic acid or arbutin with 3-(2-hydroxyphenylamino)-1,3-dihydro-indol-2-one demonstrated a synergistic effect. However, the mixture of phenylthiourea with the indole derivative demonstrated an additive effect. Conclusions. The combined usage of tyrosinase inhibitors in various combinations displayed both additive and synergistic effects. The synergistic effect of using two inhibitors simultaneously presents significant opportunities for the development of more effective and cost-efficient treatments for hyperpigmentation by reducing the concentration of each inhibitor.