Inhibitory Effects of Quercetin and Kaempferol as two Propolis Derived Flavonoids on Tyrosinase Enzyme

Background: Tyrosinase is a copper-containing enzyme, which is widely distributed in microorganisms, animals and plants. It is also a key enzyme in melanin biosynthesis, which plays a crucial role in determining the color of mammalian skin and hair. In addition, unfavorable enzymatic browning of plant-derived foods by tyrosinase causes a decrease in nutritional quality and economic loss of food products. Objectives: In the present study the activity of this enzyme was examined against quersetin and kaempferol as two potentially flavonoid inhibitors. Materials and Methods: In this work, the effects of quercetin and kaempferol as propolis-derived compounds on activity of mushroom tyrosinase (MT) were studied. These flavonoids showed inhibitory activity on catecholase and cresolase reactions in presence of caffeic acid and p-comaric acid, respectively. The inhibition mode of quercetin and kaempferol were competitive towards both catecholase and cresolase activities of the enzyme. Results: The inhibition constants (Ki) were determined as 0.072 and 0.112 mM for catecholase activity, and 0.016 and 0.06 mM for cresolase activity, respectively. Conclusions: In general, quercetin and kaempferol can be used as good candidates in melanogenesis inhibition. Moreover they should be considered as good blockers of enzyme activity in hyper pigmentation and clinical application.