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.