Biological evaluation of coumarin derivatives as mushroom tyrosinase inhibitors.

A series of coumarin derivatives were synthesised and their inhibitory effects on the diphenolase activity of mushroom tyrosinase were evaluated. The results showed that some of the synthesised compounds exhibited significant inhibitory activities. Especially, 2-(1-(coumarin-3-yl)ethylidene)hydrazinecarbothioamide bearing thiose-micarbazide group exhibited the most potent tyrosinase inhibitory activity with IC(50) value of 3.44μM. The inhibition mechanism analysis of 2-(1-(coumarin-3-yl)-ethylidene)hydrazinecarbothioamide and 2-(1-(6-chlorocoumarin-3-yl)ethylidene)-hydrazinecarbothioamide demonstrated that the inhibitory effects of the compounds on the tyrosinase were irreversible. Preliminary structure activity relationships' (SARs) analysis suggested that further development of such compounds might be of interest.