Inhibitory effects of 5-benzylidene barbiturate derivatives on mushroom tyrosinase and their antibacterial activities

A series of novel 5-benzylidene barbiturate and thiobarbiturate derivatives were synthesized and evaluated as tyrosinase inhibitors and antibacterial agents. The results demonstrated that some compounds had more potent inhibitory activities than the parent compound 4-hydroxybenzaldehyde (IC₅₀ = 1.22 mM). Particularly, compounds 1a and 2a were found to be the most potent inhibitors with IC₅₀ value of 13.98 μM and 14.49 μM, respectively. The inhibition mechanism study revealed that these compounds were irreversible inhibitors. The circular dichroism spectra indicated that these compounds induced conformational changes of mushroom tyrosinase upon binding. In addition, these compounds exhibited selectively antibacterial activity against Staphylococcus aureus. All these results suggested that further development of such compounds may be of interest.