Synthesis and tyrosinase inhibitory activity of novel N-hydroxybenzyl-N-nitrosohydroxylamines

Several novel N-substituted N-nitrosohydroxylamines were synthesized. They all inhibited mushroom tyrosinase, but the type of inhibition was different depending on the substituent. Some N-(mono- or dihydroxybenzyl)-N-nitrosohydroxylamines exhibited uncompetitive inhibition with respect to l-dopa. Among them, compound 6 was also a competitive inhibitor with respect to oxygen. This observation suggests that another interaction by the meta- or para-hydroxyl group might stabilize the binding of the inhibitor to the enzyme through the oxygen binding site.