OXYRESVERATROL AS THE POTENT INHIBITOR ON DOPA OXIDASE ACTIVITY OF MUSHROOM TYROSINASE

Oxyresveratrol (2,3',4,5'-tetrahydroxystilbene), a naturally occurring compound particularly found in Morus alba L., exhibited a potent inhi bitory effect on dopa oxidase activity of tyrosinase which catalyzes r ate limiting steps of melanin biosynthesis. Oxyresveratrol with 0.3 to 5 mu M exhibited potent and dose dependent inhibitions (25 to 84%) on the enzyme activity, where 50% of inhibition was shown at the concent ration of about 1 mu M. Oxyresveratrol seemed to inhibit the dopa oxid ase activity of tyrosinase via a noncompetitive manner (Ki = 9.1 x 10( -7) M) when L-dopa was used as a substrate. Oxyresveratrol exhibited a bout a 150-fold more potent inhibitory effect than resveratrol (3,4',5 -trihydroxystilbene). The more hydroxy groups of the hydroxystilbenes are methylated to be methoxy groups, while the less inhibitory effects on the enzyme activity were exhibited. The results indicate that both the number and positions of hydroxy groups in oxyresveratrol seem to play a critical role in exerting the inhibitory effect on dopa oxidase activity of mushroom tyrosinase, (C) 1998 Academic Press.