Effects of quercetin on mushroom tyrosinase and B16-F10 melanoma cells.
In searching for tyrosinase inhibitors from plants using L-3,4-dihydroxyphenylalanine (L-DOPA) as a substrate, quercetin was found to be partially oxidized to the corresponding o-quinone under catalysis by mushroom tyrosinase (EC 1.14.18.1). Simultaneously, L-DOPA was also oxidized to dopaquinone and both o-quinones were further oxidized, respectively. The remaining quercetin partially formed adducts with dopaquinone through a Michael type addition. In general, flavonols form adducts with dopaquinone as long as their 3-hydroxyl group is free. Quercetin enhanced melanin production per cell in cultured murine B16-F10 melanoma cells, but this effect may be due in part to melanocytotoxicity. The concentration leading to 50% viable cells lost was established as 20 microM and almost complete lethality was observed at 80 microM.
Kubo
Isao
I
Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720-3114, USA. ikubo@berkeley.edu
Nitoda
Teruhiko
T
Nihei
Ken-ichi
K
D000363:Agaricales / Q000201:enzymology*; D000818:Animals; D002384:Catalysis; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007700:Kinetics; D008543:Melanins / Q000096:biosynthesis; D008546:Melanoma, Experimental / Q000378:metabolism / Q000473:pathology*; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D011794:Quercetin / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D008543:Melanins; D011794:Quercetin; D014442:Monophenol Monooxygenase