Tyrosinase (EC 1.14.18.1) is a copper-containing enzyme that catalyzes two distinct reactions of melanin synthesis: the hydroxylation of tyrosine with monophenolase and the oxidation of 3,4-dihydroxyphenylalanine (L-DOPA) to o-dopaquinone by diphenolase. Tyrosinase inhibitors have become increasingly import in cosmetic and medicinal products to reduce hyperpigmentation. Effects of flavonoids on melanogenesis have been reported. We now compare the effects of flavonoids (0.03 – 0.5 mmol.L^-1): quercetin (3,3’,4’,5,7-pentahydroxyflavone), rutin (quercetin-3-O-rhamnosylglucoside) and eupafolin (6-methoxy 5, 7, 3’, 4’ tetrahydroxyflavone) on tyrosinase activity using L-DOPA as substrate and their capacity of Cu(II) chelation (UV/Vis studies). Quercetin inhibited tyrosinase activity in a dose-dependent manner and the greatest inhibition was of 60%. Rutin and eupafolin did not significantly affect this activity. The ability of Cu(II) chelation of flavonoids was determined by the characteristic bathochromic shifts in the UV-visible spectra of quercetin and eupafolin, by adding an excess of Cu(II). Rutin does not form complex with Cu(II) since the bathochromic shift was not detected. The copper chelation mechanism can be involved in tyrosinase inhibition by quercetin, since the characteristic shift to short wavelengths was also observed when this flavonoid was incubated with the enzyme. The same shift was not observed with eupafolin and rutin. These results suggest that: i) quercetin inhibits diphenolase activity by chelating copper in the enzyme; ii) eupafolin chelates Cu(II) in solution probably due to the presence of the vicinal 3’, 4’-dihydroxy groups in ring B; iii) eupafolin and rutin, despite the presence of the catechol ring, were not able to form a complex with the copper of the enzyme and neither inhibited tyrosinase diphenolase activity; and iv) rutin does not chelate Cu(II) in solution probably since the sugar moiety, which is located at the 3–position, could block sterically its the chelate formation site.