Fig. 3.

Lineweaver-Burk plots for the inhibition of mushroom tyrosinase activity by (Z)-5-(substituted benzylidene)-3-phenyl-2-thioxooxazolidin-4-one derivatives (a) 1c and (b) 1j. Inhibition types were investigated using Lineweaver-Burk plots. Data are shown as mean values of 1/V, defined as the inverse of increased absorbance at 475 nm per min as determined by three independent experiments at five different L-tyrosine concentrations. Concentrations of 1c were 0 μM (filled circles), 2.5 μM (unfilled circles), 5.0 μM (filled triangles), and 10.0 μM (unfilled triangles) and the concentrations of 1j were 0 μM (filled circles), 5.0 μM (unfilled circles), 10.0 μM (filled triangles), and 20.0 μM (unfilled triangles). The modified Michaelis-Menten equation was used: 1/V_max = (1/K_M)(1 + [S]/K_i), where V_max is maximum reaction rate, K_M is a Michaelis-Menten constant, [S] is L-tyrosine concentration, and K_i is the inhibition constant. All experiments were independently performed in triplicate.