Relationships between Inhibition Constants, Types of Inhibition and IC50: Calculation and Comparison on IC50 of Two Model Tyrosinase Inhibitors

Calculating methods for inhibitor concentration (IC₅₀) leading to 50% activity lost (for diphenolase activity) of a novel parabolic competitive inhibitor (the trifluoromethyl-containing 1,2,3-triazole, TF-TA) and a novel mixed inhibitor ([E]-4-(1-imidazoylmethyl) cinnamic acid (ozagrel) were derived on the basis of kinetics of tyrosinase inhibition. These methods were applied to calculate IC₅₀ values of the two tyrosinase inhibiting compounds. The experimental IC₅₀ values of TF-TA and ozagrel were 41.9 μM and 3.45 mM, respectively. Moreover, the calculated IC₅₀ value of TF-TA and ozagrel were 82.8 μM and 3.15 mM, respectively. The calculation result of ozagrel is closer to experimental data.