Kojic acid-amino acid conjugates as tyrosinase inhibitors.

Kojic acid (KA), a well known tyrosinase inhibitor, has insufficient inhibitory activity and stability. We modified KA with amino acids and screened their tyrosinase inhibitory activity. Among them, kojic acid-phenylalanine amide (KA-F-NH(2)) showed the strongest inhibitory activity, which was maintained for over 3 months at 50 degrees C, and acted as a noncompetitive inhibitor as determined by kinetic analysis. It also exhibited dopachrome reducing activity. We also propose a new tyrosinase inhibition mechanism based on the docking simulation data.