Inhibition of mushroom tyrosinase by kojic acid octanoates

Octanoic acid 2-hydroxymethyl-4-oxo-4H-pyran-5-yl ester (kojic acid 5-O-capryloate, 2), octanoic acid 4-oxo-2-(1-oxooctyloxymethyl)-4N-pyran-5-yl ester (kojic acid 5,7-di-O-di-capryloate, 3), and octanoic acid (5-hydroxy-4-oxo-4N-pyran-2-yl)-methyl ester (kojic acid 7-O-capryloate, 5) were prepared from 5-hydroxy-2-hydroxymethyl-4H-4-pyrone (kojic acid, 1) and caprylic acid. We also describe the synthesis of 11-aminoundecanoic acid (5-hydroxyl -oxo-4H-pyran-2-yl)-methyl ester (6). In solution, the monoesters are non-competitive inhibitors of mushroom tyrosinase (EC 1.14.18.1) (2. IC50 = 107 mu M, 5: IC50; 15 mu M, 6: IC50 = 20 mu M; Cf. 1: IC50 = 45 I mu M, mixed type inhibition). When tyrosinase is immobilized in a polyvinvlalcohol membrane, 5 is a weaker inhibitor than 1 or 2.