Synthesis of N-kojic-amino acid and N-kojic-amino acid-kojiate and their tyrosinase inhibitory activity

Ten amino acid derivatives of kojic acid were synthesized to improve the tyrosinase inhibitory activity of kojic acid. Almost all derivatives showed stronger activities than kojic acid, and in general, N-kojic-amino acid-kojiate was found to have a higher inhibitory potency than N-kojic-amino acid. Among them, the N-kojic-L-phenylalanyl kojiate was the strongest inhibitor and its IC50 value was 1/380 that for kojic acid. The inhibition mechanism of these derivatives is considered to be noncompetitive which is similar to that of kojic acid.