Design and synthesis of hydroxypyridinone-l-phenylalanine conjugates as potential tyrosinase inhibitors

A range of hydroxypyridinone-l-phenylalanine conjugates were synthesized starting from kojic acid. Their tyrosinase activity was determined, and it was found that one of the compounds ((S)-(5-(benzyloxy)-1-octyl-4-oxo-1,4- dihydropyridin-2-yl)methyl 2-amino-3-phenylpropanoate, 5e) showed potent inhibitory effect against mushroom tyrosinase, the IC₅₀ values for monophenolase and diphenolase activities being 12.6 and 4.0 μM, respectively. It was also demonstrated that these conjugates are mixed-type inhibitors, suggesting they could bind to both the free enzyme and the enzyme-substrate complexes. MTT assay indicated that 5e was nontoxic to three cell lines. This compound may find applications in food preservation and cosmetics.