“…Many Cys-containing compounds, such as glutathione, inhibited TYR-catalyzed melanin synthesis by acting as a reactant for the thiol conjugation reaction with DOPAquinone as well as acting as an enzyme inhibitor [ 87 , 88 , 89 ]. A number of peptides from synthetic peptide libraries or natural sources exhibited inhibitory effects against TYR activity in vitro, and some showed antimelanogenic effects at the cell level [ 90 , 101 , 102 , 103 , 104 ]. Relatively high TYR inhibitory activities were achieved by hybrid compounds in which certain peptide sequences were conjugated with kojic acid [ 108 , 109 , 110 ], protocatechuic acid [ 111 ], caffeic acid [ 112 , 113 ], para -coumaric acid [ 113 ], or ascorbic acid [ 114 ].…”