Screeming And Determining Activity Of A Class Of Tyrosinase Inhibitors

Tyrosinase, polyphenol oxidase, a complicated and multifunctional copper-containing enzyme, is widely distributed in microorganism, plants and animals. It plays a very important role in insect wing expansion during the last step of metamorphosis:maturation of the wing and plants and vegetables browning. High topic of refreshing fruits and vegetables is tyrosinase. How to inhibit tyrosianse and how to keep fruits and vegetables fresh was widely investigatived. One of ways inhibited tyrosianse was the inhibitor. There were three ways gaining inhibitors from natural plants, goods and organic synthesis. From the inhibition mechanism inhibitors were two ways:irreversible inhibition and reversible inhibition which contained three inhibition ways with inhibition, noncompetitive inhibition and mixcompetitive inhibition.All of46samples there were24samples with tyrosianse inhibition activity, the lowest inhibition ratio was3.05%and the highest inhibition ratio was99.03%. Among the inhibition ratio of24samples there were7samples higher than50%in the inhibition concentration of100μmol/L.50%inhibiting concentration (IC50) was compound4IC50=20.4μmol/L, compound22IC50=62.46μmol/L, compound26IC50=1.76μmol/L, compound30IC50=57.73μmol/L, compound34IC50=89.23μmol/L, compound42IC50=1.1μmol/L and compound44IC50=20.85μmol/L, respectively. The enzyme kinetics test indicated that compound26was noncompetitive inhibitor of the mushroom tryrosinase and compound42was mix-competitive inhibitor.The result of acute toxicity test indicated that the half lethal dose (LD50) of4-amino-3-phenyl-1H-1,2,4-triazole-5(4H)-thione (APTT) and2-hydrazinyl benzoxazole (HBO) exceeded240mg/Kg. The inhibitor of APTT and HBO was low poison.Studied the effect of4-amino-3-phenyl-1H-1,2,4-triazole-5(4H)-thione (APTT) as the inhibitor to inhibit tyrosinase in making fresh-cut vegetables and fruits. With single test and orthogonal experiment, the optimum condition of concentration, reaction time and temperature was definite, respectively, the APTT concentration of32μmol/L, the reaction temperature of20℃and the reaction time of2075s was the optimum condition for Fuji apple tyrosinase; the APTT concentration of50μmol/L, the reaction temperature of15℃and the reaction time of480s for banana tyrosinase; the APTT concentration of28μmol/L, the reaction temperature of31℃and the reaction time of394s for yacon tyrosinase; the APTT concentration of500μmol/L, the reaction temperature of20℃and the reaction time of480s for burdock tyrosinase; the APTT concentration of550μmol/L, the reaction temperature of30℃and the reaction time of467s for pueraria tyrosinase; the APTT concentration of50μmol/L, the reaction temperature of20℃and the reaction time of700s for lily tyrosinase.