Yi-Fen Lin, Yong-Hua Hu,He-Tong Lin, Xuan Liu,

Yi-Hui Chen, Shen Zhang, Qing-Xi Chen.Journal of Agricultural and Food Chemistry,

2013. 61: 2889-2895.

Tyrosinase (EC 1.14.18.1), also known as polyphenol oxidase (PPO),

is a key enzyme in pigment biosynthesis oforganisms. The inhibitory effects of

propyl gallate on the activity of mushroom tyrosinase and effects of propyl

gallate on pericarpbrowning of harvested longan fruits in relation to phenolic

metabolism were investigated. The results showed that propyl gallatecould

potently inhibit diphenolase activity of tyrosinase. The inhibitor

concentration leading to 50% activity lost (IC50) wasdetermined to be 0.685 mM.

Kinetic analyses showed that propyl gallate was a reversible and mixed type

inhibitor on thisenzyme. The inhibition constants (KIS and KI) were determined

to be 2.135 and 0.661 mM, respectively. Furthermore, the resultsalso showed

that propyl gallate treatment inhibited activities of PPO and POD in pericarp

of harvested longan fruits, andmaintained higher contents of total phenol and

flavonoid of longan pericarp. Moreover, propyl gallate treatment also delayed

theincreases of browning index and browning degree in pericarp of harvested

longan fruits. Therefore, application of propyl gallatemay be a promising

method for inhibiting tyrosinase activity, controlling pericarp browning, and

extending shelf life of harvestedlongan fruits.

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