Effect of pyrogallol on the physiology and biochemistry of litchi fruit during storage

Fruit were treated with pyrogallol at 1 mM and then stored at ambient temperature (25°C) or low temperature (4°C). Compared with control, pyrogallol significantly reduced pericarp browning and delayed the rotting of fruit day 4 at 25°C, and on day 30 at 4°C. The chemical treatment reduced respiration rate and the activities of peroxidase (POD) and polyphenol oxidase (PPO), and delayed the loss of membrane permeability. Pyrogallol increased the activity of phenylalanine ammonia-lyase (PAL), delayed the loss of anthocyanin and phenolics, and maintained high 2,2-diphenyl-1-picrlhydrazyl (DPPH) radical scavenging activity and reducing power. High performance liquid chromatograph (HPLC) analysis clearly indicated that treated fruit contained higher concentration of the four phenolic compounds procyanidin B1, (+)-catechin, (？)-epicatechin and (？)-epicatechin-3-gallate.The application of pyrogallol partially reducing pericarp browning and changed quality-related physiological activities and, thus, pyrogallol could have beneficial effects on pericarp browning and fruit decay control, and could be helpful for litchi fruit postharvest storage.Litchi (Litchi chinensis Sonn.) is a subtropical fruit with attractive red pericarp and translucent white aril. However, the fruit rapidly lose their red color during storage and become less attractive in the market. Previous studies demonstrated that the loss of membrane integrity was involved in litchi pericarp browning [1]. The membrane deterioration results in cellular de-compartmentalization [2]. Accordingly, lipid peroxidation reduces membrane fluidity and increases membrane permeability [3], which leads to a mixing of enzymes and their substrates. Therefore, maintenance of membrane compartmentalization could be used to extend the storage life of litchi the fruit.Polyphenol oxidase (PPO) and peroxidase (POD) are involved in the degradation of anthocyanins by catalyzing the oxidization of phenolic compounds [4,5]. The loss of cellul