Abstract: We studied effects of preharvest spraying of diethyl aminoethyl hexanoate (DA-6) on the metabolism of reactive oxygen species (ROS) in longan fruit pericarp during postharvest storage. Fruit of ‘Fuyan’ longan (Dimocarpus longan Lour. cv. Fuyan) were sprayed with 10 mg/kg DA-6 or distilled water (as control) at 70, 90 and 110 days after full bloom. The fruit were harvested at 120 days, cleaned and naturally dried prior to packaging in 0.015 mm thick polyethylene bags (50 fruits per bag) and subsequent storage at (28 ± 1) ℃ and 85% relative humidity. During storage, superoxide anion radical production rate, malondialdehyde (MDA) content, the contents of endogenous antioxidant substances such as ascorbic acid (AsA) and glutathione (GSH), the activity of ROS scavenging enzymes including superoxidase dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and reducing power were determined daily. The results showed that compared with the control fruit, pre-harvest spraying of DA-6 could increase the activities of SOD, CAT, APX and GR, delay the decrease in AsA and GSH contents, maintain higher levels of DPPH radical scavenging activity and reducing power, lower superoxide anion radical production rate, and reduce the content of MDA in longan fruit pericarp, thereby improving fruit storability. This effect may be due to reduced ROS metabolism in the pericarp of harvested longan fruit during storage.

Key words: longan fruit, diethyl aminoethyl hexanoate, reactive oxygen species (ROS), ROS metabolism, ROS scavenging enzymes, storability