Short UV-B Exposure Stimulated Enzymatic and Nonenzymatic Antioxidants and Reduced Oxidative Stress of Cold-Stored Mangoes.

The effects of UV-B irradiation on reactive oxygen species (ROS) levels, antioxidant compound contents, antioxidative enzyme activities, and oxidative damage of cold-stored mangoes were examined. Superoxide anion production rate, hydrogen peroxide concentration, ion leakage level and malondialdehyde content of the cold-stored fruit preradiated with 5 KJ m(-2) UV-B for 4 h were significantly decreased as compared with control fruit. The activities of ROS generating enzymes remained unchanged in UV-B-irradiated mangoes as compared to the control, but superoxide dismutase and catalase activities, ascorbate and polyphenol contents and antioxidant capacities of the cold-stored mangoes were significantly enhanced by UV-B. The UV-B-enhanced antioxidant compounds and antioxidative enzymes were highly correlated with the reduced-ROS levels in UV-B-irradiated mangoes. The data indicated that a short UV-B exposure reduced oxidative stress and alleviated oxidative damage of the cold-stored mangoes by triggering both enzymatic and nonenzymatic antioxidant systems although ROS generation in the fruit was not affected.