Antioxidant response mechanism of Tainong No.1 mango under simulation enhanced UV-B radiation

【Objective】The purpose of the study was to investigate the response mechanism of antioxidant reduction components of Tainong No. 1 mango pulp under strong UV-B radiation， so as to provide a theoretical reference for mango production under global climate change. 【Method】Natural light irradiation was used as the control， and the artificial simulation enhanced UV-B radiation with an intensity of 96 kJ/（m²·d） was set up. In 2021， mango pulp samples were taken every 10 d from 30 d after anthesis （December 18） to 90 d after anthesis （February 17， 2022） and from 40 d after anthesis （December 1） in 2022 to 90 d after anthesis （January 21， 2023）， for a total of 7 and 6 samples， respectively. The contents of total flavonoids， total phenols， superoxide anion hydrogen peroxide （H₂O₂） and malondialdehyde （MDA）， as well as the dynamic changes of phenylalanine ammonia-lyase （PAL） and polyphenol oxidase （PPO） enzyme activities and relative electrical conductivity （REC） were measured in the pulp at each sampling period. 【Result】After enhanced UV-B radiation treatment， the content of superoxide anion in reactive oxygen species （ROS） of the first year and the second year increased gradually with the increase of time， and superoxide anion at 90 d after the first year and 70 to 90 d after the next year was significantly higher than that of control （P<0.05， the same below）. The variation trend of H2O2 under radiation treatment was firstly decreased and then increased in the first year， and only the radiation treatment at 90 d after anthesis was significantly higher than the control， H2O2 in the next year decreased， and the radiation treatment at 70 to 90 d after anthesis was significantly higher than the control. The contents of total phenol and total flavone in mango pulp showed a decreasing trend at 2 years. The contents of total phenol at 50 d after anthesis in the first year and 50 and 60 d after anthesis in the next year were significantly higher than those of control under radiation treatment. The 2-year change trend of MDA content and REC was decreased and then increased. MDA content in the first year was significantly higher than that in the control group at 40 d after anthesis and 50 d after anthesis in the next year， while MDA content and REC were significantly higher than that in the control group at 90 d after anthesis. The PAL activity of mango pulp treated with radiation showed a trend of decreasing， increasing and decreasing at the first year. The PAL activity of mango pulp treated with radiation was significantly higher than that of control at 40 d after anthesis， and there was no significant difference at 90 d after anthesis. In the next year， there was an upward-downward-upward trend， and there were significant differences between 50-70 d after radiation treatment. The dynamic changes of PPO activity at 2 years showed a trend of first decreasing and then increasing. In the first year， the activity of PPO at 40， 60， 70 and 80 d was significantly higher than that of the control， and in the next year， the activity of PPO at 60 and 90 d after anthesis was significantly higher than that of the control. 【Conclusion】Mango treated with enhanced UV-B radiation mainly control the synthesis of phenolic compounds dominated dominated by flavonoids through regulating PAL activity and act as efficient antioxidants against UV-B radiation.