Oxyradicals under UV-b stress and their quenching by antioxidants.
Formation of oxyradicals under UV-B stress was investigated using cucumber cotyledons. UV-B radiation induced production of free radicals which were analyzed by ESR spectroscopy. Evidence was obtained for the formation of superoxide and hydroxyl radicals in the tissues by comparing PBN-adducts formed with radicals obtained by chemical autooxidation of KO2 and Fenton's reaction. Addition of superoxide dismutase (SOD) to the reaction mixture partially reduced the intensity of signals confirming the production of superoxide radical as well as hydroxyl radicals. These radicals were quenched in vitro by the natural antioxidants alpha-tocopherol, ascorbic acid and benzoquinone. Changes in the level of antioxidants were also monitored under UV-B stress. The endogenous level of ascorbic acid was enhanced and alpha-tocopherol level was reduced in the tissue after exposure to UV-B radiation. The present report happens to be the first direct evidence obtained for the formation of superoxide and hydroxyl radicals in plant tissues exposed to UV-B radiation.
Jain
Karishma
K
School of Life Sciences, Devi Ahilya University, Indore 452 017, India.
Kataria
Sunita
S
Guruprasad
K N
KN
D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology; D018548:Cotyledon / Q000528:radiation effects*; D018553:Cucumis sativus / Q000528:radiation effects*; D004578:Electron Spin Resonance Spectroscopy; D017665:Hydroxyl Radical / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000528:radiation effects*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D014466:Ultraviolet Rays; D024502:alpha-Tocopherol / Q000494:pharmacology
D000975:Antioxidants; D016227:Benzoquinones; D013481:Superoxides; D017665:Hydroxyl Radical; C004532:quinone; D013482:Superoxide Dismutase; D024502:alpha-Tocopherol; D001205:Ascorbic Acid