Ultraviolet-B radiation applied to detached peach fruit: A study of free radical generation by EPR spin trapping.
In peaches, phenolic compounds are the major sources of antioxidants, and cyanidin-3-O-glucoside is the main anthocyanin present, above all in the skin. Anthocyanin content has been shown to increase after UV-B irradiation, which may be very harmful for all biological organisms due to the induction of the generation of reactive oxygen species (ROS). Peach fruits (cv. 'Suncrest') were exposed during post-harvest to supplemental ultraviolet-B radiation. A spin-trapping technique was used to monitor the generation of free radicals under UV-B, and 5-(diethoxy-phosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) was used as the spin trap. The flesh of peaches was essentially unaffected by the treatment, whereas the skin was responsive at the end of the treatment, accumulating ascorbate, flavonoids, cyanidin-3-O-glucoside, and showing a higher antioxidant activity. The levels of stable free radicals were also lower at the end of treatment. Carbon-centred radicals contributed the most to the total amounts of free radicals, whereas hydroxyl radicals and oxygen-centred free radicals contributed minimally. The carbon-centred free radical identified was the same as the one obtained after irradiation of authentic cyanidin-3-O-glucoside. During UV-B treatment cyanidin-3-O-glucoside increased and was capable of radicalization protecting the other organic molecules of the cell from oxidation. ROS, among which hydroxyl radicals, were thus maintained to minimal levels. This ability of cyanidin-3-O-glucoside displayed the mechanism underlined the tolerance to UV-B irradiation indicating that shelf life can be prolonged by the presence of anthocyanins. Thus, UV-B technique results a good approach to induce antioxidant production in peach fruits increasing their nutraceutical properties.
Department of Agriculture, Food and Environment, University of Pisa, Via Del Borghetto 80, I-56124 Pisa, Italy. Electronic address: cristina.sgherri@unipi.it.
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Sgherri
Department of Agriculture, Food and Environment, University of Pisa, Via Del Borghetto 80, I-56124 Pisa, Italy. Electronic address: claudiascattino@gmail.com.
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Scattino
Institute of Chemistry of Organometallic Compounds (ICCOM), Italian National Research Council (CNR), Area Della Ricerca Del CNR di Pisa, Via G. Moruzzi 1, I-56124 Pisa, Italy. Electronic address: rino@pi.iccom.cnr.it.
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Pinzino
Institute of Life Sciences, Scuola Superiore Sant'Anna, Piazza Martiri Della Libertà 33, I-56127 Pisa, Italy. Electronic address: pietro.tonutti@sssup.it.
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Tonutti
Department of Agriculture, Food and Environment, University of Pisa, Via Del Borghetto 80, I-56124 Pisa, Italy; Interdepartmental Research Center "Nutraceuticals and Food for Health", University of Pisa, Pisa, Italy. Electronic address: anna.maria.ranieri@unipi.it.
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Ranieri
D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D000068239:Prunus persica / Q000378:metabolism / Q000528:radiation effects*; D013113:Spin Labels; D014466:Ultraviolet Rays
D005609:Free Radicals; D013113:Spin Labels
Cyanidin-3-O-glucoside; EPR spin trapping; Free radicals; Post harvest; Prunus persica L. Batsch; UV-B radiation