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Titolo:
EPR spin trapping detection of carbon-centered carotenoid and beta-ionone radicals
Autore:
Konovalova, TA; Kispert, LD; Polyakov, NE; Leshina, TV;
Indirizzi:
Univ Alabama, Dept Chem, Tuscaloosa, AL 35487 USA Univ Alabama TuscaloosaAL USA 35487 Dept Chem, Tuscaloosa, AL 35487 USA RAS, SB, Inst Chem Kinet & Combust, Novosibirsk, Russia RAS Novosibirsk Russia , Inst Chem Kinet & Combust, Novosibirsk, Russia
Titolo Testata:
FREE RADICAL BIOLOGY AND MEDICINE
fascicolo: 7, volume: 28, anno: 2000,
pagine: 1030 - 1038
SICI:
0891-5849(20000401)28:7<1030:ESTDOC>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
CATION RADICALS; ABSORPTION-SPECTRA; OXYGEN; ANTIOXIDANT; RADIOLYSIS; RESONANCE; DICATIONS; POLYENES; IONS; AM1;
Keywords:
carotenoid; beta-ionone; protonation; deprotonation; free radical; spin trapping;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
38
Recensione:
Indirizzi per estratti:
Indirizzo: Kispert, LD Univ Alabama, Dept Chem, Box 870336, Tuscaloosa, AL 35487 USA Univ Alabama Box 870336 Tuscaloosa AL USA 35487 , AL 35487 USA
Citazione:
T.A. Konovalova et al., "EPR spin trapping detection of carbon-centered carotenoid and beta-ionone radicals", FREE RAD B, 28(7), 2000, pp. 1030-1038

Abstract

Free radical intermediates were detected by the electron paramagnetic resonance spin trapping technique upon protonation/deprotonation reactions of carotenoid and beta-ionone radical ions. The hyperfine coupling constants oftheir spin adducts obtained by spectral simulation indicate that carbon-centered radicals were trapped. The formation of these species was shown to be a result of chemical oxidation of neutral compounds by Fe3+ or I-2 followed by deprotonation of the corresponding radical cations or addition of nucleophilic agents to them. Bulk electrolysis reduction of beta-ionone and carotenoids also leads to the formation of free radicals via protonation of the radical anions. Two different spin adducts were detected in the reactionof carotenoid polyenes with piperidine in the presence of 2-methyl-2-nitroso-propane (MNP). One is attributable to piperidine radicals (C5H10N.) trapped by MNP and the other was identified as trapped neutral carotenoid (beta-ionone) radical produced via protonation of the radical anion. Formation of these radical anions was confirmed by ultraviolet-visible spectroscopy. It was found that the ability of carotenoid radical anions/cations to produce neutral radicals via protonation/deprotonation is more pronounced for unsymmetrical carotenoids with terminal electron-withdrawing groups. This effect was confirmed by the radical cation deprotonation energy (H-D) estimatedby semiempirical calculations. The results indicate that the ability of carotenoid radical cations to deprotonate decreases in the sequence: beta-ionone > unsymmetrical carotenoids > symmetrical carotenoids. The minimum H-D values were obtained for proton abstraction from the C(4) atom and the C(5)-methyl group of the cyclohexene ring. It was assumed that deprotonation reaction occurs preferentially at these positions. (C) 2000 Elsevier Science Inc.

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Documento generato il 18/09/20 alle ore 10:44:45