Autoxidation of biological molecules. 1. Antioxidant activity of vitamin E and related chain-breaking phenolic antioxidants in vitro

Burton, Graham W.; Ingold, K. U.

doi:10.1021/ja00411a035

Cited by 1,062 publications

(608 citation statements)

References 2 publications

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“…60,000 times faster than the self-propagation reaction of methyl linoleate (k=62 M -1 s -1 , Roschek et al 2006). Kinetic studies suggest that the stoichiometric value for -tocopherol is two (Burton & Ingold 1981) i.e. one -tocopherol molecule traps two peroxyl radicals.…”

Section: Figure 12mentioning

confidence: 99%

“…-Tocopherol is one of the best chain-breaking phenolic antioxidants known (Burton et al 1980(Burton et al , 1985Burton & Ingold 1981). Kinetic studies have established that -tocopherol is, in vitro, not only the most active of the four tocopherols but also a much better antioxidant than simple phenols or otherwise similar phenols that lack the fused 6-membered heterocyclic ring, including one of the major commercial antioxidants 2,6-ditert-butyl-4-methylphenol (Burton & Ingold 1981;Burton et al 1985).…”

Section: Figure 12mentioning

confidence: 99%

“…Kinetic studies have established that -tocopherol is, in vitro, not only the most active of the four tocopherols but also a much better antioxidant than simple phenols or otherwise similar phenols that lack the fused 6-membered heterocyclic ring, including one of the major commercial antioxidants 2,6-ditert-butyl-4-methylphenol (Burton & Ingold 1981;Burton et al 1985). The high activity of -tocopherol compared to other tocopherols and simple phenols stems from the structural features of -tocopherol, such as the extent of methylation of the benzene ring and the orientation of the p-type lone pair on the para oxygen with respect to the aromatic plane, that stabilize the resulting tocopheroxyl radical (Burton & Ingold 1981, 1986Burton et al 1983). The fully methylated aromatic ring of -tocopherol makes it not only more lipophilic than other tocopherols but also, in comparison, provides maximum inductive effect.…”

Section: Figure 12mentioning

confidence: 99%

“…17, the peroxidation reactions leading to conjugated peroxyl radicals are, however, drawn in one way only to emphasize the effect of -tocopherol, i.e. creation of nearly kinetic conditions, and because the reverse reactions, -fragmentations to the initial pentadienyl radicals, can be expected to be slow (k ß =30 to 620 s -1 ; Porter & Wujek 1984;Tallman et al 2001Tallman et al , 2004 compared to the transfer of the phenolic hydrogen atom from -tocopherol to the peroxyl radicals (k=3.2 x10 6 to 3.8 x10 6 M -1 s -1 ; Burton & Ingold 1981;Burton et al 1983Burton et al , 1985Tallman et al 2001Tallman et al , 2004, particularly in the presence of a high amount of -tocopherol. Stereochemically unproductive -fragmentation of the bisallylic peroxyl radicals 5 and 10 (k ß =1.9x 10 6 s -1 ; Tallman et al 2001) into the initial pentadienyl radicals 2A and 2B may, however, compete with the hydrogen atom transfer step.…”

Section: Figure 16mentioning

confidence: 99%

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Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Pajunen

Johansson

Hase

et al. 2008

Lipids

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The autoxidation of conjugated linoleic acid (CLA) is poorly understood in spite of increasing interest in the beneficial biological properties of CLA and growing consumption of CLA-rich foods. In this thesis, the autoxidation reactions of the two major CLA isomers, 9-cis,11-transoctadecadienoic acid and 10-trans,12-cis-octadecadienoic acid, are investigated. The results contribute to an understanding of the early stages of the autoxidation of CLA methyl ester, and provide for the first time a means of producing and separating intact CLA methyl ester hydroperoxides as well as basic knowledge on lipid hydroperoxides and their hydroxy derivatives.Conjugated diene allylic monohydroperoxides were discovered as primary autoxidation products formed during autoxidation of CLA methyl esters in the presence and absence oftocopherol. This established that one of the autoxidation pathways of CLA methyl ester is the hydroperoxide pathway.Hydroperoxides were produced from the two major CLA methyl esters by taking advantage of the effect of -tocopherol to promote hydroperoxide formation. The hydroperoxides were analysed and separated first as methyl hydroxyoctadecadienoates and then as intact hydroperoxides by HPLC. The isolated products were characterized by UV, GC-MS, and NMR techniques. In the presence of a high amount of -tocopherol, the autoxidation of CLA methyl ester yields six kinetically-controlled conjugated diene monohydroperoxides and is diastereoselective in favour of one particular geometric isomer as a pair of enantiomers. The primary autoxidation products produced from the two major CLA isomers include new positional isomers of conjugated diene monohydroperoxides, the 8-, 10-, 12-, and 14-hydroperoxyoctadecadienoates. Furthermore, two of these new positional isomers have an unusual structure for a cis,trans lipid hydroperoxide where the allylic methine carbon is adjacent to the cis instead of the usual trans double bond.The 1 H and 13 C NMR spectra of nine isomeric methyl hydroxyoctadecadienoates and of ten isomeric methyl hydroperoxyoctadecadienoates including the unusual cis,trans hydroperoxides, i.e. Me 8-OOH-9c,11t and Me 14-OOH-10t,12c, were fully assigned with the aid of 2D NMR spectroscopy. The assigned NMR data enabled determination of the effects of the hydroxyl and hydroperoxyl groups on the carbon chemical shifts of CLA isomers, identification of diagnostic signals, and determination of chemical shift differences of the olefinic resonances that may help with the assignment of structure to as yet unknown lipid hydroperoxides either as hydroxy derivatives or as intact hydroperoxides.A mechanism for the hydroperoxide pathway of CLA autoxidation in the presence of a high amount of -tocopherol was proposed based on the characterized primary products, their relative distribution, and theoretical calculations. This is an important step forward in CLA research, where exact mechanisms for the autoxidation of CLA have not been presented before. Knowledge of these hydroperoxide formation steps is of cr...

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Section: Figure 12mentioning

confidence: 99%

Section: Figure 12mentioning

confidence: 99%

Section: Figure 12mentioning

confidence: 99%

Section: Figure 16mentioning

confidence: 99%

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Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Pajunen

Johansson

Hase

et al. 2008

Lipids

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“…Vitamin E is the most reactive anti-oxidant (17,18). The most important function of vitamin E In the body is to protect polyunsaturated fatty acid from oxidation (19).…”

Section: Discussionmentioning

confidence: 99%

Effect of vitamin E on the platelet xanthine oxidase and lipid peroxidation in the patients of myocardial infarction

Raghuvanshi

Chandra

Misra

et al. 2005

Indian J Clin Biochem

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Platelets play important role in precipitating ischaemic myocardial syndromes in many ways. One of the consequences of ischaemic diseases is excessive generation of oxygen derived free radicals that have numerous pathophysiological consequences. Platelet pro-oxidant enzyme, xanthine oxidase is one of the sources of generation of free radicals. In the present paper, we report the effect of administration of vitamin E along with aspirin on the levels of platelet xanthine oxidase and extent of free radical mediated damage in the patients reperfused after myocardial infarction.Our findings show that administration of 400 mg. vitamin E for six days along with 80 mg. aspirin has an excellent anti-oxidant effect as evidenced by reduced platelet xanthine oxidase activity and lowering of malondialdehdye (MDA) levels which is an index of the extent of free radical mediated damage.

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Antioxidative effects of sesamol and tocopherols at various concentrations in oils during microwave heating

Yoshida

Takagi

1999

J. Sci. Food Agric.

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Autoxidation of biological molecules. 1. Antioxidant activity of vitamin E and related chain-breaking phenolic antioxidants in vitro

Cited by 1,062 publications

References 2 publications

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Effect of vitamin E on the platelet xanthine oxidase and lipid peroxidation in the patients of myocardial infarction

Antioxidative effects of sesamol and tocopherols at various concentrations in oils during microwave heating

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