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The β -carotene dilemma: ESR study with coordinated peroxyl radicals
Tkáč, A. and Scott, G. The β -carotene dilemma: ESR study with coordinated peroxyl radicals Chemical Papers, Vol.60, No. 3, 2006, 179-185
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Document type:
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Článok z časopisu / Journal Article |
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Collection:
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Chemical papers
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| Author(s) |
Tkáč, A.
Scott, G.
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| Title |
The β -carotene dilemma: ESR study with coordinated peroxyl radicals
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| Journal name |
Chemical Papers
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| Publication date |
2006
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| Year available |
2006
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| Volume number |
60
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| Issue number |
3
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| ISSN |
0366-6352
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| Start page |
179
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| End page |
185
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| Place of publication |
Poland
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| Publisher |
Versita
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| Collection year |
2006
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| Language |
english
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| Subject |
250000 Chemical Sciences
250100 Physical Chemistry (incl. Structural)
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| Abstract/Summary |
he apparently unpredictable behaviour of β-carotene in the supplementation of the diet of smokers is discussed in the light of the reactions of peroxyl radicals with β-carotene in the absence of oxygen. The decay of tert-butylperoxyl radicals in the presence of β-carotene was studied at ambient temperature in non-polar solvents by ESR spectroscopy. The primary reaction in the absence of oxygen is interpreted as a spin-trapping effect of a peroxyl radical by β-carotene producing an intermediate labile free radical, which disappears after recombination with a second tert-butylperoxyl radical. The result is the transformation of β-carotene to a diamagnetic compound with two peroxy bonds. In the presence of chelating transition metals with unpaired d-electrons as electron donors the peroxy group of the oxidized β-carotene can be split to alkoxyl free radicals. The primary attack of tert-butylperoxyl radicals is completely inhibited in the presence of vitamin E followed by production of free aryloxy radicals and the presence of oxygen has no significant effect on this reaction. Spin-trapping of peroxyl radicals by the double bond of vitamin A leads to its oxidation in the absence of vitamin E. Transition metal ions such as Co, Cr, Fe, and Mn, known to be present in the aerosol of cigarette smoke, homolyse the peroxyl bonds of peroxidised β-carotene, which results in cell damage.
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