A kinetic study of reactions of tocopherols with a substituted phenoxyl radical

Mukai, Kazuo; Fukuda, Kazuyuki; Tajima, Kunihiko; Ishizu, Kazuhiko

doi:10.1021/jo00237a040

Cited by 58 publications

(58 citation statements)

References 2 publications

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“…• ) by the antioxidants, which was previously estimated by us [7,[10][11][12][13], and unpublished data by Mukai et al]. It is particularly interesting to compare the relative Toc biopotency in vivo with the fats-and-oils oxidation-protecting activity of Toc in vitro.…”

Section: Introductionmentioning

confidence: 78%

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Why is the order reversed? peroxyl‐scavenging activity and fats‐and‐oils protecting activity of vitamin E

Mukai

Noborio

Nagaoka

2005

Int J of Chemical Kinetics

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The orders of relative tocopherol biopotency, scavenging activity of lipid peroxyl radicals, and quenching activity of singlet oxygen are as follows: α-tocopherol > β-tocopherol ≥ γ-tocopherol > δ-tocopherol. However, the reverse is the case for the activity to protect fats and oils from oxidation: α-tocopherol < β-tocopherol < γ-tocopherol < δ-tocopherol. The reason for this reverse has been studied by measuring weight gains of solutions including methyl linoleate and various antioxidants at daily intervals. Antioxidant activity is expressed as an induction period in days. Induction periods are compared with the second-order rate constants for scavenging of an aroxyl radical by the antioxidants. A plot of the logarithm of the secondorder rate constant vs. the induction period is found to give a good linear fit, and the slope is negative. From these results, it is considered that the larger the peroxyl-radical-scavenging activity of a tocopherol, the more favorable the production of the tocopheroxyl radical, and thus the more efficient the oxidation of fats and oils by the tocopheroxyl radical. This is not the case for tocopherols in vivo, because vitamin C and ubiquinol reduce tocopheroxyl radicals formed from tocopherols. C 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: [605][606][607][608][609][610] 2005

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Section: Introductionmentioning

confidence: 78%

“…k s is a measure of scavenging activity of lipid peroxyl radicals by the antioxidants [10,31]. The longest τ was obtained for KME-4 (25).…”

Section: Loomentioning

confidence: 99%

Why is the order reversed? peroxyl‐scavenging activity and fats‐and‐oils protecting activity of vitamin E

Mukai

Noborio

Nagaoka

2005

Int J of Chemical Kinetics

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“…Mukai and coworkers 148,149 developed the use of the stable, colored 2,6-di-tert-butyl-4-(4 -methoxyphenyl)phenoxyl radical (ArO ž ) and other para derivatives in stopped-flow measurements of hydrogen bond donating ability of a wide variety of chromanol-type antioxidants, and some of their results are reviewed below.…”

Section: Monohydroxy Phenols: Substituent Effectsmentioning

confidence: 99%

Phenols as Antioxidants

Ross

Barclay

Vinqvist

2009

Patai's Chemistry of Functional Groups

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“…Burton et al 5 suggested that the hydrogen atom transfer from TocH to LOO " is rate controlling in reaction ͑1͒, while Mukai et al 6 suggested that the mechanism of reaction ͑1͒ can be explained in terms of ET from TocH to LOO " . The mechanism of reaction ͑1͒ has attracted much attention in both experimental and theoretical studies.…”

Section: Investigation Of Photoinduced Electron Transfer In Model Sysmentioning

confidence: 99%

Investigation of photoinduced electron transfer in model system of vitamin E-duroquinone by time-dependent density functional theory

Duan

et al. 2004

The Journal of Chemical Physics

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Photoinduced electron transfer of the model system composed of vitamin E and duroquinone has been investigated using time-dependent density functional theory. Calculations for the excited states tell that the photoexcitation of the model system can directly yield the charge transfer states in which the vitamin E moiety is positively charged but the duroquinone moiety is negatively charged. Our theoretical investigations indicate that the second charge transfer state of the model system can also be produced through the decay of higher locally excited state S(4). Since S(4) state in the model system corresponds to S(1) state of the isolated duroquinone used as a model for peroxyl radical, and S(2) state has the character of electron transfer from the tertiary amine group of the vitamin E moiety to the duroquinone moiety, the decay from S(4) to S(2) corresponds to the dynamic process following the photoexcitation of the duroquinone moiety of the model system, i.e., the initial stage of antioxidant reaction of vitamin E. Calculations of the kinetic parameters for the electron transfer have been carried out in the framework of the Marcus-Jortner-Levich formalism. Our calculations confirm that the electron transfer from S(4) to S(2) possesses the character of the inverted regime and the barrier is negligibly small.

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A kinetic study of reactions of tocopherols with a substituted phenoxyl radical

Cited by 58 publications

References 2 publications

Why is the order reversed? peroxyl‐scavenging activity and fats‐and‐oils protecting activity of vitamin E

Why is the order reversed? peroxyl‐scavenging activity and fats‐and‐oils protecting activity of vitamin E

Phenols as Antioxidants

Investigation of photoinduced electron transfer in model system of vitamin E-duroquinone by time-dependent density functional theory

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