UV‐Spektren und Konstitution von <i>p</i>‐Benzochinonen

Flaig, Wolfgang; Salfeld, Johann-Christoph; Baume, Erwin

doi:10.1002/jlac.19586180115

Cited by 57 publications

(9 citation statements)

References 9 publications

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“…( 6) Duroquinone was supplied by Fluka A. G. and purified by sublimation. The extinction coefficients (Flaig, Salfeld & Baume 1958) and melting point (.Dictionary of organic compounds 1965) were in good agreement with the literature, (c) a-Tocopherylquinone and a-tocopherol were supplied by Eastm an Kodak and used without further purification, (d) Vitamin K x. N atural phytol material, sup plied by Mann Research Laboratories, (e) Durohydroquinone was supplied by K. and K. Laboratories. This contained approximately 2 % duroquinone, but was not further purified as recrystallization is not a satisfactory method of separating these compounds.…”

Section: Outgassing Of Samplessupporting

confidence: 81%

The interaction of photo-excited chlorophyll a with duroquinone, α -tocopherylquinone and vitamin K ₁

Kelly

Porter

1970

Proc. R. Soc. Lond. A

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The reversible electron transfer between photoexcited chlorophyll a and duroquinone has been studied in neutral, acid and alkaline ethanolic solutions. Rates for the reaction of chlorophyll a singlet and triplet states with duroquinone have been determined, and the kinetics for the decay of the radicals so formed have been investigated. In neutral and alkaline solution, evidence has been found for the recombination of the chlorophyll radical cation with the semiquinone radical anion of duroquinone at a rate close to that for a diffusion controlled reaction. In acidic solutions, the chlorophyll radical cation decays by two processes: 60% reacts by second-order process within milliseconds, and the residual 40% decays by the first-order process having a lifetime of approximately 1 s. The decay rate of these oxidized chlorophyll a species is greatly increased by durohydroquinone. Analogous reactions have been found for triplet chlorophyll a with α -tocopherylquinone and with vitamin K 1 .

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Section: Outgassing Of Samplessupporting

confidence: 81%

The interaction of photo-excited chlorophyll a with duroquinone, α -tocopherylquinone and vitamin K ₁

Kelly

Porter

1970

Proc. R. Soc. Lond. A

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“…The volume of the ethereal solution was reduced and cooled on ice to allow crystallization. The yellow platelets were dissolved in dried CH3CN [76% yield; 364nm ) 1.2 × 10 3 M -1 cm -1 (17)]. N-Acetylglutathione (75 µmol in 5 mL of H2O at pH 5.5) was allowed to react with 2-OH-BQ (50 µmol in 5 mL of CH3CN) for 10 min under argon.…”

Section: Methodsmentioning

confidence: 99%

Ring Addition of the α-Amino Group of Glutathione Increases the Reactivity of Benzoquinone Thioethers

Alt

Eyer

1998

Chem. Res. Toxicol.

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2-(Glutathion-S-yl)-1,4-benzoquinone was found to be remarkably unstable in phosphate buffer (pH 7.4) even in the absence of oxygen. Intramolecular addition of the alpha-amino group of the glutamate residue to the quinone ring yielded ultimately 2,3-(glutathion-N, S-yl)-1,4-benzoquinone and 2,6-(glutathion-N,S-yl)-1,4-benzoquinone in a 3:1 ratio along with 2-(glutathion-S-yl)-1,4-hydroquinone. Kinetic studies indicated that the cyclization reactions proceeded at a rate k1 of 0.093 min-1, while intermolecular reactions followed a second-order kinetics with a k2 of 94 M-1 min-1 (pH 7.4, 37 degreesC), resulting in multiple polymerization products. Both intramolecular amino adducts of 2-(glutathion-S-yl)-1,4-benzoquinone are prone to hydrolysis, leading to the insertion of an additional OH group in the ring. These S-substituted trihydroxybenzene derivatives are particularly susceptible to autoxidation. The model compound 6-(N-acetylcystein-S-yl)-2-hydroxy-1,4-hydroquinone was shown to form readily two atropoisomeric biphenyls upon autoxidation: 2,4'-bis(N-acetylcystein-S-yl)-2',3,3',4,6, 6'-hexahydroxybiphenyl, indicating C-C coupling, presumably via semiquinone radical intermediates. Thus, the sequence of glutathione S-addition, followed by oxidation, N-addition, oxidation, and hydrolysis, constitutes a novel and very effective activation pathway of quinones for eliciting oxidative stress. These data underline the fact that glutathione conjugates of autoxidizable aromatics are no obligatory stable end products of a detoxication reaction. The possible toxicological impacts of intra- and intermolecular addition reactions of quinoid thiol conjugates are discussed.

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“…This article describes the isolation, structural eludication, and synthesis of these two compounds, irisoquin (8) and deoxyirisoquin (5).…”

Section: Scheme Imentioning

confidence: 99%

Isolation, Structural Elucidation, and Chemical Synthesis of 2-Hydroxy-3-octadecyl-5-methoxy-1,4-benzoquinone (Irisoquin), a Cytotoxic Constituent of Iris missouriensis

Wong

Pezzuto

Fong

et al. 1985

Journal of Pharmaceutical Sciences

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UV‐Spektren und Konstitution von p‐Benzochinonen

Cited by 57 publications

References 9 publications

The interaction of photo-excited chlorophyll a with duroquinone, α -tocopherylquinone and vitamin K ₁

The interaction of photo-excited chlorophyll a with duroquinone, α -tocopherylquinone and vitamin K ₁

Ring Addition of the α-Amino Group of Glutathione Increases the Reactivity of Benzoquinone Thioethers

Isolation, Structural Elucidation, and Chemical Synthesis of 2-Hydroxy-3-octadecyl-5-methoxy-1,4-benzoquinone (Irisoquin), a Cytotoxic Constituent of Iris missouriensis

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UV‐Spektren und Konstitution von p‐Benzochinonen

Cited by 57 publications

References 9 publications

The interaction of photo-excited chlorophyll a with duroquinone, α -tocopherylquinone and vitamin K 1

The interaction of photo-excited chlorophyll a with duroquinone, α -tocopherylquinone and vitamin K 1

Ring Addition of the α-Amino Group of Glutathione Increases the Reactivity of Benzoquinone Thioethers

Isolation, Structural Elucidation, and Chemical Synthesis of 2-Hydroxy-3-octadecyl-5-methoxy-1,4-benzoquinone (Irisoquin), a Cytotoxic Constituent of Iris missouriensis

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The interaction of photo-excited chlorophyll a with duroquinone, α -tocopherylquinone and vitamin K ₁

The interaction of photo-excited chlorophyll a with duroquinone, α -tocopherylquinone and vitamin K ₁