Investigation of Hydrogen and Electron Transfer Reactions of Antioxidants by Electron Spin Resonance

Tkáč, A.

doi:10.1007/978-94-009-3429-0_3

Cited by 4 publications

(1 citation statement)

References 97 publications

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“…However, free radical photoproducts were not detected for this chemical under the modified ESR‐PT conditions. Free radicals generated from bisphenols with the sulfur atom between two phenolic rings, such as bithionol and fenticlor, are especially stabilized (Tkáč, 1987). However, the radical product generated from hexachlorophene, in which a carbon atom instead of a sulfur atom bridges two phenolic rings, may be instable and short‐lived.…”

Section: Discussionmentioning

confidence: 99%

Modified ESR‐based photosafety test (ESR‐PT) detecting singlet oxygen and free radical formation

Hinoshita,

Abe,

Sato

et al. 2023

J of Applied Toxicology

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The electron spin resonance‐based photosafety test (ESR‐PT) was modified using a new parameter, photoreactivity index (PRI), to detect singlet oxygen and free radical photoproducts simultaneously. With this modification, the modified ESR‐PT is expected to reduce the number of false negative results due to chemicals producing free radical photoproducts other than singlet oxygen. The assay performance of the modified ESR‐PT was evaluated using 56 chemicals, including hydrophobic chemicals. When using the PRI cutoff value of 2.0 in the modified ESR‐PT, the accuracy relative to photosafety reference data was 91.1%, and the applicability (100%) was better than the other non‐animal photosafety test. Among the chemicals producing positive results, bithionol, fenticlor, and doxycycline HCl were considered positive based on the detection of free radical photoproducts, suggesting that these three chemicals may have phototoxic or photoallergic potential via radical reactions. Additionally, this finding demonstrated the fundamental advantage of the modified ESR‐PT using ESR spectroscopy, which can detect radicals selectively and quantitatively. Accordingly, the new parameter PRI is effective for photosafety evaluations based on not only singlet oxygen but also free radical photoproducts generated from chemicals. Therefore, the modified ESR‐PT has a great potential for a photosafety test method applicable to various chemicals.

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Section: Discussionmentioning

confidence: 99%

Modified ESR‐based photosafety test (ESR‐PT) detecting singlet oxygen and free radical formation

Hinoshita,

Abe,

Sato

et al. 2023

J of Applied Toxicology

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Stabilisation of polymers by catalytic antioxidants

Scott

1989

Makromolekulare Chemie. Macromolecular Symposia

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Two types of catalytic antioxidant are now recognised. The first involves the catalytic destruction of hydroperoxides to non‐radical products and the second consists of “stable” redox couples with the ability to remove both alkyl (CB‐A) and alkylperoxyl (CB‐D) radicals in autoxidising systems. The conditions under which both types of antioxidant can operate effectively are reviewed and the limitations to their activity are outlined.

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Reduced Enzymic Control of Free Radical and electron transport reactions in the mitochondria of zajdela hepatoma ascitic cells: A model for the stepwise transformation of healthy to tumorous cells involving a progressive loss of antioxidant activity

Tkáč¹,

Hanušovská‐Tkáčová

1989

J. Prakt. Chem.

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Differences in the radical chemistry of normal and tumorous rat liver cells were demonstrated using e.s.r. techniques. In healthy cells the one‐electron transfer from hemoproteins to peroxides and hydroperoxides is accompanied by radical formation and proceeds predominantly in the endoplasmatic reticulum. Their mitochondria are effectively shielded against autoxidation. The opposite is true for Zajdela hepatoma ascitic cells and mitochondria. Mitochondria isolated from this type of cancerous cell are sensitive targets for radical attack and irreversible oxidation of thier hemoproteins from the FeII to FeIII oxidative state. A probable location for electron leakage in cancerous rat liver cells, depleted of the enzyme Mn‐SOD, controlling the O 2− level, and of catalase, controlling the H2O2 level, seems to be the ubisemiquinone‐cytochrome c component of the mitochondrial respiration redox chain, where the active center of cytochrome oxidase is blocked and so the controlled four‐electron transfer to molecular oxygen is prevented. A model is proposed to explain the stepwise transformation of a highly organized differentiated cell to an uncontrolled proliferating tumor cell. The transition is brought about by a progressive loss of protective capacity which allows transition metal coordinated radicals, carried by hemoproteins, to cross the nuclear membrane. Inside the nucleus decomplexation of the stabilized radicals will release damaging short‐lived radical species.

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Investigation of Hydrogen and Electron Transfer Reactions of Antioxidants by Electron Spin Resonance

Cited by 4 publications

References 97 publications

Modified ESR‐based photosafety test (ESR‐PT) detecting singlet oxygen and free radical formation

Modified ESR‐based photosafety test (ESR‐PT) detecting singlet oxygen and free radical formation

Stabilisation of polymers by catalytic antioxidants

Reduced Enzymic Control of Free Radical and electron transport reactions in the mitochondria of zajdela hepatoma ascitic cells: A model for the stepwise transformation of healthy to tumorous cells involving a progressive loss of antioxidant activity

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