The Pecking Order of Free Radicals and Antioxidants: Lipid Peroxidation, α-Tocopherol, and Ascorbate

Buettner, Garry R.

doi:10.1006/abbi.1993.1074

Cited by 2,252 publications

(1,416 citation statements)

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“…The observed effect of GSH on steady state concentration of ascorbate radical allows quantitative description in terms of the bimolecular reaction. However, it worth to note that direct reaction of ascorbate radical with GSH with formation of ascorbate and thiyl radical is thermodynamically unfavorable [44], and the mechanism of ascorbate radical scavenging by GSH might be complex. The apparent bimolecular rate constant of the ascorbate radical reduction by GSH was found to be comparatively low, 10 M −-1 s −1 , therefore it hardly could play significant role in vivo.…”

Section: Discussionmentioning

confidence: 99%

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Bobko

Kirilyuk

Grigor'ev

et al. 2007

Free Radical Biology and Medicine

134

123

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Biological applications of stable nitroxyl radicals, NR, include their use as contrast agents for magnetic resonance imaging, spin labels, superoxide dismutase mimics, and antioxidants. The rapid reduction of NR in biological samples into hydroxylamines, HA, significantly limits their application. In its turn, reoxidation of HA back to the NR has been used for detection of reactive oxygen species, ROS. In this work comparative studies of the reduction of pyrrolidine, imidazoline and imidazolidine NR by ascorbate were performed taking advantage of recently synthesized tetraethyl substituted NR with much higher stability towards reduction both in vitro and in vivo. Surprisingly, these NR kept 10-50% of initial intensity of electron paramagnetic resonance signal for about 1 h in the presence of hundred fold excess of ascorbate. To explain this data, reoxidation of the corresponding HA by ascorbate radical and dehydroascorbic acid back to the NR was proposed. This hypothesis was supported by direct measurement of the NR appearance from the HA upon ascorbate radical generation by ascorbate oxidase, or in the presence of the dehydroascorbic acid. The reversible reaction between NR and ascorbate was observed for the various types of the NR, and the rate constants for direct and reverse reactions were determined. The equilibrium constants for oneelectron reduction of the tetraethyl substituted NR by ascorbate were found to be in the range from 2.65×10 −6 to 10 −5 which is significantly lower than corresponding values for the tetramethyl substituted NR (less or about 10 −4 ). This explains an establishment of EPR-detectable quasiequilibrium level of tetraethyl substituted NR in the presence of excess of ascorbate. The redox reactions of the NR-HA couple in ascorbate containing medium was found to be significantly affected by glutathione, GSH. This effect was attributed to the reduction of ascorbate radical by GSH, and the rate constant of this reaction was found to be equal to 10 M −1 s −1 . In summary, the data provide new insight into the redox chemistry of NR and HA, and significantly affect interpretation and strategy of their use as redox-and ROS-sensitive probes, or as antioxidants.

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Section: Discussionmentioning

confidence: 99%

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Bobko

Kirilyuk

Grigor'ev

et al. 2007

Free Radical Biology and Medicine

134

123

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“…It is generally believed that α-tocopherol intercalates into the lipid bilayers of cell membranes and acts there directly to scavange free radicals. Hydroxyl radical attack on tocopherol forms a stabilized phenolic radical that is reduced back to the phenol by ascorbate and NADH/NADPH reductase enzyme (28). Vitamin E may largely modulate the expression of the toxicity by GSH depleting agents (29).…”

Section: Discussionmentioning

confidence: 99%

Effect of lecithin in the treatment of ethanol mediated free radical induced hepatotoxicity

Das

Vasudevan

2006

Indian J Clin Biochem

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Alcoholic liver disease (ALD) develops as a consequence of priming and sensitizing mechanisms rendered by cross-interactions of primary mechanistic factors and secondary risk factors. Liver damage due to consumption of alcohol may be caused by oxygen radicals such as superoxide and hydroxyl radicals, generated during the metabolism of ethanol by the microsomal oxidizing system. Lecithin, an important class of phospholipids contains choline, which is considered as lipotropic factor. The effects of this lecithin as a hepatoprotective drug on body weight and antioxidant status of ethanol-exposed rats were studied. The results were compared with the effects of tocopheryl acetate. From the present study, it can be concluded that ethanol-induced stress can be partly prevented by tocopheryl acetate, and showed best result. Abstination from alcohol also involved for little hepatic regeneration. Supplementation of lecithin showed better effect compared to abstination from alcohol on reversing the effect of ethanol induced liver damage in the present study. Moreover, preventive measures were found to be better than curative treatment. Antioxidants are likely to provide beneficial effects on hepatocyes via desensitization against oxidant stress while inhibiting primary mechanism for expression of proinflammatory and cytotoxic mediators. However, abstinence from alcohol, proper nutrition, and supplementation of antioxidants, vitamins and hepatoprotective drugs are some of the therapeutic options.

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“…Vitamin C is a water-soluble vitamin and is the major antioxidant component in extracellular fluids [11,12]. Supplementation of bovine culture medium with vitamin C improved the porcine denuded oocyte maturation and blastocyst rate after parthenogenetic activation [13].…”

Section: Introductionmentioning

confidence: 99%

Antioxidants rescue stressed embryos at a rate comparable with co-culturing of embryos with human umbilical cord mesenchymal cells

Moshkdanian

Nematollahi‐Mahani

Pouya

et al. 2011

J Assist Reprod Genet

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Purpose During laboratory manipulations, oocytes and embryos are inevitably exposed to suboptimal conditions that interfere with the normal development of embryos. Materials and methods In this study, we examined the effects of antioxidants, feeder cells and a conditioned medium on embryo development and cleavage rate following exposure of the embryos to suboptimal conditions. We exposed mouse two-cell embryos to visible light and divided them into four groups: control (E-ctr), co-culture (Co-c), conditioned medium (Cndm) and antioxidant-plus medium (Aopm). We used human umbilical cord matrixderived mesenchymal cells for co-culture. A group of embryos was not exposed to visible light and served as the non-exposed control (NE-ctr) group. ResultsThe developmental rate was higher in NE-ctr embryos than in the E-ctr group. Exposed embryos in the various groups showed a comparable developmental rate at different stages. Blastomere number significantly increased (P<0.05) in the Co-c and Aopm groups compared with the E-ctr and Cndm groups. No significant difference was observed between the Co-c and Aopm groups. Conclusions Our data indicate that in suboptimal conditions, antioxidants could improve the embryo cleavage rate in the same way as feeder cells. Antioxidants probably improve embryo quality through their ability to scavenge reactive oxygen species.

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The Pecking Order of Free Radicals and Antioxidants: Lipid Peroxidation, α-Tocopherol, and Ascorbate

Cited by 2,252 publications

References 0 publications

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Reversible reduction of nitroxides to hydroxylamines: Roles for ascorbate and glutathione

Effect of lecithin in the treatment of ethanol mediated free radical induced hepatotoxicity

Antioxidants rescue stressed embryos at a rate comparable with co-culturing of embryos with human umbilical cord mesenchymal cells

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