Base-Promoted Reaction of 5-Hydroxyuracil Derivatives with Peroxyl Radicals

Amorati, Riccardo; Valgimigli, Luca; Pedulli, Gian Franco; Grabovskii, S. A.; Kabal'nova, N. N.; Chatgilialoglu, Chryssostomos

doi:10.1021/ol1017245

Cited by 25 publications

(10 citation statements)

References 22 publications

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“…a-Tocopherol was also used as reference antioxidant to measure the rate of initiation R i . [17,35] Numerical simulation of oxygen consumption traces was performed using Gepasi software, version 3.30, [38] as described elsewhere. [33,39] EPR spectroscopy: Autoxidation experiments were performed on air-saturated solutions of styrene (4.3 m) in chlorobenzene using AIBN (0.05 m) as the initiator and 3 (33 mm) as the inhibitor.…”

Section: Methodsmentioning

confidence: 99%

“…[17] Instead, it would appear that the kinetics depend on a preliminary equilibrium to yield the "true" antioxidant species (i.e., Scheme 6, Reaction (9)), requiring its incorporation in to the analysis of the kinetic data (Scheme 6). [35] By using our reported data for the decomposition of 2 in chlorobenzene at 37 8C (in the absence of ethyl propiolate, see Figure 2 B in ref. [11] and the fit in the Supporting Information, Figure S2), [11] we obtained rate constants k 9 = 6.4 10 À5 s À1 and k À9 = 1.3 10 2 m À1 s À1 for the reversible Cope elimination of phenylmethanesulfenic acid from the thiosulfinate 2 (at 37 8C).…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

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The Reaction of Sulfenic Acids with Peroxyl Radicals: Insights into the Radical‐Trapping Antioxidant Activity of Plant‐Derived Thiosulfinates

Amorati

Lynett

Valgimigli

et al. 2012

Chemistry A European J

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Sulfenic acids play a prominent role in biology as key participants in cellular signaling relating to redox homeostasis, in the formation of protein-disulfide linkages, and as the central players in the fascinating organosulfur chemistry of the Allium species (e.g., garlic). Despite their relevance, direct measurements of their reaction kinetics have proven difficult owing to their high reactivity. Herein, we describe the results of hydrocarbon autoxidations inhibited by the persistent 9-triptycenesulfenic acid, which yields a second order rate constant of 3.0×10(6) M(-1) s(-1) for its reaction with peroxyl radicals in PhCl at 30 °C. This rate constant drops 19-fold in CH(3)CN, and is subject to a significant primary deuterium kinetic isotope effect, k(H)/k(D) = 6.1, supporting a formal H-atom transfer (HAT) mechanism. Analogous autoxidations inhibited by the Allium-derived (S)-benzyl phenylmethanethiosulfinate and a corresponding deuterium-labeled derivative unequivocally demonstrate the role of sulfenic acids in the radical-trapping antioxidant activity of thiosulfinates, through the rate-determining Cope elimination of phenylmethanesulfenic acid (k(H)/k(D) ≈ 4.5) and its subsequent formal HAT reaction with peroxyl radicals (k(H)/k(D) ≈ 3.5). The rate constant that we derived from these experiments for the reaction of phenylmethanesulfenic acid with peroxyl radicals was 2.8×10(7) M(-1) s(-1); a value 10-fold larger than that we measured for the reaction of 9-triptycenesulfenic acid with peroxyl radicals. We propose that whereas phenylmethanesulfenic acid can adopt the optimal syn geometry for a 5-centre proton-coupled electron-transfer reaction with a peroxyl radical, the 9-triptycenesulfenic is too sterically hindered, and undergoes the reaction instead through the less-energetically favorable anti geometry, which is reminiscent of a conventional HAT.

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Section: Methodsmentioning

confidence: 99%

Section: Wwwchemeurjorgmentioning

confidence: 99%

The Reaction of Sulfenic Acids with Peroxyl Radicals: Insights into the Radical‐Trapping Antioxidant Activity of Plant‐Derived Thiosulfinates

Amorati

Lynett

Valgimigli

et al. 2012

Chemistry A European J

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“…149 5-Hydroxy-4-methyluracil (5-HMU), an immunotropic drug, is structurally related to ascorbic acid and has been found to undergo identical behavior with peroxyl radicals: its k inh in acetonitrile (at 30 • C) was determined to be 1.5 × 10 4 M −1 s −1 and was found to be dramatically enhanced in the presence of bases, as a result of partial deprotonation of the ring N-H moiety at the 3-position (pK a = 8.5 in water). 206 …”

Section: Ascorbic Acid and Related Compoundsmentioning

confidence: 99%

Antioxidants in Chemistry and Biology

Valgimigli

Pratt

2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

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109

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Antioxidants are omnipresent in nature and industry; they are used to slow down the autoxidative degradation of both organic tissues and petroleum‐derived products. Various mechanisms by which antioxidants can act are known, the most common of which are introduced here. Since autoxidation is a radical chain reaction, radical‐trapping antioxidants play a particularly important role; therefore, we will discuss these compounds in most detail. To introduce and develop central concepts relating to this topic, we present kinetic and thermodynamic data obtained for the reactions of phenols, the archetypical radical‐trapping antioxidants, with chain‐carrying peroxyl radicals, and describe the means to obtain these data. We then extend our discussion to other important classes of radical‐trapping antioxidants, beginning with the closely related polyphenols and newly developed pyridinol and pyrimidinol antioxidants, and then further to aromatic amines, organosulfur compounds, and their derivatives. We go on to touch upon the synergistic behavior in antioxidant combinations, and the effects of the medium on these interactions, and finally round things up with a few more important biological examples: ascorbate and β‐carotene. A few comments on the state of the field and areas requiring further research and development are included.

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“…Most of the effects have belonged to the role of free radicals . It is known that free radicals constantly formed in living organisms by x‐rays, radiation therapy, and ultraviolet radiations could react with organic cellular components, such as protein, lipid, and nucleic acid . Especially, OH radical, as a highly reactive oxygen species, has an extremely short lifetime and plays a vital character for DNA damage .…”

Section: Introductionmentioning

confidence: 99%

DFT study on addition reaction mechanism of guanine-cytosine base pair with OH radical

Ling

Liao

et al. 2015

J. Phys. Org. Chem.

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C. The hydroxylation reactions at G . C C5 and G C8.C sites appear to be barrierless, and the sequence of the barrier energy is G .C. The results indicate that hydroxylation at G C base pair. Considering the solvent effects by using the polarizable continuum model, the stabilities of all the compounds are increased significantly. Little change is taken place on the data of the reaction energies and barrier energies. Their sequences and the stability order follow the same trends like them in gas phase. The fluctuation of natural bond orbital charge further confirms that the hydroxylation reactions are exothermic. And transient spectra computed with the time-dependent density functional theory (TD-DFT) match well with the previous experimental and theoretical reports. Our deduced mechanism is in good agreement with the experimentally observed hydroxylated adducts.

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Base-Promoted Reaction of 5-Hydroxyuracil Derivatives with Peroxyl Radicals

Cited by 25 publications

References 22 publications

The Reaction of Sulfenic Acids with Peroxyl Radicals: Insights into the Radical‐Trapping Antioxidant Activity of Plant‐Derived Thiosulfinates

The Reaction of Sulfenic Acids with Peroxyl Radicals: Insights into the Radical‐Trapping Antioxidant Activity of Plant‐Derived Thiosulfinates

Antioxidants in Chemistry and Biology

DFT study on addition reaction mechanism of guanine-cytosine base pair with OH radical

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