Two Pathways of Carbon Dioxide Catalyzed Oxidative Coupling of Phenol by Peroxynitrite (original) (raw)
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Carbon Dioxide Modulation of Hydroxylation and Nitration of Phenol by Peroxynitrite
Archives of Biochemistry and Biophysics, 1997
nitrocarbonate; carbon dioxide; tyrosine; nitrotyrosine; radical. We have examined the formation of hydroxyphenols, nitrophenols, and the minor products 4-nitrosophenol, benzoquinone, 2,2-biphenol, and 4,4-biphenol from the reaction of peroxynitrite with phenol in the presence and absence of added carbonate. In the absence Peroxynitrite 2 can be formed in vivo from the diffuof added carbonate, the product yields of nitrophenols sion-controlled reaction of nitric oxide and superoxide and hydroxyphenols have different pH profiles. The radicals (1, 2). In vitro, peroxynitrite has been shown to rates of nitration and hydroxylation also have differreact with almost all classes of biomolecules, including ent pH profiles and match the trends observed for the proteins, lipids, carbohydrates, antioxidants, and nuproduct yields. At a given pH, the sum of the rate concleic acids (3-12). The nitration of tyrosine residues in stants for nitration and hydroxylation is nearly identiproteins, which may be involved in signal transduction cal to the rate constant for the spontaneous decompo-(13), is often taken as evidence for the formation of sition of peroxynitrite. The reaction of peroxynitrite peroxynitrite in vivo (14), since tyrosine and other phewith phenol is zero-order in phenol, both in the presnolics are nitrated by peroxynitrite (14-16) but not by ence and absence of added carbonate. In the presence nitric oxide (17, 18). of added carbonate, hydroxylation is inhibited, Peroxynitrite is known to nitrate and hydroxylate whereas the rate of formation and yield of nitrophearomatic compounds (4, 15, 16, 19, 20). Halfpenny and nols increase. The combined maximum yield of o-and Robinson , who first studied these reactions, sugp-nitrophenols is 20 mol% (based on the initial concengested a radical mechanism. Hydroxyl and • NO 2 tration of peroxynitrite) and is about fourfold higher than the maximal yield obtained in the absence of radicals have been suggested to be formed during the added carbonate. The o/p ratio of nitrophenols is the decomposition of peroxynitrite (21) and have been sugsame in the presence and absence of added carbonate. gested as the species responsible for the peroxynitrite-These results demonstrate that hydroxylation and nimediated hydroxylation and nitration of phenylalanine tration occur via two different intermediates. We sugand tyrosine (15). However, several lines of evidence, gest that the activated intermediate formed in the including the lack of effect of typical hydroxyl radical isomerization of peroxynitrous acid to nitrate, ONOOH*, scavengers (3), experiments performed using spin is the hydroxylating species. We propose that intermetraps (e.g., 5,5-dimethylpyrroline-N-oxide) (22-25), diate 1, O|N{OO{CO 0 2 , or secondary products deand a study on the effect of viscosity on the rate of rived from it, is (are) responsible for the nitration of decomposition of peroxynitrite (26), do not indicate the phenol. The possible mechanisms responsible for niformation of free hydroxyl radical during the decompotration are discussed. ᭧ 1997 Academic Press sition of peroxynitrous acid. The nitronium ion, / NO 2 , Key Words: peroxynitrite; nitrophenol; hydroxyformed from peroxynitrous acid at low pH (16) or from phenol; nitration; kinetics; nitrosoperoxycarbonate; 2 The term peroxynitrite is used to refer to the sum of both peroxy-1 To whom correspondence should be addressed at 711 Choppin nitrite anion (ONOO 0 ) and its conjugated acid, peroxynitrous acid (ONOOH). The term carbonate represents the sum of all carbonated Hall, species (CO 2 , H 2 CO 3 , HCO 0 3 , and CO 0 3 ). If a particular carbonated species is referred to, it is represented by its chemical formula.
Acceleration of Peroxynitrite Oxidations by Carbon Dioxide
Archives of Biochemistry and Biophysics, 1996
oxidizing nitric oxide ( • NO) (1-9). The reaction be-Stopped-flow kinetic studies of the isomerization of tween O •0 2 and • NO is a radical-radical combination peroxynitrite to give nitrate have been performed in car-and, therefore, is extremely rapid (k Å 4-7 1 10 9 M 01 bonate-enriched buffers using pH jump and carbonic ans 01 ) (10-12) and does not require enzymatic catalysis. hydrase as probes. The data are consistent with the reac-Peroxynitrite is a versatile oxidant that is capable of tion of CO 2 and the peroxynitrite anion rapidly forming reacting with all major classes of biomolecules, includan unstable nitrosoperoxycarbonate anion adduct, ing antioxidants (such as ascorbate, glutathione, a-to-O|N{OOCO 0 2 (1). The CO 2 catalysis of the isomerizacopherol, and uric acid) (13-19), carbohydrates (20), tion of peroxynitrite is not accompanied by the formalipids (21, 22), nucleic acids (23-26), and proteins (27tion of nitrite, hydrogen peroxide, or other hydroperox-34). The reactions of peroxynitrite that have been idenidic material like peroxycarbonate. The reaction protified to date can be divided into at least five mechanisceeds via the transient formation of an oxidant or tic classes: (a) isomerization to nitrate, (b) one-electron oxidants that is (are) capable of promoting electrophilic or (c) two-electron oxidations, (d) oxygen atom transnitration reactions. We propose that O|N{OOCO 0 2 refers, and (e) electrophilic nitrations (35-39). arranges to give a nitrocarbonate anion, O 2 N{OCO 0 2 (2)
Homolytic Pathways Drive Peroxynitrite-Dependent Trolox C Oxidation
Chemical Research in Toxicology, 2004
Peroxynitrite is a powerful oxidant implicated as a mediator in nitric oxide (• NO)-and superoxide (O 2 •-)-dependent toxicity. Peroxynitrite homolyzes after (i) protonation, yielding hydroxyl (• OH) and nitrogen dioxide (• NO 2) free radicals, and (ii) reaction with carbon dioxide (CO 2), yielding carbonate radical anion (CO 3 •-) and • NO 2. Additionally, peroxynitrite reacts directly with several biomolecules. It is currently accepted that R-tocopherol is one important antioxidant in lipid compartments and its reactions with peroxynitrite or peroxynitrite-derived radicals may be relevant in vivo. Previous reports on the peroxynitrite reaction with Trolox C (TxOH)san R-tocopherol water soluble analoguessuggested a direct and fast reaction. This was unexpected to us as judged from the known reactivities of peroxynitrite with other phenolic compounds; thus, we thoroughly investigated the kinetics and mechanism of the reaction of peroxynitrite with TxOH and its modulation by CO 2. Direct electron paramagnetic resonance studies revealed that Trolox C phenoxyl radical (TxO •) was the only paramagnetic species detected either in the absence or in the presence of CO 2. Stopped-flow spectrophotometry experiments revealed a sequential reaction mechanism, with the intermediacy of TxO • and the production of Trolox C quinone (TxQ). Reactions were zero-order with respect to TxOH and first-order in peroxynitrite and CO 2 , demonstrating that the reaction of peroxynitrite with TxOH is indirect. In agreement, TxOH was unable to inhibit the direct peroxynitrite-mediated oxidation of methionine to methionine sulfoxide. TxOH oxidation yields to TxO • and TxQ with respect to peroxynitrite were ∼60 and ∼31%, respectively, and increased to ∼73 and ∼40%, respectively, in the presence of CO 2. At peroxynitrite excess over TxOH, the kinetics and mechanism of oxidation are more complex and involve the reactions of CO 3 •with TxO • and the possible intermediacy of unstable NO 2-TxOH adducts. Taken together, our results strongly support that H +-or CO 2-catalyzed homolysis of peroxynitrite is required to cause TxOH, and hence, R-tocopherol oxidation.
Tetrahedron Letters, 1999
The reaction of peroxynitrite (ONOO-) with a series ofpara-substituted phenols has been examined in aqueous phosphate buffer and acetonitrile solutions. Major products were the corresponding 2-nitro derivative and the 4-substituted catechol. Kinetic study showed good correlation with Hammett (rp ÷ parameters and reduction potentials, suggesting the possible one-electron transfer process involving the nitrosoniun ion (NO +) as initial electrophile generated from peroxynitrous acid.
Archives of Biochemistry and Biophysics, 1996
adduct (ONOOCO 0 2) which can participate in oxidation and nitration processes, thus redirecting the primary Peroxynitrite is a strong oxidant produced in vivo reactivity of peroxynitrite. ᭧ 1996 Academic Press, Inc. as the reaction product of superoxide anion and nitric Key Words: peroxynitrite; superoxide; nitric oxide; oxide (k Ç 5 1 10 9 M 01 s 01) and can be formed and medibicarbonate; carbon dioxide; reaction kinetics; ate reactions in the extracellular environment. It has stopped-flow spectrophotometry; free radicals. recently been reported that peroxynitrite and carbon dioxide react in a second-order process (S. V. Lymar and K. Hurst (1995) J. Am. Chem. Soc. 117, 8867-8868). Since one of the most abundant constituents of the extracellular milieu is bicarbonate anion (25 mM in Peroxynitrite 2 production by endothelial cells (1), plasma) which is in equilibrium with carbon dioxide neutrophils (2), and macrophages (3) occurs following (1.3 mM in plasma) we have further studied the kinetics the almost diffusion-controlled reaction (k Ç 5 1 10 9 of the reaction between peroxynitrite and carbon diox-M 01 s 01 ; Refs. 4 and 5) between cell-derived nitric oxide ide/bicarbonate and the effect of bicarbonate on differ-(• NO) and superoxide (O •0 2). Peroxynitrite is capable of ent peroxynitrite-mediated oxidations. The apparent oxidizing a variety of biomolecules including thiols (6), second-order rate constant for the reaction is (2.3 { 0.1) lipids (7), carbohydrates (8), and DNA (9) via complex 1 10 3 M 01 s 01 at 37ЊC and pH 7.4 and a pH-independent and strongly pH-dependent oxidative reaction mechasecond-order rate constant of (5.8 { 0.2) 1 10 4 M 01 s 01 at nisms. Peroxynitrite anion (ONOO 0) directly reacts 37ЊC was obtained considering peroxynitrite anion and with sulfhydryls (6), a reaction implicated to be a major carbon dioxide as the reacting species. The enthalpy mechanism for peroxynitrite-mediated inactivation of and entropy of activation are DH # Å /10.7 { 0.8 kcal enzymes (10, 11). Once protonated (pK a Å 6.8; Ref. 6) mol 01 and DS # Å 06.5 { 0.5 cal mol 01 K 01 , respectively. to peroxynitrous acid (ONOOH), this unstable species The presence of bicarbonate had variable influence on isomerizes to nitric acid with a half-life of less than 1 peroxynitrite-mediated oxidations. While bicarbonate s at pH 7.4 and 37ЊC (8) and will undergo both one-or significantly enhanced peroxynitrite-mediated nitratwo-electron oxidation to target molecules. The ground tion of aromatics, it partially inhibited the oxidation of state form of peroxynitrous acid reacts with methionine thiols, dimethylsulfoxide, oxyhemoglobin, and cytochrome c /2 and totally inhibited the hydroxylation of (12), cytochrome c 2/ (13), ascorbate (14), and tryptobenzoate. Spontaneous chemiluminescence studies phan (15). Peroxynitrous acid also undergoes transition suggest the formation of bicarbonate radicals during to a vibrationally activated state (ONOOH*), 17 kcal the interactions of peroxynitrite with carbon dioxide/ mol 01 above the energy level of the ground state (16), bicarbonate. Our results support that peroxynitrite anion rapidly reacts with carbon dioxide to yield an 2 The term ''peroxynitrite'' is used to refer to either the anion (ONOO 0) or its conjugate acid (ONOOH). When a discussion is spe-1 To whom correspondence and reprint requests should be ad-cifically limited to either the anion or the free acid, either its name or its structure will be given. IUPAC recommended name for peroxy-dressed at Depto.
A study of the reaction of different phenol substrates with nitric oxide and peroxynitrite
Tetrahedron, 1999
The reactivity of different phenol substrates with nitric oxide and peroxynitrite was investigated. In general, nitration is the major reaction with peroxynitrite, while reactions with aqueous solutions of nitric oxide led to mixtures of nitro and nitroso derivatives depending upon the phenol. Nitrosation occurs on phenol substrates bearing a free para- position with respect to the OH group with the
Nitrosation by Peroxynitrite: Use of Phenol as a Probe
Archives of Biochemistry and Biophysics, 1998
Nitrosation is an important pathway in the metabolism of nitric oxide, producing S-nitrosothiols that may be critical signal transduction species. The reaction of peroxynitrite with aromatic compounds in the pH range of 5 to 8 has long been known to produce hydroxylated and nitrated products. However, we here present evidence that peroxynitrite also can promote the nitrosation of nucleophiles. We chose phenol as a substrate because the nitrosation reaction was first recognized during a study of the CO 2 -modulation of the patterns of hydroxylation and nitration of phenol by peroxynitrite (Lemercier et al., Arch. Biochem. Biophys. 345, 160 -170, 1997). 4-Nitrosophenol, the principal nitrosation product, is detected at pH 7.0, along with 2-and 4-nitrophenols; 4-nitrosophenol becomes the dominant product at pH > 8.0. The yield of 4-nitrosophenol continues to increase even after pH 11.1, 1.2 units above the pK a of phenol, suggesting that the phenolate ion, and not phenol, is involved in the reaction. Hydrogen peroxide is not formed as a by-product. The nitrosation reaction is zeroorder in phenol and first-order in peroxynitrite, suggesting the phenolate ion reacts with an activated nitrosating species derived from peroxynitrite, and not with peroxynitrite itself. Under optimal conditions, the yields of 4-nitrosophenol are comparable to those of 2-and 4-nitrophenols, indicating that the nitrosation reaction is as significant as the nitration of phenolic compounds by peroxynitrite. Low concentrations of CO 2 facilitate the nitrosation reaction, but excess CO 2 dramatically reduces the yield of 4-nitrosophenol. The dual effects of CO 2 can be rationalized if O|NOOO ؊ reacts with the peroxynitrite anion-CO 2 adduct (O|NOOOCO 2 ؊ ) or secondary intermediates derived from it, including the nitrocarbonate anion (O 2 NOOCO 2 ؊ ), the carbonate radical (CO 3 •؊ ), and • NO 2 . The product resulting from these reactions can be envisioned as an activated intermediate XON|O (where X is OOONO 2 , ONO 2 , or OCO 3 ؊ ) that could transfer a nitrosyl cation (NO ؉ ) to the phenolate ion. An alternative mechanism for the nitrosation of phenol involves the one-electron oxidation of the phenolate ion by CO 3
Chemical Research in Toxicology, 1995
Peroxynitrite, the reaction product of nitric oxide and superoxide, is a potent and versatile oxidant that can attack a wide range of targets. In this work, we studied the oxidation of hydrogen peroxide by peroxynitrite, which led to oxygen evolution. Oxygen yields increased at alkaline pH with a n apparent pKa of 7.05 f 0.04. The maximum yields were 16% and 32% of added peroxynitrite at pH 5.9 and 7.4, respectively, assuming that two molecules of peroxynitrite are needed to produce one of oxygen. Hydroxyl radical scavengers (dimethyl sulfoxide, mannitol, ethanol, formate, and acetate) inhibited oxygen evolution to a similar extent to that predicted from their rate constants with hydroxyl radical. The apparent rate constant of peroxynitrite decomposition was zero-order in hydrogen peroxide at acidic pH. At neutral and alkaline pH, the rate of peroxynitrite disappearance decreased in the presence of millimolar concentrations of hydrogen peroxide by up to 50%. The apparent activation enthalpy and entropy for peroxynitrite decomposition increased by 1.7 kcal mol-' and 4.7 cal mol-l K-l, respectively, in the presence of hydrogen peroxide. We propose that a n activated intermediate of peroxynitrous acid is responsible for hydrogen peroxide oxidation at acidic pH, while a t more alkaline pH the formation of a stabilizing complex between hydrogen peroxide and trunsperoxynitrite anion is involved.
Catalytic oxidation of monosubstituted phenols by hydrogen peroxide
Reaction Kinetics & Catalysis Letters, 1991
Studies of kinetic peculiarities in hydroxylation of phenols by H20 2 in the presence of ferric sulfate have revealed general regularities of this process. A scheme of this process is suggested accounting for the stepwise conversion of Fe 3+ into various complex forms. The reaction is suggested to take place in the coordination sphere of Fe 3+. Hccne~oBaHN KHHeTHqeCKHe 3aBHCHMOCTH peaKUHH F~pOKCH-nHpOBaHHH ~eHOnOB H202 B HpHCyTCTBHH Cynb~aTa ~ene3a. BbI~BneHN 06~He 3aEOHOMepHOCTH 9TOFO npoKecca. Ha OCHO-BaHHH no~yqeHHbIX ~aHHblX Hpe~o~eHa cxeMa eFo npoTeKa-HHS yqHTbIBam~a~ nOCTa~HHHblH nepexo~ Fe 3+ , B pa3~HqHbIe KOMn~eKCHbIe ~OpMbI.
Unexpected Acid Catalysis in Reactions of Peroxyl Radicals with Phenols
Angewandte Chemie International Edition, 2009
The formal transfer of a hydrogen atom from a phenol to a peroxyl radical [Eq. (1)] is a reaction widely recognized for its central role in the radical-trapping antioxidant activity of phenols, such as a-tocopherol (1), and as a model for formal hydrogen-atom-transfer processes involving tyrosine (and tyrosyl radicals) in enzymatic reactions (e.g. prostaglandin and DNA biosynthesis). The past ten years have brought a wealth of contributions that greatly enhance our understanding of this reaction, including the realization that it probably occurs by a concerted proton-coupled electron transfer (PCET) mechanism, and that have clarified the basis for the long-observed structure-reactivity relationships, whereby electron-rich phenols react fastest because of weaker O À H bonds.