Quinone Oxidation Research Articles

Factors affecting the mutagenic activity of quercetin for Salmonella typhimurium TA98: metal ions, antioxidants and pH

The mutagenic activity of quercetin for salmonella typhimurium TA98 was inhibited by addition of metal salts. MnCl 2 was a potent inhibitor, followed by CuCl 2, FeSO 4, and FeCl 2, the probable mechanism being facilitated catalytic oxidation of quercetin. With quercetin incorporated at a level of 100 nmoles/plate, approximate doses (nmoles/plate) to give 50% inhibition of mutagenic activity were: MnCl 2<10 (−S9), 18 (+S9); CuCl 2 65 (−S9), >100 (+S9); FeSO 4 190 (−S9), > 300 (+S9); or FeCl 3 275 (−S9), > 300 (+S9). Ascorbate, superoxide dismutase, and, to a lesser extent, NADH and NADPH, all enhanced the mutagenic activity of quercetin in the absence of the mammalian-microsome (S9) system, but had no significant effect in the presence of the S9 mix. The maximum enhancement of activity by ascorbate or superoxide dismutase was approximately 87% of the increase achieved by addition of the S9 mix. Tyrosinase (catechol oxidase) substantially reduced the mutagenic activity of quercetin in the absence of the S9 mix. At lower levels of tyrosinase, activity was restored by incorporation of the S9 mix. It is proposed that the S9 mix enhances the mutagenic activity of quercetin by scavenging superoxide radicals, thus inhibiting the autoxidation of quercetin, and possibly by reducing quinone oxidation products of quercetin. The mutagenic activity of quercetin increased substantially when the pH of the media was decreased. This may be due in part to a decreases in ionization by quercetin at lower pH, thereby icreasing its absorption by the tester strain, to a decrease in the rate of autoxidation of quercetin at lower pH, or to a combination of these.

Herbicide/Quinone Binding Interactions in Photosystem II

Many inhibitors prevent the oxidation of the primary electron-accepting quinone (QA) by the secondary quinone (Qв) in photosystem II by displacement of Qв from its binding site. On the other hand, plastoquinone-1 and 6-azido-5-decyl-2,3-dim ethoxy-p-benzoquinone displace herbicides. Binding studies show the herbicide/quinone interaction to be (apparently) competitive. The herbicide binding is influenced differentially by various treatments. In this paper it is shown that the affinity of, for example, bromoxynil is decreased by thylakoid unstacking or by light-or reductant-induced reduction of certain thylakoid components, whereas atrazine affinity remains unchanged. Furthermore, absence of HCO- 3 in the presence of form ate leads to an affinity decrease of bromoxynil and atrazine, but to an increase in i-dinoseb affinity. Other differential photosystem II herbicide effects are known from the literature. Since different and unrelated groups of Q- A oxidation inhibitors have been found, and because of the above-mentioned dissimilarities in binding characteristics for different inhibitor groups, the hypothesis of non-identical, but “overlapping” binding sites for different herbicide groups and the native quinone must be more extensively defined. In this manuscript we evaluate both the competitive herbicide/quinone binding model, and a model in which binding of one ligand alters the protein conformation resulting in a dramatic decrease in the binding affinity of ligands from other chemical groups; in this model ligands from the same or related chemical groups bind competitively. Thus, the latter model proposes that only one herbicide or quinone molecule can be bound with high affinity to the herbicide/quinone binding environment, but it depends on the chemical structure of the ligands whether the binding interaction between two ligands is truly competitive or more indirect (allosteric), mediated through the protein conformation.

Conjugation of dopa and 5- S-cysteinyldopa with cysteine mediated by superoxide radical

Cytotoxicity of catechols has been ascribed to their binding with proteins through sulfhydryl groups. Superoxide radical (O 2 −) generated in hypoxanthine-xanthine oxidase system at pH 7.4 mediated conjugation of dopa with cysteine to form cysteinyldopas. Similarly, 5- S-cysteinyldopa gave 2,5- S, S- dicysteinyldopa. The rates of oxidation of the catechols by O 2 − appear to be comparable to that of reduction of nitro-blue tetrazolium by O 2 −. These results suggest that catechols may exert cytotoxicity in cells where biochemical defence against O 2 − or the quinone oxidation products is not sufficient.

ChemInform Abstract: THE OXIDATION OF HYDROQUINONE BY PROTONATED QUINONE

Chemischer InformationsdienstVolume 13, Issue 20 Article ChemInform Abstract: THE OXIDATION OF HYDROQUINONE BY PROTONATED QUINONE O. HAMMERICH, O. HAMMERICHSearch for more papers by this authorV. D. PARKER, V. D. PARKERSearch for more papers by this author O. HAMMERICH, O. HAMMERICHSearch for more papers by this authorV. D. PARKER, V. D. PARKERSearch for more papers by this author First published: May 18, 1982 https://doi.org/10.1002/chin.198220086AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue20May 18, 1982 RelatedInformation

ChemInform Abstract: ARYLATION OF QUINONES WITH ARENES AND PALLADIUM ACETATE

AbstractDurch Umsetzung von p‐Benzochinon (I) mit den aromatischen Verbindungen (II) in Gegenwart von Palladiumacetat erhält man die arylierten Chinone (IV)‐(VI).

A proposed mechanism of benzene toxicity: Formation of reactive intermediates from polyphenol metabolites

Male Fischer-344 rats were given 100 μCi (14 mg/kg) [ 14C]catechol or [ 14C]hydroquinone by injection into the lateral tail vein. For a period of at least 24 hr, soluble radioactivity associated with either compound was retained in the bone marrow, but not in the liver or thymus. The amount of covalently bound radioactivity increased with time in all tissues examined and was significantly depressed in liver, white blood cells, and bone marrow in rats pretreated with Aroclor 1254, a regimen which protects against benzene toxicity. Potential enzymatic and nonenzymatic activation pathways for catechol, hydroquinone, and other known benzene metabolites were examined. In air-saturated 50 m m phosphate buffer (pH 7.4) at 37°C, only hydroquinone and 1,2,4-benzenetriol autoxidized. The oxidation product of hydroquinone had an uv absorption maximum (248 nm) identical to that of benzoquinone. With 250 units superoxide dismutase, hydroquinone autoxidation increased fivefold, whereas the oxidation of 1,2,4-benzenetriol was inhibited (4% of control). Epinephrine autoxidation, an indirect measure of superoxide anion generation, was stimulated by 1,2,4-benzenetriol and hydroquinone, but was barely detectable in the presence of catechol. Of the compounds studied, only benzoquinone augmented the oxidation of NADPH by a 3000 g rat bone marrow supernatant. These data support a mechanism for benzene toxicity in which the formation of potentially cytotoxic metabolites, semiquinone, and quinone oxidation products and superoxide radicals, result from autoxidation of at least two polyphenol metabolites of benzene, hydroquinone, and 1,2,4-benzenetriol.

Arylation of quinones with arenes and palladium acetate

Oxidation of quinones with palladium acetate in acetic acid, which contained arenes, gave arylated quinones.

ChemInform Abstract: OXIDATION OF METHOXYHYDROXYCYCLOHEXADIENYL RADICALS BY QUINONES. THE INFLUENCE OF THE ISOMERIC STRUCTURE OF THE RADICAL ON THE RATE CONSTANT FOR ELECTRO TRANSFER

Chemischer InformationsdienstVolume 11, Issue 10 Preparative Organic Chemistry ChemInform Abstract: OXIDATION OF METHOXYHYDROXYCYCLOHEXADIENYL RADICALS BY QUINONES. THE INFLUENCE OF THE ISOMERIC STRUCTURE OF THE RADICAL ON THE RATE CONSTANT FOR ELECTRO TRANSFER S. STEENKEN, S. STEENKENSearch for more papers by this authorN. V. RAGHAVAN, N. V. RAGHAVANSearch for more papers by this author S. STEENKEN, S. STEENKENSearch for more papers by this authorN. V. RAGHAVAN, N. V. RAGHAVANSearch for more papers by this author First published: March 11, 1980 https://doi.org/10.1002/chin.198010113Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue10March 11, 1980 RelatedInformation

Spin-trapping of the N-methylacridanyl radical in a quinone oxidation of N-methylacridan

The N-methylacridanyl radical has been trapped by 2-methyl-2-nitrosopropane in the oxidation of N-methylacridan by 2,3-dicyano-1,4-benzoquinone, providing direct evidence for a stepwise electron-proton-electron transfer pathway for this reaction.

Kinetic analysis of the oxidative degradation of polyaryl-orthophosphate

Thermogravimetric study of poly-aryl-orthophosphate indicates that in presence of air the decomposition is a two step process. The first step is the chain scission to form quinone and the subsequent step the oxidation of quinone to maleic anhydride. The kinetic parameters were determined for the oxidative thermal degradation process.

Chemical and biological studies of 1-(2,5-dihydroxy-4-methylphenyl)-2-aminopropane, an analog of 6-hydroxydopamine

Autoxidation of the bis(O-demethyl)-p-hydroquinone metabolite of the psychotomimetic amine 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) at pH 7.4 leads exclusively to a bicyclic imino quinone. This imino quinone is a good alkylating agent, forming covalent adducts via 1,4 addition to thiols. The autoxidation appears to be dependent on trace metal catalysis and is dramatically inhibited by components of the 10000g supernatant fraction of rabbit liver homogenates. Incubation of tritium-labeled hydroquinone with bovine serum albumin under oxidizing conditions leads to significant amounts of nonextractable radioactivity which presumably is dependent on imino quinone alkylation of nucleophilic functionalities present on macromolecules. Incubation of tritium-labeled DOM with rabbit microsomes in the presence of NADPH leads to irreversible binding of the label to macromolecular components of the microsomes. Since this binding is NADPH dependent, it is likely that metabolic conversion of DOM to the hydroquinone is involved. The imino quinone oxidation product is highly lypophilic and is capable of crossing the blood-brain barrier. Intravenous administration of tritium-labeled imino quinone to rats resulted in significant nonextractable radioactivity in brain tissue. These properties of the hydroquinone metabolite parallel those reported for the structurally related sympatholytic compound 6-hydroxydopamine and have led to the hypothesis that the psychotomimetic properties of DOM may be mediated through 6-hydroxydopamine-type interactions of the hydroquinone with important macromolecules in the brain.

CHEMILUMINESCENCE AND THE FORMATION OF SINGLET OXYGEN IN THE OXIDATION OF CERTAIN POLYPHENOLS AND QUINONES

Abstract— The possibility of 1O2 (1Δg) participation in the oxidation of polyphenols and quinones has been investigated in two systems: (1) the system involving autooxidation leading to oxidative polymerization and destruction, and (2) the modified Trautz‐Schorigin reaction, i.e. oxidation of polyphenols and HCHO with H2O2 in concentrated alkaline solutions. The red band with maximum at 635 nm observed in chemiluminescence of pyrocatechol, adrenaline, pyrogallol, gallic acid, adrenochrome and p‐benzoquinone corresponds to the transition 2O2(1Δg) → 2O2(3Σ‐g). Emission bands in the range 475–540 nm arise from the superposition of the 2O2(1Δg) → 2O2(3Σ‐g) transition and radiative deactivation of excited oxidation products. In system (2) chemiluminescence has a broad band from 580 nm beyond 800 nm and much higher intensity than in system (1). Formaldehyde was found to enhance light emission in system (1) by a factor of about 30. The influence of solvents, including D2O in which 1O2 has varying lifetimes, on kinetics of chemiluminescence as well as quenching effect of β‐carotene, hydroquinone, cysteine, bilirubin and biliverdin strongly support the involvement of 1O2 in the chemiluminescence of both systems.

Sensitized photooxidation of α‐tocopherol and of 2,2,5,7,8‐pentamethyl‐6‐chromanol in ethyl acetate

AbstractThe major product of each photo‐oxidation was an equimolar mixture of quinone oxide and quinone. The yield of this mixture was 64% and 67% when the substrate was α‐tocopherol and 2,2,5,7,8‐pentamethyl‐6‐chromanol, respectively. Neither spirodienone dimer nor trimer was present in the product mixture. Evidently the reaction intermediate is an adduct of tocopherol and singlet oxygen. Tocopherol may protect biological lipids from singlet oxygen degradation.

Investigation of the three-dimensional structure of a quinone oxide

On the basis of the measurement of the dipole moment and molar Kerr constant it was shown that the quinone oxide molecule exists in the form of a boat with syn-orientation of the oxide ring, stabilized by conjugation of the carbonyl groups with the three-membered ring and by the energies of orientation of the bonds.

Preparation de quelques cyclohexène-2 diones-1,4 et de leurs dérivés

The osmic acid catalyzed oxidation of quinones has yielded for the first time to our knowledge the monomers of some cis-5,6-dihydroxycyclohex-2-ene-1,4-diones. Toluquinone and o-xyloquinone give mixtures of the two possible isomers. Observation of the n.m.r. spectra suggests that this new class of compounds are in general conformationally more mobile than quinonedihalides. The conversion of cyclohex-2-ene-1,4-diones into oximes allows the easy evaluation of all the important coupling constants.

Mechanism of hydride transfer. III. Rates and isotope effects in the quinone oxidation of leuco triphenylmethane dyes

Mechanism of hydride transfer. III. Rates and isotope effects in the quinone oxidation of leuco triphenylmethane dyes

The Quinone Oxidation of Ethanol Catalyzed by Chromic Ion

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Quinone Oxidation of Ethanol Catalyzed by Chromic IonRobert G. LinckCite this: J. Am. Chem. Soc. 1963, 85, 14, 2187–2189Publication Date (Print):July 1, 1963Publication History Published online1 May 2002Published inissue 1 July 1963https://doi.org/10.1021/ja00897a049RIGHTS & PERMISSIONSArticle Views95Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (410 KB) Get e-Alerts Get e-Alerts

The Bactericidal Action of Quinone and Other Phenol Oxidation Products as Determined by the Rideal-Walker Method

The Bactericidal Action of Quinone and Other Phenol Oxidation Products as Determined by the Rideal-Walker Method