Quinonic substance

Maesa perlarius (Lour.) Merrill. Sha Gui Hua (leaf, root) Alkaloids, quinonic substance.73 Crushed leaves are bound over broken bones or treat measles. Root is diuretic, stomachic. 

Quinene Quinic acid Quinochalone Quinonic substance Quinonoid Quinoric acid Quinquenosides Quisqualic acid r-cadinene... 

Pereira Netto et al. (2000) cite another two mechanisms to explain PAHs activation. The first would be related with the formation of benzilic esters, electrophilic, by a series of substitution reactions. The second would be the de-hydrogenation of dihydrodiols metabolites, which lead to the production of quinones, substances that are capable of reacting, directly, with DNA or with O2, generating reactive oxygen species such as hidroxil radicals or superoxide anions, which attack DNA. 

The name ubiquinone is a shortened form of ubiquitous quinone a term coined to describe the observation that this substance can be found m all cells The length of its side chain varies among different organisms the most common form m vertebrates has n = 10 and ubiquinones m which n = 6 to 9 are found m yeasts and plants... 

Another physiologically important quinone is vitamin K Here K stands for koag ulation (Danish) because this substance was first identified as essential for the normal clotting of blood... 

Cosolvents ana Surfactants Many nonvolatile polar substances cannot be dissolved at moderate temperatures in nonpolar fluids such as CO9. Cosolvents (also called entrainers, modifiers, moderators) such as alcohols and acetone have been added to fluids to raise the solvent strength. The addition of only 2 mol % of the complexing agent tri-/i-butyl phosphate (TBP) to CO9 increases the solubility ofnydro-quinone by a factor of 250 due to Lewis acid-base interactions. Veiy recently, surfac tants have been used to form reverse micelles, microemulsions, and polymeric latexes in SCFs including CO9. These organized molecular assemblies can dissolve hydrophilic solutes and ionic species such as amino acids and even proteins. Examples of surfactant tails which interact favorably with CO9 include fluoroethers, fluoroacrylates, fluoroalkanes, propylene oxides, and siloxanes. 

The ready reversibility of this reaction is essential to the role that quinones play in cellular respiration, the process by which an organism uses molecular- oxygen to convert its food to carbon dioxide, water, and energy. Electrons are not transfened directly from the substrate molecule to oxygen but instead are transfened by way of an electron transport chain involving a succession of oxidation-reduction reactions. A key component of this electron transport chain is the substance known as ubiquinone, or coenzyme Q ... 

Tile constitution of the hydrociiioride is doulitfui but the so-cailed gi/i/w/wi/l structure, by which the substance is lepre-sented as a derivative of quinone, is generally accepted,... 

Any substance capable of reacting with free radicals to form products that do not reinitiate the oxidation reaction could be considered to function as free-radical traps. The quinones are known to scavenge alkyl free radicals. Many polynuclear hydrocarbons show activity as inhibitors of oxidation and are thought to function by trapping free radicals [25]. Addition of R to quinone or to a polynuclear compound on either the oxygen or nitrogen atoms produces adduct radicals that can undergo subsequent dimerization, disproportionation, or reaction with a second R to form stable products. 

An excellent review by Roth and Eisner (63) summarized the chemical defense substances found in arthropods up to 1962. These authors listed 31 defense substances of known structure one anhydride, three carboxylic acids, nine aldehydes, one furan, three hydrocarbons, two ketones, one lactone, eight quinones, and three inorganic compounds. Many of these same compounds (unsaturated aldehydes and quinones) have been found in other arthropods since 1962 (38). The compounds are discharged when the animal is disturbed by predators, and there can be no doubt that the action of most of them... 

A chemical process occurs involving the formation of a new substance with corresponding energetic ground state N (Fig. 14, 15/V). For instance, on aluminium oxide or silica gel layers in the presence of oxygen, anthracene initially yields anthra-quinone, that is then oxidized further to yield 1,2-dihydroxyanthraquinone [4, 5]. Alizarin and chrysazin are also formed depending on the properties of the aluminium oxide used [6]. 

The ortho diphenolic structure of apomorphine makes it a strongly reducing substance hence, in acid medium it forms the blue colored ortAo-quinone (6) with iodine or other oxidizing agent which is in equilibrium with its zwitterionic limiting structure (7) (Pellargi s reaction [14]). 

Peroxidases are found in milk and in leukocytes, platelets, and other tissues involved in eicosanoid metabolism (Chapter 23). The prosthetic group is protoheme. In the reaction catalyzed by peroxidase, hydrogen peroxide is reduced at the expense of several substances that will act as electron acceptors, such as ascorbate, quinones, and cytochrome c. The reaction catalyzed by peroxidase is complex, but the overall reaction is as follows ... 

Scott DT, DM McKnight, EL Blunt-Harris, SE Kolesar, DR Lovley (1998) Quinone moieties act as electron acceptors in the reduction of humic substances by humics-reducing microorganisms. Environ Sci Tech-nol 32 2984-2989. 

Electrochemical equilibria between the oxidized and reduced forms of an organic substance are observed in only a few cases. The best known instance is the equilibrium between quinone and hydroquinone (or their derivatives) ... 

The anodic oxidation of organic substances is a complex multistep process. The question as to the depth of oxidation required (and sufficient) lias to be answered in each case. Where intermediate oxidation products pose no ecological risk, one can stop at incomplete oxidation. However, in the anodic oxidation of many aromatic substances, the corresponding quinones are formed in the first step, and these are more harmful than the original substances. Upon more profound oxidation, the benzene rings are broken and aliphatic substances are formed that are almost as harmless as carbon dioxide. 

Ortho quinones (and also aromatic a-diketones, e.g., benzil) react with o-phenylenediamine to yield quinoxalines as follows. Dissolve the substance... 

Quinones, lipid-soluble substances involved in electron transport, can also be used as biomarkers. Lipski et al. (155) u.sed quinone analyses, physiological tests, and fatty acid profiles to differentiate Gram-negative non-fermentative bacteria isolated from biofilters. Quinone type was found to be an efficient method to group isolates prior to the analysis of results from the physiological tests. The detection of quinones appears to be restricted to the discrimination of isolated colonies and has limited potential to the analysis of mixed populations. 

It is well known that the selective transport of ions through a mitochondrial inner membrane is attained when the oxygen supplied by the respiration oxidizes glycolysis products in mitochondria with the aid of such substances as flavin mononucleotide (FMN), fi-nicotinamide adenine dinucleotide (NADH), and quinone (Q) derivatives [1-3]. The energy that enables ion transport has been attributed to that supplied by electron transport through the membrane due to a redox reaction occurring at the aqueous-membrane interface accompanied by respiration [1-5],... 

Applications Sollinger and Sawatzki [793] have reported the use of TLC-Raman for routine applications, e.g. TLC of hydroxybenzenes (including hydro-quinone and pyrogallol) on conventional, silica gel and specific Raman-TLC plates (coated with spherical silica gel). Databases were used for identification of substances. Typical detection limits were in the low p,g region per application, Micro-Raman spectrometry has been employed in analysing TLC fractions from polymer additives within a detection limit... 

The initial oxidation of the flavanol components of fresh leaf to quinone structures through the mediation of tea polyphenol oxidase is the essential driving force in the production of black tea. While each of the catechins is oxidizable by this route, epigallocatechin and its galloyl ester are preferentially oxidized.68 Subsequent reactions of the flavonoid substances are largely nonenzymic. 

Elastomers (natural and synthetic) employ as vulcanising agent a quantity (2.5 phr on average) of elemental sulphur. The use of any other substance (TMT, peroxides, quinones, etc.) is termed non-sulphur vulcanisation. 

Field JA, Cervantes FJ (2005) Microbial redox reactions mediated by humus and structurally related quinones. In Perminova IV, Hatfield K, Hertkom N (eds) Use of humic substances to remediate polluted environments from theory to practice, vol 52. Springer, Dordrecht, pp 343-352... 

Although a patent claims the synthesis of the quinone shown below, the method is ambiguous and it is doubtful that a substance of this precise structure has been prepared.108 It should exist as a polymeric peroxide or as a diradical. 

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