Disease relevance of methane

• These results suggest the formation of quinone methide intermediates from three alkylphenols during oxidative metabolism and demonstrate a correlation between the amount of reactive intermediate formed and toxicity observed in liver slices [1].
• 4-ethylphenol methylenehydroxylase from Pseudomonas putida JD1 acts by dehydrogenation of its substrate to give a quinone methide, which is then hydrated to an alcohol [2].
• We propose that the formation of this pyrimidine iminoquinone methide by both hepatic microsomes and neutrophils may be responsible for trimethoprim-induced idiosyncratic hepatotoxicity and agranulocytosis [3].
• The formation of a unique glutathione adduct was observed in rat bile, which was proposed to occur via N-dealkylation, followed by reduction of the putative aldehyde product to form the alcohol, and dehydration of the alcohol to generate a reactive quinone methide intermediate [4].

High impact information on methane

• A simple strategy for target-promoted alkylation is now illustrated by an intramolecular adduct formed by an oligonucleotide-quinone methide conjugate [5].
• Only complementary base pairing induces a conformational change necessary to promote intermolecular transfer of the quinone methide [5].
• Stopped-flow analysis showed that the H422A mutant is still able to form a stable binary complex of reduced enzyme and a quinone methide product intermediate, a crucial step during vanillyl-alcohol oxidase-mediated catalysis [6].
• 4-alkyl-o-quinone/2-hydroxy-p-quinone methide isomerase from the larval hemolymph of Sarcophaga bullata. I. Purification and characterization of enzyme-catalyzed reaction [7].
• In the course of enzymatic catalysis, the suicide substrate is activated by one- or two-electron reduction, and then a highly reactive quinone methide is generated upon elimination of the fluorine [8].

Chemical compound and disease context of methane

• Quinone methide formation from para isomers of methylphenol (cresol), ethylphenol, and isopropylphenol: relationship to toxicity [1].
• Deuteration of the methyl group should slow the rate of production of the corresponding imine methide and diminish the toxicity of deutero-3-methylindole, if C-H bond breakage occurs prior to or during the rate-determining step [9].

Biological context of methane

• However, the acyl enzymes formed from 3-alkoxy-4-chloro-7-guanidinoisocoumarins or 7-amino-4-chloro-3-(3-isothiureidopropoxy)-isocoumarin will decompose further, probably through a quinone imine methide, to give an irreversibly inactivated enzyme by reaction with an active-site nucleophile such as His-57 [10].
• Hydrolysis studies described herein indicate that the hypoxanthine-like hydroquinone derivative eliminates HBr to afford an extended quinone methide species [11].
• These molecules show a free N-terminus, necessary for binding to the CD26 catalytic site, and a latent quinoniminium methide electrophile, responsible for inactivation [12].
• A new and efficient method for o-quinone methide intermediate generation: application to the biomimetic synthesis of (+/-)-Alboatrin [13].
• Kinetics and mechanism of hydration of o-thioquinone methide in aqueous solution. Rate-determining protonation of sulfur [14].

Anatomical context of methane

• When DNA adduct 2 formed by incubation of eugenol quinone methide with deoxyguanosine-3'-phosphate was compared with DNA 2 adduct formed in HL-60 cells treated with eugenol results demonstrated that they were the same [15].
• Finally, in the presence of microsomes and GSH, 4-hydroxytamoxifen gave predominantly quinone methide GSH conjugates as reported in the previous paper in this issue [Fan, P. W., et al. (2000) Chem. Res. Toxicol. 13, XX-XX] [16].
• Treatment of calf thymus DNA with this quinone methide yielded N6-dA and N2-dG adducts with the former predominating [17].
• Comparative kinetic analyses of the mechanisms of toxicity of the alkylphenol eugenol and its putative toxic metabolite (quinone methide, EQM) were carried out in cultured rat liver cells (Clone 9, ATCC) using a variety of vital fluorescence bioassays with a Meridian Ultima laser cytometer [18].
• Subsequent oxidation of BHTOH produces the quinone methide 6-tert-butyl-2-(hydroxy-tert-butyl)-4-methylene-2,5-cyclohexadienone (BHTOH-QM), and this highly reactive electrophile may be directly responsible for the pulmonary effects of BHT [19].

Associations of methane with other chemical compounds

• The thermodynamic driving force for transfer of the elements of water from formaldehyde hydrate to p-quinone methide to form formaldehyde and p-(hydroxymethyl)phenol (4-hydroxybenzyl alcohol) is determined as 6 kcal/mol [20].
• Quinone methide mediates in vitro induction of ornithine decarboxylase by the tumor promoter butylated hydroxytoluene hydroperoxide [21].
• These adducts had retention times comparable with those obtained from in vitro reactions of alpha-acetoxytamoxifen and 4-hydroxytamoxifen quinone methide with DNA [22].
• Nogalamycin is reduced to its hydroquinone, which slowly converts in a first-order process [k = (1.2 +/- 0.2) X 10(-3) s-1, pH 8.0, 30 degrees C] to the quinone methide, which is then quenched by protonation [23].
• Substitution of the 4-methyl group of BHTOOH with alkyl groups of incrementally larger size is known to reduce accordingly quinone methide production; comparative study of these BHTOOH analogs demonstrated a corresponding loss of potency for ODC induction, indicating that BHT-quinone methide mediates the in vitro induction of ODC by BHTOOH [21].

Gene context of methane

• Irreversible inactivation could then occur upon alkylation of an active site nucleophile (probably histidine-57) by the acyl quinone imine methide [24].
• In this study, we demonstrated that trimethoprim was oxidized by activated human neutrophils, as well as a combination of myeloperoxidase/hydrogen peroxide/chloride or hypochlorous acid, to a reactive pyrimidine iminoquinone methide intermediate with a protonated molecular ion of m/z 289 as detected by mass spectrometry [3].
• It is therefore concluded that laccase, which is present as a contaminant in the commercial preparations of mushroom tyrosinase--and not tyrosinase (o-diphenoloxidase)--is the enzyme responsible for catalyzing the new conversion of dimethoxyallyl phenol to its corresponding quinone methide [25].
• The catecholic xanthones (3-8), being able to convert quinone methide intermediate, showed potent cytotoxicities against human cancer cell lines (HT-29, HL-60, SK-OV3, AGS, and A549) [26].
• The inhibition of a class C beta-lactamase was turnover dependent, as expected of mechanism-based inhibitor, but the small leaving group dependence of the inhibition suggested that the quinone methide, if it was in fact responsible for the inhibition, was generated in solution subsequent to release of the product phenol from the active site [27].

Analytical, diagnostic and therapeutic context of methane

• Here we report the results of a study using high-performance liquid chromatography to quantify two important chemical secretions of the flour beetle Tribolium confusum, methyl-1, 4-benzoquinone (MBQ) and ethyl-1,4-benzoquinone (EBQ) [28].
• Additionally, UV-vis titrations in the series of 5H-benzo[b]carbazoles indicated interactions with calf thymus DNA only for the highly active quinone methide 15c [29].
• Covalent modification of a melanoma-derived antigenic peptide with a natural quinone methide. Preliminary chemical, molecular modelling and immunological evaluation studies [30].

References