Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: CAS:7782-44-7 (oxygen)
 369,292 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lipid peroxidation (LPO) is the oxidative deterioration of polyunsaturated fatty acids (PUFA) with the production of lipid hydroperoxides, cyclic peroxides, cyclic endoperoxides, and finally fragmentation to ketones and aldehydes (including malonaldehyde, MDA). Estimation of LPO through MDA formation measured by assaying thiobarbituric acid (TBA) reactive products remains the method of choice to study the development of oxidative stress in tissues. However, MDA estimation by TBA reactive products is non-specific and often gives erroneous results. In this report we describe a method using high-performance liquid chromatographic separation to estimate MDA, formaldehyde (FDA), acetaldehyde (ADA), acetone, and propionaldehyde (PDA), the degradation products of oxygen-derived free radicals (ODFR) and PUFA, as presumptive markers for LPO. Oxidative stress was induced in the tissue by perfusing an isolated rat heart with hydroxyl radical generating system (xanthine + xanthine oxidase + FeCl3 + EDTA). The coronary effluents were collected, derivatized with 2,4-dinitrophenylhydrazine (DNPH), and extracted with pentane. Aliquots of 25 microliters in acetonitrile were injected onto a Beckman Ultrasphere C18 (3 microns) column. The products were eluted isocratically with a mobile phase containing acetonitrile-water-acetic acid (40:60:0.1, v/v/v), measured at three different wavelengths (307, 325 and 356 nm) using a Waters M-490 multichannel UV detector and collected for gas chromatography-mass spectrometry (GC-MS) analysis. The peaks were identified by cochromatography with DNPH derivatives of authentic standards, peak addition, UV pattern of absorption at the three wavelengths, and by GC-MS. The retention items of MDA, FDA, ADA, acetone, and PDA were 5.3, 6.6, 10.3, 16.5, and 20.5 min, respectively. The results of our study indicated progressive increase of all five lipid metabolites as a function of the duration of ODFR perfusion. Hydroxyl radical scavengers, superoxide dismutase plus catalase, completely inhibited the formation of these lipid metabolites, demonstrating that the release of lipid metabolites from the isolated heart was indeed in response to oxidative stress. Since MDA, FDA, ADA, acetone, and PDA are the products of ODFR-PUFA interactions, this method allows proper estimation of LPO which monitors the oxidative stress developed during the reperfusion of ischemic myocardium.
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PMID:High-performance liquid chromatographic method for the simultaneous detection of malonaldehyde, acetaldehyde, formaldehyde, acetone and propionaldehyde to monitor the oxidative stress in heart. 813 6

In aqueous solutions, dalvastatin (1) undergoes epimerization as well as hydrolysis. The transformation of the drug was studied as a function of pH at 25 degrees C in aqueous solutions containing 20% acetonitrile. At all pH values, first-order plots for the conversion are biphasic, indicating rapid equilibration of 1 with its epimer (2) and slower hydrolysis of 1 to the corresponding beta-hydroxy acid (3). Apparent first-order rate constants for the biexponential equation are given as a function of pH. The alkyl-oxygen cleavage of the lactone ring results in the epimerization of 1 to 2, whereas the acyl-oxygen cleavage results in the hydrolysis of 1 to 3. The epimerization is an SN1 reaction reaching an equilibrium of [1]eq/[2]eq = 1.27. The epimerization rate is increased with an increase in the water content of the solvent. The hydrolysis of 1 to 3 is acid and base catalyzed. The hydrolysis is reversible in acidic media and irreversible in neutral and basic media. At pH values greater than 9, the hydrolysis reaction proceeds more rapidly than the epimerization.
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PMID:Epimerization and hydrolysis of dalvastatin, a new hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor. 814 49

The mechanism of oxidation of alkylpyrroles (1a-d) by molecular oxygen in the presence of nucleophiles is explored. Contrary to previous reports, oxidation of these pyrroles resulted in dimers with both the aromatic rings intact. In the presence of additional nucleophiles these pyrroles entered into substitution reactions. With 2-mercaptoethanol the site of substitution on 1a was the 3-position rather than the side chain. The first-order rate constant for this reaction in acetonitrile with excess oxygen was found to be (7.8 +/- 1.2) x 10(-7) s-1. The rate was unaffected by the presence of either BHT or catechol. Replacing hydrogens at all the potential sites of reaction by deuterium (as in 1aD) did not reduce the rate of substitution. However, the product suffered loss of deuterium from all sites. These observations support a mechanism involving the formation of a complex 20 between the pyrrole and triplet oxygen. Electron transfer from the pyrrole to oxygen in the rate-limiting step is followed by the generation of pyrrolylmethyl intermediate 23 that can react with available nucleophiles including unoxidized pyrroles.
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PMID:The mechanism of nucleophilic substitution of alkylpyrroles in the presence of oxygen. 815 25

The effects of solvents and media on the antioxidant activity of alpha-tocopherol were studied. The antioxidant activities of alpha-tocopherol in different solvents decreased in the order of acetonitrile = hexane > ethanol = methanol, which indicates that the antioxidant activity of alpha-tocopherol is smaller in protic solvent than in aprotic solvent. The antioxidant activity of 2-(4,8,12-trimethyltridecyl)-5-hydroxy-2,4,6,7-tetramethylindan , which has similar structure to alpha-tocopherol but does not have ether oxygen, was also measured in protic and aprotic solvents. Its antioxidant activity was smaller than that of alpha-tocopherol in every solvent, but interestingly, substantially the same solvent effects were observed. These results show that the hydrogen bonding between the protic solvent and either oxygen is not important but that the hydrogen binding between protic solvent and phenolic group reduces the activity of alpha-tocopherol. Antioxidant activities of alpha-tocopherol in micelle system and liposomal membrane were markedly reduced compared with that in homogeneous solution. Solvent effect on the alpha-tocopheroxyl radical was also studied by using electron spin resonance. The hyperfine splitting constants of a5CH3H and a7CH3H were smaller in protic solvent than in aprotic solvent, which shows that lone-pair orbital energy on 5-CH3 and 7-CH3 is smaller in protic solvent. The ESR spectra of alpha-tocopheroxyl radical in liposomal membrane and micelle were similar to those observed in aprotic solvent and in protic solvent, respectively, suggesting that alpha-tocopheroxyl radical is located predominantly in the lipophilic domain of the liposomal membrane but in or closer to water phase of micelle aqueous suspensions.
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PMID:Effects of solvents and media on the antioxidant activity of alpha-tocopherol. 818 28

The photochemistry, photophysics, and photosensitization (Type I and II) of indomethacin (IN) (N-[p-chlorobenzoyl]-5-methoxy-2-methylindole-3-acetic acid) has been studied in a variety of solvents using NMR, high performance liquid chromatography-mass spectroscopy, transient spectroscopy, electron paramagnetic resonance in conjunction with the spin trapping technique, and the direct detection of singlet molecular oxygen (1O2) luminescence. Photodecomposition of IN (lambda ex > 330 nm) in degassed or air-saturated benzene proceeds rapidly to yield a major (2; N-[p-chlorobenzyl]-5-methoxy-2-methyl-3-methylene-indoline) and a minor (3; N-[p-chlorobenzoyl]-5-methoxy-2,3-dimethyl-indole) decarboxylated product and a minor indoline (5; 1-en-5-methoxy-2-methyl-3- methylene-indoline), which is formed by loss of the p-chlorobenzoyl moiety. In air-saturated solvents two minor oxidized products 4 (N-[p-chlorobenzoyl]-5-methoxy-2-methyl-indole-3-aldehyde) and 6 (5-methoxy-2-methyl-indole-3-aldehyde) are also formed. When photolysis was carried out in 18O2-saturated benzene, the oxidized products 4 and 6 contained 18O, indicating that oxidation was mediated by dissolved oxygen in the solvent. In more polar solvents such as acetonitrile or ethanol, photodecomposition is extremely slow and inefficient. Phosphorescence of IN at 77 K shows strong solvent dependence and its emission is greatly reduced as polarity of solvent is increased. Flash excitation of In in degassed ethanol or acetonitrile products no transients. A weak transient is observed at 375 nm in degassed benzene, which is not quenched by oxygen.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Spectroscopic studies of cutaneous photosensitizing agents. XVIII. Indomethacin. 823 71

Pseudomonas putida, capable of utilizing acetonitrile as a sole source of carbon and nitrogen, was isolated from contaminated soil and water samples collected from industrial sites. The P. putida cells were immobilized in calcium alginate beads. The degradation of acetonitrile by the immobilized cells of P. putida was investigated. The immobilized cells degraded different concentrations of acetonitrile into ammonia and carbon dioxide. The effect of aeration on the degradation rate was also studied. Oxygen limitation was suggested in the alginate-immobilized system. The rate of degradation of acetonitrile increased with increase in the rate of aeration.
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PMID:Degradative capability of Pseudomonas putida on acetonitrile. 832 68

Estimation of lipid peroxidation (LPO) through malonaldehyde (MDA) formation measured by assaying thiobarbituric acid reactive products remains the method of choice to study the development of oxidative stress to assess myocardial ischemic reperfusion injury. However, MDA estimation by this assay is non-specific and often gives erroneous results. In this report, we describe a method to estimate MDA, formaldehyde (FDA), acetaldehyde (ADA), and acetone, the degradation products of oxygen free radicals (OFR) and polyunsaturated fatty acids (PUFA), as presumptive markers for LPO. Isolated rat hearts were made ischemic for 30 min, followed by 60 min of reperfusion. The perfusates were collected, derivatized with 2,4-dinitrophenylhydrazine, and extracted with pentane. Aliquots of 25 microliters in acetonitrile were injected on a Beckman Ultrasphere C18 (3 microns) column. The products were eluted isocratically with a mobile phase containing acetonitrile-water-acetic acid (40:60:0.1, v/v/v). The peaks were identified by co-chromatography with the hydrazine derivatives of authentic standards. The retention times of MDA, FDA, ADA and acetone were 5.0, 6.3, 9.8 and 15.7 min, respectively. The results of our study indicated progressive increase in all four lipid metabolites with reperfusion time. Thus, our results demonstrate that the release of lipid metabolites from the isolated heart increased in response to oxidative stress. Since MDA, FDA, ADA, and acetone are the products of OFR-PUFA interactions, this method allows proper estimation of LPO to monitor the oxidative stress developed during the reperfusion of ischemic myocardium.
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PMID:Estimation of the extent of lipid peroxidation in the ischemic and reperfused heart by monitoring lipid metabolic products with the aid of high-performance liquid chromatography. 845 21

The dye-sensitized photooxidation of L-histidine (His) and L-methionine (Met) and their simplest dipeptides with glycine (Gly) (His-Gly, Gly-His Gly-Met) and Met-methyl ester (Met-ME) mediated by singlet molecular oxygen (O2[1 delta g]) was studied. The overall rate constants in acetonitrile-H2O (kt) for O2(1 delta g) quenching were measured by time-resolved phosphorescence detection. In H2O a competitive kinetic method was employed. In both solvents the reactive rate constants (kr) were determined to discriminate between the overall and physical contributions to the quenching. The kinetic and mechanistic aspects of the interaction are discussed. For His-Gly, the peptide bond has practically no effect on the kinetics of photooxidation. For Gly-His the overall rate constant is much higher than that for His and His-Gly, in both H2O and acetonitrile-H2O. The main contribution to kt (for Gly-His) is the physical quenching of O2(1 delta g). In water the kt/kr ratio for free His and His-Gly is 1.0, reaching a value of 2.0 in the organic solvent-H2O mixture. The rates of -NH2 loss upon sensitized photooxidation in all cases parallel the trend of kr values. The main results for the His series indicate that: (1) a polar environment favors autoprotection (i.e. an increase in the contribution of physical quenching) against photodynamic effects; (2) only the rate constant for reactive interaction with O2(1 delta g) does not depend on the location of the peptide bond involving His. For Met derivatives the kt values are higher in both solvents than that for free Met.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Influence of the peptide bond on the singlet molecular oxygen-mediated (O2[1 delta g]) photooxidation of histidine and methionine dipeptides. A kinetic study. 847 78

Fluorescence spectra of alpha-tocopherol and its mixtures with oxygenated derivatives of fatty acids--linoleic acid hydroperoxide, hydroxylinoleic and ricinoleic acids--were investigated in terms of the excitation and emission dependence on the concentration of components in acetonitrile solution. In accordance with our results, formation of the alpha-tocopherol excimer and exciplex with the oxygen-containing derivatives of polyunsaturated fatty acids was suggested. The character of the interaction between components of the excited complexes and their possible role in peroxidation of lipids are discussed.
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PMID:[Interaction of vitamin E (alpha-tocopherol) with oxygenated fatty acid derivatives]. 849 69

Accurate estimation of the oxidative stress in heart is necessary because the pathogenesis of many heart diseases are believed to be mediated at least in part from the development of oxidative stress resulting from the generation of oxygen free radicals and reduced antioxidant defense system. The most widely used method for this purpose has been the estimation of malonaldehyde (MDA), a lipid peroxidation product, by the thiobarbituric acid (TBA) reaction method. However, because of the nonspecificity of this method, the results are often erroneous. The present report describes a method using high-performance liquid chromatography (HPLC) to estimate MDA. To develop the oxidative stress, two different models were used: ischaemic-reperfused heart and perfusing the heart with a hydroxyl radical (OH+) generating system. The coronary effluents obtained from the isolated rat heart before ischaemia and during the reperfusion of ischaemic heart, as well as during the perfusion of the heart with the OH+ generating system were collected, derivatized with 2,4-dinitrophenylhydrazine (DNPH) and extracted with pentane. Aliquots of 25 microliters in acetonitrile were injected onto a Beckman Ultrasphere C18 (3 microns) column. The products were eluted isocratically with a mobile phase containing acetonitrile-water-acetic acid (40:60:0.1, v/v/v), measured at 307 nm using a Waters M-490 multichannel UV detector and collected for gas chromatography-mass spectrometry (GC-MS). The peaks were identified by co-chromatography with DNPH derivatives of authentic standards, peak addition, and by GC-MS. The retention time for MDA-DNPH was 5.3 min.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Detection of oxidative stress in heart by estimating the dinitrophenylhydrazine derivative of malonaldehyde. 852 27


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