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At least 19 recordsLinked to original sources
PubMed1990

The action of hydrogen peroxide on the formation of thiobarbituric acid-reactive material from microsomes, liposomes or from DNA damaged by bleomycin or phenanthroline. Artefacts in the thiobarbituric acid test.

Incubation of rat-liver microsomes, previously azide-treated to inhibit catalase, with H2O2 caused a loss of cytochrome P-450 but not of cytochrome b5. This loss of P-450 was not prevented by scavengers of hydroxyl radical, chain-breaking antioxidants or metal ion-chelating agents. Application of the thiobarbituric acid (TBA) assay to the reaction mixture suggested that H2O2 induces lipid peroxidation, but this was found to be due largely or completely to an effect of H2O2 on the TBA assay. By contrast, addition of ascorbic acid and Fe(III) to the microsomes led to lipid peroxidation and P-450 degradation: both processes were inhibited by chelating agents and chain-breaking antioxidants, but not by hydroxyl radical scavengers. H2O2 inhibited ascorbate/Fe(III)-induced microsomal lipid peroxidation, but part of this effect was dues to an action of H2O2 in the TBA test itself. H2O2 also decreased the colour measured after carrying out the TBA test upon authentic malondialdehyde, tetraethoxypropane, a DNA-Cu2+/o-phenanthroline system in the presence of a reducing agent, ox-brain phospholipid liposomes in the presence of Fe(III) and ascorbate, or a bleomycin-ion iron/DNA/ascorbate system. Caution must be used in interpreting the results of TBA tests upon systems containing H2O2.

Animals↗
PubMed1976

Cyclic peroxides and the thiobarbituric assay.

Several monocyclic peroxide compounds and two acyclic hydroperoxides have been tested for activity in the thiobarbituric acid test. All cyclic peroxides tested which have beta dioxygen functionality on non-tertiary carbons gave positive thiobarbituric acid tests at 532 nm. (epsilon = 10(3) --10(4)) Two acyclic unsaturated hydroperoxides which were derived from gamma-linolenic acid also gave positive thiobarbituric acid tests. In addition to the 532-nm-absorbing species, all peroxidic compounds tested showed a transient absorption at 450 nm during the thiobarbituric acid test. The species responsible for this 450 nm absorption appears to be an intermediate in a series reaction sequence. This intermediate is converted, in time, to the 532-nm-absorbing species. Thiobarbituric acid assay of the crude autoxidation product mixture of gamma-linolenic acid also shows this transient 450-nm-absorbing species. Added ferric ion enhances the 532 nm abosrbance of the thiobarbituric acid assay of cyclic peroxides.

Methods↗
PubMed1965

The mechanism of the periodate-thiobarbituric acid reaction of sialic acids.

1. The chromogen formation from N-acetylneuraminic acid in the periodate-thiobarbituric acid reaction was investigated. Measurement of periodate consumption showed an uptake of approx. 3moles/mole of substrate in neutral as well as in strongly acidic solution. Therefore the chromogen beta-formylpyruvic acid is not a direct product of the periodate oxidation; it is presumed to be formed from the true oxidation product, a hexos-5-uluronic acid, by aldol splitting during the reaction in hot acidic solution with thiobarbituric acid. 2. Methyl (methyl beta-l-threo-hexos-4-enepyranosid)uronate, an analogue of the pre-chromogen, has been shown to yield with thiobarbituric acid in acidic solution a pigment exhibiting an identical absorption spectrum and showing the same behaviour on paper chromatography as the pigment obtained from N-acetylneuraminic acid in the periodate-thiobarbituric acid assay. 3. The substitution at C-2 of methoxyneuraminic acid does not inhibit the periodate-thiobarbituric acid reaction. In neutral solution methoxyneuraminic acid is oxidized by periodate to a substance that reacts readily with thiobarbituric acid in acidic solution. When periodate oxidation is attempted in acidic solution, protonation of the amino group protects this group against oxidation, rendering methoxyneuraminic acid negative in the assay systems of Warren (1959a,b) and Aminoff (1959, 1961).

Barbiturates↗
PubMed1989

Thiobarbituric acid-reactive malondialdehyde formation during superoxide-dependent, iron-catalyzed lipid peroxidation: influence of peroxidation conditions.

A systematic study of the influence of biological lipid peroxidation conditions on lipid hydroperoxide decomposition to thiobarbituric acid-reactive malondialdehyde is presented. A superoxide-dependent, iron-catalyzed peroxidation system was employed with xanthine oxidase plus hypoxanthine plus ferric iron-adenosine diphosphate complex as free radical generator. Purified cardiac membrane phospholipid (as liposomes) was the peroxidative target, and 15-hydroperoxy-eicosatetraenoic acid was used as a standard lipid hydroperoxide. Exposure of myocardial phospholipid to free radical generator at physiological pH (7.4) and temperature (37 degrees C) was found to support not only phospholipid peroxidation, but also rapid lipid hydroperoxide breakdown and consequent malondialdehyde formation during peroxidation. Under lipid peroxidation conditions, oxidative injury to the phospholipid polyunsaturated fatty acids required superoxide radical and ferric iron-adenosine diphosphate complex, whereas 37 degrees C temperature and trace iron were sufficient for lipid hydroperoxide decomposition to malondialdehyde. Harsh thiobarbituric acid-test conditions following peroxidation were not mandatory for either lipid hydroperoxide breakdown or thiobarbituric acid-reactive malondialdehyde formation. However, hydroperoxide decomposition that had begun in the peroxidation reaction could be completed during a subsequent thiobarbituric acid test in which no lipid autoxidation took place. Iron was more critical than heat in promoting the observed hydroperoxide decomposition to malondialdehyde during the lipid peroxidation reaction at 37 degrees C and pH 7.4. These data demonstrate that the radical generator, at physiological pH and temperature, serves a dual role as both initiator of membrane phospholipid peroxidation and promotor of lipid peroxide breakdown and thiobarbituric acid-reactive malondialdehyde formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Visible-light initiator system using thiobarbituric acid derivatives with methyl substituent].

Seven 2-thiobarbituric acid derivatives with methyl substituents were synthesized. Experimental visible-light curing resins were prepared using these compounds as a reducing agent in the dl-camphorquinone (CQ)-reducing agent initiator system. The effects of methyl substitution for thiobarbituric acid on initiation behavior of CQ-thiobarbituric acid initiator system were examined by analysis of polymerization of triethylene glycol dimethacrylate (3 G) in DSC and depth of cure. The solubility of thiobarbituric acid derivatives in 3 G was markedly changed by the introduction of the methyl group. Although the methyl group substitution at position 1 (3) in thiobarbituric acid improved the solubility of the acid in 3 G, it did not enhance the initiation ability. Maximum exothermic rate, time at maximum exothermic peak, amount of insufficiently polymerized layer and depth of cure were significantly improved by the introduction of one methyl group at the position 5. Thus the initiation ability was enhanced by the substitution. However, the introduction of two methyl groups at position 5 did not promote polymerization, but the inhibitory effect became apparent as the concentration of the reducing agent was increased.

Composite Resins↗
PubMed1990

Effects of thiobarbiturates on smooth muscle reactivity in isolated aortas from spontaneously hypertensive rats.

The direct effects of thiobarbiturates on helical strips of aortas from spontaneously hypertensive (SH) rats were compared with those from Wistar-Kyoto (WKY) rats. At 5-6 wk of age, the arterial pressure of SH and WKY rats did not differ, and the effects of thiobarbiturates on aortic strips from SH and WKY rats were similar. By contrast, at the age of 10-12 or 20-21 wk arterial pressure was higher in SH than in WKY rats, and responses to thiobarbiturates differed in aortic strips from SH and WKY rats: contractile responses were greater in WKY than in SH rats, and relaxing effects were greater in SH than in WKY rats. Responses to sodium nitroprusside did not differ in the aortas of SH and WKY rats, but the effects of nifedipine were greater in strips from SH rats than from WKY rats at the age of 10-12 wk. Ca2(+)-induced contractions of strips exposed to Ca2(+)-free media and depolarized by high K+ were inhibited by treatment with thiamylal; the inhibition was greater in SH than in WKY rats. The increase in smooth-muscle relaxation induced by thiobarbiturates in strips from SH rats may be due to increased sensitivity to the Ca2(+)-channel blocking action of thiobarbiturates.

Animals↗
PubMed1976

Stable thiobarbituric acid chromophore with dimethyl sulphoxide. Application to sialic acid assay in analytical de-O-acetylation.

With dimethyl sulphoxide instead of butanol in the thiobarbituric acid assay for sialic acid, a non-fading chromophore with lambdamax. = 549 nm was produced in a homogeneous solution, allowing dilution of the test mixture in case of high colour yield. This test adapted well to studies on alkaline de-O-acetylation. Bovine and rat submaxillary mucins, and rabbit Tamm-Horsfall urinary sialoproteins contain O-acetyl isomers of neuramine acid that are resistant to the thiobarbituric acid assay. Alkaline de-O-acetylation converted resistant O-acetylneuraminic acid into thiobarbituric acid-reactive sialic acid, and such conversion paralleled de-O-acetylation as measured by the ferric hydroxamate method. The colour increment was similar when the alkaline treatment of bovine submaxillary mucin either preceded or followed the acid hydrolysis. Only alkaline preptreatment was effective with rat submaxillary mucin. By selecting optimal conditions for alkaline de-O-acetylation, O-acetyl isomers can be accurately assessed by the thiobarbituric acid assay.

Acetylation↗
PubMed1989

[Studies on visible-light initiator system using thiobarbituric acid derivatives].

Experimental visible-light curing resins were prepared by the combination of dl-camphorquinone and a thiobarbituric acid derivative, such as 5-methyl-2-thiobarbituric acid (5 MS), 5-n-butyl-2-thiobarbituric acid (5 BS), and 1,3,5-trimethyl-2-thiobarbituric acid (135 MS). The ability of their initiator systems to polymerize resins was investigated and was also compared with that of initiator systems containing 5-n-butyl-barbituric acid (5 B) or N,N-dimethylaminoethyl methacrylate (DMAEMA) as the most popular reducing agent. The amount of insufficiently polymerized layer was small in 135 MS at a low concentration, and in DMAEMA at a high concentration, respectively. 135 MS was superior to DMAEMA in curing time, maximum exothermic rate and depth of cure at a concentration of 1.0 mole%. 135 MS, therefore, seemed comparable or superior to DMAEMA. The order of increasing activity as a reducing agent was 5 BS less than 5 MS less than DMAEMA less than or equal to 135 MS. When analogous 5 B and 5 BS were compared, the sulfur-containing 5 BS was more effective as a reducing agent.

Acrylic Resins↗
PubMedDate not supplied

Peroxyoxalate chemiluminescence detection of condensates of malondialdehyde with thiobarbituric acids using a flow system.

The peroxyoxalate chemiluminescence(CL) detection method for the evaluation of the CL intensity of malondialdehyde(MDA) condensates with seven 2-thiobarbituric acid derivatives is described. The method consists of a flow injection technique together with a CL detection system using bis(2,4,6-trichlorophenyl) oxalate(TCPO) and hydrogen peroxide as chemiluminogenic reagents. Linear correlations between CL intensity and concentration are obtained for pmol levels of condensates. Among the condensates, 1,3-diethyl-2-thiobarbituric acid(DETBA)-MDA shows the largest CL intensity. High performance liquid chromatography (HPLC)/CL detection of DETBA-MDA and 1,3-diphenyl-2-thiobarbituric acid(DPTBA)-MDA using a mixture of TCPO and hydrogen peroxide in acetonitrile as a postcolumn reagent solution is also described. The detection limits for DETBA-MDA and DPTBA-MDA are 20 and 200 fmol, respectively, per 20 microL injection at a signal-to-noise ratio of 2. This HPLC/CL detection system was applied to the determination of MDA in rat brains by using DETBA as a fluorescent derivatizing reagent.

Animals↗
PubMed1975

Novel interference in thiobarbituric acid assay for lipid peroxidation.

The thiobarbituric acid test for lipid peroxidation, when applied to a mixture of acetaldehyde and sucrose, produces a 532 nm aborbing chromogen which is indistinguishable from that formed by malonaldehyde and thiobarbituric acid. Unless special procedures are adopted to correct for this effect, the combined action of acetaldehyde and sucrose interferes seriously with the assay of lipid peroxidation reactions, notably those implicated in alcohol-induced liver injuries. However, this unusual thiobarbituric acid effect also can be used as a sensitive method for the detection of acetaldehyde.

Acetaldehyde↗
PubMed1988

Inaccuracy in measuring glycated albumin concentration by thiobarbituric acid colorimetry and by boronate chromatography.

We compared thiobarbituric acid colorimetry and boronate chromatography for measuring glycation of serum proteins. With 14C-glycated human albumin as a test material, both methods were acceptably linear and precise. However, comparable estimates (mmol/L) of albumin glycation ranged from 0.22 for thiobarbituric acid to 0.05 for boronate, representing yields relative to [14C]glycosylprotein of 42% and 10%, respectively. The low yield with thiobarbituric acid was corroborated independently on the basis of kinetic differences between the reactions of fructose standards and of glycosylprotein, leading to underestimation of glycosylprotein concentration. The lower estimate of glycosylprotein by boronate chromatography was related to an apparent requirement for two [14C]glyco groups per albumin molecule to effect binding.

Chromatography↗
PubMed1992

Differential sensitivity of diabetic rat papillary muscles to negative inotropic effects of oxybarbiturates versus thiobarbiturates.

The negative inotropic effects of oxybarbiturates and thiobarbiturates were examined in papillary muscles isolated from streptozotocin-induced diabetic rats and in papillary muscles from age-matched control rats. The muscles from diabetic rats exhibited less negative inotropic responses to pentobarbital and secobarbital than the muscles from control rats. Conversely, the negative inotropic responses to thiopental and thiamylal were significantly enhanced in diabetic muscles. Differences in sensitivity to pentobarbital between control and diabetic muscles became less marked by treatment with ouabain or by lowering [Na+]o. Enhancement of the negative inotropic effect of thiamylal observed in diabetic muscles remained unchanged with these treatments. In both control and diabetic muscles, the negative inotropic effect of pentobarbital was completely reversed by increasing [Ca2+]o, but the effect of thiamylal was only partially reversed. These results suggest a difference in mechanism of action involved in establishment of the negative inotropic effects of oxybarbiturates vs thiobarbiturates. Oxybarbiturates appear to exclusively reduce the influx of extracellular Ca2+, whereas thiobarbiturates appear to affect Ca2+ movements at the Ca2+ storage sites in addition to the Ca2+ influx inhibition.

Animals↗
PubMed1989

A modification of the thiobarbituric acid reaction.

A simple modification of the thiobarbituric acid reaction, which removes nonspecific chromogenic reaction products, involves incubation at room temperature for 16-20 hr and a column chromatographic step. The chromogen-concentrating capacity of the latter step is useful for determination of low concentrations of thiobarbituric acid-reactive materials in biological preparations.

Humans↗
PubMed1989

Induction of profound hypouricemia by a non-sedating thiobarbiturate.

5-[N-phenylcarboxamido]-2-thiobarbituric acid (merbarone) is a non-sedating derivative of thiobarbituric acid originally developed for anticancer use. In the initial clinical study, a profound reduction in serum uric acid was observed. In 20 patients who received five daily doses of merbarone ranging from 100 to 750 mg/m2, serum uric acid concentration was reduced from a mean pretreatment value of 5.7 +/- 1.6 mg/dL to a mean lowest value of 1.3 +/- 0.5 mg/dL. In most patients, the onset of the effect occurred with 24 hours and was maximal by 48 to 72 hours. Metabolic studies in two patients showed an increase in urinary uric acid excretion within 24 hours after initiation of drug treatment. A marked increase in fractional excretion of uric acid was sustained throughout the period of drug treatment. Urinary excretion of total oxypurines (xanthine and hypoxanthine) was increased twofold to threefold relative to baseline levels. Ultrafiltration studies showed that merbarone did not significantly displace binding of urate from albumin. When merbarone was incubated with xanthine oxidase in vitro, several reaction products were observed, including 2-oxo-2-desthio-merbarone and a compound with retention time similar to 4'-OH-merbarone. Both of these compounds have been described previously as metabolites of merbarone in human subjects. The parent drug and both metabolites were found to inhibit xanthine oxidase (Ki = 41, 36, and 240 mumols/L, respectively). However, this inhibitory effect was substantially less potent than allopurinol (Ki = 0.025 mumols/L). This study indicates that merbarone induces profound hypouricemia primarily by increasing uric acid excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Agents↗
PubMed1986

Application of the thiobarbiturate assay to the measurement of lipid peroxidation products in microsomes.

By applying two different thiobarbiturate assay procedures in parallel to aliquots of a microsomal incubation mixture one can simultaneously monitor free malondialdehyde and malondialdehyde plus labile lipid peroxidation products. The levels of malondialdehyde increase continuously during the incubation of microsomes, NADPH and ferrous-ADP complex, while the lipid precursors of MDA stop forming when the system becomes depleted in NADPH. In contrast to systems in which lipids are undergoing autooxidation, NADPH-dependent lipid peroxidation does not appear to generate significant amounts of water-soluble malondialdehyde precursors. As a result, quantitative interpretation of results is straightforward in the microsomal system. In spite of the lack of specificity of the thiobarbiturate coupling reaction, interferences can be easily compensated for by using zero time controls.

Animals↗
PubMedDate not supplied

Synthesis and CVS activity of 1-(2,3, 2,5, 2,6 dichlorophenyl)-3-morpholinophenyl-5-substituted benzylidene-thiobarbituric acids (3-17).

Fifteen new thiobarbituric acids have been prepared by the Knoevenagel condensation of appropriate aldehydes with 1-(2,3, 2,5, 2,6 dichlorophenyl)-3-morpholinophenyl thiobarbituric acids. Five compounds of this series were found to be biphasic in nature whereas some compounds showed appreciable hypotensive activity of varying magnitude and duration.

Animals↗
PubMed1976

Circular dichroism and carbon-13 nuclear magnetic resonance spectra of (S)-5-alkyl-5-(2'-pentyl)-2-thiobarbituric acids.

The circular dichroism (CD) and carbon-13 nuclear magnetic resonance (13C NMR) spectra of (S)-5-(2'-pentyl)-2-thiobarbituric acid and several (S)-5-alkyl-5-(2'-pentyl)-2-thiobarbituric acids were obtained. The results were compared to CD and 13C NMR spectral data obtained from (S)-5-(2'-pentyl)bartituric acid and (S)-5-alkyl-5-(2'-pentyl)barbituric acids.

Carbon Isotopes↗
PubMed1986

Regional distributions of thiobarbituric acid-reactive products, activities of enzymes regulating the metabolism of oxygen free radicals, and some of the related enzymes in adult and aged rat brains.

Regional distributions of thiobarbituric acid-reactive products, activities of enzymes regulating metabolism of oxygen free radicals, and some of the related enzymes were studied in 10 areas of adult and aged rat brains. Thiobarbituric acid-reactive products were lower in cerebral cortex, septal area, hippocampus, caudate-putamen, and substantia nigra compared with other areas studied in adult rats; however, they increased significantly in the former areas with aging. A slight but significant reduction in superoxide dismutase activity was noted in frontal cortex, septal area, caudate-putamen, and substantia nigra with aging. Glutathione peroxidase and reductase activities were highest in caudate-putamen and in substantia nigra. Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities were lowest in cortical areas. Phosphofructokinase activity was lowest in septal area and hippocampus in aged rats. Glyceraldehyde-3-phosphate dehydrogenase activity showed only small regional and evolutional changes. Lactate dehydrogenase activity declined with age in most of the areas studied. sn-Glycerol-3-phosphate dehydrogenase activity showed small changes with aging except in hippocampus, where 40% reduction was noted. Generally, cerebral cortical areas, hippocampus, and septal areas were not particularly enriched in enzymes regulating the metabolism of oxygen free radicals. The results were discussed in relation to the role of free radicals in aging.

Aging↗