Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “BARBITURIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51Linked to original sources
PubMed2004

Multiple recognition of barbiturate guests by Hamilton-receptor-functionalized dendrimers.

The well-known unsubstituted "Hamilton receptor" was monofunctionalized with an amino group and attached at the periphery of poly(propyleneamine) dendrimers through the use of an activated ester. Four generations of Hamilton-receptor-functionalized dendrimers (HR-dendrimers) were synthesized and characterized by (1)H and (13)C NMR spectroscopy and MALDI-TOF mass spectrometry. The photophysical properties of the HR-dendrimers were investigated by UV/Vis as well as with steady-state and time-resolved fluorescence spectroscopy. The dendrimers were used as multivalent hosts for the barbiturate guests Barbital (7) and [Re(Br)(CO)(3)(barbi-bpy)] (8; barbi-bpy=5-[4-(4'-methyl)-2,2'-bipyridyl]methyl-2,4,6-(1 H,3 H,5 H)-pyrimidinetrione). The stable adducts formed between the dendritic architectures (the hosts) and the barbiturate guests 7 and 8 were investigated by (1)H NMR spectroscopy and photophysical methods. The binding constants of the barbiturate guests for binding to reference compound 2 (with a single receptor unit) in chloroform were found to be 1.4 x 10(3) M(-1) and 1.5 x 10(5) M(-1) for 7 and 8, respectively. Binding of 7 to the dendrimers enhances the weak emission of the Hamilton receptor. This increase in emission is also generation dependent; it was found to be most pronounced in the case of 2 and the least in the case of the fourth-generation dendrimer 6. The unexpected increase in the quantum yield of emission from the HR-dendrimers with increasing generation could be caused by the rather rigid conformation of the Hamilton receptors in later-generation compounds, which is a result of intramolecular aggregation and steric hindrance at the periphery of the dendrimer. The photoinduced energy transfer from the excited state of the HR-dendrimers to the lower-lying excited state of the guest 8 was used to probe the formation of host-guest complexes. The rate of energy transfer was calculated to be 3.6 x 10(10) s(-1). Energy transfer in 2 subset 8 only occurred in the presence of a strong base, which shows that the basic amine core in the HR-dendrimers is crucial for this photoinduced process. The binding of 8 to the dendrimers is completely reversible: 8 can be exchanged with a competitive guest such as 7 and the emission of the HR-dendrimer is restored.

Amino Acids↗
PubMedDate not supplied

Effects of barbiturates on responses evoked by excitatory amino acids in slices of rat olfactory cortex.

A study has been made of the effects of ranges of concentrations of phenobarbitone, pentobarbitone and thiopentone on responses evoked by gamma-aminobutyric acid (GABA), L-glutamate, L-aspartate, N-methyl-D-aspartate, kainate and quisqualate in slices of olfactory cortex of the rat. All three barbiturates affected GABA-evoked depolarizations similarly in that responses were potentiated by small doses but markedly inhibited at greater concentrations. Responses to L-aspartate and L-glutamate were little affected except at the largest dose of phenobarbitone tested (10 mM). The responses evoked by the selective agonists of excitatory amino acid receptors were inhibited by the barbiturates, the relative sensitivities being quisqualate greater than or equal to N-methyl-D-aspartate greater than or equal to kainate with phenobarbitone, quisqualate greater than or equal to kainate greater than N-methyl-D-aspartate with pentobarbitone and quisqualate greater than kainate = N-methyl-D-aspartate with thiopentone. The possible significance of these findings is discussed.

Amino Acids↗
PubMed2005

Foundations of chemical microscopy. 3. Derivatives of some chiral phenylalkylamines and phenylalkylamino acids with 5-nitrobarbituric acid.

At one time, 5-nitrobarbituric acid (also known as dilituric acid) was extensively used as a chemical reagent for the qualitative identification of a variety of basic substances by light microscopy. This methodology was based on evaluation of observed crystal morphologies, because skilled observers could associate a unique crystal habit with the products formed with analytes when those were crystallized using standardized methods. As part of a study to understand the scientific foundations that permitted chemical microscopy to function as a useful analytical technique during its heyday, the products formed by dilituric acid with resolved and racemic phenylalkylamines and phenylalkylamino acids were characterized using a variety of physical analytical techniques. It was found that the different crystal morphologies associated with each of the crystalline adducts were derived from the ability of the systems to form differing structural types and/or hydrate crystal forms upon crystallization.

Alkylation↗
PubMed2006

Ascorbate-mediated iron release from ferritin in the presence of alloxan.

Release of iron from ferritin requires reduction of ferric to ferrous iron. The iron can participate in the diabetogenic action of alloxan. We investigated the ability of ascorbate to catalyze the release of iron from ferritin in the presence of alloxan. Incubation of ferritin with ascorbate alone elicited iron release (33 nmol/10 min) and the generation of ascorbate free radical, suggesting a direct role for ascorbate in iron reduction. Iron release by ascorbate significantly increased in the presence of alloxan, but alloxan alone was unable to release measurable amounts of iron from ferritin. Superoxide dismutase significantly inhibited ascorbate-mediated iron release in the presence of alloxan, whereas catalase did not. The amount of alloxan radical (A.(-)) generated in reaction systems containing both ascorbate and alloxan decreased significantly upon addition of ferritin, suggesting that A.(-) is directly involved in iron reduction. Although release of iron from ferritin and generation of A.(-) were also observed in reactions containing GSH and alloxan, the amount of iron released in these reactions was not totally dependent on the amount of A.(-) present, suggesting that other reductants in addition to A.(-) (such as dialuric acid) may be involved in iron release mediated by GSH and alloxan. These results suggest that A.(-) is the main reductant involved in ascorbate-mediated iron release from ferritin in the presence of alloxan and that both dialuric acid and A.(-) contribute to GSH/alloxan-mediated iron release.

Alloxan↗
PubMed1984

Transition metals mediate enzymatic inactivation caused by favism-inducing agents.

Enzymatic activity of purified or membrane-bound acetylcholine esterase was lost when incubated aerobically in the presence of both favism-inducing agent (isouramil or divicine) and copper ions. The requirement for oxygen could be substituted by hydrogen peroxide. Chelating agents provided total protection to the proteins. The suggested mechanism of enzymatic inactivation is analogous to that suggested earlier for the effects of superoxide and ascorbate, and involves the site-specific formation of hydroxyl radicals in the metal-mediated Haber-Weiss reaction. These findings may be relevant to the understanding of the pathogenesis of favism.

Ascorbic Acid↗
PubMed1986

Reduction of the metallochromic indicators murexide and tetramethylmurexide to their free radical metabolites by cytoplasmic enzymes and reducing agents.

Murexide underwent reduction by rat liver cytosolic fraction or a hypoxanthine-xanthine oxidase system to produce a free radical metabolite. Reduction of murexide by the freshly prepared cytosolic fraction depended upon the presence of ascorbic acid. N1-Methylnicotinamide, xanthine or hypoxanthine, in that order, could also serve as a source of reducing equivalents for the production of that free radical by the cytosolic fraction. Several thiol compounds (GSH, cysteine, and cysteamine), pyridine nucleotides (NADH, NADPH) and ascorbic acid were also effective in generating the murexide-derived free radical. Tetramethyl murexide was also reduced to its free radical derivative by a hypoxanthine-xanthine oxidase system.

Animals↗
PubMed1996

Horseradish peroxidase-catalyzed sulfoxidation of promethazine and properties of promethazine sulfoxide.

Promethazine sulfoxide was obtained with a quantitative yield in a horse radish peroxidase-catalyzed reaction of promethazine and hydrogen peroxide and was also prepared by direct chemical synthesis. The enzymatic sulfoxidation of promethazine was studied in vitro as a function of pH, promethazine, and hydrogen peroxide concentration. Promethazine sulfoxide inhibits with an apparent K(i) of 59.7 microM at pH 5.5 the enzymatic reaction, followed spectrophotometrically, polarographically, potentiometrically, and luminometrically. The reaction was also inhibited by ascorbic acid (K(i) 26.8 microM) and glutathione (K(i) 41.8 microM). The spectrophotometric techniques employed, together with ESR spectrometry, allowed the identification of at least three radical species formed in the course of the reaction. Promethazine sulfoxide is devoid of the antioxidant effect exhibited by promethazine on rat brain synaptosomes. The sulfoxide also lacks photosensitizing action, while retaining the neuroleptic effect of the parent compound.

Animals↗
PubMed2006

Neuroprotective role of Bacopa monniera extract against aluminium-induced oxidative stress in the hippocampus of rat brain.

Bacopa monniera is a nerve tonic used extensively in traditional Indian medicinal system "Ayurveda". Reports regarding its various antioxidative, adaptogenic and memory enhancing roles have already appeared in the last few decades. In the present study, aluminium chloride (AlCl(3)) was used to generate neurotoxicity. We have investigated the neuroprotective effect of Bacopa extract against aluminium-induced changes in peroxidative products, such as thio-barbituric acid-reactive substance (TBA-RS) and protein carbonyl contents and superoxide dismutase (SOD) activity. Effect on lipofuscin (age pigments) accumulation and ultrastructural changes were also studied. Bacopa effects were compared with those of l-deprenyl. Co-administration of Bacopa extract during aluminium treatment significantly prevented the aluminium-induced decrease in SOD activity as well as the increased oxidative damage to lipids and proteins. Protective effect was also observed at microscopic level. Fluorescence and electron microscopic studies revealed considerable inhibition of intraneuronal lipofuscin accumulation and necrotic alteration in the CA1 region of the hippocampus. Observations showed that Bacopa's neuroprotective effects were comparable to those of l-deprenyl at both biochemical and microscopic levels.

Aluminum Chloride↗