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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Neurochemical research 25 (2000), S. 211-215 
    ISSN: 1573-6903
    Keywords: Glutamate ; guanine nucleotides ; antinoception ; naturally-occurring compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Glutamate is to be considered a nociceptive neurotransmitter and glutamatergic antagonists present antinoceptive activity. In this study we investigated the effects of the naturally occurring antinociceptive compounds rutin, geraniin and quercetine extracted from Phyllanthus, as well as the diterpene jatrophone, extracted from Jatropha elliptica on the binding of [3H]glutamate and [3H]GMP-PNP [a GTP analogue which binds to extracellular site(s), modulating the glutamatergic transmission] in rat brain membrane. Jatrophone inhibited [3H]glutamate binding and geraniin inhibited [3H]GMP-PNP binding. Quercetine inhibited the binding of both ligands. These results may indicate a neurochemical parameter possibly related to the antinoceptive activity of these natural compounds.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 620-626 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Nitrone formation from furfural and 5-nitrofurfural with phenylhydroxylamine was studied in water at 25°C and ionic strength 1·0 (KCl). The reaction exhibits general acid catalysis (α = 0·52), specific base catalysis and a pH-independent process. The results are consistent with a mechanism where dehydration of an N,N′-dihydroxy addition intermediate, formed by a rapid pre-equilibrium, is the only rate-determining step over the pH range studied (1-11). In contrast, nitrone formation from p-chlorobenzaldehyde and N-methylhydroxylamine exhibits a clear change of rate-determining step, from dehydration of the addition intermediate to attack of the nucleophile on the aldehyde, with increase in pH. The profile of log k2 (k2 = second-order rate constant) vs pH indicates, by comparison with the corresponding profile for similar reaction, that phenylhydroxylamine exhibits unexpected nucleophilic behaviour in this reaction. The pH-indpendent dehydration process, which has a higher rate constant than that predicted from the Brønsted line for the water catalysis, appears to involve intramolecular catalysis rather than bifunctional catalysis by water.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 7 (1994), S. 399-402 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of nitrosobenzene with aniline, to give azobenzene, in basic conditions was studied. It was shown that the reaction exhibits general base catalysis by different buffers giving a Brønsted coefficient β = 0·318. As in previous studies, a two-step process with a first step of attack of aniline on nitrosobenzene to give an addition intermediate and a second step of dehydration of this intermediate is proposed to interpret the mechanism of the reaction. The analysis of the Brønsted relationship and of the intermediate of the reaction led to the suggestion that hydoxide ion catalyses the reaction by a mechanism of general base catalysis in the dehydration step.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 9 (1996), S. 545-551 
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of barbiturate and 1,3-dimethylbarbiturate ions with o-, p- and 2,4-dinitrobenzaldehyde was studied. The reactions of barbiturate anion with o- and p-nitrobenzaldehyde exhibit a pH-rate profile different to that the corresponding to the reactions of barbiturate and 1,3-dimethylbarbiturate ions with 2,4-dinitrobenzaldehyde. The dependence of the rate constant on the viscosity of the medium in the pH range 2-4, for all the reactions, indicates the contribution of a diffusion-controlled proton transfer from the hydronium ion to an addition intermediate, T-, in the rate-determining step. Surprisingly, in the reaction of 2,4-dinitrobenzaldehyde with barbiturate and 1,3-dimethylbarbiturate anions, the Brønsted plot for general acid catalysis for carboxylic acids of pKa between 2 to 5 gives a linear relationship with α = 0·707 (r = 0·991), whereas α = 0 is expected, considering the pKa of the addition intermediate T-. On the other hand, the point for the rate constant, considering water as a general acid catalyst, falls approximately 105 times above the corresponding Brønsted line. The tautomerism existing in the intermediate T- permits these surprising facts to be explained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of natural products 51 (1988), S. 617-618 
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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