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51.
Liquid chromatographic/electrospray ionization tandem mass spectrometric study of the phenolic composition of cocoa (Theobroma cacao) 总被引:2,自引:0,他引:2
Sánchez-Rabaneda F Jáuregui O Casals I Andrés-Lacueva C Izquierdo-Pulido M Lamuela-Raventós RM 《Journal of mass spectrometry : JMS》2003,38(1):35-42
Liquid chromatography coupled with ionspray mass spectrometry in the tandem mode (LC/MS/MS) with negative ion detection was used for the identification of a variety of phenolic compounds in a cocoa sample. Gradient elution with water and acetonitrile, both containing 0.1% HCOOH, was used. Standard solutions of 31 phenolic compounds, including benzoic and cinnamic acids and flavonoid compounds, were studied in the negative ion mode using MS/MS product ion scans. At low collisional activation, the deprotonated molecule [M - H](-) was observed for all the compounds studied. For cinnamic and benzoic acids, losses of CO(2) or formation of [M - CH(3)](-*) in the case of methoxylated compounds were observed. However, for flavonol and flavone glycosides, the spectra present both the deprotonated molecule [M - H](-) of the glycoside and the ion corresponding to the deprotonated aglycone [A - H](-). The latter ion is formed by loss of the rhamnose, glucose, galactose or arabinose residue from the glycosides. Different fragmentation patterns were observed in MS/MS experiments for flavone-C-glycosides which showed fragmentation in the sugar part. Fragmentation of aglycones provided characteristic ions for each family of flavonoids. The optimum LC/MS/MS conditions were applied to the characterization of a cocoa sample that had been subjected to an extraction/clean-up procedure which involved chromatography on Sephadex LH20 and thin-layer chromatographic monitoring. In addition to compounds described in the literature, such as epicatechin and catechin, quercetin, isoquercitrin (quercetin-3-O-glucoside) and quercetin-3-O-arabinose, other compounds were identified for the first time in cocoa samples, such as hyperoside (quercetin-3-O-galactoside), naringenin, luteolin, apigenin and some O-glucosides and C-glucosides of these compounds. 相似文献
52.
Simultaneous thermogravimetry–differential thermal analysis (TG–DTA) and gas and liquid chromatography with mass spectrometry detection have been used to study the kinetics and decomposition of 2-hydroxybenzoic acid, 2-carboxyphenyl ester, commercially known as salsalate. Samples of salsalate were heated in the TG–DTA apparatus in an inert atmosphere (100 ml min−1 nitrogen) in the temperature range 30–500 °C. The data indicated that the decomposition of salsalate is a two-stage process. The first decomposition stage (150–250 °C) had a best fit with second-order kinetics with Ea=191–198 kJ/mol. The second decomposition stage (300–400 °C) is described as a zero-order process with Ea=72–80 kJ/mol. The products of the decomposition were investigated in two ways:
- (a)Salsalate was heated in a gas chromatograph at various isothermal temperatures in the range 150–280 °C, and the exit gas stream analyzed by mass spectrometry (GC–MS). This approach suggested that salsalate decomposes with the formation of salicylic acid, phenol, phenyl salicylate, and cyclic oligomers of salicylic acid di- and tri-salicylides.
- (b)One gram samples of salsalate were heated in a vessel under nitrogen to 150 °C, and the residues were analyzed by liquid chromatography–mass spectrometry (LC–MS). The major compound detected was a linear tetrameric salicylate ester.
53.
Olga N. Kataeva Aidar T. Gubaidullin Igor A. Litvinov Olga A. Lodochnikova Lenar R. Islamov Alexander I. Movchan Galina A. Chmutova 《Journal of Molecular Structure》2002,610(1-3):175-179
Crystal and molecular structure of 1-phenyl-3-benzoylamino-4-benzoylpyrazol-2-in-5-one as a product of the benzoylation of 1-phenyl-3-benzoylaminopyrazol-2-in-5-one was characterised by X-ray single crystal diffraction. It is shown that 1-phenyl-3-benzoylamino-4-benzoylpyrazol-2-in-5-one exists in the solid phase in an NH-tautomeric form, which is stabilised by two intramolecular hydrogen bonds and one intermolecular bond with the solvate dioxane molecule, the latter being used as a solvent for recrystallisation. 相似文献
54.
A facile seven-step sequence was developed from 4′-bromopropiophenone, utilizing a Suzuki-type coupling with an alkene, to give several novel 5-substituted pyrazole derivatives in overall yields of 11-31%. They are potent CB1 antagonists and have binding affinities similar to SR 141716A. Like SR 141716A, they may prove to be clinically useful for the treatment of obesity. 相似文献
55.
Josep Castells Elisabet Duñach Fernando Geijo Francisco López-Calahorra Margarita Prats Olga Sanahuja Laura Villanova 《Tetrahedron letters》1980,21(23):2291-2294
Triethylamine catalyzed Michael additions of benzoins to chalcone can prevail over the expected Michael-Stetter additions when certain thiazolium ion conjugate bases - prepared from the pertinent thiazolium salts and triethylamine- are used as catalysts. 相似文献
56.
Hay Robert W. Pujari Mahesh P. Hideg Kaiman Hankovszky Olga H. 《Transition Metal Chemistry》1985,10(5):188-191
Summary The new macrocyclic ligand 7,14-o-hydroxyphenyl-5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene (1=L) has been prepared and complexes with copper(II), nickel(II) and cobalt(III) characterised. The nickel(II) complex is a yellow square-planar species, while the purple-red copper(II) complex is probably tetragonal in both the solid state and solution. The complexes appear to have an N-meso arrangement of the chiral nitrogen centres with the HOC6H4 groups occupying equatorial sites so that axial interactions with the metal do not occur. A variety oftrans-[CoLX2]ClO4 complexes (X=Cl, Br, NO2, or N3) have been characterised. 相似文献
57.
Olga Hadžija 《Mikrochimica acta》1968,56(5):917-921
Summary Körbl-catalyst and manganese dioxide absorb chlorine and bromine quantitatively at room temperature. This property is applied to simultaneous microanalytical determination of carbon, hydrogen and chlorine or bromine in compounds containing carbon, hydrogen, oxygen, chlorine or bromine, but not nitrogen or sulphur.
Zusammenfassung Der Körbl-Katalysator und Mangandioxid absorbieren Chlor und Brom bei Raumtemperatur quantitativ. Sie wurden daher zur gleichzeitigen Bestimmung von C, H sowie Cl oder Br in Verbindungen verwendet, die C, H, O, Cl (oder Br), nicht aber N oder S enthalten.相似文献
58.
Olga V. Vorobyeva Tatyana A. Samoylova Vladimir I. Yusupov 《Photochemistry and photobiology》2020,96(5):1116-1123
This paper deals with the effect of photobiomodulation (PBM) on Daphnia magna S. and their sensitivity to cadmium sulfate, a known high toxic pollutant. In a first series of experiments, the effect of different He-Ne laser fluences irradiation (range 0.9-4300 mJ cm−2) on the fertility of both parent and filial generations (F1–F3) of the crustacean was studied. It was found that PBM in some cases significantly influenced the fertility of both irradiated crustaceans and their nonirradiated offspring. By selecting two fluences (9 ± 2 mJ cm−2 reducing fertility and 4.3 ± 0.9 J cm−2 increasing it), the effect of these on toxicity of cadmium sulfate was evaluated. These experiments have shown that prior irradiation with low-intensity light of a helium–neon laser with 632.8 nm wavelength can change the sensitivity of aquatic organisms to toxin cadmium sulfate. The degree and direction of changes depend on the toxicant concentration and the irradiation dose. 相似文献
59.
Singh SB Zink DL Heimbach B Genilloud O Teran A Silverman KC Lingham RB Felock P Hazuda DJ 《Organic letters》2002,4(7):1123-1126
[structure: see text] HIV-1 integrase is a critical enzyme for viral replication, and its inhibition is an emerging target for potential antiviral chemotherapy. We have discovered a novel inhibitor, integramycin, from screening of fermentation extracts using an in vitro assay. Integramycin possesses a hexacyclic ring system and exhibited an IC50 value of 4 microM against HIV-1 integrase (strand transfer). The isolation, structure elucidation, stereochemistry, conformation, and biological activity has been described. 相似文献
60.
Olga Taussky Alfred P. Sloan 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1979,30(2):370-373
Matrices and operators of the formA
–1
A
* have received a certain amount of attention in recent years. Here some of the literature is surveyed and the caseA
–1
A is studied for complex matrices withA denoting the transpose ofA. A generalization ofA
–1
A is introduced.
Dedicated to Eduard Stiefel by a long time admirer 相似文献
Zusammenfassung Matrizen und Operatoren, die in der FormA –1 A * ausgedrückt werden können, sind in den letzten Jahren häufig studiert worden. Hier wird ein Ueberblick über Teil der relevanten Literatur gegeben und auch der FallA –1 A für komplexe Matrizen studiert, wobeiA die Transponierte vonA ist. Es wird auch eine Verallgemeinerung vonA –1 A eingeführt.
Dedicated to Eduard Stiefel by a long time admirer 相似文献