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排序方式: 共有162条查询结果,搜索用时 15 毫秒
61.
Determination of polyphenolic compounds by liquid chromatography–mass spectrometry in Thymus species
Borbála Boros Silvia Jakabová Ágnes Dörnyei Györgyi Horváth Zsuzsanna Pluhár Ferenc Kilár Attila Felinger 《Journal of chromatography. A》2010,1217(51):7972-7980
Polyphenolic compounds represent a wide group of phytochemicals, including well-known subgroups of phenolic acids, flavonoids, natural dyes, lignans etc., which are produced by plants. These natural bioactive compounds possess a variety of beneficial effects including antioxidant and anticarcinogenic activities, protection against coronary diseases as well as antimicrobial properties. Thymus species have already been reported as sources of different phenolic acids and flavonoids. Moreover, the composition and content of flavonoids in Thymus species play important role as taxonomic markers providing distinction of species. High-performance liquid chromatography (HPLC) coupled with diode array detector (DAD) and on-line mass spectrometry (ESI-MS) method was used for analysis. The method was evaluated for a number of validation characteristics (repeatability and intermediate precision, LOD, LOQ, calibration range, and recovery). The polyphenolic pattern of five native Hungarian Thymus species (T. glabrescens Willd., T. pannonicus All., T. praecox Opiz, T. pulegioides L., and T. serpyllum L.) was characterized. The dominant compound was rosmarinic acid, which ranged between 83.49 μg g−1 and 1.436 mg g−1. Other phenolic acids (ferulic acid, caffeic acid and its other derivatives, chlorogenic acid and p-coumaric acids) were present in every examined Thymus species, as well as flavanones: naringenin, eriodictyol and dihydroquercetin; flavones: apigenin and apigenin-7-glucoside, flavonols: quercetin and rutin. The polyphenolic pattern was found to be a useful additional chemotaxonomic tool for classification purposes and determination of the locality of origin. 相似文献
62.
Paola L. Lucero Walter J. Peláez Zsuzsanna Riedl György Hajós Elizabeth L. Moyano Gloria I. Yranzo 《Tetrahedron》2012,68(4):1299-1305
2-Aryl-5-acroleinyl-1,2,3,4-tetrazoles (1a–d) and 2-aryl-5-butadienyl-1,2,3,4-tetrazoles (1e–g) were subjected to flash vacuum pyrolysis. Acroleinyl derivatives resulted in nitrogen extrusion to give nitrilimines followed by ring closure to give the corresponding indazoles 3a–d in good yields. On the other hand, butadiene derivatives underwent ring fragmentation to give p-substituted anilines without formation of the expected indazoles. Differences between thermal behaviour of 2-(4-chlorophenyl)-5-acroleinyl-1,2,3,4-tetrazole (1c) and 1-(4-chlorophenyl)-4-acroleinyl-1,2,3-triazole (2) were studied in details. DFT calculations have been used to examine the nitrilimine and carbene nature of the intermediates involved in the thermal reactions of azolyl derivatives. 相似文献
63.
Zsuzsanna Szabó Gyozo Jordan Csaba Szabó Ákos Horváth Óskar Holm Gábor Kocsy 《Isotopes in environmental and health studies》2014,50(2):211-225
Radon and thoron isotopes are responsible for approximately half of the average annual effective dose to humans. Although the half-life of thoron is short, it can potentially enter indoor air from adobe walls. Adobe was a traditional construction material in the Great Hungarian Plain. Its major raw materials are the alluvial sediments of the area. Here, seasonal radon and thoron activity concentrations were measured in 53 adobe dwellings in 7 settlements by pairs of etched track detectors. The results show that the annual average radon and thoron activity concentrations are elevated in these dwellings and that the proportions with values higher than 300 Bq m?3 are 14–17 and 29–32% for radon and thoron, respectively. The calculated radon inhalation dose is significantly higher than the world average value, exceeding 10 mSv y?1 in 7% of the dwellings of this study. Thoron also can be a significant contributor to the inhalation dose with about 30% in the total inhalation dose. The changes of weather conditions seem to be more relevant in the variation of measurement results than the differences in the local sedimentary geology. Still, the highest values were detected on clay. Through the year, radon follows the average temperature changes and is affected by the ventilation, whereas thoron rather seems to follow the amount of precipitation. 相似文献
64.
Pál Perjési Krisztina Takács-Novák Zsuzsanna Rozmer Pál Sohár Richard E. Bozak Theresa M. Allen 《Central European Journal of Chemistry》2012,10(5):1500-1505
Cyclic chalcone analogues (2–5) and their ferrocenyl counterparts (6–10) were synthesized and their logP and P388 cyctotoxity were investigated. The structures of the newly synthesized compounds were confirmed by IR 1H and 13NMR spectroscopy. Comparison of conjugation and stereochemistry of the respective derivatives showed similar characteristics compared to ones with some higher degree of conjugation in the ferrocenyl series. Comparison of logP of the ferrocenyl derivatives determined by a validated RP-TLC method showed the ferrocenyl derivatives to have higher logP TLC. The results demonstrate that the differences in three dimensional shape, conjugation and lipophilicity do not have strong influence on the P388 cytotoxicity of the investigated phenyl (1−5) and ferrocenyl (6−10) enones. 相似文献
65.
Nagy HÉ Szabó Z Jordán G Szabó C Horváth A Kiss A 《Isotopes in environmental and health studies》2012,48(3):464-472
A long-term radon concentration monitoring was carried out in the Pál-v?lgy cave, Budapest, Hungary, for 1.5 years. Our major goal was to determine the time dependence of the radon concentration in the cave to characterise the air exchange and define the most important environmental parameters that influence the radon concentration inside the cave. The radon concentration in the cave air was measured continuously by an AlphaGuard radon monitor, and meteorological parameters outside the cave were collected simultaneously. The air's radon concentration in the cave varied between 104 and 7776?Bq?m(-3), the annual average value was 1884±85?Bq?m(-3). The summer to winter radon concentration ratio was as high as 21.8. The outside air temperature showed the strongest correlation with the radon concentration in the cave, the correlation coefficient (R) was 0.76. 相似文献
66.
Visky D Haghedooren E Dehouck P Kovács Z Kóczián K Noszál B Hoogmartens J Adams E 《Journal of chromatography. A》2006,1101(1-2):103-114
In this paper, the performance of a previously developed classification system applied to pharmaceutical chromatographic analyses, is investigated. The separation of seven different drug substances from their respective impurities was studied. The chromatographic procedure for acetylsalicylic acid, clindamycin hydrochloride, buflomedil hydrochloride, chloramphenicol sodium succinate, nimesulide and phenoxymethylpenicillin was performed according to the corresponding European Pharmacopoeia (Ph. Eur.) monograph. The separation of dihydrostreptomycin sulphate was performed according to the literature. It is shown that the column ranking system is a helpful tool in the selection of a suitable column in these analyses. 相似文献
67.
Krisztina Rácz Maria Burger István Lagzi Zsuzsanna Ungvarai-Nagy 《Reaction Kinetics and Catalysis Letters》2008,95(1):135-142
The water-soluble iron(III) complex of meso-tetra(4-sulfonatophenyl)porphine is oxidized by bromate in nearly neutral aqueous
solutions in an overall six-electron three-step consecutive reaction. Kinetics and mechanism of the reaction are described. 相似文献
68.
69.
Reaction of azolylacroleins with phosphoranes bearing a conjugated double bond was found to yield either azolyltrienes in a Wittig reaction, or to undergo cyclization to a dihydrobenzene containing the azole substituent. Transformation with an aza-Wittig reagent gave tetrazolylpyridines. The ambident reactivity was found to be dependent on the substituent of the phosphorane, which was rationalized by ab initio (DFT) calculation of the atomic charges of the reaction centres. 相似文献
70.
Edina Lempel Zsuzsanna Czibulya Sándor Kunsági-Máté József Szalma Balázs Sümegi Katalin Böddi 《Chromatographia》2014,77(17-18):1137-1144
The purpose of the study was to analyze the correlation between the quantity of eluted monomers from dental resin-based composite using reverse-phase HPLC and the degree of conversion (DC) using micro-Raman spectroscopy, and to evaluate the influence of the energy of polymerization delivered on the composite material and the applied resin layer thickness on these properties. There was direct proportion in degree of conversion and inverse proportion in monomer elution when the energy of light polymerization was increased from 20 to 40 J cm?2; however, further increase in energy density did not influence significantly the DC and the elution of monomers. Investigating the depth of cure significant differences could be measured both in DC and the elution of monomers. 1 mm layer increment up to 3 mm from the top led to 10 % decrease in DC and 30–35 % increase in monomer elution. Further increase in depth from 3 to 4 mm caused 30 % drop in DC and 55 % increase in the amount of leached monomers. The overall result of the findings indicates that direct correlation exists between DC of composite and the elution of unreacted monomers. 相似文献