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81.
Maja Friščić Franz Bucar Kroata Hazler Pilepić 《Journal of mass spectrometry : JMS》2016,51(12):1211-1236
Plants produce a great number of metabolites with potentially useful biological activities. Species from the genus Globularia (Plantaginaceae) are known as sources of different phenolic and iridoid compounds. Globularia alypum L. is a medicinal plant used as a healing agent in many Mediterranean countries. Similarities in phytochemical composition are often observed for related species. For Globularia spp., such findings were mostly based on identification of several isolated compounds from distinct species. To our knowledge, this is the first study that enables simultaneous comparison of phytochemical profiles from several members of the genus Globularia. Liquid chromatography‐photodiode array detection‐electrospray ionization‐tandem mass spectrometry was used for the analysis of methanolic extracts of aerial parts obtained from four Globularia species (G. alypum, G. punctata, G. cordifolia and G. meridionalis). In total, 85 compounds were identified or tentatively identified based on comparison of their retention time, UV and MSn (up to MS4) spectra to those of standard compounds and/or to literature data. Among these, high relative amounts of bioactive molecules such as globularin, globularifolin, asperuloside and verbascoside (acteoside) were found. Apart from providing new insights into the phytochemistry and chemotaxonomy of selected Globularia species, results of this study complement existing MS/MS spectral data and could enable easier mass spectrometric profiling of certain bioactive compounds such as iridoids and phenylethanoids in related plant species, genera and families. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
82.
Versace F Uppugunduri CR Krajinovic M Théorêt Y Gumy-Pause F Mangin P Staub C Ansari M 《Analytical and bioanalytical chemistry》2012,404(6-7):1831-1838
The role of busulfan (Bu) metabolites in the adverse events seen during hematopoietic stem cell transplantation and in drug interactions is not explored. Lack of availability of established analytical methods limits our understanding in this area. The present work describes a novel gas chromatography-tandem mass spectrometric assay for the analysis of sulfolane (Su) in plasma of patients receiving high-dose Bu. Su and Bu were extracted from a single 100 μL plasma sample by liquid-liquid extraction. Bu was separately derivatized with 2,3,5,6-tetrafluorothiophenolfluorinated agent. Mass spectrometric detection of the analytes was performed in the selected reaction monitoring mode on a triple quadrupole instrument after electronic impact ionization. Bu and Su were analyzed with separate chromatographic programs, lasting 5?min each. The assay for Su was found to be linear in the concentration range of 20-400?ng/mL. The method has satisfactory sensitivity (lower limit of quantification, 20?ng/mL) and precision (relative standard deviation less than 15?%) for all the concentrations tested with a good trueness (100?±?5?%). This method was applied to measure Su from pediatric patients with samples collected 4?h after dose 1 (n?=?46), before dose 7 (n?=?56), and after dose 9 (n?=?54) infusions of Bu. Su (mean?±?SD) was detectable in plasma of patients 4?h after dose 1, and higher levels were observed after dose 9 (249.9?±?123.4?ng/mL). This method may be used in clinical studies investigating the role of Su on adverse events and drug interactions associated with Bu therapy. 相似文献
83.
Majerić Elenkov M Primožič I Hrenar T Smolko A Dokli I Salopek-Sondi B Tang L 《Organic & biomolecular chemistry》2012,10(26):5063-5072
A novel activity of halohydrin dehalogenases towards spiroepoxides has been found. The enzyme from Arthrobacter sp. (HheA) catalysed highly regioselective azidolysis of spiroepoxides containing 5, 6 and 7-membered cycloalkane rings, while the enzyme from Agrobacterium radiobacter (HheC), besides high regioselectivity, also displayed moderate to high enantioselectivity (E up to >200) that can be applied for the kinetic resolution of chiral spiroepoxides. The orientations of spiroepoxides in the active site of halohydrin dehalogenases were studied by quantum-chemical calculations and docking simulations. Analyses of the complexes obtained revealed the origins of diastereoselectivity and enantioselectivity of the investigated biotransformations. 相似文献
84.
Tadeusz Micha?owski Agustin G. Asuero Maja Ponikvar-Svet Marcin Toporek Andrzej Pietrzyk Maciej Rymanowski 《Journal of solution chemistry》2012,41(7):1224-1239
The paper compares two approaches to the simulated argentometric titration of cyanide with the use of the modified Liebig?CDenigès (L-D) method, carried out according to GATES and applied with (1) classical and (2) pH-static titrations. Both approaches are discussed thoroughly and the results obtained from calculations are presented graphically. The calculations are performed with the use of an iterative computer program, based on charge and concentration balances and expressions for equilibrium constants, providing all physicochemical knowledge of the dynamic system in question. This way, physicochemical knowledge on complex electrolytic systems can be gained during the analytical procedure, i.e., the physicochemical and analytical knowledge are interrelated. The simulations follow the analytical procedures applied in experimental titrations and so provide an example of searching for the best a priori conditions for the quantitative analysis of cyanide. The computer program for pH-static titrations (described in this paper) enables one to carry out the simulation procedures with different preliminary data (concentrations, volumes). 相似文献
85.
86.
Structural Chemistry - The newly measured ionization potential of atomic astatine is discussed and compared with that of the recently determined value for polonium and for the other atomic... 相似文献
87.
JPC – Journal of Planar Chromatography – Modern TLC - Experiments and calculations show the importance of analytical management to reliable analytical results. A method with a... 相似文献
88.
89.
In this article, I discuss Hawthorne’s contextualist solution to Benacerraf’s dilemma. He wants to find a satisfactory epistemology
to go with realist ontology, namely with causally inaccessible mathematical and modal entities. I claim that he is unsuccessful.
The contextualist theories of knowledge attributions were primarily developed as a response to the skeptical argument based
on the deductive closure principle. Hawthorne uses the same strategy in his attempt to solve the epistemologist puzzle facing
the proponents of mathematical and modal realism, but this problem is of a different nature than the skeptical one. The contextualist
theory of knowledge attributions cannot help us with the question about the nature of mathematical and modal reality and how
they can be known. I further argue that Hawthorne’s account does not say anything about a priori status of mathematical and modal knowledge. Later, Hawthorne adds to his account an implausible claim that in some contexts
a gettierized belief counts as knowledge. 相似文献
90.
(E)‐4‐Hydroxy‐3‐methylbut‐2‐enyl diphosphate ( 1 ) is a key intermediate of the deoxyxylulose phosphate pathway of isoprenoid biosynthesis and a precursor of the plant hormone zeatin. The availability of this intermediate with various labeling patterns is pivotal for its use in biosynthetic studies. The number of positions, however, that can be easily labeled by chemical synthesis is limited, and the synthesis by means of recombinant enzymes is laborious and time consuming. We demonstrated that chromoplasts from Capsicum annuum, whose enzyme activity was impaired by freeze‐thawing, accumulate 1 . This observation built the basis for the development of a cell‐free system allowing the synthesis of this intermediate with labels in various positions. With 2C‐methyl‐D ‐erythritol 2,4‐cyclodiphosphate ( 5 ) as substrate, yields were in the range of 50%. 相似文献