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51.
Reda Mohammady Abdel-rahman 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):315-357
Abstract Studies on the chemical constituents of sulfur containing the 5-oxo-1,2,4-triazin-3-yl moiety are reviewed. The synthesis. unique features of the structures and biological significance of these constituents are discussed. 相似文献
52.
《Journal of Coordination Chemistry》2012,65(2):193-206
Interaction of dipropyltin(IV) with selected amino acids, peptides, dicarboxylic acids or DNA constituents was investigated using potentiometric techniques. Amino acids form 1?:?1 and 1?:?2 complexes and, in some cases, protonated complexes. The amino acid is bound to dipropyltin(IV) by the amino and carboxylate groups. Serine is complexed to dipropyltin(IV) with ionization of the alcoholic group. A relationship exists between the acid dissociation constant of the amino acids and the formation constants of the corresponding complexes. Dicarboxylic acids form both 1?:?1 and 1?:?2 complexes. Diacids forming five- and six-membered chelate rings are the most stable. Peptides form complexes with stoichiometric coefficients 111(MLH), 110(ML) and 11-1(MLH?1)(tin: peptide: H+). The mode of coordination is discussed based on existing data and previous investigations. DNA constituents inosine, adenosine, uracil, uridine, and thymine form 1?:?1 and 1?:?2 complexes and the binding sites are assigned. Inosine 5′-monophosphate, guanosine 5′-monophosphate, adenosine 5′-monophosphate and adenine form protonated species in addition to 1?:?1 and 1?:?2 complexes. The protonation sites and tin-binding sites were elucidated. Cytosine and cytidine do not form complexes with dipropyltin(IV) due to low basicity of the donor sites. The stepwise formation constants of the complexes formed in solution were calculated using the non-linear least-square program MINIQUAD-75. The concentration distribution of the various complex species was evaluated as a function of pH. 相似文献
53.
《Journal of separation science》2018,41(12):2672-2680
54.
《Journal of separation science》2018,41(13):2846-2853
An integrated strategy based on high‐resolution mass spectrometry coupled with multiple data mining techniques was developed to screen the metabolites in rat biological fluids after the oral administration of Xanthoceras sorbifolia Bunge husks. Mass defect filtering, product ion filtering, and neutral loss filtering were applied to detect metabolites from the complex matrix. As a result, 55 metabolites were tentatively identified, among which 45 barrigenol‐type triterpenoid metabolites were detected in the feces, and six flavonoids and four coumarins metabolites were in the urine. Moreover, eight prototype constituents in plasma, 36 in urine and 23 in feces were also discovered. Due to the poor bioavailability of barrigenol type triterpenoids, most of them were metabolized by intestinal flora. Phase I metabolic reactions such as deglycosylation, oxidation, demethylation, dehydrogenation, and internal hydrolysis were supposed to be their principal metabolic pathways. Coumarins were found in all the biosamples, whereas flavonoids were mainly in the urine. Unlike the saponins, they were mainly metabolized through phase II metabolic reactions like glucuronidation and sulfonation, which made them eliminated more easily by urine. This work suggested the metabolic profile of X. sorbifolia husks for the first time, which will be very valuable for its further development. 相似文献
55.
An analytical system for the analysis of volatiles entrained in polymers is described. This system is based on a thermal desorption oven connected to a cold trap. After enrichment of headspace vapor, trapped material is reinjected and analyzed by open tubular gas chromatography/Fourier transform infrared spectroscopy, OTGC/FTIR. The thermal desorption oven is designed to provide different modes of sample introduction: use of a pyroprobe; insertion of a piece of quartz tubing with applied sample; or syringe injection. Headspace enrichment is carried out in a piece of fused silica capillary tubing filled with glass beads. The trap may be cooled either electrically using Peltier elements or with liquid nitrogen. A six-port rotary valve is used for flow switching between enrichment and reinjection modes. All system parameters, temperatures, and timed events, are controlled from the gas chromatograph. Dynamic headspace analysis is demonstrated as a method for polymer characterization. 相似文献
56.
中国芦荟化学成分研究——芦荟大黄素的分离与结构鉴定 总被引:1,自引:0,他引:1
首次报道湛江地区徐闻县打银村产的芦荟主要有效成分,并通过化学和光谱分析(MS,^1H-NMR,IR,UV)鉴定其结构为芦荟大黄素(Aloe-emodin)。 相似文献
57.
Summary Supercritical fluid extraction (SFE) connected to open tubular gas chromatography has been used for the analysis of non-polar to medium polar volatiles entrained in polymers. This polymer sheets, prepared with the aid of a microtome, have been extracted with supercritical carbon dioxide. The influence of sample area/weight ratio and extraction cell volume on the SFE performance has been investigated. Further, quantitative analysis was executed by stepwise extractions.A set of polybutylene terephthalate polymers, originating from different manufactures, has been analysed regarding entrained volatiles. 相似文献
58.
Discrimination of extracted lipophilic constituents of Angelica with multi-steps infrared macro-fingerprint method 总被引:2,自引:0,他引:2
It is the most pressing task that fast and effective analysis methods monitor the inherent qualities of traditional Chinese medicine (TCM) and its corresponding extract products as a complicated mixture system. Owing to the unique fingerprint character and extensive applicability to test sample, infrared spectral method has been used in many research fields. In recent years, Fourier transform infrared spectroscopy (FT-IR), accompanied with the development of spectroscopic technology and combined with computer science, plays an important role in the TCM research. In this paper, we use FT-IR, second derivative infrared spectroscopy and two-dimensional correlation infrared spectroscopy (2D-IR) step by step to analyze the lipophilic constituents in Angelica extracted by two different extract crafts. As a result, all spectra can not only supply lots of structural information of main constituents in the complicated system, but also can differentiate the tiny differences between the similar systems according to the infrared macro-fingerprint characters. This is a very quick, effective and well repetitive method for monitoring the process of the TCM. 相似文献
59.
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