Journal of chromatography. A
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Alkaloids in Gelsemium elegans possess a variety of therapeutic properties, including tumor suppression, analgesic and anti-inflammatory effects. In China, G. elegans has been used for centuries to treat a variety of medical conditions, including chronic pain and skin ulcer. Methods currently used to separate the active components of G. elegans are time-consuming and have low recovery. ⋯ From 1.5 g of crude extract, we obtained 312 mg gelsemine, 420 mg koumine and 195 mg gelsevirine, with purities at 94.8%, 95.9% and 96.7%, respectively, which were determined by HPLC at 256 nm. The chemical identity of the isolated compounds was verified by electrospray ionization-mass spectrometry (ESI-MS), ¹H NMR and ¹³C NMR. These results demonstrated that pH-zone-refining counter-current chromatography is an effective method to separate and purify major alkaloids from G. elegans.
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During the past two decades, chiral capillary electrophoresis (CE) emerged as a promising, effective and economic approach for the enantioselective determination of drugs and their metabolites in body fluids, tissues and in vitro preparations. This review discusses the principles and important aspects of CE-based chiral bioassays, provides a survey of the assays developed during the past 10 years and presents an overview of the key achievements encountered in that time period. ⋯ Chiral CE was extensively employed for research purposes to investigate the stereoselectivity associated with hydroxylation, dealkylation, carboxylation, sulfoxidation, N-oxidation and ketoreduction of drugs and metabolites. Enantioselective CE played a pivotal role in many biomedical studies, thereby providing new insights into the stereoselective metabolism of drugs in different species which might eventually lead to new strategies for optimization of pharmacotherapy in clinical practice.
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The availability of robust and highly efficient separation methods represents a major requirement for proteome analysis. This study investigated the characteristics of two different gel-free proteomic approaches to the fractionation of proteolytic peptides and intact proteins, respectively, in a first separation dimension. Separation and mass spectrometric detection by matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS) were performed at the peptide level in both methods. ⋯ The identification of more basic and larger proteins was slightly favored in the BU approach, most probably due to higher losses of these proteins during intact protein handling and separation in the STD method. A significant degree of complementarity was revealed by an approximately 33% overlap between one BU and STD replicate, while 33% each of the protein identifications were unique to both methods. In the STD method, peptides obtained upon digestion of the proteins contained in fractions of the first separation dimension covered a broad elution window in the second-dimension separation, which demonstrates a high degree of "pseudo-orthogonality" of protein and peptide separation by IP-RPC in both separation dimensions.
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In this work, a methodology to characterise the volatile and semi-volatile compounds from marine salt by headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC/TOFMS) was developed. Samples from two saltpans of Aveiro, in Portugal, with diverse locations, obtained over three years (2004, 2005, and 2007) were analysed. A 50/30microm divinylbenzene/carboxen/polydimethylsiloxane SPME fibre was used. ⋯ The large number of co-elutions on the first column that were resolved by the GCxGC system revealed the complexity of marine salt volatile composition. The existence of a structured 2D chromatographic behaviour according to volatility, in the first dimension ((1)D), and primarily polarity, in the second dimension ((2)D), was demonstrated, allowing more reliable identifications. The resolution and sensitivity of GCxGC/TOFMS enabled the separation and identification of a higher number of volatile compounds compared to GC-qMS, allowing a deeper characterisation of this natural product.
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A new, simple and versatile method is presented for the determination of different concentration levels of alkenylbenzenes (eugenol, isoeugenol, eugenol methyl ether, myristicin, anethole and estragole) and the related flavour compounds (coumarin and pulegone) in food samples. The method involves the use of a stationary phase (capillary column) for the enrichment with appropriate elution. After the sample had completely passed through the capillary column the eluent was changed and the separation/detection was achieved. ⋯ Evidence for a matrix effect was not found and recoveries between 92 and 110% were obtained. The precision of the method, expressed as relative standard deviation values, was below 5% in all cases. The applicability of this methodology was tested by analyzing synthetic and real food samples.