Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 10.524
Filtrar
1.
Phys Chem Chem Phys ; 22(14): 7537-7545, 2020 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-32219231

RESUMO

Understanding how electrons and protons move in a coupled manner and affect one another is important to the design of proton-electron conductors and achieving biological transport in synthetic materials. In this study, a new methodology is proposed that allows for the quantification of the degree of coupling between electrons and protons in tyrosine-rich peptides and metal oxide hybrid films at room temperature under a voltage bias. This approach is developed according to the Onsager principle, which has been thoroughly established for the investigation of mixed ion-electron conductors with electron and oxide ion vacancies as carriers at high temperatures. Herein, a new device platform using electron-blocking electrodes provides a new strategy to investigate the coupling of protons and electrons in bulk materials beyond the molecular level investigation of coupled proton and electron transfer. Two Onsager transport parameters, αi* and σe', are obtained from the device, and the results of these transport parameters demonstrate that the coupled transport of electrons and protons inside the hybrid film plays an important role in the macroscopic-scale conduction. The results suggest that an average of one electron is dragged by one proton in the absence of a direct driving force for electron movement ∇ηe.


Assuntos
Técnicas de Química Analítica/instrumentação , Transporte de Elétrons/fisiologia , Elétrons , Compostos de Manganês/química , Óxidos/química , Peptídeos/química , Prótons , Transporte Biológico/fisiologia
2.
Artigo em Inglês | MEDLINE | ID: mdl-32065955

RESUMO

Developing dissolution testing methods to measure the nicotine release profiles from smokeless tobacco products is valuable for product assessment and product-to-product comparisons. In this work, we developed a robust dissolution method to study the in vitro release of nicotine from smokeless tobacco products using the U.S. Pharmacopeia flow-through cell dissolution apparatus 4 (USP-4). We further developed and validated a sensitive Ultra Performance Liquid Chromatography coupled to Photodiode Array detector (UPLC-PDA) method for the accurate quantitation of the released nicotine into artificial saliva, which is our selected dissolution medium. We have successfully shown the applicability of the validated method by investigating the release profiles of nicotine from various commercial and CORESTA reference smokeless tobacco products [CRP 1.1 (Swedish-style snus pouch), CRP 2.1 (American-style loose moist snuff), CRP 4 (loose-leaf chewing tobacco) and CRP 4.1 (chopped loose-leaf chewing tobacco)]. Nicotine release profiles were analyzed by calculating the difference factor (f1) and similarity factor (f2) by adopting a methodology referenced in the Guidance for Industry from FDA's Center for Drug Evaluation and Research (CDER) and by fitting the release profile curves using a first order kinetic model. Nicotine release was found to be dependent on the form and cut of the smokeless tobacco products, with a slower release observed for snus and loose-leaf, compared to chopped and loose moist snuff smokeless tobacco. This dissolution methodology can be extended to measure and compare release of other constituents from smokeless tobacco products and has the potential for method standardization.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Nicotina/análise , Tabaco sem Fumaça/análise , Técnicas de Química Analítica/instrumentação , Técnicas de Química Analítica/métodos , Desenho de Equipamento , Humanos , Limite de Detecção , Modelos Lineares , Modelos Biológicos , Nicotina/farmacocinética , Reprodutibilidade dos Testes , Saliva/química
3.
J Chromatogr A ; 1618: 460896, 2020 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-32005529

RESUMO

Complex chemical mixtures found in soils at contaminated sites typically includes polycyclic aromatic compounds (PACs), thus posing potential environmental and human health risks. Pressurized liquid extraction (PLE) followed by silica clean-up is one of the most often used extraction methods for PACs in soil. While silica clean-up provide satisfactory recovery of oxygenated polycyclic aromatic hydrocarbons (OPAHs), this technique provides limited recovery of azaarenes. In this work, we used PLE and in-cell clean up with basic silica to increase the recovery of OPAHs and azaarenes. The optimized selective pressurized liquid extraction (SPLE) method used 4 g basic silica, dichloromethane, 100% flush volume, 100 and 120 °C extraction temperatures, with two static cycles for each temperature, no rinse in between the two extractions, and 20 and 120 s purge for the first and second extraction temperature, respectively. The method was validated for a wide range of PAC groups, including OPAHs, azaarenes, alkylated PAHs, and sulfur heterocycles (SPACs), in total 87 PACs, using certified reference material and in comparison to the results from previous inter-laboratory data. Our SPLE method yielded results that are in agreement with certified values and inter-laboratory data from prior analysis. The SPLE method also yielded lower variation than the results from the inter-laboratory data for analysis of OPAH and azaarenes, suggesting better precision than previous methods. More importantly, the SPLE method increases sample analysis throughput as extra clean-up step is not necessary anymore. The SPLE method was then successfully applied to rapidly screen PACs in three soil samples.


Assuntos
Técnicas de Química Analítica/métodos , Extração Líquido-Líquido , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação , Dióxido de Silício/química , Solo/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Pressão , Poluentes do Solo/análise , Poluentes do Solo/isolamento & purificação , Temperatura
4.
J Chromatogr A ; 1619: 460918, 2020 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-32008819

RESUMO

The anionic phospholipid class of cardiolipins (CL) is increasingly attracting scientific attention in the recent years. CL can be found as a functional component of mitochondrial membranes in almost all living organisms. Changes in the CL composition are favored by oxidative stress. Based on this finding, the investigation of CL and their oxidation products in relation to various disease patterns, including neurodegenerative ones, is moving into the focus of current research. The analysis of this diverse lipid class is still challenging and requires sensitive and selective methods. In this work, we demonstrate an online two-dimensional liquid chromatography (2D-LC) approach by means of a heart-cut setup. In the first dimension, a fast hydrophilic interaction liquid chromatography (HILIC) method was developed for the separation of CL and their oxidation products from other phospholipid classes, but more important from nonpolar lipid classes, such as triacylglycerol and cholesterol. Those classes can negatively affect the electrospray ionization and also the chromatography. For the heart-cut approach, the CL fraction was selectively transferred to a loop using a six-port valve followed by the transfer to a reversed phase (RP) column in second dimension. On the RP column, the transferred CL fraction including the oxidation products were separated according to the hydrophobicity of acyl chain moieties. Matrix effects were significantly reduced compared to the one-dimensional LC-MS method. In addition, the total separation time had not to be prolonged by shifting the equilibration step of the RP column parallel to the separation in first dimension. The heart-cut LC-LC approach was applied to artificially oxidized lipid extracts of bovine heart and yeast by means of Fenton reaction. In summary, 42 species have been identified by high resolution mass spectrometry and database matching. 31 species thereof have been further characterized by MS/MS experiments.


Assuntos
Cardiolipinas/análise , Técnicas de Química Analítica/métodos , Cromatografia Líquida , Espectrometria de Massas em Tandem , Animais , Bovinos , Humanos , Interações Hidrofóbicas e Hidrofílicas , Oxirredução , Fosfolipídeos/análise
5.
J Chromatogr A ; 1619: 460931, 2020 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-32008823

RESUMO

Hydrophilic Interaction Liquid Chromatography (HILIC) is a technique for retaining polar analytes that uses polar stationary phases and acetonitrile-rich mobile phases. While this technique has several advantages over reversed-phase liquid chromatography (RPLC), one main drawback is the reported need for longer column equilibration. The reason for this is not fully understood and is a topic of current investigation. In order to better understand and reduce the equilibration needs, accurate characterization of column equilibration under varying conditions is required. The current method of characterizing HILIC column equilibration produces limited data points per test, or low time resolution, and is highly dependent on the column and probe compounds being used. There is a need for an improved method for characterizing HILIC column equilibration, especially if trends across stationary phases are to be observed. In this work, MISER, or Multiple Injections in a Single Experimental Run, is evaluated as a possible tool for characterizing HILIC column equilibration. MISER improves time resolution by allowing for replicate injections without interruption of data collection, enabling a more thorough evaluation of column equilibration compared to traditional techniques. Experimental results gathered using MISER show that equilibration of a BEH Amide column is notably shorter when equilibrating from acetonitrile to mobile phases containing higher percentages of water. Column equilibration to a 10% aqueous mobile phase was found to be approximately 5-fold faster than equilibration to a 3% aqueous mobile phase.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Líquida , Cromatografia de Fase Reversa/normas , Interações Hidrofóbicas e Hidrofílicas
6.
Nat Protoc ; 15(3): 1013-1040, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32051616

RESUMO

Atmospheric new particle formation (NPF), which is observed in many environments globally, is an important source of boundary-layer aerosol particles and cloud condensation nuclei, which affect both the climate and human health. To better understand the mechanisms behind NPF, chamber experiments can be used to simulate this phenomenon under well-controlled conditions. Recent advancements in instrumentation have made it possible to directly detect the first steps of NPF of molecular clusters (~1-2 nm in diameter) and to calculate quantities such as the formation and growth rates of these clusters. Whereas previous studies reported particle formation rates as the flux of particles across a specified particle diameter or calculated them from measurements of larger particle sizes, this protocol outlines methods to directly quantify particle dynamics for cluster sizes. Here, we describe the instrumentation and analysis methods needed to quantify particle dynamics during NPF of sub-3-nm aerosol particles in chamber experiments. The methods described in this protocol can be used to make results from different chamber experiments comparable. The experimental setup, collection and post-processing of the data, and thus completion of this protocol, take from months up to years, depending on the chamber facility, experimental plan and level of expertise. Use of this protocol requires engineering capabilities and expertise in data analysis.


Assuntos
Técnicas de Química Analítica/métodos , Material Particulado/química , Aerossóis , Tamanho da Partícula
7.
Nat Commun ; 11(1): 838, 2020 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-32047166

RESUMO

Protein-protein interactions are spatially regulated in living cells to realize high reaction efficiency, as seen in naturally existing electron-transfer chains. Nevertheless, arrangement of chemical/biochemical components at the artificial device interfaces does not possess the same level of control. Here we report a tetrahedral DNA framework-enabled bulk enzyme heterojunction (BEH) strategy to program the multi-enzyme catalytic cascade at the interface of electrochemical biosensors. The construction of interpenetrating network of BEH at the millimeter-scale electrode interface brings enzyme pairs within the critical coupling length (CCL) of ~10 nm, which in turn greatly improve the overall catalytic cascade efficiency by ~10-fold. We demonstrate the BEH generality with a range of enzyme pairs for electrochemically detecting clinically relevant molecular targets. As a proof of concept, a BEH-based sarcosine sensor enables single-step detection of the metabolic biomarker of sarcosine with ultrasensitivity, which hold the potential for precision diagnosis of early-stage prostate cancer.


Assuntos
Técnicas Biossensoriais/métodos , DNA/química , Técnicas Eletroquímicas/métodos , Eletrodos , Enzimas Imobilizadas , Técnicas Biossensoriais/instrumentação , Catálise , Técnicas de Química Analítica/métodos , Técnicas Eletroquímicas/instrumentação , Enzimas/química , Desenho de Equipamento , Humanos , Limite de Detecção , Nanopartículas Metálicas , Modelos Teóricos , Nanotecnologia/métodos , Sarcosina
8.
Nat Protoc ; 15(3): 1132-1157, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32005983

RESUMO

It is important to assess the identity and purity of proteins and protein complexes during and after protein purification to ensure that samples are of sufficient quality for further biochemical and structural characterization, as well as for use in consumer products, chemical processes and therapeutics. Native mass spectrometry (nMS) has become an important tool in protein analysis due to its ability to retain non-covalent interactions during measurements, making it possible to obtain protein structural information with high sensitivity and at high speed. Interferences from the presence of non-volatiles are typically alleviated by offline buffer exchange, which is time-consuming and difficult to automate. We provide a protocol for rapid online buffer exchange (OBE) nMS to directly screen structural features of pre-purified proteins, protein complexes or clarified cell lysates. In the liquid chromatography coupled to mass spectrometry (LC-MS) approach described in this protocol, samples in MS-incompatible conditions are injected onto a short size-exclusion chromatography column. Proteins and protein complexes are separated from small molecule non-volatile buffer components using an aqueous, non-denaturing mobile phase. Eluted proteins and protein complexes are detected by the mass spectrometer after electrospray ionization. Mass spectra can inform regarding protein sample purity and oligomerization, and additional tandem mass spectra can help to further obtain information on protein complex subunits. Information obtained by OBE nMS can be used for fast (<5 min) quality control and can further guide protein expression and purification optimization.


Assuntos
Técnicas de Química Analítica/métodos , Espectrometria de Massas/métodos , Proteínas/química , Tampões (Química) , Cromatografia em Gel
9.
Phys Chem Chem Phys ; 22(7): 4240-4251, 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-32043094

RESUMO

In the research and development of new drugs, theoretical and computational studies play an increasingly important role in discriminating native and decoy structures by their binding free energies. Predicting the binding free energy using the molecular mechanics/Poisson-Boltzmann (Generalized Born) surface area (MM/PB(GB)SA) methods to identify the native structure as the lowest-energy conformation is more theoretically rigorous than most scoring functions, but the main challenge of this method is the calculation of the entropic contribution. In this study, we add the entropic contribution to the MM/PBSA and two MM/GBSA (GBHCT and GBOBC1) models using the interaction entropy (IE) method. We then systemically evaluate the performance of these methods in recognizing the native structures by predicting the binding affinities of 176 protein-ligand and protein-protein systems of the Bcl-2 family. By calculating a series of statistical metrics, sensitivity, specificity, accuracy, Matthews correlation coefficient, the G-mean, and the receiver operating characteristic (ROC) curve, we find that the ability to discern the native structure from a decoy ensemble is improved significantly by the modification of the binding free energy using the IE method in both protein-ligand and protein-protein systems. Furthermore, the maximum area under the ROC curve (AUC) was 0.97, which was obtained by the GBHCT model combined with the IE method, indicating that this method has the best performance. The largest improvement occurs in the PB method, with a change in the AUC of 0.32. The modification of the energy is more obvious for protein-protein interactions than for protein-ligand interactions. This study indicates the effectiveness of the IE method in successfully recognizing the native structure, which is critical in rational drug design.


Assuntos
Técnicas de Química Analítica/normas , Modelos Químicos , Proteínas Proto-Oncogênicas c-bcl-2/química , Estrutura Terciária de Proteína
10.
J Chromatogr A ; 1618: 460869, 2020 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-31959456

RESUMO

Prostaglandins (PGs) are vitally important unsaturated fatty acids involved in arachidonic acid (AA) metabolism, participating in numerous pathophysiological processes, especially in maintaining the homeostasis of uterus. Therefore, quantitative analysis of PGs is of great importance for uncovering potential mechanisms of PGs related diseases. However, methods for determining PGs in uterine samples have not been reported. In this study, an ultra high-performance liquid chromatography/mass spectrometry (UHPLC-MS/MS) method was established to quantify PGs in uterine samples, using N,N-Dimethylethylenediamine (DMED) and N,N-Diethylethylenediamine (DEED) as derivatization reagents. The derivatization could be finished at 37 °C for 30 min catalyzed by 1-N,N,N',N'-Tetramethyl-O-(7-azabenzotriazol-1-yl) uronium hexafluorophosphate (HATU). This is a mild condition suitable for most of biological samples. The DMED labeling of PGs could significantly enhance their response compared to those of underived ones. This method exhibited excellent linearity (R2 > 0.997) and precision for the determination of PGs in uterine samples (CV ≤ 12.9%). The extraction recoveries of PGs were ranged from 83.0 to 100% and matrix effects were ranged from 86.3 to 106%, indicating DEED labeled standards could be used as internal standards for PGs quantification. With the proposed method, we successfully quantified PGs in rat uterus. The results showed their levels were significant changed in abnormal uterine bleeding (AUB) rats, suggesting that PGs might be involved in the pathological process of AUB. This established analogous reagents derivatization based UHPLC-MS/MS method could be used as a powerful tool to monitor PGs, providing insights to the precise mechanism of PG action on the endometrium.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Líquida de Alta Pressão , Prostaglandinas/análise , Espectrometria de Massas em Tandem , Útero/química , Animais , Feminino , Indicadores e Reagentes/química , Ratos , Doenças Uterinas/fisiopatologia , Útero/fisiopatologia
11.
J Chromatogr A ; 1618: 460872, 2020 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-31959458

RESUMO

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are high nutritional components. Evidence for unique effects of them is increasing. Further understanding of their independent biological functions urgently needs more efficient separation techniques. Nowadays, most of the commercially available fish oil products are the mixture of eicosapentaenoic acid ethyl ester (EPAEE) and docosahexaenoic acid ethyl ester (DHAEE). It will be convenient to directly separate esterified EPA and DHA without saponification pretreatment. However, it is of great challenge to separate EPAEE and DHAEE because of their extremely fat-soluble nature and the equivalent chain length rule. In this research, the suitability of green guanidinium ionic liquid (IL) in countercurrent chromatography (CCC) solvent system for the separation of them was evaluated for the first time. Compared with imidazolium IL and phosphonium IL, guanidinium IL based non-aqueous biphasic system showed more outstanding separation performance. The separation mechanism was elucidated in depth through quantum mechanical calculations. It was found that guanidinium IL acted a crucial role in the CCC separation, which resulted in difference of partition behavior of EPAEE and DHAEE via different hydrogen-bonding affinity. EPAEE and DHAEE were successfully separated by solvent system (n-heptane/methanol/propylguanidinium chloride ([C3Gun]Cl, 1:1:5%, v/v/m)) with high purity (>95%) in one step, which was not achieved beforehand. Moreover, an easy recycling procedure of IL had also been devised, which significantly reduced waste generated. It opens up a new way for reasonable design water-free two-phase solvent system for efficient separation of very non-polar lipid compounds.


Assuntos
Técnicas de Química Analítica/métodos , Distribuição Contracorrente , Ácidos Docosa-Hexaenoicos/isolamento & purificação , Ácido Eicosapentaenoico/análogos & derivados , Óleos de Peixe/química , Guanidina/química , Líquidos Iônicos/química , Ácido Eicosapentaenoico/isolamento & purificação , Heptanos/química , Metanol/química , Solventes/química
12.
J Chromatogr A ; 1618: 460890, 2020 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-31980261

RESUMO

p53 is a tumour suppressor gene that has been explored for cancer gene therapy as a possible alternative to the common treatments. The use of plasmid DNA (pDNA) to carry the therapeutic gene has been considered, but it is requisite to preserve its supercoiled (sc) structure, for eliciting a more effective gene expression and therapeutic action. The purification of the sc pDNA using amino acids-based affinity chromatography has been successfully applied, exploring different amino acids and supports. From these studies, it stood out the selectivity of arginine for the recognition of sc pDNA. However, some limitation on the binding capacity was found in the arginine-agarose support, and in the case of monoliths, some fouling and clogging can limit sequential runs. By using macroporous support modified with arginine it was expected to take advantage of the selectivity of the ligand combined with the flow properties and binding capacity offered by the support. The arginine-modified macroporous support was characterized by SEM, EDX and FTIR also to verify the correct immobilization of arginine, and then used for pDNA purification. The support showed to be effective on the sc p53-pDNA isolation, and the robustness was also achieved by accomplishing the purification of plasmids with different sizes, only by slightly adjusting the experimental conditions. Regarding the dynamic binding capacity of the arginine-modified macroporous support, it was achieved an improvement of more than 50% in the pDNA binding capacity when compared with their homologous arginine-agarose commercial matrix, suggesting potential economic feasibility in case of scale-up.


Assuntos
Arginina/química , Técnicas de Química Analítica/métodos , Cromatografia de Afinidade , DNA Super-Helicoidal/isolamento & purificação , Plasmídeos/isolamento & purificação , Proteína Supressora de Tumor p53/genética , Sefarose/química
13.
J Chromatogr A ; 1618: 460876, 2020 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-31980262

RESUMO

For this work, a novel air-assisted liquid-liquid microextraction based on solidification of floating deep eutectic solvent (AA-LLME-SFDES), coupled with a high performance liquid chromatography (HPLC) method was developed for the detection of benzophenone and salicylate ultraviolet filters in water samples. Three types of fatty acid-based hydrophobic deep eutectic solvents (DESs) with low viscosity, low-density, and melting point close to room temperature were prepared and employed as extraction solvents. This air-assisted liquid-liquid microextraction was carried out in a glass centrifuge tube. Subsequently, the glass tube was introduced into ice-water bath and held for 3 min, during which the upper DES phase was solidified. The water phase was easily extracted using a syringe equipped with a long needle, and later, the glass tube was removed from ice-water bath. The solidified DES phase was immediately melted at room temperature and used for HPLC analysis. The response surface methodology was employed to optimize some influencing parameters such as the volume of the extraction solvent, the pH value of sample solution, the number of extraction cycles, and the addition of salt. A quadratic model, namely a central composite design, was used to replace the conventional single factor analysis. It was found that under optimal conditions, the limits of determination and quantification were 0.045-0.54 µg L-1 and 0.15-2.0 µg L-1, respectively. The relative standard deviations for inter-day (n = 5) and intra-day (n = 5) precision were ≤ 4.2%, whereas the enrichment factors for the ultraviolet filters were obtained from 41 to 50. Furthermore, this novel method was successfully employed for the detection of benzophenone and salicylate ultraviolet filters from real water samples. The recoveries ranged from 87.5% to 105.8%, whereas the RSDs were lower than 3.6%.


Assuntos
Benzofenonas/análise , Técnicas de Química Analítica/métodos , Cromatografia Líquida de Alta Pressão , Microextração em Fase Líquida , Salicilatos/análise , Solventes/química , Ácidos Graxos/análise , Interações Hidrofóbicas e Hidrofílicas , Limite de Detecção , Raios Ultravioleta , Água/química , Poluentes Químicos da Água/análise
14.
J Chromatogr A ; 1618: 460870, 2020 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-31987526

RESUMO

The present contribution reports on the practical implementation and validation of a new experimental method to determine the radial dispersion (Drad) in packed bed liquid chromatography columns, as well as on the results obtained with it. A first important validation was that the measured Drad-values were independent of the applied relative central flow rate (varied from 25% to 57%). The obtained Drad-values did not vary significantly when changing the concentration of the injected tracer to check potential mass overloading effects (25, 50 or 75 ppm of tracer for the acetophenone measurements; 12.5 and 25 ppm of tracer for the toluene measurements). And yet another important validation step was the observation that the Drad-values clearly converged to the value of Deff for velocities going to zero, as physically and theoretically expected. Plotting the obtained results as a plot of Drad/Dmol versus the reduced velocity ν, a quasi-linear relationship is obtained. The slope of the curve (ß = 0.38 and ß = 0.46 for toluene and acetophenone, respectively) is significantly larger than the value that is most frequently cited in engineering literature. However, the obtained ß-values and Drad/Dmol-values still fall within the broad range of ß- and Drad/Dmol-values cited in literature.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Líquida , Acetofenonas/química , Tolueno/química
15.
Phytomedicine ; 67: 153165, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31954259

RESUMO

BACKGROUND: Quality control of traditional Chinese medicine (TCM) is the basis of clinical efficacy. Due to the complexity of TCM, it is difficult to unify the quality control, and hinders the further implementation of the quality standardization of TCM. As a new concept, quality-marker (Q-marker) plays a powerful role in promoting the standardization of quality control system of TCM. HYPOTHESIS/PURPOSE: The present review aims to provide reference and scientific basis for further development of Q-marker and assist standardization of quality control of TCM. METHODS: Extensive search of various documents and electronic databases such as Pubmed, Royal Society of Chemistry, Science Direct, Springer, Web of Science, and Wiley, etc., were used to search scientific contributions. Other online academic libraries, e.g. Google Scholars, Scopus and national pharmacology literature were also been employed to learn more relevant information about Q-marker. RESULTS: Q-markers play vital role in promoting the standardization of quality control of TCM. The factors that affect the quality of TCM, the advantages and disadvantages of the analytical techniques commonly used in Q-marker research were reviewed, as well as the systematic research strategies, which were verified by practices. CONCLUSION: The proposal of Q-marker not only provided a new perspective to break through the bottleneck of current quality control, but also can be used in the evaluation of pharmacological efficiency, therapeutic discovery, toxicology, etc. In addition, the Q-marker analysis strategies summarized in this paper is helpful to standardize the quality control of TCM and promote the internationalization of TCM.


Assuntos
Biomarcadores/análise , Técnicas de Química Analítica/métodos , Medicamentos de Ervas Chinesas/análise , Medicamentos de Ervas Chinesas/química , Medicina Tradicional Chinesa/normas , Controle de Qualidade , Reprodutibilidade dos Testes
16.
J Chromatogr A ; 1616: 460774, 2020 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-31937408

RESUMO

Bananas and plantains (Musa spp.) are used as nutritious foods, and at the same time, are a source of phytoconstituents for the pharmaceutical industry. As biological activities of especially the pulp and peel of Musa spp. have been documented, this study investigated the variation in the secondary metabolite profiles of the leaves from field, in vitro-grown and acclimatized accessions. The genetic fidelity of the diverse accessions was assessed using diversity array technology sequencing. It showed that the in vitro-grown accessions were true-to-type with the field samples. The antioxidant and anticholinesterase activities of the samples from different culture systems (field and in vitro) were evaluated by UV-spectrophotometry and compared to high-performance thin-layer chromatography-effect-directed analysis (HPTLC-EDA). The latter was applied for the first time for effect-directed profiling of the polar and medium polar sample components via different biochemical and biological assays. Compound zones showed acetyl-/butylrylcholinesterase inhibition (zones 1-4), α-/ß-glucosidase inhibition (zones 1 and 2) as well as antioxidative (zones 1-3) and antimicrobial (zone 4) activities. Structures were preliminary assigned by HPTLC-HRMS. The HPTLC was effective for bioactivity-guided characterization of the bioactive constituents in Musa spp. accessions. Accumulation of useful metabolites, especially compounds with antioxidant and anticholinesterase properties, was higher in samples from in vitro system. This validated the use of plant tissue culturing as an alternative method for large scale production of plant material and supply of bioactive constituents.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia em Camada Delgada , Espectrometria de Massas , Musa/química , Anti-Infecciosos/isolamento & purificação , Antioxidantes/química , Antioxidantes/isolamento & purificação , Técnicas de Química Analítica/instrumentação , Inibidores da Colinesterase/isolamento & purificação , Inibidores de Glicosídeo Hidrolases/isolamento & purificação , Musa/crescimento & desenvolvimento
17.
J Agric Food Chem ; 68(7): 1910-1934, 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-31999115

RESUMO

Setting regulatory limits for arsenic in food is complicated, owing to the enormous diversity of arsenic metabolism in humans, lack of knowledge about the toxicity of these chemicals, and lack of accurate arsenic speciation data on foodstuffs. Identification and quantification of the toxic arsenic compounds are imperative to understanding the risk associated with exposure to arsenic from dietary intake, which, in turn, underscores the need for speciation analysis of the food. Arsenic speciation in seafood is challenging, owing to its existence in myriads of chemical forms and oxidation states. Interconversions occurring between chemical forms, matrix complexity, lack of standards and certified reference materials, and lack of widely accepted measurement protocols present additional challenges. This review covers the current analytical techniques for diverse arsenic species. The requirement for high-quality arsenic speciation data that is essential for establishing legislation and setting regulatory limits for arsenic in food is explored.


Assuntos
Arsenicais/química , Técnicas de Química Analítica/métodos , Análise de Alimentos/métodos , Contaminação de Alimentos/análise , Alimentos Marinhos/análise , Animais , Arsenicais/isolamento & purificação
18.
J Chromatogr A ; 1614: 460728, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31785896

RESUMO

Triazine rings-containing porous aromatic framework (PAF-56p) was synthesized through a Friedel-Crafts reaction and investigated as a coating for the stir bar sorptive extraction (SBSE) of interest triazines. The triazine rings and conjugated groups in PAF-56p could interact with triazine rings-containing herbicides by hydrophobic and π-π interactions. The PAF-56p coated stir bar showed superior extraction performance over commercial PDMS and EG coated stir bar in terms of extraction efficiency and dynamics towards six triazine herbicides with different polarity. Based on it, a method by combining PAF-56p-SBSE with high performance liquid chromatography (HPLC)-diode array detector (DAD) was established for the analysis of six target triazine herbicides, including simazine, atrazine, ametryn, prometon, prometryne and prebane. The affecting factors of SBSE were investigated by single-factor test. Under the optimized conditions, the limits of detection of the proposed method were ranged from 0.037 to 0.089 µg/L with the linear range within 0.1-200 µg/L for six triazine herbicides. High enrichment factors (EFs) of 61.8-89.5-fold (theoretical EF is 100-fold) were achieved. The developed PAF-56p-SBSE-HPLC-DAD method was successfully applied for trace triazine herbicides analysis in maize and maize leaf samples, with recoveries in the range of 86.5-115% and 85.1-114% for spiked maize and maize leaf samples, respectively.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Líquida de Alta Pressão , Herbicidas/análise , Triazinas/análise , Zea mays/química , Técnicas de Química Analítica/instrumentação , Herbicidas/isolamento & purificação , Limite de Detecção , Porosidade , Reprodutibilidade dos Testes , Triazinas/isolamento & purificação
19.
J Agric Food Chem ; 68(10): 2917-2926, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-31013083

RESUMO

An improved analytical depolymerization method for characterizing condensed tannins was developed with menthofuran (3,6-dimethyl-4,5,6,7-tetrahydro-1-benzofuran) as the nucleophilic trapping reagent. Herein, menthofuran was compared with routinely used nucleophiles, phloroglucinol and 2-mercaptoethanol. At 30 °C and in the presence of 0.1 M HCl, menthofuran displayed the outstanding ability to enable the fast and full depolymerization of procyanidin B2 using only a 1:1 molar ratio of both reactants. Under the same conditions, phloroglucinol and 2-mercaptoethanol led to a reaction equilibrium with significantly lower conversion yields. Application to commercial tannin extracts showed that a menthofuran-to-extract weight ratio of 1 gave the same yields of procyanidin constitutive units as 10-fold higher molecular equivalent phloroglucinol and 100-fold 2-mercaptoethanol. Finally, guidelines for implementing the menthofuran depolymerization method are proposed to assess the tannin content and composition of extracts as well as of plant materials without prior extraction.


Assuntos
Técnicas de Química Analítica/métodos , Extratos Vegetais/química , Taninos/química , Biflavonoides/química , Catequina/química , Monoterpenos/química , Polimerização , Proantocianidinas/química
20.
J Chromatogr A ; 1613: 460676, 2020 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-31727351

RESUMO

Due to the trace levels of polycyclic aromatic hydrocarbons (PAHs) in soil and the complexity of soil matrices, effective sample pretreatment methods are of great significance to obtain accurate analytical results. In this paper, polydopamine (PDA) encapsulated Fe3O4 particles were used as seeds for in situ polymerization of divinylbenzene (DVB) to derive magnetic hybrid material Fe3O4@PDA@PDVB. Coupled with pressurized liquid extraction, Fe3O4@PDA@PDVB was investigated as a selective adsorbent for the extraction and cleanup of PAHs in soil. The prepared magnetic material was characterized and demonstrated to possess strong hydrophobicity and superparamagnetism. Under optimal conditions, Fe3O4@PDA@PDVB can effectively extract 15 PAHs from a 30% methanol solution within 2 min, and it is more selective for PAHs than for n-alkane in soil extracts. The matrix effect significantly decreased after extraction by the prepared material, which showed superiority to a silica gel column method (EPA 3630C Method). The developed method was linear (5-1000 ng g-1) with coefficient of determination (R2) ranging from 0.9986-0.9998, and the limits of detection were 0.13-0.54 ng g-1. Additionally, repetitive experiments indicated that the prepared material was reproducible and reusable with relative standard deviations below 8.4% and 8.6%, respectively. Finally, the new method was successfully employed to determine the concentrations of PAHs in genuine soil and standard reference material, and the results were comparable to those of widely utilized EPA methodology.


Assuntos
Técnicas de Química Analítica/métodos , Indóis/síntese química , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação , Polímeros/síntese química , Poluentes do Solo/isolamento & purificação , Solo/química , Compostos de Vinila/química , Interações Hidrofóbicas e Hidrofílicas , Limite de Detecção , Extração Líquido-Líquido , Fenômenos Magnéticos , Hidrocarbonetos Policíclicos Aromáticos/análise , Polimerização , Poluentes do Solo/análise
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA