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1.
Phys Chem Chem Phys ; 21(32): 17893-17900, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31380529

RESUMO

The dispersion interaction was reported to play a critical role in the stabilization of model dipeptide Z-Arg-OH, even greater than the conventional hydrogen bond (HB), which is opposite to the traditional opinion. Here the conformation of Z-Arg-OH has been systematically searched by the effective fragment based step-by-step strategy. All the newly-found low-energy conformers determined at the advanced DSD-PBEP86-D3(BJ)/aug-cc-pVTZ level are clearly in the stretched form with strong conventional HBs, rather than the reported folded structures with emphasis on the dispersion interactions. The simulated IR spectra of the stretched conformers fit better than those of the folded ones compared with the previous experimental observations. Near-edge X-ray absorption fine-structure (NEXAFS) spectra and X-ray photoelectron spectra (XPS) at C, N and O K-edges have also been simulated to unambiguously identify different isomers. This work thus provides valuable insight into the competitions between the conventional HB and the dispersion interactions and demonstrates that the conventional hydrogen bonding is still more important for such small peptides.


Assuntos
Arginina/análogos & derivados , Arginina/química , Dipeptídeos/química , Modelos Moleculares , Ligações de Hidrogênio , Isomerismo , Fenômenos Físicos , Conformação Proteica , Estabilidade Proteica , Solventes/química , Termodinâmica
2.
Pharm Res ; 36(10): 142, 2019 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-31376020

RESUMO

BACKGROUND: With the recent approval of the first small interfering RNA (siRNA) therapeutic formulated as nanoparticles, there is increased incentive for establishing the factors of importance for the design of stable solid dosage forms of such complex nanomedicines. METHODS: The aims of this study were: (i) to identify factors of importance for the design of spray-dried siRNA-loaded lipidoid-poly(DL-lactic-co-glycolic acid) hybrid nanoparticles (LPNs), and (ii) to evaluate their influence on the resulting powders by using a quality-by-design approach. Critical formulation and process parameters were linked to critical quality attributes (CQAs) using design of experiments, and an optimal operating space (OOS) was identified. RESULTS: A series of CQAs were identified based on the quality target product profile. The loading (ratio of LPNs to the total solid content) and the feedstock concentration were determined as critical parameters, which were optimized systematically. Mannitol was chosen as stabilizing excipient due to the low water content of the resulting powders. The loading negatively affected the colloidal stability of the LPNs, whereas feedstock concentration correlated positively with the powder particle size. The optimal mannitol-based solid formulation, defined from the OOS, displayed a loading of 5% (w/w), mass median aerodynamic diameter of 3.3 ± 0.2 µm, yield of 60.6 ± 6.6%, and a size ratio of 1.15 ± 0.03. Dispersed micro-embedded LPNs had preserved physicochemical characteristics as well as in vitro siRNA release profile and gene silencing, as compared to non-spray-dried LPNs. CONCLUSION: The optimal solid dosage forms represent robust formulations suitable for higher scale-up manufacturing.


Assuntos
Dessecação/métodos , Lipídeos/química , Nanopartículas/química , Copolímero de Ácido Poliláctico e Ácido Poliglicólico/química , RNA Interferente Pequeno/química , Administração por Inalação , Animais , Composição de Medicamentos , Excipientes/química , Inativação Gênica , Técnicas de Transferência de Genes , Manitol/química , Camundongos , Nanomedicina , Tamanho da Partícula , Pós , Células RAW 264.7 , RNA Interferente Pequeno/administração & dosagem , Solubilidade , Solventes/química
3.
Phys Chem Chem Phys ; 21(35): 19209-19215, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31441478

RESUMO

Pure-shift NMR experiments provide highly resolved spectra, which could be perfect for precise monitoring of chemical shift variations under different conditions, such as temperature or concentration. However, their sensitivity is relatively low and signal sampling is time-consuming, which leads to long experimental times, making such serial acquisition problematic. In this paper we present a new method of NMR spectroscopy which improves the speed and sensitivity of serial pseudo-two-dimensional pure-shift experiments. The example of variable-temperature study of atorvastatin reveals the potential of the method in verifying the theoretical predictions of solvent-dependent spectral effects.


Assuntos
Atorvastatina/química , Técnicas de Química Analítica/métodos , Espectroscopia de Ressonância Magnética , Solventes/química , Temperatura Ambiente , Técnicas de Química Analítica/normas
4.
Phys Chem Chem Phys ; 21(35): 19469-19479, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31461098

RESUMO

Using all-atom molecular dynamics simulations of aqueous solutions of the globular protein SNase, the dynamic behavior of water molecules and cosolvents (trimethylamine-N-oxide (TMAO) and urea) in the hydration shell of the protein was studied for different solvent compositions. TMAO is a potent protein-stabilizing osmolyte, whereas urea is known to destabilize proteins. For molecules that are initially located in successive narrow layers at a given distance from the protein, the mean displacements and the distribution of displacements for short time intervals are calculated. For molecules that are initially located in solvation shells of a given thickness around the protein, the characteristic residence times in these shells are determined to characterize the dynamic behavior of the solvent molecules as a function of the distance to the protein. A combined consideration of these characteristics allows to reveal additional features of the dynamics of the cosolvents. It is shown that TMAO molecules leave the nearest vicinity of the protein faster than urea molecules, despite the fact that the mobility of TMAO molecules, measured by their mean displacements, is lower than that of urea. Moreover, we show that the rate of release of TMAO molecules from the hydration shell is lower in ternary (TMAO + urea + H2O) solvent mixtures than in the binary ones. This is consistent with a recent observation that the fraction of TMAO near the protein decreases in the presence of urea. From the analysis of the decay of the number of particles initially located in the region of the first peak of the distribution function of solvent molecules around the protein, we estimated that about 20 water molecules and 6-7 urea molecules stay near the protein for more than 1000 ps.


Assuntos
Endodesoxirribonucleases/química , Endodesoxirribonucleases/metabolismo , Metilaminas/química , Simulação de Dinâmica Molecular , Ureia/química , Água/química , Estabilidade Proteica , Solventes/química
5.
Pharm Res ; 36(10): 138, 2019 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-31350675

RESUMO

PURPOSE: This study aimed to incorporate ondansetron hydrochloride (ODS), a water-soluble drug into nanostructured lipid carriers (NLCs) to improve the pharmacokinetic properties of the drug. METHODS: NLCs were produced by solvent injection method. Various parameters of formulation and process were assessed to enhance the drug incorporation into NLCs. Physicochemical analyses, in vitro drug release, and pharmacokinetic studies were performed. RESULTS: Entrapment efficiency (EE) of ODS was considerably improved (>90%) by increasing pH of the aqueous phase. The use of an appropriate level of liquid lipid resulted in small, monodispersed NLCs with the enhanced EE and drug loading (DL). The optimized NLCs formulation exhibited particle size of 185.2 ± 1.9 nm, polydispersity index of 0.214 ± 0.006, EE of 93.2 ± 0.5%, and DL of 10.43 ± 0.05% as well as an in vitro sustained-release profile of ODS. Differential scanning calorimetry and X-ray powder diffraction suggested the amorphous state of ODS in the NLCs. The pharmacokinetic study in rats exhibited the sustained-release characteristic of the optimized ODS-loaded NLCs following subcutaneous administration with an extended Tmax and mean residence time as well as the enhanced systemic exposure compared to the ODS solution. CONCLUSIONS: The ODS-loaded NLCs appear potential for prolongation of drug action and reduction in dosing frequency.


Assuntos
Antieméticos/farmacocinética , Lipídeos/química , Nanocápsulas/química , Ondansetron/farmacocinética , Solventes/química , Administração Cutânea , Animais , Antieméticos/administração & dosagem , Liberação Controlada de Fármacos , Estabilidade de Medicamentos , Concentração de Íons de Hidrogênio , Masculino , Ondansetron/administração & dosagem , Tamanho da Partícula , Ratos Sprague-Dawley , Resultado do Tratamento
6.
Anticancer Res ; 39(7): 3697-3709, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31262896

RESUMO

BACKGROUND/AIM: Cervical cancer is considered poorly chemo-sensitive in women and its treatment remains unsatisfactory. Cyperus rotundus is used in Chinese medicine as a therapeutic agent for women's disease. The effects and molecular mechanisms of the ethanol extraction of C. rotundus (CRE) on cervical cancer remain unclear. We aimed to explore the mechanisms and genetic influence of CRE on cervical cancer. MATERIALS AND METHODS: HeLa, human cervical cancer cells were treated with various doses of CRE and changes in cell morphology and cell viability were assessed using microscopy and flow cytometry. Finally, we performed a microarray analysis to scan related genes. RESULTS: The treatment of CRE on HeLa cells caused morphological changes and induced chromatin condensation. DNA microarray analysis showed that CRE led to up-regulation of 449 genes and down-regulation of 484 genes, which were classified in several interaction pathways. CONCLUSION: CRE changed HeLa cell morphology and induced gene expression which associated with apoptosis and cell-cycle arrest. These results provide important information at the transcription level for targeting treatments of human cervical cancer.


Assuntos
Antineoplásicos Fitogênicos/farmacologia , Apoptose/efeitos dos fármacos , Cyperus , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Extratos Vegetais/farmacologia , Neoplasias do Colo do Útero/genética , Apoptose/genética , Ciclo Celular/efeitos dos fármacos , Etanol/química , Feminino , Células HeLa , Humanos , Solventes/química , Neoplasias do Colo do Útero/tratamento farmacológico
7.
Food Chem ; 299: 125065, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31284246

RESUMO

Determination of lead at trace levels was achieved by slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS) after the preconcentration with deep eutectic solvent-based liquid phase microextraction (DES-LPME). A green solvent was used to extract lead from the aqueous solution. Parameters affecting the extraction efficiency and determination were optimized in the aim to lower the detection limit. Under the optimum experimental and instrumental conditions, the proposed method exhibited a linear range between 50 and 1000 µg L-1, and the limits of detection and quantitation (LOD and LOQ) were found to be 8.7 and 29.0 µg L-1, respectively. The detection power was improved by 48 times using DES-LPME-SQT-FAAS method with respect to conventional FAAS system. Recovery studies were carried out in raw milk samples to check the accuracy and the applicability of the developed method and the percent recoveries obtained were between 102.5 and 103.2% for the spiked raw milk samples.


Assuntos
Análise de Alimentos/métodos , Contaminação de Alimentos/análise , Chumbo/análise , Microextração em Fase Líquida , Leite/química , Solventes/química , Espectrofotometria Atômica , Animais , Chumbo/isolamento & purificação , Limite de Detecção , Quartzo , Água/química
8.
Molecules ; 24(13)2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31288489

RESUMO

Black mulberry is a widely acknowledged ancient traditional medicine. Its extract and constituents have been reported to exert various bioactivities including antimicrobial, hypotensive, analgesic etc. effects. While black mulberry preparations are also used as antispasmodic agents in folk medicine, no related studies are available on its isolated constituents. Through an extensive chromatographic purification, seven phenolic compounds were isolated from the methanol extract of Morus nigra root bark, including morusin (1), kuwanon U (2), kuwanon E (3), moracin P (4), moracin O (5), albanol A (6), and albanol B (7). A complete NMR signal assignment of moracin P and O was achieved, and related literature errors confusing the identity of moracin derivatives are hereby clarified. Compounds 2, 5 and 7 were identified as strong antispasmodic agents on isolated rat ileum and tracheal smooth muscles, while compound 3, a methoxy derivative of 2, was inactive. Moracin O (5) inhibited the ileal and tracheal smooth muscle contractions with Emax values of 85% and 302 mg, respectively. Those actions were superior as compared with papaverine. Our findings demonstrate that prenylated arylbenzofurans, geranylated flavonoids and Diels-Alder adducts from Morus nigra are valuable antispasmodic agents. Compounds 2, 5 and 7 are suggested as marker compounds for quality control of antispasmodic mulberry preparations. Moracin O (5) is a new lead compound for related drug development initiatives.


Assuntos
Morus/química , Parassimpatolíticos/química , Fenóis/química , Casca de Planta/química , Extratos Vegetais/química , Raízes de Plantas/química , Benzofuranos/metabolismo , Avaliação Pré-Clínica de Medicamentos , Flavanonas/metabolismo , Metanol/química , Parassimpatolíticos/farmacologia , Prenilação , Resorcinóis/metabolismo , Solventes/química , Relação Estrutura-Atividade
9.
Food Chem ; 298: 125067, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260989

RESUMO

An ultra-high performance supercritical fluid chromatography-photodiode array detection-mass spectrometry (UHPSFC-MS) method for quality control of Piper longum L. has been developed and optimized. Hexane/isopropanol (70/30, v/v) was determined as the final injection solvent and methanol as the organic modifier. A design-of-experimental (DoE) approach was used to optimize column temperature, back-pressure and the gradient slope simultaneously using Trefoil CEL1 column. The back-pressure, temperature, flow rate were set at 130 bar, 32.5 °C and 1.0 mL/min, respectively. Positive electrospray ionization was used in the single ion monitoring mode. The 12 analytes were analyzed within 8 min using the optimized conditions. The linearities of the standard calibrations were satisfactory with coefficients of determination (R2) > 0.995. The recovery measured varied from 96.34% to 105.00% with relative standard deviation (RSD) ≤ 4.68%. The method was sensitive, reliable and effective, and successfully applied to simultaneous determination of 12 compounds in 28 batches of P. longum.


Assuntos
Alcaloides/química , Cromatografia com Fluido Supercrítico/métodos , Piper/química , Alcaloides/isolamento & purificação , Benzodioxóis/química , Benzodioxóis/isolamento & purificação , Cromatografia Líquida de Alta Pressão , Cromatografia com Fluido Supercrítico/normas , Frutas/química , Frutas/metabolismo , Limite de Detecção , Espectrometria de Massas , Metanol/química , Piper/metabolismo , Piperidinas/química , Piperidinas/isolamento & purificação , Alcamidas Poli-Insaturadas/química , Alcamidas Poli-Insaturadas/isolamento & purificação , Análise de Componente Principal , Controle de Qualidade , Solventes/química , Temperatura Ambiente
10.
Phytochemistry ; 166: 112075, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31351332

RESUMO

Isoflavonoids are one of the most important groups of naturally occurring antioxidants. Their structural features are important for evaluating their antioxidative activity. In this work, density functional theory (DFT) methods were applied to investigate the influence of the C2=C3 double bond on the antioxidative activity of isoflavonoids based on three currently accepted radical scavenging mechanisms from the viewpoint of thermodynamics. The C2=C3 double bond can make the compounds more flat, which would extend the conjugated system in the molecule and make the isoflavonoids higher antioxidant activity. The C2=C3 double bond would not alter the strongest antioxidative hydroxyl group of the isoflavonoids. In the gas, benzene and CHCl3 phases, the C2=C3 double bond will enhance the antioxidative activity of isoflavonoids by lowering the bond dissociation enthalpies of the hydroxyl groups in the B ring that are the strongest antioxidative sites for the hydrogen atom transfer (HAT) mechanism. In polar phases, a similar result is obtained by weakening the proton affinity of 7-OH that is the strongest antioxidative hydroxyl group in the sequential proton loss electron transfer (SPLET), mechanism. Thus, the C2=C3 double bond will enhance the antioxidative activity of isoflavonoids irrespective of the studied phases.


Assuntos
Antioxidantes/química , Carbono/química , Teoria da Densidade Funcional , Flavonoides/química , Solventes/química , Termodinâmica
11.
J Chromatogr A ; 1602: 135-141, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31255246

RESUMO

In this study, we investigated the potential of mixtures of tetrahydrofuran (THF) and water as tunable solvents for the microextraction of contaminants in solid and in liquid matrices. These two miscible solvents have very different dielectric constant and Hildebrand solubility parameters, so that tunable mixtures spanning a wide range of dispersion and hydrogen bonding forces could be easily prepared by simply changing their composition. In this way, rapid and more efficient extraction methods can be developed. A liquid-liquid and a solid-liquid microextraction method for the determination of bisphenol A (BPA) in urine and ochratoxin A (OTA) in cereal baby food were developed as a proof of concept. Both, the chemical composition and the relative solvency of the THF-water mixtures, expressed as Teas solubility parameters, were studied in order to gain some insights into the chemical interactions governing analyte extraction. For urine, the salting-out extraction with THF:water and NaCl was evaluated, a process which is still scarcely investigated for analytical purposes. These methods featured good recoveries (above 95%), satisfactory standard deviation (5-6%) and good sensitivity (detection limits of 0.l µg L-1 for BPA and of 0.l ng g-1 for OTA) with the advantages of simplicity, rapidity and low consumption of reagents. Recoveries for other compounds and matrices (bisphenols ad phosphorus flame retardants in dust and in tap water, dyes in tap water and OTA in powder milk) were also assessed to prove the wide potential of these tunable solvent mixtures.


Assuntos
Furanos/química , Solventes/química , Poluentes Químicos da Água/isolamento & purificação , Água/química , Compostos Benzidrílicos/urina , Criança , Feminino , Humanos , Alimentos Infantis/análise , Limite de Detecção , Microextração em Fase Líquida , Ocratoxinas/isolamento & purificação , Transição de Fase , Fenóis/urina , Solubilidade
12.
J Chromatogr A ; 1602: 350-358, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31257039

RESUMO

This work describes development of a quick and accurate online solid-phase extraction (SPE) liquid chromatography tandem mass spectrometry method for simultaneous determination of 87 emerging organic compounds, including 22 per- and polyfluoroalkyl substances, 58 pharmaceuticals and personal care products, and 7 organophosphorus flame retardants, in diverse water matrices. Considering the wide range of physicochemical properties for the target contaminants, efficient analysis in one injection is challenging. Thus, key extraction and analytical parameters, including online SPE sorbent, mobile phase additives, sample pH, loading solvent pH and composition, injection volume, and valve-switching time, were systematically optimized. The final conditions, namely a polymeric reversed-phase column with alkaline samples and an acidic loading solvent, provided satisfactory results for all target analytes compared to conventional methods that employ acidic samples for multi-residue analysis. The method detection limits (MDLs) ranged from 0.16 to 5.13 ng L-1 with 85% of MDLs lower than 2 ng L-1 for sample volumes of just 1.8 mL. The method also demonstrated satisfactory accuracy with 82% of analytes exhibiting 70-130% recovery. Importantly, only 30 min was required per sample. The optimized method was successfully applied to investigate the removal efficiency of emerging contaminants in a drinking water treatment plant and to analyze the environmental occurrence of target analytes. The method is sensitive, reliable, labor-saving, and cost effective, and therefore has the potential to advance large-scale environmental monitoring programs.


Assuntos
Cromatografia Líquida/métodos , Retardadores de Chama/análise , Fluorcarbonetos/análise , Produtos Domésticos/análise , Preparações Farmacêuticas/análise , Extração em Fase Sólida/métodos , Espectrometria de Massas em Tandem/métodos , Poluentes Químicos da Água/análise , Automação , Monitoramento Ambiental , Concentração de Íons de Hidrogênio , Internet , Limite de Detecção , Solventes/química , Fatores de Tempo
13.
Chem Commun (Camb) ; 55(49): 7085-7088, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31150032

RESUMO

A luminescent biosensor has been developed for matrix metalloproteinase 9 (MMP-9) assays based on the selective interaction between an Ir(iii) solvent complex and a histidine-rich peptide, which avoids the complicated double labeling of substrate polypeptides commonly-used in FRET MMP detections and provides a promising strategy for MMP detection in clinical applications.


Assuntos
Técnicas Biossensoriais , Complexos de Coordenação/química , Histidina/química , Irídio/química , Metaloproteinase 9 da Matriz/análise , Peptídeos/química , Complexos de Coordenação/metabolismo , Transferência Ressonante de Energia de Fluorescência , Histidina/metabolismo , Humanos , Metaloproteinase 9 da Matriz/metabolismo , Peptídeos/metabolismo , Solventes/química
14.
J Chromatogr A ; 1599: 35-45, 2019 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-31151693

RESUMO

What is known in the literature as the fundamental equation for gradient elution (FEGE) was previously proven only for conventional gradient LC - uniform (the same at any distance from the inlet) static (fixed in time) solvent velocity (um) in a column of uniform and static internal structure, cross-section and thermodynamic properties. A published alternative to the FEGE - the general migration equation - is valid for any column-based linear chromatography (GC, LC, SFC etc.). It allows one to theoretically or numerically predict a solute migration time to any location along the column. Starting from that general equation, several migration equations in gradient LC under different operational conditions including non-uniform non-static um, Neue-Kuss retention model and others have been developed in this report. It has been shown that the conditions of validity of the FEGE can be expanded to include non-uniform um. On the other hand, the FEGE is not valid for other unconventional operations of LC including gradient LC with dynamic (changing in time) um. This implies that FEGE cannot be applied to, e.g., gradient LC operating at constant pressure where, due to the change in solvent composition, the solvent viscosity changes causing the change in um with time. Applications of newly developed equations to other unconventional operations of gradient LC were also considered. Several new time parameters of the mobile phase flow were identified, interpreted, and evaluated.


Assuntos
Cromatografia Líquida , Modelos Químicos , Solventes/química , Termodinâmica
15.
J Chem Phys ; 150(21): 215103, 2019 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-31176332

RESUMO

The denaturing or stabilizing influence of a cosolvent on a protein structure is governed by a fine balance of the energetics of the excluded volume effect and the energetics of direct protein-cosolvent interactions. We have previously characterized the energetic contributions of excluded volume and direct interactions with urea for proteins and protein groups. In this work, we examine the molecular origins underlying the relatively weak temperature and urea dependences of the m-values of globular proteins. Our combined experimental and computational results collectively paint a picture in which the relative independence of protein m-values of urea concentration originates from fortuitous compensatory effects of a progressive increase in the solvent-accessible surface area of the unfolded state and a slightly higher urea binding constant of the unfolded state relative to the folded state. Other denaturing cosolvents which lack such a compensation make poor candidates for linear extrapolation model-based protein stability determination studies. The observed diminution in m-values with increasing temperature reflects, in addition to the aforementioned compensatory effects, a decrease in protein-urea binding constants with temperature in accordance with the negative sign of the binding enthalpy.


Assuntos
Proteínas/química , Temperatura Ambiente , Ureia/química , Desdobramento de Proteína , Solventes/química , Termodinâmica
16.
Phys Chem Chem Phys ; 21(25): 13826-13834, 2019 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-31211310

RESUMO

Free energy perturbation (FEP) approaches with stratification have seen widespread and increasing use in computational studies of biologically relevant molecules. However, when the molecular systems are characterized by a complex conformational free energy landscape, the assessment of convergence remains a concern for many practitioners. The sampling problem in FEP has been authoritatively addressed in a recent perspective paper [D. Mobley, J. Comput.-Aided Mol. Des., 2012, 26, 93], incisively entitled "Let's get honest about sampling". Here, I return to the issue of sampling in the determination of the octanol-water partition coefficient for a synthetic precursor of kinase inhibitors that has been included in the recent extension of the SAMPL6 blind challenge of log P coefficients. I will show that even for this simple compound, whose conformational space is essentially dictated by two sp3 rotable bonds connecting rigid planar units, canonical sampling using standard techniques can be surprisingly hard to achieve. I will also show how the conformational sampling problem can be effectively bypassed using unidirectional and bidirectional nonequilibrium work methods, reliably recovering the solvation energy with minimal methodological uncertainty.


Assuntos
Modelos Moleculares , Inibidores de Proteínas Quinases/química , Quinazolinas/química , Solventes/química , Conformação Molecular , Octanóis/química , Termodinâmica , Incerteza , Água/química
17.
Anal Bioanal Chem ; 411(16): 3631-3640, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31175397

RESUMO

In this research, electrospun polycaprolactam nanofibers were collected on a fine stainless steel mesh sheet without a binder, and a layer of conductive polyaniline was chemically deposited on the nanofibers. The polyaniline immobilized on the polycaprolactam nanofibers provided high electrical conductivity, acceptable mechanical stability, and a large surface area. This assembly was then used as a working electrode in electrochemically controlled solid-phase microextraction (EC-SPME), a fast and environmentally friendly method. The polymer layers were characterized by SEM and FTIR techniques. Significant factors affecting the EC-SPME efficiency were investigated, including the desorption conditions, the sorbent used, the pH of the sample solution, the extraction voltage, the extraction time, and the ionic strength. Under the optimum conditions, the limits of detection and quantification for the target analytes were 0.9-1.8 µg L-1 and 3.0-6.1 µg L-1, respectively. The linear dynamic range was 5-2000 µg L-1, with R2 > 0.993. The method was coupled with HPLC analysis and applied to the determination of angiotensin ΙΙ receptor antagonists (ARA-ΙΙs) in human plasma, and relative recoveries of 91.1-104.3% with RSDs of ≤8.3% were obtained.


Assuntos
Antagonistas de Receptores de Angiotensina/sangue , Compostos de Anilina/química , Caprolactama/química , Cromatografia Líquida de Alta Pressão/métodos , Técnicas Eletroquímicas/métodos , Nanofibras/química , Microextração em Fase Sólida/métodos , Adsorção , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção , Microscopia Eletrônica de Varredura , Concentração Osmolar , Reprodutibilidade dos Testes , Solventes/química , Espectroscopia de Infravermelho com Transformada de Fourier
18.
ChemSusChem ; 12(15): 3481-3490, 2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31211476

RESUMO

Chitin is not only the most abundant nitrogen-containing biopolymer on the planet, but also a renewable feedstock that is often treated as a waste. Current chemical methods to break down chitin typically employ harsh conditions, large volumes of solvent, and generate a mixture of products. Although enzymatic methods have been reported, they require a harsh chemical pretreatment of the chitinous substrate and rely on dilute solution conditions that are remote from the natural environment of microbial chitinase enzymes, which typically consists of surfaces exposed to air and moisture. We report an innovative and efficient mechanoenzymatic method to hydrolyze chitin to the N-acetylglucosamine monomer by using chitinases under the recently developed reactive aging (RAging) methodology, based on repeating cycles of brief ball-milling followed by aging, in the absence of bulk solvent. Our results demonstrate that the activity of chitinases increases several times by switching from traditional solution-based conditions of enzymatic catalysis to solventless RAging, which operates on moist solid substrates. Importantly, RAging is also highly efficient for the production of N-acetylglucosamine directly from shrimp and crab shell biomass without any other processing except for a gentle wash with aqueous acetic acid.


Assuntos
Acetilglucosamina/química , Quitina/química , Quitinases/química , Animais , Aspergillus niger/enzimologia , Biomassa , Crustáceos , Hidrólise , Solventes/química
19.
Anal Bioanal Chem ; 411(21): 5455-5464, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31227847

RESUMO

The preparation and fractionation of oligomeric proanthocyanidins (OPCs) are particularly important for the application of tannins in the biomedical field. By use of two different methods-gel filtration chromatography (GFC) with Sephadex LH-20 and progressive solvent precipitation-the OPCs were prepared and fractionated from mangosteen pericarp. The fractions were compared by reversed-phase and normal-phase high-performance liquid chromatography-electrospray ionization mass spectrometry and gel permeation chromatography. GFC directly purified oligomers (monomer to pentamer) with polydispersity values close to 1 and generated fractions with a higher level of total phenols (800.59 mg gallic acid equivalents per gram) but a lower yield (7.72%). Progressive solvent precipitation rapidly prepared and fractionated OPCs with a lower level of total phenols (609.57 mg gallic acid equivalents per gram) but a higher yield (24.74%) and higher polydispersity. Additionally, we found pronounced structural and quantitative differences among different tannin-rich fractions, and fractions obtained by GFC better reflected the structural diversity and complexity of OPCs from mangosteen pericarp. This study presents different ways of preparing and fractionating OPCs in the biomedical field.


Assuntos
Cromatografia em Gel/métodos , Garcinia mangostana/química , Proantocianidinas/isolamento & purificação , Solventes/química , Cromatografia Líquida de Alta Pressão/métodos , Fenóis/análise , Espectrometria de Massas por Ionização por Electrospray/métodos
20.
Ultrason Sonochem ; 57: 89-97, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31208622

RESUMO

This paper presents the successful application of ultrasound-assisted packed-bed (UAE-PB) method for the extraction of hypericin from the Hypericum perfuratum L. The Soxhlet system was utilized for the determination of suitable solvent from ethanol, methanol or from the mixture of different proportions of ethanol-methanol. The mixture of 50:50 v/v ethanol-methanol was obtained to be the most suitable solvent since it led to the highest extraction amount of hypericin. The extraction amount of hypericin increased by 13.6% and 21.4% when the solvent changed from pure methanol to the mixture of 50:50 v/v ethanol-methanol for the extraction time of 3 and 8 h, respectively. Subsequently, the extraction was conducted through the UAE-PB, and the effects of temperature, time, and the ratio of solvent to the dried plant were studied. The response surface method (RSM) was used to investigate the effect of parameters on the extraction in the UAE-PB system. At the temperature of 60 °C, extraction time of 105 min, and the solvent to plant ratio of 15.3, the maximum extraction yield of hypericin was achieved. In the optimal conditions, the amount of extraction was 0.112 mg hypericin/g dried plant, which was in accordance with the optimized predicted value (0.111 mg hypericin/g dried plant) from Design-Expert software.


Assuntos
Hypericum/química , Perileno/análogos & derivados , Ondas Ultrassônicas , Cromatografia Líquida de Alta Pressão/métodos , Etanol/química , Metanol/química , Modelos Químicos , Perileno/análise , Reprodutibilidade dos Testes , Solventes/química , Temperatura Ambiente , Fatores de Tempo
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