Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.546
Filtrar
1.
J Chromatogr A ; 1601: 385-387, 2019 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-31122730

RESUMO

Although the inverse gas chromatography technique has been used to measure the surface acid-base properties for almost 50 years, several basic problems still hinder its further development and application. One of the problems is that for the polar probe molecules of dichloromethane, acetone, ethyl acetate, tetrahydrofuran, and ethanol, the molecular area of each probe has different values in literature. In this paper, we point out the incorrect molecular area values presented in the literature by comparing these values with those indicated in Smallwood's Handbook of Organic Solvent Properties. The correct molecular area values of 11 polar probes are determined by plotting the molecular areas of the polar probes versus the van der Waals surface areas reported in the handbook. The correct molecular areas for six common polar probes, namely, dichloromethane, trichloromethane, acetone, ethyl acetate, diethyl ether, and tetrahydrofuran, are 38.0, 44.0, 42.5, 48.0, 47.0, and 45.0 Å2, respectively. Benzene is a specific molecule with a conjugated π-bond structure, and its molecular area is estimated to be larger than that of other molecules. Therefore, benzene is unsuitable for use as a probe molecule.


Assuntos
Cromatografia Gasosa/métodos , Cromatografia Gasosa/normas , Sondas Moleculares/química , Acetatos/química , Acetona/química , Ácidos/química , Etanol/química , Furanos/química , Cloreto de Metileno/química , Solventes/química , Propriedades de Superfície , Termodinâmica
2.
J Chromatogr A ; 1599: 55-65, 2019 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-31036361

RESUMO

Peak broadening in small columns is dominated by spreading in the extra column volume and not by hydrodynamic dispersion or mass transfer resistances. Computational fluid dynamics (CFD) permits to study the influence of these effects separately. Here, peak broadening of three single component solutes - silica nanoparticles, acetone, and lysozyme - was experimentally determined for two different columns (100 mm × 8 mm inner diameter and 10 mm × 5 mm inner diameter) under non-binding conditions. A mass transfer model between mobile and stationary phases as well as a hydrodynamic dispersion model were implemented in the CFD environment STAR-CCM+®. The mass transfer model combines a model of external mass transfer with a model of pore diffusion. The model was validated with experiments performed on the larger column. We find that extra column volume plays an important role in peak broadening of the silica nanoparticles pulse in that column; it is less important for acetone and is weakly pronounced for lysozyme. Hydrodynamic dispersion plays the dominant role at low and medium flow rates for acetone because we are in a regime of 1-10 ReSc. Mass transfer is important for high flow rates of acetone and for all flow rates of lysozyme. Then, peak broadening was predicted in the smaller column with the packed bed parameters taken from larger column. The scalability of the prepacked columns is demonstrated for acetone and silica nanoparticles by excellent agreement with the experimental data. In contrast to the larger column, peak broadening in the smaller column is dominated by extra column volume for all solutes. Peak broadening of lysozyme is controlled only at high flow rates by mass transfer and overrides extra column volume and hydrodynamic dispersion. CFD simulations with implemented mass transfer models successfully model peak broadening in chromatography columns taking all broadening effects into consideration and therefore are a valuable tool for scale up and scale down. Our simulations underscore the importance of extra column volume.


Assuntos
Cromatografia , Modelos Químicos , Acetona/química , Simulação por Computador , Difusão , Muramidase/química , Dióxido de Silício/química
3.
BMC Vet Res ; 15(1): 162, 2019 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-31118023

RESUMO

BACKGROUND: Diarrhoea, a global economically important disease burden affecting swine and, especially piglets, is commonly caused by infection with entero-toxigenic E. coli (ETEC). Adherence of ETEC to porcine intestinal epithelial cells following infection, is necessary for its pathogenesis. While antimicrobials are commonly given as therapy or as feed additives for prophylaxis against microbial infections, the concern over increased levels of antimicrobial resistance necessitate the search for safe and effective alternatives in livestock feed. Attention is shifting to natural products including plants as suitable alternatives to antimicrobials. The activity of acetone crude leaf extracts of nine under-explored South African endemic plants from the Myrtaceae family with good antimicrobial activity were tested against pathogenic E. coli of porcine origin using a microplate serial dilution method. Bioautography, also with p-iodonitrotetrazolium violet as growth indicator was used to view the number of bioactive compounds in each extract. In vitro toxicity of extracts was determined against Caco-2 cells using the 3-(4,5-dimethythiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay. The antimicrobial susceptibility of E. coli isolates was tested on a panel of antimicrobials using the Kirby-Bauer agar diffusion method while the anti-adherence mechanism was evaluated using a Caco-2 cell enterocyte anti-adhesion model. RESULTS: The MIC of the extracts ranged from 0.07-0.14 mg/mL with S. legatii having the best mean MIC (0.05 mg/mL). Bioautography revealed at least two active bands in each plant extract. The 50% lethal concentration (LC50) values ranged between 0.03-0.66 mg/mL. Eugenia zeyheri least cytotoxic (LC50 = 0.66 mg/ml) while E. natalitia had the highest cytotoxicity (LC50 = 0.03 mg/mL). All the bacteria were completely resistant to doxycycline and colistin sulphate and many of the plant extracts significantly reduced adhesion of E. coli to Caco-2 cells. CONCLUSIONS: The extracts of the plants had good antibacterial activity as well as a protective role on intestinal epithelial cells against enterotoxigenic E. coli bacterial adhesion. This supports the potential use of these species in limiting infection causes by E. coli. Some of these plants or extracts may be useful as phytogenic feed additives but it has to be investigated by animal feed trials.


Assuntos
Antibacterianos/farmacologia , Resistência a Múltiplos Medicamentos/efeitos dos fármacos , Escherichia coli Enterotoxigênica/efeitos dos fármacos , Eugenia/química , Extratos Vegetais/farmacologia , Syzygium/química , Acetona/química , Células CACO-2 , Sobrevivência Celular/efeitos dos fármacos , Farmacorresistência Bacteriana/efeitos dos fármacos , Humanos , Dose Letal Mediana , Testes de Sensibilidade Microbiana , Extratos Vegetais/toxicidade , Folhas de Planta/química
4.
Environ Sci Pollut Res Int ; 26(16): 16166-16180, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30972669

RESUMO

Sulfur-doped activated carbons (SACs) with high sulfur content and large specific surface area were synthesized from polythiophene for acetone removal. The sulfur content of carbons (3.10-8.43 at.%) could be tunable by adjusting the activation temperature. The BET surface area and pore volume of the obtained samples were 916-2020 m2 g-1 and 0.678-1.100 cm3 g-1, with a significant proportion of microporosity (up to 84% and 72% for BET surface area and pore volume, respectively). The resulting SACs show a superior acetone adsorption capacity (i.e., 716.4 mg g-1 at 15 °C and 705 mg g-1 at 25 °C for SAC700). In terms of the adsorption behavior of acetone on the activated carbons, compared to the Langmuir model, the Langmuir-Freundlich model showed better agreement with the adsorption amount. The results reveal that the surface area and micropore volume are the key factors for acetone adsorption, while the sulfur-doped functional groups, especially oxidized sulfur functional groups, can enhance the acetone adsorption capacity at a certain low pressure. Temperature programmed desorption (TPD) experiments were performed to get desorption activation energy of acetone on SAC samples, and the results ranged from 23.54 to 38.71 kJ mol-1. The results of the molecular simulation show that the introduction of sulfur element can increase the binding energy between acetone molecule and carbon surface, and the tri-oxidized sulfur (sulfonic acid) functional group has the highest binding energy of - 0.4765 eV. Graphical abstract.


Assuntos
Acetona/química , Carvão Vegetal/química , Polímeros/química , Enxofre/química , Tiofenos/química , Adsorção , Carbono/química , Porosidade , Propriedades de Superfície , Temperatura Ambiente , Compostos Orgânicos Voláteis/química , Compostos Orgânicos Voláteis/isolamento & purificação
5.
Molecules ; 24(7)2019 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-30974893

RESUMO

Eurycoma longifolia is a popular folk medicine in South East Asia. This study was focused on saccharide-containing compounds including saponins, mainly because of their medical potentials. Different organic solvents such as ethyl acetate, butanol, and chloroform were used to fractionate the phytochemical groups, which were consequently precipitated in cold acetone. Solvent fractionation was found to increase the total saponin content based on colorimetric assay using vanillin and sulfuric acid. Ethyl acetate fraction and its precipitate were showed to have the highest crude saponins after acetone precipitation. The samples were shown to have anti-proliferative activity comparable with tamoxifen (IC50 = 110.6 µg/mL) against human breast cancer cells. The anti-proliferative activities of the samples were significantly improved from crude extract (IC50 = 616.3 µg/mL) to ethyl acetate fraction (IC50 = 185.4 µg/mL) and its precipitate (IC50 = 153.4 µg/mL). LC-DAD-MS/MS analysis revealed that the saccharide-containing compounds such as m/z 497, 610, 723, 836, and 949 were abundant in the samples, and they could be ionized in negative ion mode. The compounds consisted of 226 amu monomers with UV-absorbing property at 254 nm, and were tentatively identified as formylated hexoses. To conclude, solvent fractionation and acetone precipitation could produce saccharide-containing compounds including saponins with higher anti-proliferative activity than crude extract against MCF-7 cells. This is the first study to use non-toxic solvents for fractionation of bioactive compounds from highly complex plant extract of E. longifolia.


Assuntos
Acetona/química , Antineoplásicos Fitogênicos , Neoplasias da Mama/tratamento farmacológico , Eurycoma/química , Saponinas , Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/isolamento & purificação , Antineoplásicos Fitogênicos/farmacologia , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Feminino , Humanos , Saponinas/química , Saponinas/isolamento & purificação , Saponinas/farmacologia
6.
Molecules ; 24(8)2019 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-31018540

RESUMO

Jelly fig (Ficus awkeotsang Makino) is used to prepare drinks and desserts in Asia, owing to the gelling capability of its pectin via endogenous pectin methylesterase (PE) catalyzation. Meanwhile, substances with PE inhibitory activity (SPEI) in jelly fig achenes (JFA) residue were noticed to be able to impede the gelation. In this study, we characterized and isolated SPEI from JFA by a series of PE inhibition-guided isolations. Crude aqueous extract of JFA residue was mixed with acetone, and 90% acetone-soluble matter was further fractionated by Diaion HP-20 chromatography. The retained fraction with dominant PE inhibitory activity was collected from 100% methanol eluate. Results from high-performance liquid chromatography mass spectrometry (HPLC/MS) and hydrolysis-induced chromogenic transition revealed the SPEI as complex tannins. Total tannins content was determined in each isolated fraction, and was closely related to PE inhibitory activity. In addition, SPEI in this study could inhibit activities of digestive enzymes in vitro and may, therefore, be assumed to act as non-specific protein binding agent.


Assuntos
Hidrolases de Éster Carboxílico/antagonistas & inibidores , Inibidores Enzimáticos/isolamento & purificação , Ficus/química , Frutas/química , Proteínas de Plantas/antagonistas & inibidores , Taninos/isolamento & purificação , Acetona/química , Bebidas/análise , Hidrolases de Éster Carboxílico/química , Hidrolases de Éster Carboxílico/isolamento & purificação , Cromatografia por Troca Iônica , Ensaios Enzimáticos , Inibidores Enzimáticos/química , Ficus/enzimologia , Frutas/enzimologia , Géis , Humanos , Metanol/química , Pectinas/química , Transição de Fase , Extratos Vegetais/química , Proteínas de Plantas/química , Proteínas de Plantas/isolamento & purificação , Solventes/química , Taiwan , Taninos/química , Água/química
7.
Food Chem ; 287: 265-272, 2019 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-30857698

RESUMO

In this study, the degradation of tropane alkaloids in pasta under boiling (100 °C during 10 min) and tea making (100 °C and let cool 5 min) conditions has been evaluated for the first time. Pasta and green tea were contaminated with Datura Stramonium and Brugmansia Arborea seeds (pasta and green tea), whereas coca leaf tea was directly analysed. The compounds were extracted using solid-liquid extraction coupled to a preconcentration stage (only for the cooking water), and the compounds were analysed by liquid chromatography coupled to mass spectrometry (Exactive-Orbitrap analyser). Degradation studies indicate that concentration of tropane alkaloids decreases, and it depends on the compound, observing the highest degradation for tropinone, tropane, cuscohygrine and tropine, as well as it was observed that compounds migrated to the aqueous phase during cooking step. Finally, post-targeted analysis was performed and other tropane alkaloids were found, as scopine, tigloidine or convolvine, showing a similar behaviour under cooking conditions.


Assuntos
Coca , Contaminação de Alimentos , Solanaceae , Chá/química , Tropanos/química , Acetona/análogos & derivados , Acetona/química , Cromatografia Líquida , Datura stramonium , Fagopyrum , Espectrometria de Massas , Folhas de Planta , Pirrolidinas/química , Sementes , Extração em Fase Sólida , Temperatura de Transição
8.
J Ethnopharmacol ; 236: 196-204, 2019 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-30844488

RESUMO

ETHNOPHARMACOLOGICAL RELEVANCE: Hopea ponga (Dennst.) Mabb. Is used in traditional herbal formulations for diabetes complications. The aim of this study is to evaluate the antidiabetic effect of extracts and compounds from H. ponga. MATERIALS AND METHODS: Silica gel column chromatography was performed to identify various chemical components of the plant extract. Different extracts of H. ponga and isolated compounds were screened for their antidiabetic effect by modulation of digestive enzymes and protein glycation. The effect of glucose uptake by the compounds and the pathways through which the compounds mediate the glucose uptake potential were confirmed by fluorescent microscopy, flow cytometry and western blot analysis. RESULTS: Acetone and ethanol extracts of the stem bark of Hopea ponga (Dennst.) Mabb. Afforded six resveratrol oligomers namely, E-resveratrol (1), (-)-ε-viniferin (2), (-)-α-viniferin (3), trihydroxyphenanthrene glucoside (THPG) (4), vaticaphenol A (5), (-)-hopeaphenol (6), along with four phytosterols. The structures were determined on the basis of spectroscopic analyses including nuclear magnetic resonance (NMR) spectroscopy and high resolution mass spectrometry (HRMS) data. Compounds 1-5 and 7-10 were tested for their α-glucosidase, α-amylase and glycation inhibitiory activities. All the resveratrol oligomers (1-5) showed prominent α-glucosidase inhibition with IC50 values, 12.56 ±â€¯1.00, 23.98 ±â€¯1.11, 7.17 ±â€¯1.10, 31.74 ±â€¯0.42 and 16.95 ±â€¯0.39 µM, respectively. Molecular docking studies also supported the observed α-glucosidase inhibition. Compound 3 displayed IC50 values of 4.85 ±â€¯0.06 and 27.10 ±â€¯0.04 µM in α-amylase and glycation inhibitory assays activity. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay revealed that the compounds 3 and 4 were found to be less toxic at a concentration of 100 µM (<10%) and 25 µM (<20%), respectively. The effect of glucose uptake performed by 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) in L6 myoblast were measured by fluorescent microscopy and flow cytometry. The compounds 3 and 4 showed 2-NBDG uptake of 49.6% and 38.8% respectively. By examining the molecular pathway through which the compounds elicit their glucose uptake potential, it was observed that both the compounds mainly act via AMPK pathway. CONCLUSION: This is the first report on the isolation of compounds from H. ponga. Altogether, the results of this study reveal the antidiabetic effects of H. ponga extracts and isolated compounds promoting traditional use of this plant in the treatment of diabetes.


Assuntos
Dipterocarpaceae/química , Hipoglicemiantes/farmacologia , Extratos Vegetais/farmacologia , Resveratrol/farmacologia , Acetona/química , Animais , Linhagem Celular , Diabetes Mellitus/tratamento farmacológico , Ensaios Enzimáticos , Etanol/química , Glicosilação/efeitos dos fármacos , Hipoglicemiantes/química , Hipoglicemiantes/isolamento & purificação , Concentração Inibidora 50 , Medicina Tradicional/métodos , Simulação de Acoplamento Molecular , Estrutura Molecular , Mioblastos , Casca de Planta/química , Extratos Vegetais/química , Caules de Planta/química , Ratos , Resveratrol/química , Resveratrol/isolamento & purificação , Testes de Toxicidade , alfa-Amilases/antagonistas & inibidores , alfa-Amilases/química , alfa-Amilases/metabolismo , alfa-Glucosidases/química , alfa-Glucosidases/metabolismo
9.
Prep Biochem Biotechnol ; 49(5): 464-476, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30821596

RESUMO

Four organic solvents along with water were applied for the conventional extraction of Eucalyptus camaldulensis (Myrtaceae), phenolic contents and antioxidant activities were investigated through variable protocols and correlation coefficients were considered, the phenolic composition was also characterized by Gas chromatography-mass spectrometry (GC-MS). Using solvents with dissimilar polarities affected the phenolic yields extracted from E. camaldulensis and their related antioxidant activities varied significantly among the four investigated plant organs. The leaf extract of acetone 70% contained the highest amount of phenolic compounds (46.56 mg/g dry weight); while the bud-water boiled extract maintained the maximum value of tannins (45.68 mg/g dry weight). Correlation coefficients indicated that phenolic compounds were mostly accountable for the phosphomolybednum antioxidant potentials (0.520), followed by tannins (0.460). Also, both the reducing power activities and hydrogen peroxide scavenging of E. camaldulensis extracts positively correlated with tannins, but at different significance degrees. However, the GC-MS analysis revealed that most of the detected phenolic constituents were more abundant in the plant seed. So, the existence of some other compounds such as organic acids, along with phenolics, may have increased the antioxidant potentials of leaf and bud. Undeniably, the optimization of extraction conditions could stimulate the antioxidant capabilities of the plant extracts of E. camaldulensis.


Assuntos
Eucalyptus/química , Depuradores de Radicais Livres/isolamento & purificação , Fenóis/isolamento & purificação , Acetatos/química , Acetona/química , Etanol/química , Flavonoides/isolamento & purificação , Flores/química , Frutas/química , Cromatografia Gasosa-Espectrometria de Massas , Metanol/química , Folhas de Planta/química , Sementes/química , Extração em Fase Sólida/métodos , Solventes/química , Taninos/isolamento & purificação , Água/química
10.
J Chromatogr A ; 1595: 127-135, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-30837162

RESUMO

Various retention models have been widely used for understanding the retention mechanisms of solutes in reversed-phase chromatography systems. The models have been used to interpret the often-observed linear plots of the logarithms of retention factor k versus the solvent modifier concentration CM and ln k versus ln⁡CM. In this study, the retention behaviors of nine solutes as a function of acetonitrile (ACN) concentration were systematically investigated using a commercially available C18 column. The thermodynamic properties of solute adsorptions in neat water, determined using van' t Hoff plots, were investigated. Slightly concave upward and downward retention curves were identified for the plots of ln k versus CACN and ln k versus ln CACN, respectively. A three-equilibrium-constant stoichiometric displacement retention model was used to interpret the retention behaviors of the solutes. The model was demonstrated to account for the nonlinearity of the retention curves. The linear fits of the ln k versus ln⁡CACN and ln k versus CACN plots were implied to be more suitably used for high and low ACN concentration ranges, respectively. The model fitted the experimental data satisfactorily over a full range of ACN concentrations; thus, the nonlinearity of ln k versus ln⁡CACN plots was implied to mainly be attributed to the weak ACN-sorbent interactions. U-shaped retention curves were observed for acetone, tetrahydrofuran, tert-butanol, and benzyl alcohol at high ACN concentrations, indicating that the retention behaviors of these solutes may involve two types of interactions, with complementary effects on solute retention factor with increasing ACN concentration.


Assuntos
Cromatografia de Fase Reversa , Modelos Químicos , Acetona/química , Acetonitrilos/química , Adsorção , Furanos/química , Solventes/química , Termodinâmica , Água/química
11.
Environ Sci Pollut Res Int ; 26(14): 13999-14012, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30737716

RESUMO

The concerns regarding potential environmental release and ecological risks of multi-walled carbon nanotubes (MWCNTs) rise with their increased production and use. As a result, there is the need for an analytical method to determine the environmental concentration of MWCNTs. Although several methods have been demonstrated for the quantification of well-characterized MWCNTs, applying these methods to field samples is still a challenge due to interferences from unknown characteristics of MWCNTs and environmental media. To bridge this gap, a recently developed microwave-induced heating method was investigated for the quantification of MWCNTs in field samples. Our results indicated that the microwave response of MWCNTs was independent of the sources, length, and diameter of MWCNTs; however, the aggregated MWCNTs were not able to convert the microwave energy to heat, making the method inapplicable. Thus, a pre-treatment process for dispersing bundled MWCNTs in field samples was crucial for the use of the microwave method. In the present paper, a two-step pre-treatment procedure was proposed: the aggregated MWCNTs loaded environmental samples were first exposed to high temperature (500 °C) and then dispersed by using an acetone-surfactant solution. A validation study was performed to evaluate the effectiveness of the pre-treatment process, showing that an 80-120% recovery range of true MWCNT loading successfully covered the microwave-measured MWCNT mass.


Assuntos
Técnicas de Química Analítica/métodos , Nanotubos de Carbono/análise , Nanotubos de Carbono/química , Acetona/química , Calefação , Micro-Ondas , Tamanho da Partícula , Reprodutibilidade dos Testes , Poluentes do Solo/análise , Tensoativos/química , Temperatura Ambiente
12.
Molecules ; 24(3)2019 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-30709040

RESUMO

In order to obtain acetone sensor with excellent sensitivity, selectivity, and rapid response/recovery speed, graphene-like ZnO/graphene oxide (GO) nanosheets were synthesized using the wet-chemical method with an additional calcining treatment. The GO was utilized as both the template to form the two-dimensional (2-D) nanosheets and the sensitizer to enhance the sensing properties. Sensing performances of ZnO/GO nanocomposites were studied with acetone as a target gas. The response value could reach 94 to 100 ppm acetone vapor and the recovery time could reach 4 s. The excellent sensing properties were ascribed to the synergistic effects between ZnO nanosheets and GO, which included a unique 2-D structure, large specific surface area, suitable particle size, and abundant in-plane mesopores, which contributed to the advance of novel acetone vapor sensors and could provide some references to the synthesis of 2-D graphene-like metals oxide nanosheets.


Assuntos
Acetona/química , Grafite/química , Óxidos/química , Óxido de Zinco/química , Estrutura Molecular , Nanocompostos/química , Tamanho da Partícula , Porosidade , Análise Espectral
13.
J Chromatogr A ; 1592: 9-18, 2019 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-30711322

RESUMO

Solid phase microextraction (SPME) Arrows with enlarged sorption phases and Arrow-shaped tips are good alternatives to classic SPME fibers. Developing SPME Arrows with functionalized coatings has become a growing area of SPME research. In this study, a zirconium metal organic framework/molybdenum disulfide (UiO-66/MoS2) composite coating modified SPME Arrow was developed and coupled with gas chromatography-mass spectrometry for the headspace extraction and detection of 16 polycyclic aromatic hydrocarbons (PAHs). The coating preparation can be easily manipulated by the assembly strategy using silicone gels to adhere UiO-66/MoS2 powder onto the surface of the Arrows. The prepared UiO-66/MoS2 coated SPME Arrows exhibited clearly enhanced adsorption capacity (2.1-4.5 folds) and an improved degree of affinity to PAHs species when compared to commercial PDMS/CARS/DVB SPME Arrows or fibers. The improved mechanism may be due to the high specific area, hierarchical micropores and mesopores, and the largely increased and immobilized amount of UiO-66/MoS2 coating on the stainless-steel Arrow. Under optimized conditions, the SPME Arrow-based assay was successfully applied to determine PAH levels in fish samples with satisfactory recoveries of 80.2-101% and relative standard deviations (RSDs) of less than 6%. The detection limits of PAHs were between 0.11-1.40 ng kg-1. The coating showed satisfied reproducibility and repeatability (RSD <8.6%) with only 10 mL of 10% (v/v) acetone in water used as the extraction phase in an effort to be environmentally friendly. All of the results showed that the method is simple, sensitive, and robust. SPME Arrows with UiO-66/MoS2 coatings can provide new opportunities for the efficient extraction of persistent organic pollutants in food safety applications.


Assuntos
Dissulfetos/química , Peixes , Análise de Alimentos/instrumentação , Estruturas Metalorgânicas/química , Molibdênio/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Microextração em Fase Sólida/instrumentação , Zircônio/química , Acetona/química , Adsorção , Animais , Dimetilpolisiloxanos , Cromatografia Gasosa-Espectrometria de Massas , Limite de Detecção , Polivinil , Reprodutibilidade dos Testes , Aço Inoxidável/química , Água/química , Poluentes Químicos da Água/análise
14.
Microb Cell Fact ; 18(1): 6, 2019 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-30642338

RESUMO

BACKGROUND: The shortage of food based feedstocks has been one of the stumbling blocks in industrial biomanufacturing. The acetone bioproduction from the traditional acetone-butanol-ethanol fermentation is limited by the non-specificity of products and competitive utilization of food-based substrates. Using genetically modified Escherichia coli to produce acetone as sole product from the cost-effective non-food based substrates showed great potential to overcome these problems. RESULTS: A novel acetone biosynthetic pathway were constructed based on genes from Clostridium acetobutylicum (thlA encoding for thiolase, adc encoding for acetoacetate decarboxylase, ctfAB encoding for coenzyme A transferase) and Escherichia coli MG1655 (atoB encoding acetyl-CoA acetyltransferase, atoDA encoding for acetyl-CoA: acetoacetyl-CoA transferase subunit α and ß). Among these constructs, one recombinant MG1655 derivative containing the hybrid pathway consisting of thlA, atoDA, and adc, produced the highest level of acetone from acetate. Reducing the gluconeogenesis pathway had little effect on acetone production, while blocking the TCA cycle by knocking out the icdA gene enhanced the yield of acetone significantly. As a result, acetone concentration increased up to 113.18 mM in 24 h by the resting cell culture coupling with gas-stripping methods. CONCLUSIONS: An engineered E. coli strain with optimized hybrid acetone biosynthetic pathway can utilize acetate as substrate efficiently to synthesize acetone without other non-gas byproducts. It provides a potential method for industrial biomanufacturing of acetone by engineered E. coli strains from non-food based substrate.


Assuntos
Ácido Acético/metabolismo , Acetona/metabolismo , Escherichia coli/metabolismo , Engenharia Metabólica , Ácido Acético/química , Acetona/química , Acetil-CoA C-Acetiltransferase/genética , Acetil-CoA C-Acetiltransferase/metabolismo , Carboxiliases/genética , Carboxiliases/metabolismo , Ciclo do Ácido Cítrico/genética , Clostridium acetobutylicum/genética , Escherichia coli/química , Deleção de Genes , Gluconeogênese/genética , Fosfoenolpiruvato Carboxiquinase (ATP)/genética , Especificidade por Substrato
15.
Nanoscale ; 11(5): 2476-2483, 2019 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-30672548

RESUMO

Highly selective, fast detection of specific lung-cancer biomarkers (CMs) in exhaled human breath is vital to the development of enhanced sensing devices. Today, e-nose is a promising approach for the diagnosis of lung cancer. Nevertheless, considerable challenges to early-stage disease diagnostics still remain: e.g. decrease in sensor sensitivities in the presence of water vapor, sensor drift leading to the inability to calibrate exactly, relatively short sensor lifetimes, and difficulty discriminating between multiple diseases. However, there is a wide scope for breath diagnostics techniques, and all advanced electrodes applicable to e-nose devices will benefit them. Here, we present the promising sensing capabilities of bare multi-layer graphene (MLG) as a proof of concept for advanced e-nose devices and demonstrate its utility for biomolecule discrimination of the most common lung CMs (ethanol, isopropanol, and acetone). We report on a comparative study involving exposure of the three CM solutions on flat MLG (f-MLG) and patterned MLG (p-MLG) electrodes, where the electrical conductivity of p-MLG is significantly increased while applying acetone. Based on sensitivity tests, we demonstrate the ability to monitor the electrical response of graphene electrodes employing graphene of various wettabilities. Specifically, the f-MLG electrode displays almost 2 times higher sheet resistance (30 Ω sq-1) compared to the hydrophilic p-MLG (12 Ω sq-1). We show significant sensitivity to selected specific molecules of pristine f-MLG and p-MLG while applying CM solutions with a 1.4 × 105 ppm concentration. Finally, we show the selectivity of f-MLG and p-MLG-based sensors when exposed to 2.0 × 105 ppm solutions containing different CM combinations. Both sensors were selective in particular to acetone, since the presence of acetone leads to a sheet resistance increase. We demonstrate that an advanced e-nose approach integrated with MLG electrodes has significant potential as a design concept for utilization of molecular detection at variable concentrations such as in early-stage disease diagnosis. This early-stage approach will provide convenient and reusable complex monitoring of CMs compared to typical contact sensors which require target analysis and are limited by disposable measuring. Moreover, further integration of the Internet of Things will introduce advanced e-nose devices as a biotechnological innovation for disease resilience with the potential for commercialization.


Assuntos
Técnicas Biossensoriais/métodos , Testes Respiratórios/métodos , Nariz Eletrônico , Grafite/química , Neoplasias Pulmonares/diagnóstico , 2-Propanol/química , Acetona/química , Biomarcadores Tumorais/química , Calibragem , Condutividade Elétrica , Eletrodos , Etanol/química , Humanos , Óxidos/química , Oxigênio/química
16.
Environ Sci Pollut Res Int ; 26(7): 6773-6781, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30628003

RESUMO

Non-thermal plasma (NTP) degradation of low-concentration acetone was investigated in a cylindrical dielectric barrier discharge reactor. The effects of oxygen content and flow rate on the removal efficiency at various discharge powers were examined in real-time. The acetone removal efficiency decreases drastically and then remains stable or increases gradually as the O2 content increases from 0 to 25%, and further to 50%. The organic by-products were characterized and quantified using a real-time proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) instrument. The observed organic compounds, with concentrations about ppbv/ppmv by volume, were mainly formaldehyde, methanol, ketene, acetaldehyde, formic acid, acetone, and acetic acid. The discharge power was a critical factor affecting the concentration of the organic by-products and the selectivity toward CO2. The mechanism study based on the by-product monitor in real-time showed that acetone firstly fragments into methyl radicals, acetyl radicals, and H; then, the methyl and acetyl radicals are oxidized by O or OH radicals into acetaldehyde, methanol, and other compounds. It seems that acetaldehyde could be an intermediate in acetone decomposition. Firstly, most of the acetone molecules were decomposed into acetaldehyde molecules; then, the acetaldehyde molecules continued to be decomposed and oxidized into other compounds, such as acetic acid and formaldehyde. These investigations not only proposed a detail decomposition mechanism for acetone in dielectric barrier discharge reactor, but also provided a potential way to analyze and evaluate the practicability of NTP removal of VOCs.


Assuntos
Acetona/química , Modelos Químicos , Acetaldeído/química , Formaldeído/química , Espectrometria de Massas , Metanol/química , Gases em Plasma
17.
Bioresour Technol ; 275: 123-129, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30579102

RESUMO

Cellulose extracted from cornstalk was liquefied in supercritical organic solvents at different liquefaction parameters. Different organic solvents (methanol, ethanol and acetone) were used to disintegrate cellulose at different temperatures (240, 260, 280, 300 and 320 °C), reaction time (0, 30, 60, 90 and 120 min) and solvents dosage (0, 80, 120, 160 and 200 mL). The results showed that similar liquefaction characteristics of cellulose were observed in three different solvents. The larger bio-oil yield and smaller residue yield obtained from cellulose liquefaction in solvents were achieved under the suitable conditions (320 °C, 160 mL, 60-90 min), respectively. And the type of solvents was the main effect to the distribution of the composition of bio-oil. The dominant constituents of bio-oil that were produced in supercritical methanol was hydrocarbon, and ketones and esters were mainly produced in supercritical ethanol, whereas ketones compounds were primarily derived in supercritical acetone.


Assuntos
Acetona/química , Celulose/química , Etanol/química , Metanol/química , Óleos Vegetais/química , Óleos Vegetais/metabolismo , Polifenóis/química , Polifenóis/metabolismo , Solventes/química , Temperatura Ambiente
18.
Food Chem ; 277: 279-288, 2019 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-30502146

RESUMO

Baobab fruit (Adansonia digitata) pulp has received a growing attention globally for its numerous nutritional and medicinal values. However, only limited information is available about its phytochemical composition. The purpose of this study was to identify the phytochemicals in baobab fruit pulp using LC-MS/QTOF and evaluate the effects of solvents on phenolic compounds content and antioxidant activity. The LC-MS analysis led to the identification of 46 compounds, based on standards and comparison with literature reports. Proanthocyanidins, phenolic acids, flavonols, and saponins were the most common compounds. The best solvent for Total Phenolic Compounds Content (TPCC), TPC, TFC and antioxidant activity was also defined: 80% acetone was the best for TPCC, TFC and FRAP, 30% acetone for TPC and 50% methanol for DPPH. Considering all the results, 80% acetone was determined as the best solvent for sample extraction. A high correlation was observed between phenolic compounds content and antioxidant activity.


Assuntos
Adansonia/química , Antioxidantes/análise , Frutas/química , Fenóis/análise , Compostos Fitoquímicos/análise , Acetona/química , Cromatografia Líquida , Flavonóis/análise , Análise de Alimentos , Hidroxibenzoatos/análise , Espectrometria de Massas , Metanol/química , Proantocianidinas/análise , Saponinas/análise , Solventes/química
19.
PLoS One ; 13(12): e0202238, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30557402

RESUMO

Protein extracts obtained from cells or tissues often require removal of interfering substances for the preparation of high-quality protein samples in proteomic analysis. A number of protein extraction methods have been applied to various biological samples. TCA/acetone precipitation and phenol extraction, a common method of protein extraction, is thought to minimize protein degradation and activity of proteases as well as reduce contaminants like salts and polyphenols. However, the TCA/acetone precipitation method relies on the complete pulverization and repeated rinsing of tissue powder to remove the interfering substances, which is laborious and time-consuming. In addition, by prolonged incubation in TCA/acetone, the precipitated proteins are more difficult to re-dissolve. We have described a modified method of TCA/acetone precipitation of plant proteins for proteomic analysis. Proteins of cells or tissues were extracted using SDS-containing buffer, precipitated with equal volume of 20% TCA/acetone, and washed with acetone. Compared to classical TCA/acetone precipitation and simple acetone precipitation, this protocol generates comparable yields, spot numbers, and proteome profiling, but takes less time (ca. 45 min), thus avoiding excess protein modification and degradation after extended-period incubation in TCA/acetone or acetone. The modified TCA/acetone precipitation method is simple, fast, and suitable for proteomic analysis of various plant tissues in proteomic analysis.


Assuntos
Acetona/química , Proteínas de Plantas/química , Proteômica/métodos , Ácido Tricloroacético/química , Zea mays/química , Precipitação Química , Proteínas de Plantas/análise
20.
Bioresour Technol ; 267: 319-325, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30029177

RESUMO

In this study, a compound nitrogen source, integrating the advantages of ammonium acetate and soybean meal, was proposed to further improve acetone-butanol-ethanol fermentation. Unfortunately, this compound nitrogen source was found to effectively inhibit cellular performance, as the introduction of NH4+ significantly decreased the yield of butanol and total solvents by 34.78% and 35.14%, to only 6.62 g/L and 10.76 g/L, respectively. Meanwhile, the regulatory mechanism was further elucidated at different levels. As a result, the NH4+ could down-regulate the transcriptional levels of key genes involved in butanol synthesis, and the activity of acetoacetyl-CoA/acyl-CoA transferase, and then decrease the accumulation of key intermediates. Therefore, ammonium acetate has a dual function in ABE fermentation, as it effectively improves ABE fermentation when it is the sole nitrogen source but significantly decreases fermentation performance in the presence of soybean meal, broadening the understanding of nitrogen regulation mechanism of C. acetobutylicum.


Assuntos
Acetatos/química , Clostridium acetobutylicum , Fermentação , Acetona/química , Butanóis/química , Etanol/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA