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1.
Food Chem ; 305: 125429, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31505415

RESUMO

A simple and rapid magnetic solid-phase extraction (MSPE) method using PEGylated multi-walled carbon nanotubes magnetic nanoparticles (PEG-MWCNTs-MNP) as absorbents is proposed for isolation and enrichment of aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), aflatoxin G2 (AFG2), aflatoxin M1 (AFM1), aflatoxin M2 (AFM2), ochratoxin A (OTA), zearalenone (ZEA), zearalanone (ZAN), α-zeralanol (α-ZAL), ß-zeralanol (ß-ZAL), α-zeralenol (α-ZOL), and ß-zeralenol (ß-ZOL) from liquid milk. Combined with ultra-high performance liquid chromatography Q-Exactive high resolution mass spectrometry, simultaneous qualification of these mycotoxins was achieved with sensitivity and specificity. The proposed method showed a good linearity (R2 ≥ 0.995), high sensitivity (limit of detection in the range of 0.005-0.050 µg/kg and limit of quantification in the range of 0.015-0.150 µg/kg), adequate recovery (81.8-106.4%), and good repeatability (intra-day precision in the range of 2.1-8.5% and inter-day precision in the range of 3.9-11.7%). It has been successfully applied to the determination of 13 mycotoxins in real liquid milk samples.

2.
J Sep Sci ; 42(6): 1289-1298, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30653844

RESUMO

In this work, monoamine oxidase B was immobilised onto magnetic nanoparticles to prepare a new type of affinity solid-phase extraction adsorbent, which was used to extract the possible anti-neurodegenerative components from the Lonicera japonica flower extracts. Coupled with high-performance liquid chromatography with mass spectrometry, two monoamine oxidase B ligands were fished-out and identified as isochlorogenic acid A and isochlorogenic acid C, which were found to be inhibitors of the enzyme for the first time, with similar half maximal inhibitory concentration values of 29.05 ± 0.49 and 29.77 ± 1.03 µM, respectively. Furthermore, equilibrium-dialysis dissociation assay of enzyme-inhibitor complex showed that both compounds have reversible binding patterns to monoamine oxidase B, and kinetic analysis demonstrated that they were mixed-type inhibitors for monoamine oxidase B, with Ki and Kis values of 9.55 and 37.24 µM for isochlorogenic acid A, 9.53 and 35.50 µM for isochlorogenic acid C, respectively. The results indicated that isochlorogenic acid A and isochlorogenic acid C were the major active components responsible for the anti-degenerative activity of the flowers of L. japonica, while magnetic nanoparticles immobilised monoamine oxidase B could serve as an efficient solid-phase extraction adsorbent to specifically extract monoamine oxidase B inhibitors from complex herbal extracts.


Assuntos
Lonicera/química , Nanopartículas de Magnetita/química , Monoaminoxidase/química , Fármacos Neuroprotetores/isolamento & purificação , Extratos Vegetais/isolamento & purificação , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Flores/química , Ligantes , Lonicera/metabolismo , Monoaminoxidase/metabolismo , Fármacos Neuroprotetores/química , Fármacos Neuroprotetores/metabolismo , Extratos Vegetais/química , Extratos Vegetais/metabolismo , Extração em Fase Sólida
3.
J Sep Sci ; 41(19): 3772-3781, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30152917

RESUMO

A microchip capillary electrophoresis coupled with laser induced fluorescence detection method for the fast determination of aloin was developed and comprehensively applied for the quantification of aloin A and B present in seven aloe plant species, 42 aloin-containing crude drugs, ten aloe pharmaceutical preparations, and four aloe gel-containing functional foods. The excitation and emission wavelengths for detection of both aloins were set at 473 and 520 nm, respectively. Sample analysis on a 35 mm length of glass microchip channel was completed within 40 s. An interference study indicated that the other main anthraquinones present in the samples did not interrupt with the target aloins detection, demonstrating the good selectivity of this method. It is demonstrated that this method is fast, facile, and specific for determination of aloin A and B from matrix samples which can be applied to the quality control of a wide varieties of aloe species and aloe-derived products.

4.
J Chromatogr A ; 1569: 222-228, 2018 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-30037541

RESUMO

An aptamer-based microchip capillary electrophoresis coupled with laser induced fluorescence (MCE-LIF) detection method for fast determination of Aflatoxin B1 (AFB1) and Ochratoxin A (OTA) was developed. Aptamers that are specific to these two mycotoxins were first hybridized with their aptamer complementary oligonucleotides. The double strand DNA that comes in contact with mycotoxin-containing environment would be unwound into separate aptamer-mycotoxin complex and aptamer complementary single strand. Different types of oligonucleotides can be separated in MCE and detected under the aid of fluorescent dye SYBR gold in LIF detection unit. Under the optimal conditions, on-chip aptamer-mycotoxin conjugates analysis was achieved within 3 min with extremely low LODs (0.026 ng/mL for AFB1 and 0.021 ng/mL for OTA). Specificity study indicated that other major mycotoxins would not cross-react with these two aptamers, demonstrating the good selectivity of the proposed method. Quantification of trace AFB1 and OTA in real food samples was carried out and satisfactory recoveries were obtained. It is demonstrated that this method is fast, facile and specific for Simultaneous determination of trace AFB1 and OTA from foodstuffs.


Assuntos
Aflatoxina B1/análise , Aptâmeros de Nucleotídeos/química , Eletroforese Capilar/métodos , Eletroforese em Microchip/métodos , Análise de Alimentos/métodos , Ocratoxinas/análise , Fluorescência , Corantes Fluorescentes/química , Limite de Detecção , Compostos Orgânicos/química
5.
Anal Chim Acta ; 995: 99-105, 2017 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-29126486

RESUMO

Tyrosinase (TYR) is a key enzyme in melanin biosynthesis and its activity is an important biomarker for dermatological disorders, such as vitiligo, melanoma and actinic damages. Sensitive assay for TYR activity is significant for basic and clinical research. In this work, a facile fluorescent assay for TYR activity based on dopamine functionalized carbon quantum dots (CQDs-Dopa) has been developed. Dopamine (Dopa) was covalently bond to CQDs through a simple one-pot hydrothermal method, and the prepared CQDs-Dopa exhibited a fluorescence emission at 499 nm under exciting wavelength at 310 nm with a quantum yield of approximately 2.1%. When TYR was mixed with CODs-Dopa, the dopamine moiety in CQDs-Dopa conjugate was oxidized to O-dopaquinone, and an intra-particle photo-induced electron transfer (PET) process consequently occurred between CQDs and O-dopaquinone to quench the fluorescence of CQDs-Dopa. TYR activity can be determined based on the fluorescence quenching degree of CQDs-Dopa. This assay covered two broad linear ranges: 44.4-711.1 U L-1 and 711.1-2925.4 U L-1, with detection limit of 17.7 U L-1. The proposed fluorescent assay was applied to TYR activity measurement in human serum samples. It showed promising potential for TYR activity assay in clinical applications.


Assuntos
Técnicas Biossensoriais , Carbono , Dopamina , Monofenol Mono-Oxigenase/análise , Pontos Quânticos , Humanos , Monofenol Mono-Oxigenase/sangue
6.
J Sep Sci ; 40(20): 4022-4031, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28782879

RESUMO

A new, rapid, green, and cost-effective magnetic solid-phase extraction of ochratoxin A from red wine samples was developed using polydopamine-coated magnetic multi-walled carbon nanotubes as the absorbent. The polydopamine-coated magnetic multi-walled carbon nanotubes were fabricated with magnetic multi-walled carbon nanotubes and dopamine by an in situ oxidative self-polymerization approach. Transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy and vibrating sample magnetometry were used to characterize the absorbents. Ochratoxin A was quantified with high-performance liquid chromatography coupled with fluorescence detection, with excitation and emission wavelengths of 338 and 455 nm, respectively. The conditions affecting the magnetic solid-phase extraction procedure, such as pH, extraction solution, extraction time, absorbent amount, desorption solution and desorption time were investigated to obtain the optimal extraction conditions. Under the optimized conditions, the extraction recovery was 91.8-104.5% for ochratoxin A. A linear calibration curve was obtained in the range of 0.1-2.0 ng/mL. The limit of detection was 0.07 ng/mL, and the limit of quantitation was 0.21 ng/mL. The recoveries of ochratoxin A for spiked red wine sample ranged from 95.65 to 100.65% with relative standard deviation less than 8%. The polydopamine-coated magnetic multi-walled carbon nanotubes showed a high affinity toward ochratoxin A, allowing selective extraction and quantification of ochratoxin A from complex sample matrixes.


Assuntos
Dopamina , Contaminação de Alimentos/análise , Nanotubos de Carbono , Ocratoxinas/isolamento & purificação , Vinho/análise , Extração em Fase Sólida
7.
Artigo em Inglês | MEDLINE | ID: mdl-28401806

RESUMO

The detection of mycotoxin contamination in foodstuffs is highly significant for public health. Herein we report an analytical method based on magnetic solid-phase extraction (MSPE) and UPLC-MS/MS for the simultaneous determination of mycotoxins, including fumonisins B1 (FB1), zearalenone (ZON) and ochratoxin A (OTA), in vegetable oil. Magnetic nanoparticles coated with double layers of silicon dioxide were synthesised and found to be an effective MSPE adsorbent for mycotoxins. The proposed MSPE procedure serves not only for sample clean-up but also for mycotoxin enrichment that enhances greatly the assay's sensitivity. Under the selected MSPE conditions, linear matrix-matched calibration curves were obtained for mycotoxins in a concentration range from 0.178 to 625 µg kg-1. The limits of detection were 0.210 µg kg-1 for FB1, 0.0800 µg kg-1 for OTA and 1.03 µg kg-1 for ZON. The proposed MSPE UPLC-MS/MS method was applied for the determination of mycotoxins in vegetable oil samples, including maize oil, rapeseed oil and soybean oil. ZON was detected in a maize oil at 101 µg kg-1, which is below the European Union limit of 200 µg kg-1 in foodstuffs.


Assuntos
Magnetismo , Micotoxinas/análise , Óleos Vegetais/química , Extração em Fase Sólida , Cromatografia Líquida de Alta Pressão , Espectrometria de Massas em Tandem
8.
Artigo em Inglês | MEDLINE | ID: mdl-28277175

RESUMO

Sensitive detection of gizzerosine, a causative agent for deadly gizzard erosion in chicken feeds, is very important to the poultry industry. In this work, a new method was developed based on microchip capillary electrophoresis (MCE) with laser-induced fluorescence (LIF) detection for rapid analysis of gizzerosine, a biogenic amine in fish meals. The MCE separation was performed on a glass microchip using sodium dodecyl sulfate (SDS) as dynamic coating modifier. Separation conditions, including running buffer pH and concentration, SDS concentration, and the separation voltage were investigated to achieve fast and sensitive quantification of gizzerosine. The assay proposed was very quick and could be completed within 65 s. A linear calibration curve was obtained in the range from 0.04 to 1.8 µg ml-1 gizzerosine. The detection limit was 0.025 µg ml-1 (0.025 mg kg-1), which was far more sensitive than those previously reported. Gizzerosine was well separated from other endogenous components in fish meal samples. Recovery of gizzerosine from this sample matrix (n = 3) was determined to be 97.2-102.8%. The results from analysing fish meal samples indicated that the present MCE-LIF method might hold the potential for rapid detection of gizzerosine in poultry feeds.


Assuntos
Ração Animal/análise , Peixes , Fluorescência , Imidazóis/análise , Lasers , Animais , Eletroforese em Microchip
9.
Zhongguo Zhong Yao Za Zhi ; 41(10): 1823-1834, 2016 May.
Artigo em Chinês | MEDLINE | ID: mdl-28895328

RESUMO

This study, based on the findings for Perilla resources, aimed to describe the species, distribution, importance, features, utilization and status of quantitative Perilla resources in China. This not only helps people to know well about the existing resources and researching development, but also indicates the overall distribution, selection and rational use of Perilla resource in the future. According to the output types, Perilla resources are divided into two categories: wild resources and cultivated resources; and based on its common uses, the cultivated resources are further divided into medicine resources, seed-used resources and export resources. The distribution areas of wild resources include Henan, Sichuan, Anhui, Jiangxi, Guangxi, Hunan, Jiangsu and Zhejiang. The distribution areas of medicine resources are concentrated in Hebei, Anhui, Chongqing, Guangxi and Guangdong. Seed-used resources are mainly distributed in Gansu, Heilongjiang, Jilin, Chongqing and Yunnan. Export resource areas are mainly concentrated in coastal cities, such as Zhejiang, Jiangsu, Shandong and Zhejiang. For the further study, the essential oil of leaf samples from different areas were extracted by the steam distillation method and analyzed by GC-MS. The differences in essential oil chemotypes among different Perilla leaves were compared by analyzing their chemical constituents. The main 31 constituents of all samples included: perillaketone (0.93%-96.55%), perillaldehyde (0.10%-61.24%), perillene (52.15%), caryophyllene (3.22%-26.67%), and α-farnesene (2.10%-21.54%). These samples can be classified into following five chemotypes based on the synthesis pathways: PK-type, PA-type, PL-type, PP-type and EK-type. The chemotypes of wild resources included PK-type and PA-type, with PK-type as the majority. All of the five chemotypes are included in cultivated resources, with PA-type as the majority. Seed-used resources are all PK-type, and export resources are all PA-type. The P. frutescens var. frutescens include five chemotypes, with PK-type as the majority. The PK-type leaves of P. frutescens var. acuta are green, while the PA-type leaves are reddish purple. The P. fruteseens var. crispa was mainly PA type with reddish purple leaves. The differences of the main chemotypes provide a scientific basis for distinguishing between Zisu and Baisu in previous literatures. Based on the lung toxicity of PK and the traditional use of Perilla, the testing standard of essential oil and Perilla herb shall be built, and PA type is recommended to be used in traditional Chinese medicine.


Assuntos
Óleos Voláteis/química , Perilla frutescens/química , China , Perilla frutescens/classificação , Folhas de Planta/química , Plantas Medicinais/química , Plantas Medicinais/classificação
10.
PLoS One ; 8(6): e65277, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23750250

RESUMO

Understanding greenhouse gases (GHG) emissions is becoming increasingly important with the climate change. Most previous studies have focused on the assessment of soil organic carbon (SOC) sequestration potential and GHG emissions from agriculture. However, specific experiments assessing tillage impacts on GHG emission from double-cropped paddy fields in Southern China are relatively scarce. Therefore, the objective of this study was to assess the effects of tillage systems on methane (CH4) and nitrous oxide (N2O) emission in a double rice (Oryza sativa L.) cropping system. The experiment was established in 2005 in Hunan Province, China. Three tillage treatments were laid out in a randomized complete block design: conventional tillage (CT), rotary tillage (RT) and no-till (NT). Fluxes of CH4 from different tillage treatments followed a similar trend during the two years, with a single peak emission for the early rice season and a double peak emission for the late rice season. Compared with other treatments, NT significantly reduced CH4 emission among the rice growing seasons (P<0.05). However, much higher variations in N2O emission were observed across the rice growing seasons due to the vulnerability of N2O to external influences. The amount of CH4 emission in paddy fields was much higher relative to N2O emission. Conversion of CT to NT significantly reduced the cumulative CH4 emission for both rice seasons compared with other treatments (P<0.05). The mean value of global warming potentials (GWPs) of CH4 and N2O emissions over 100 years was in the order of NT

Assuntos
Agricultura/métodos , Metano/metabolismo , Óxido Nitroso/metabolismo , Oryza/metabolismo , China , Metano/análise , Óxido Nitroso/análise , Porosidade , Chuva , Solo/química , Temperatura Ambiente
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