A rapid and sensitive UPLC–MS/MS method for quantitative determination of arformoterol in rat plasma,lung and trachea tissues

A rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC–MS/MS) method was developed and fully validated for determination of arformoterol in rat plasma, lung and trachea tissues.     

Synthesis and antiviral bioactivity of novel chalcone derivatives containing purine moiety

A series of novel chalcone derivatives containing purine group was synthesized and evaluated for their antiviral activities against cucumber mosaic virus and tobacco mosaic virus. Compound 3o exhibited remarkable antiviral activities and strong combining capacity to tobacco mosaic virus coat protein.     

Poly(m-ferrocenylaniline) modified carbon nanotubes-paste electrode encapsulated in nafion film for selective and sensitive determination of dopamine and uric acid in the presence of ascorbic acid

A nafion covered carbon nanotubes-paste electrode modified with poly(m-ferrocenylaniline), (Nf/p(FcAni)-CNTsPE), provides a novel voltammetric sensor for the selective determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). We studied the electrochemical activity of Nf/p(FcAni)-CNTsPE toward DA, UA, and AA by differential pulse voltammetry (DPV). DA and UA anodic peaks appear at 0.30 and 0.45 V, respectively while an anodic peak for AA was not observed. DPV oxidation peak values are linearly dependent on DA concentration over the range 1–150 μM (r² = 0.992), and on UA concentration over the range 5–250 μM (r² = 0.997). DA and UA detection limits are estimated to be 0.21 and 0.58 μM, respectively. The modified electrode shows both good selectivity and reproducibility for the selective determination of DA and UA in real samples. Finally, the modified electrode was successfully applied for the determination of DA and UA in pharmaceutical or biological sample fluids.     

Mucin 4 detection with a label-free electrochemical immunosensor

Mucin 4 (MUC4) is a useful biomarker for endometriosis and cancers of the pancreas, esophagus and breast. The very first electrochemical immunosensor for the detection of MUC4 is reported, using carbon-based screen-printed electrodes modified by reaction with the diazonium salt of p-aminophenylacetic acid. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize and optimize the electrografting process. The in situ surface modification through diazotation with phenylacetic groups enables the chemical binding of the specific antibody, followed by its affinity reaction with MUC4. The immunosensor was optimized with respect to several parameters and is very promising for clinical applications, having a limit of detection of 0.33 μg mL^− 1 and a linear domain between 1 and 15 μg mL^− 1 obtained by electrochemical impedance spectroscopy measurements.     

Stability-indicating HPLC method for the determination of nicardipine in capsules and spiked human plasma. Identification of degradation products using HPLC/MS

In this stability-indicating, reversed-phase high-performance liquid chromatographic method for nicardipine (NIC), forced degradation has been employed and the formed degradants were separated on a C18 (150 mm × 3.9 mm, 5 μm) analytical column using a mobile phase consisted of 70% methanol: acetic acid containing 0.01 M triethylamine with pH 4. The flow rate was 1.0 mL/min and the photodiode array detection wavelength was 353 nm. Forced degradation of the drug was carried out under acidic, basic, photolytic, and oxidative stress conditions. Chromatographic peak purity data indicated no co-eluting peaks with the main peaks. This method resulted in the detection of seven degradation products. Among these, two major degradation products from basic hydrolysis, one from oxidation by H₂O₂ and four from photolytic stress were identified by mass spectral data. A good linear response was achieved over the range of 0.5–40 μg/mL with a limit of detection (LOD) of 0.011 μg/mL and limit of quantification (LOQ) of 0.036 μg/mL. The suggested method was successfully applied for the analysis of NIC in its commercial capsules, with mean% recovery value of 100.11 ± 2.26%. The method was extended to the in vitro determination on NIC in spiked human plasma samples with mean% recovery of 99.04 ± 5.67%. The suggested method was utilized to investigate the kinetics of photolytic induced degradation.     

A disposable amperometric enzyme immunosensor for rapid detection of Vibrio parahaemolyticus in food based on agarose/Nano-Au membrane and screen-printed electrode

Recent outbreaks of foodborne illnesses continue to support the need for rapid and sensitive methods for detection of foodborne pathogens. A disposable electrochemical immunosensor for detection of Vibrio parahaemolyticus (VP) based on the screen-printed electrode (SPE) coated with agarose/Nano-Au membrane and horseradish peroxidase (HRP) labeled VP antibody (HRP-anti-VP) has been developed in this paper. Then, the immunosensor was characterized by cyclic voltammetry (CV) and laser scanning confocal microscope (LSCM). The immunosensor was incubated with the one-step immunoassay format involving VP for 30 min at room temperature (25 ± 0.5 °C). The access of the active center of HRP catalyzing the oxidation reaction of thionine by H₂O₂ was partly inhibited by VP, which connected on the surface of the immunosensor by immunoreaction. VP could be quantificationally detected according to the shift of reduction current while CV was used as electrochemical means to detect the products of the enzymatic reaction. Under the optimum conditions of immunoreaction and electrochemical detection, VP was rapidly detectable by sigmoidal curve method and form a linear calibration between 10⁵ and 10⁹ cfu/ml with an associated detection limit of 7.374 × 10⁴ cfu/ml (S/N = 3). The immunosensor had acceptable specificity, reproducibility, stability and accuracy, indicating that the immunosensor could satisfy the need of practical sample detection.     

Novel dual inhibitors against FP-2 and PfDHFR as potential antimalarial agents: Design,synthesis and biological evaluation

A series of novel 2,4-diaminopyrimidine-modified compounds was designed and synthesized. Compound 14 showed micromolar dual inhibitory effect on both FP-2 and PfDHFR, and potential inhibition to the proliferation of P. falciparum 3D7 strain and chloroquine-resistant P. falciparum Dd2 strain.     

Diterpenoids from the aerial parts of Leonurus macranthus

One cis clerodane-type (1) and three highly oxygenated labdane-type diterpenes (2-4) were isolated from the aerial parts of Leonurus macranthus. Compound 1 represents the first example of cis clerodane-type diterpene in the plants of Leonurus genus.     

One-pot photoreduction to prepare NIR-absorbing plasmonic gold nanoparticles tethered by amphiphilic polypeptide copolymer for synergistic photothermal-chemotherapy

We developed one-pot photoreduction strategy to fabricate the NIR-absorbing plasmonic PLC-b-PEO@Au NPs. It possessed strong NIR absorption at 700-1100 nm, an ultrahigh photothermal conversion efficiency of 62.1%, and good photostability.     

Synthesis and antimicrobial activities of novel quinazolin-4(3H)-one derivatives containing a 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole moiety

A series of novel quinazolin-4(3H)-one derivatives (6a–6y) containing a 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole moiety were designed and synthesized, and their structures were fully characterized by ¹H NMR, ¹³C NMR, HRMS and IR spectra. Among them, the structure of compound 6u was unambiguously confirmed via single crystal X-ray diffraction analysis. The obtained bioassay results showed that compounds 6h, 6k, 6l and 6y had the EC₅₀ (half-maximal effective concentration) values of 34.8, 28.2, 41.5 and 42.5 μg/mL against the phytopathogenic bacterium Xanthomonas oryzae pv. oryzae (Xoo), respectively, which were significantly better than commercial bactericide Bismerthiazol (EC₅₀ = 95.8 μg/mL). Additionally, compounds 6a and 6b exhibited the strong inhibition activity against the pathogen Xanthomonas axonopodis pv. citri (Xac).     

G-quadruplex-assisted enzyme strand recycling for amplified label-free fluorescent detection of UO22+

A G-quadruplex-assisted enzyme strand recycling strategy was developed for amplified label-free fluorescent detection of uranyl ion (UO₂²⁺).     

Electrochemical detection of perchloroethylene using differential pulse voltammetry

We demonstrate the application of differential pulse voltammetry (DPV) for the electrochemical detection of perchloroethylene (PCE) on an unmodified glassy carbon electrode surface. Detection sensitivity was substantially improved using DPV, in which dechlorination was denoted by a cathodic peak observed at approximately − 0.6 V (vs Ag/AgCl). Peak current intensity was found to correlate linearly with concentration over a tested range of 0 to 10 μM. The utility of this technique was subsequently evaluated for PCE-spiked environmental samples containing either Methylobacterium adhaesivum (1 × 10⁶ cells/mL) or creek water (10% v/v). In all environmental samples, a linear dynamic range was also observed from approximately 0 to 10 μM. The limit of detection was determined to be 0.3 μM in blank buffer, 0.4 μM in bacteria-containing samples and 1.2 μM in creek water samples.     

Determination of neomycin in water samples by high performance anion chromatography with pulsed amperometric detection

A simple, fast and reliable method, using high performance anion chromatography with pulsed amperometric detection, had been developed for the analysis of neomycin in water samples. The elution and separation were carried out with an isocratic mobile phase, containing 10 mmol/L NaOH. The influence of the concentration and pH of the mobile phase on the separation and detection was investigated. A quadruple-potential waveform used for the detection was optimized. The detection limit of neomycin was down to 0.027μg/mL. The linearity of neomycin calibration curve ranged from 0.050 to 0.505μg/mL with correlation coefficient of 0.9997. R.S.D. (n = 11) was 4.0%.     

Simultaneous determination of seven prohibited substances in cosmetic products by liquid chromatography-tandem mass spectrometry

In this paper,we developed and validated a simple,sensitive,and selective high-performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) method to identify and measure the following prohibited substances that may be found in cosmetic products:minoxidil,hydrocortisone, spironolactone,estrone,canrenone,triamcinolone acetonide and progesterone.Chromatographic separation was performed on a Waters Symmetry C18(100 mm×2.1 mm,3.5μm particle size) with a gradient elution system composed of 0.2%(v/v) formic acid aqueous solution and methanol containing 0.2%(v/v) formic acid at a flow rate of 0.3 mL/min.The substances were detected using a triple quadrupole mass spectrometer in the multiple reaction monitoring mode with an electrospray ionization source.All of the calibration curves showed good linearity(r > 0.999) within the tested concentration ranges.The limit of detection was <25 pg.The relative standard deviations for intraday precision for each of the prohibited substances were <3.5%at two concentration levels(2μg/g,10μg/g). The relative recovery rate for each of the prohibited substances ranged from 91.8%to 111%at three concentration levels(0.1μg/g,2μg/g,10μg/g),including the limit of quantification.In conclusion,we have developed and validated a method that can identify seven prohibited substances in cosmetic products.     

Novel strategy of constructing fluorescent probe for MAO-B via cascade reaction and its application in imaging MAO-B in human astrocyte

A novel strategy was developed to detect MAO-B and image MAO-B in human astrocyte by constructing coumarin via cascade reaction and intramolecular cyclization.     

Lanostane triterpenoids from fruiting bodies of the bracket fungus Fomitopsis feei

Three 24-methyl-lanostane triterpenoids, fomitopsins D–F (1–3), were isolated together with four known compounds (4–7) from fruiting bodies of the basidiomycete Fomitopsis feei. The structures were elucidated by spectroscopic analysis and chemical correlations, including the conversion of 1 into a mixture of 2 and 3 under acidic conditions. Compound 1 was previously isolated after conversion to a methyl ester derivative, however, the side-chain stereochemistry was not determined. Fomitopsins E (2) and F (3) exhibited activity against Bacillus cereus with MIC values of 6.25 μg/mL. On the other hand, fomitopsin D (1) showed activity against herpes simplex virus type 1 (HSV-1) with an IC₅₀ value of 17 μg/mL.     

Determination of sulfonamides in food samples by membrane-protected micro-solid phase extraction coupled with high performance liquid chromatography

In the present study, a simple and sensitive extraction method based on polypropylene membrane-protected micro-solid phase extraction (MP-μ-SPE) has been developed for analysis of sulfonamides in food samples. Poly (methacrylic acid-ethylene glycol dimethacrylate) (p-MAA-EDMA) was synthesized using orthogonal array experimental design, optimized with three factors at four levels and evaluated on yield, hydrophobic and cation-exchange properties. The optimized p-MAA-EDMA was then employed as the sorbent in the MP-μ-SPE for extraction of sulfonamides from milk and chicken muscle samples, followed by high performance liquid chromatographic analysis with ultraviolet detection. Under optimized extraction conditions, good linearities (0.010–1.0 μg mL^?1 with r² > 0.9900), low limits of detection (0.38–0.62 ng mL^?1), and acceptable intra-day (2.7–13.7%) and inter-day (6.7–15.2%) relative standard deviations were obtained. It was demonstrated to be an effective approach to handle semi-solid/solid samples with good resistance to interference from “dirty” samples.     

A simple and sensitive assay for apurinic/apyrimidinic endonuclease 1activity based on host-guest interaction of β-cyclodextrin polymer and pyrene

A simple and sensitive method for APE1 activity detection was developed based on fluorescence enhancement of pyrene in the presence of β-cyclodextrin polymer.     

Using enantioselective dispersive liquid–liquid microextraction for the microseparation of trans-cyclohexane-1,2-diamine enantiomers

A new chiral separation system effective for the enantioselective extraction of racemic trans-cyclohexane-1,2-diamine is presented. Enantioselective dispersive liquid–liquid microextraction has been used for the chiral microseparation of trans-cyclohexane-1,2-diamine, with a chiral azophenolic crown ether being identified as a versatile chiral selector. The influence of various process conditions on the extraction performance was studied experimentally. It was found that the operational selectivity in one extraction step is mainly related to the type and volume of the solvents, chiral selector concentration, extraction time, temperature of sample solution, and pH. At optimum conditions (300 μL of diethyl ether as the extraction solvent 1 mL of methanol as the disperser solvent, with 5 mmol L^?1 chiral selector concentration, pH of the sample equal to 4.5, 30 min extraction time and a temperature of 10 °C), the distribution ratio of (R,R)- and (S,S)-trans-cyclohexane-1,2-diamine was 18.3 and 1.8, respectively, while the enantioselectivity value of 10.2 was found at the optimum condition.     

Aptamer-quantum dots and teicoplanin-gold nanoparticles constructed FRET sensor for sensitive detection of Staphylococcus aureus

The detection of bacterial pathogen such as Staphylococcus aureus(S.aureus) is essential for the regulation of food hygiene and disease diagnosis.Herein,we developed a simple one-step fluorescence resonance energy transfer(FRET)-based sensor for specific and sensitive detection of S.aureus in food and serum samples,in which aptamer-modified quantum dots(aptamer-QDs) was employed as the energy donor and antibiotic of teicoplanin functionalized-gold nanoparticles(Teico-AuNPs) was chosen as the energy acceptor.Within 1 h,the FRET-based sensor showed a linear range of from 10 cfu/mL to 5 × 10~8 cfu/mL,with the low limit of detection(LOD,2 cfu/mL) for S.aureus in buffer.When further applied to assay S.aureus in real samples,the FRET-based sensor showed good recoveries ranging from 84.5% to 110.0%,with relative standard derivations(RSDs) of 0.01%-0.44% and a LOD of 100 cfu/mL in milk,orange juice and human serum.