Sulfonamides of homoproline and dipeptides as organocatalysts for Michael and aldol reactions

Sulfonamides of the non-natural amino acid homoproline and the dipeptide Pro-Phe were synthesised and evaluated for their catalytic activity in Michael and aldol reactions. Sulfonamides of homoproline outperform proline and Pro-Phe in the Michael reaction, whereas sulfonamides of Pro-Phe lead to better results in the aldol reaction. The results of the present study show that the conversion of the carboxylic group of either homoproline or dipeptide Pro-Phe to the bioisosteric acyl sulfonamide group lead to improved organocatalysts.     

Pre-Column Derivatization HPLC Procedure for the Quantitation of Aluminium Chlorohydrate in Antiperspirant Creams Using Quercetin as Chromogenic Reagent

This article describes the development and validation of a selective high-performance liquid chromatography method that allows, after liquid–liquid extraction and pre-column derivatization reaction with quercetin, the quantification of aluminium chlorohydrate in antiperspirant creams. Chromatographic separation was achieved on an XTerra MS C18 analytical column (150 × 3.0 mm i.d., particle size 5 μm) using a mobile phase of acetonitrile:water (15:85, v/v) containing 0.08 % trifluoroacetic acid at a flow rate of 0.30 mL min^?1. Ultraviolet spectrophotometric detection at 415 nm was used. The assay was linear over a concentration range of 3.7–30.6 μg mL^?1 for aluminium with a limit of quantitation of 3.74 μg mL^?1. Quality control samples (4.4, 17.1 and 30.6 μg mL^?1) in five replicates from five different runs of analysis demonstrated intra-assay precision (% coefficient of variation <3.8 %), inter-assay precision (% coefficient of variation <5.4 %) and an overall accuracy (% recovery) between 96 and 101 %. The method was used to quantify aluminium in antiperspirant creams containing 11.0, 13.0 and 16.0 % (w/w) aluminium chlorohydrate, respectively.     

Multi-residue determination of seven quinolones antibiotics in gilthead seabream using liquid chromatography-tandem mass spectrometry

A sensitive and selective confirmatory analytical method for the multi-residue determination of seven quinolones (ciprofloxacin, enrofloxacin, sarafloxacin, danofloxacin, oxolinic acid, nalidixic acid and flumequine) in gilthead seabream (Sparus aurata) was developed. The sample pre-treatment involves extraction with 0.1M NaOH and purification by solid-phase extraction (SPE) on Waters Oasis HLB cartridges followed by the determination of all compounds in a single LC-electrospray ionization MS/MS run. Separation was achieved on a Perfectsil ODS-2, 5mum, 250mmx4mm, analytical column (MZ Analysentechnik) by gradient elution using a mixture of 0.2% (v/v) formic acid, methanol and acetonitrile within 30min. Multiple reaction monitoring (MRM) was used for selective detection of each quinolone. Accuracy was evaluated through recovery studies at three different fortification levels. The mean recoveries are between 90 and 132% for the selected levels with RSD values lower than 20%. The method presents satisfactory results for linearity, precision and limits of quantification. The latter are much lower than the maximum residue limits (MRLs) established by the European Union for quinolones in fish tissues (6-8mug/kg).     

An electrochemical study into the interaction between complement-derived peptides and DOPC mono- and bilayers

Electrochemical methods employing the hanging mercury drop electrode were used to study the interaction between variants of the complement-derived antimicrobial peptide CNY21 (CNYITELRRQH ARASHLGLAR) and dioleoyl phosphatidylcholine (DOPC) monolayers. Capacitance potential and impedance measurements showed that the CNY21 analogues investigated interact with DOPC monolayers coating the mercury drop. Increasing the peptide hydrophobicity by substituting the two histidine residues with leucine resulted in a deeper peptide penetration into the hydrophobic region of the DOPC monolayer, indicated by an increase in the dielectric constant of the lipid monolayer (Deltaepsilon = 2.0 after 15 min interaction). Increasing the peptide net charge from +3 to +5 by replacing the histidines by lysines, on the other hand, arrests the peptide in the lipid head group region. Reduction of electroactive ions (Tl+, Pb2+, Cd2+, and Eu3+) at the monolayer-coated electrode was employed to further characterize the types of defects induced by the peptides. All peptides studied permeabilize the monolayer to Tl+ to an appreciable extent, but this effect is more pronounced for the more hydrophobic peptide (CNY21L), which also allows penetration of larger ions and ions of higher valency. The results for the various ions indicate that charge repulsion rather than ion size is the determining factor for cation penetration through peptide-induced defects in the DOPC monolayer. The effects obtained for monolayers were compared to results obtained with bilayers from liposome leakage and circular dichroism studies for unilamellar DOPC vesicles, and in situ ellipsometry for supported DOPC bilayers. Trends in peptide-induced liposome leakage were similar to peptide effects on electrochemical impedance and permeability of electroactive ions for the monolayer system, demonstrating that formation of transmembrane pores alone does not constitute the mechanism of action for the peptides investigated. Instead, our results point to the importance of local packing defects in the lipid membrane in close proximity to the adsorbed peptide molecules.     

Analytical strategies to determine antibiotic residues in fish

The accelerated growth of aquaculture has resulted in a series of harmful effects to human health. The widespread and unrestricted use of antibiotics in this industry, to prevent bacterial infections, leads to remaining amounts in the aquatic environment. This has resulted in the emergence of antibiotic-resistant bacteria in aquaculture environments, in the increase in antibiotic resistance in fish pathogens as well as in the transfer of these resistance determinants to human pathogens. Moreover, the use of large amounts of antibiotics may lead to the presence of residual antibiotics in fish tissue and fish products. Fluoroquinolones, tetracyclines, penicillins, sulphonamides and other antibiotics, exhibiting activity against both Gram-positive and Gram-negative bacteria, are widely used for the treatment and prevention of diseases in fish. An extended and comprehensive review on the recent analytical methodologies concerning antibiotic residues in fish reported in the literature is provided in the present article. Emphasis is given on sample preparation regarding isolation and purification, chromatographic conditions and method validation according to legislation. Results of published assays are comparatively presented and criticised.     

Rapid genotyping of CYP2D6, CYP2C19 and TPMT polymorphisms by primer extension reaction in a dipstick format

In recent years an increasing amount of interest has been directed at the study and routine testing of polymorphisms responsible for variations in drug metabolism. Most of the current methods involve either time-consuming electrophoresis steps or specialized and expensive equipment. In this context, we have developed a rapid, simple and robust method for genotyping of CYP2D6*3, CYP2D6*4, CYP2C19*2, CYP2C19*3 and TPMT*2 single nucleotide polymorphisms (SNP). Genomic DNA is isolated from whole blood and the segments that span the SNP of interest are amplified by PCR. The products are subjected directly (without purification) to two primer extension (PEXT) reactions (three cycles each) using normal and mutant primers in the presence of biotin-dUTP. The PEXT primers contain a (dA)₃₀ segment at the 5′ end. The PEXT products are detected visually by a dry-reagent dipstick-type assay in which the biotinylated extension products are captured from immobilized streptavidin on the test zone of the strip and detected by hybridization with oligo(dT)-functionalized gold nanoparticles. Patient samples (76 variants in total) were genotyped and the results were fully concordant with those obtained by direct DNA sequencing.