LC�CMS�CMS Method for the Analysis of New Non-Imidazole Histamine H3 Receptor Antagonist 1-[3-(4-tert-Butylphenoxy)propyl]piperidine in Rat Serum��Application to Pharmacokinetic Studies

A sensitive and specific liquid chromatography electrospray ionisation-tandem mass spectrometry method for determination of new non-imidazole histamine H(3) receptor antagonist 1-[3-(4-tert-butylphenoxy)propyl]piperidine (DL76) in rat serum has been developed and validated. Chromatography was performed on a XBridge? C18 analytical column (2.1?×?30?mm, 3.5?μm, Waters, Ireland) with gradient elution using a mobile phase containing acetonitrile and water with an addition of 0.1% of formic acid. Detection was achieved by an Applied Biosystems MDS Sciex (Concord, Ontario, Canada) API 2000 triple quadrupole mass spectrometer. Electrospray ionization (ESI) was used for ion production. The limit of detection in the SRM mode was found to be 0.5?ng?mL(-1). The limit of quantification was 1?ng?mL(-1). The precision and accuracy for both intra- and inter-day determination of DL76 ranged from 1.65 to 15.09% and from 88.74 to 113.43%. The results of this analytical method validation allow to carry out pharmacokinetic studies in rats. The method was used for the pilot study of the pharmacokinetic behavior of DL76 in rats after intravenous administration.     

A mechanistic study on the disproportionation and oxidative degradation of phenothiazine derivatives by manganese(III) complexes in phosphate acidic media

The oxidative degradation of phenothiazine derivatives (PTZ) by manganese(III) was studied in the presence of a large excess of manganese(III)-pyrophosphate (P₂O₇ ²⁻), phosphate (PO₄ ³⁻), and H⁺ ions using UV–vis. spectroscopy. The first irreversible step is a fast reaction between phenothiazine and manganese pyrophosphate leading to the complete conversion to a stable phenothiazine radical. In the second step, the cation radical is oxidized by manganese to a dication, which subsequently hydrolyzes to phenothiazine 5-oxide. The reaction rate is controlled by the coordination and stability of manganese(III) ion influenced by the reduction potential of these ions and their strong ability to oxidize many reducing agents. The cation radical might also be transformed to the final product in another competing reaction. The final product, phenothiazine 5-oxide, is also formed via a disproportionation reaction. The kinetics of the second step of the oxidative degradation could be studied in acidic phosphate media due to the large difference in the rates of the first and further processes. Linear dependences of the pseudo-first-order rate constants (k _obs) on [Mn^III] with a significant non-zero intercept were established for the degradation of phenothiazine radicals. The rate is dependent on [H⁺] and independent of [PTZ] within the excess concentration range of the manganese(III) complexes used in the isolation method. The kinetics of the disproportionation of the phenothiazine radical have been studied independently from the further oxidative degradation process in acidic sulphate media. The rate is inversely dependent on [PTZ^+.], dependent on [H⁺], and increases slightly with decreasing H⁺ concentration. Mechanistic consequences of all these results are discussed.     

Oxidation of phenothiazine dyes by manganese(III) in sulfuric acid solution

Manganese(III) sulfato complexes cause the oxidative degradation of methylene blue and its partially and fully N-demethylated derivatives, azure B and thionine dyes, respectively, in sulfuric acid media. The reaction proceeds through a colored reactive organic radical generated in the first stage via one-electron oxidation of the starting material, leading to a mixture of N-demethylated and/or deaminated species. The rates of formation of the methylene blue and azure B radicals are much higher than those of their further decomposition, whereas the generation of the thionine radical is much slower than its immeasurably fast decay. The kinetics of decomposition of all three dyes and the methylene blue and azure B radicals were studied spectrophotometrically under isolation conditions at 298 K. The first stage of each reaction proceeds according to a second-order rate expression, being first order in the dyes and in the manganese(III) concentrations. Dependence of the pseudo-first-order rate constants on the oxidant concentration for the second stage exhibits a saturation effect under the applied conditions. It is postulated that electron transfer takes place between the [Mn(SO₄)₃]³⁻ complex and the protonated form of the dye. The reactivity order of the dyes as determined from the second-order rate constants for the first reaction stage corresponds to the order of their HOMO energies.     

Soft-templating synthesis and adsorption properties of mesoporous carbons with embedded silver nanoparticles

Mesoporous carbons containing silver nanoparticles have been successfully synthesized under acidic conditions by employing resorcinol and formaldehyde as carbon precursors and triblock copolymer EO₁₀₁PO₅₆EO₁₀₁ (Lutrol F127) as a soft template. Silver nanoparticles of ∼90 nm were added to the synthesis mixture to achieve 10 wt% and 20 wt% of Ag loading in the carbon. Also, tetraethyl orthosilicate (TEOS) was introduced to the system in order to improve adsorption properties of the silver-carbon composites and to reinforce its structure. The resulting carbons with incorporated silver nanoparticles featured high surface areas, large total pore volumes and primary mesopores in the range between ∼6–7 nm.     

Callitriche cophocarpa — a new rich source of active phenolic compounds

This study was focused on the analysis of the contents (by HPLC-DAD) and antioxidant activity of phenolic compounds of aquatic higher plant Callitriche cophocarpa. The novelty of the work was: 1) the study of the species which is almost unknown in the context of investigations of bio-active compounds and, 2) the application of a unique L-band electron resonance spectroscopy (L-band EPR) to measure antioxidant activity of samples. The results were compared with those obtained for microalgae Chlorella and Spirulina which are widely distributed as the diet supplements. The obtained results are very promising with respect to the freeze-dried material of Callitriche, which revealed both high level of phenolic compounds (33 mg g^?1 dry weight) and antioxidant activity (0.14 g of reduced DPPH· g^?1 dry weight). An isoform of sinapic acid appeared to be the main fraction in this sample. The average content of the total phenolic compounds in Callitriche freeze-dried samples was ca. 43 or 25 times higher than in the case of the Chlorella or Spirulina samples, respectively. These samples showed also 16 times lower scavenging activity in relation to freeze-dried Callitriche material.      

Implementation of chemometric techniques for evaluation of antioxidant properties of Camellia sinensis extracts

In this study, antioxidant properties of commercial green teas and dietary supplements containing Camellia sinensis extracts were evaluated. Extracts were examined using two antioxidant assays (DPPH^· radical method and ABTS^·+ cation radical method). A Folin-Ciocalteu assay was used to evaluate the total polyphenol content in the extracts. In order to compare and characterize the investigated Camellia sinensis extracts, chemometric techniques based on fingerprint chromatograms, antioxidant activity and total polyphenol content were applied. Application of chemometric methods allowed for reduction of multidimensionality of the data set and grouped the samples into differentiable clusters. The relationship between the antioxidant activity and total polyphenol content was also assessed. The results indicated that extracts with the higher polyphenolic content exhibited the stronger antiradical activity against both DPPH^· radicals and ABTS^·+ cation radicals. The multivariate calibration technique (such as a tree regression algorithm) can be a useful tool for rapid determining the antioxidant activity of a herbal product based on its fingerprint chromatogram      

The use of moisture sorption isotherms and glass transition temperature to assess the stability of powdered baby formulas

The influence of adverse conditions of environment in the case of baby formulas, which are multiple mixtures, should be minimised. Water activity (a _w) and moisture content, correlated through sorption isotherms, and glass transition temperature have been considered relevant parameters to describe food stability. The aim of the study was to analyse water activity and glass transition temperature as the function of water content for samples of baby formulas. Three types of baby formulas (mixture, agglomerate, coated agglomerate) were determined by sorption isotherms, DSC and MDSC. DSC curves of mixture, agglomerate and coated agglomerate did not show differences in shape and course. The glass transition temperature of powders stored at different water activities was measured and it decreased with the increase in moisture content, confirming the strong plasticising effect of water on this property. Critical water activities varied from 0.14 to 0.68 and critical moisture contents varied from 0.032 to 0.062 g g^?1 powder.     

Turning Tryptophanase into Odor‐Generating Biosensors

An odor‐based sensor system that exploits the metabolic enzyme tryptophanase (TPase) as the key component is reported. This enzyme is able to convert an odorless substrate like S‐methyl‐L ‐cysteine or L ‐tryptophan into the odorous products methyl mercaptan or indole. To make a biosensor, TPase was biotinylated so that it could be coupled with a molecular recognition element, such as an antibody, to develop an ELISA‐like assay. This method was used for the detection of an antibody present in nM concentrations by the human nose. TPase can also be combined with the enzyme pyridoxal kinase (PKase) for use in a coupled assay to detect adenosine 5′‐triphosphate (ATP). When ATP is present in the low μM concentration range, the coupled enzymatic system generates an odor that is easily detectable by the human nose. Biotinylated TPase can be combined with various biotin‐labeled molecular recognition elements, thereby enabling a broad range of applications for this odor‐based reporting system.