HPLC analysis of a syrup containing nimesulide and its hydrolytic degradation product

The present paper deals with the evaluation of nimesulide, 2-phenoxy-4-nitroaniline, the main hydrolytic degradation product of nimesulide, of methylparaben and propylparaben, and eventually of 4-hydroxybenzoic acid by HPLC with UV detection at 254 nm in syrup as a pharmaceutical formulation. HPLC analysis was employed on the reversed phase C18 with methanol and 0.01 M dibasic ammonium phosphate (ρ _r = 60: 40, pH 4.0). Validation was performed using standards and a pharmaceutical preparation containing the compounds described above.     

Separation and quantification of 9-(alkylthio)acridines by capillary micellar electrokinetic chromatography and capillary liquid chromatography

Various thioacridine derivatives are potential chemotherapeutics against various diseases which are intensively synthesized, characterized, and investigated by many research groups. Efficient, fast, and reliable separation and quantification methods for their analysis are still to be developed. MEKC and capillary LC (CLC) were applied for the separation and quantification of five highly hydrophobic, weakly basic, and structurally similar 9-(alkylthio)acridines. Since the common anionic and cationic surfactants failed to separate the strongly hydrophobic thioacridines by MEKC, sodium cholate was used in an alkaline BGE and successfully employed for their fast separation. In CLC, the weakly basic nature of the thioacridines necessitated use of LiChrosorb RP-select B sorbent as the stationary phase, which combined with a very simple mobile phase methanol/water yielded an efficient chromatographic separation system. Both, the MEKC and CLC optimized separation methods were then applied to quantify the thioacridines within a concentration range of 1.0 x 10(-5)-1.0 x 10(-3) mol/L and the obtained experimental results were critically compared. In practical terms, the MEKC analytical method can quantify the analytes much faster but with a lower reliability while the CLC method performs slower analysis with a higher repeatability of the experimental results.     

Infrared spectroscopy and outer product analysis for quantification of fat, nitrogen, and moisture of cocoa powder

The combination of the near infrared (NIR) and Fourier-transform infrared (FTIR) absorbance spectra (1100-2500 nm and 4000-600 cm⁻¹) of 100 cocoa powder samples was used to build calibration models for the determination of the content of fat, nitrogen, and moisture. The samples that comprised the dataset had an average composition of 13.51% of fat, 3.77% nitrogen, and 3.98% moisture. The fat content ranged from 2.42 to 22.00%, the nitrogen from 0.88 to 4.48%, and moisture from 1.60 to 7.80%. For NIR, the relative root mean square error of cross-validation (RMSECV) was 7.0% (R² = 0.96) for fat, 1.7% (R² = 0.98) for nitrogen, and 5.2% (R² = 0.94) for moisture. For FTIR, the relative RMSECV was 10.4% (R² = 0.94) for fat and 3.9% (R² = 0.95) for nitrogen. However, for moisture, it was not possible to build a calibration model with suitable predictability. The combination of the NIR and FTIR domains (data fusion) by outer product analysis PLS1 allowed to predict these parameters and to characterise frequencies in one domain based on the information of the other domain. This work allows to conclude that the second derivative of NIR is the recommended procedure to quantify fat, nitrogen, and moisture content in cocoa powders by infrared spectroscopy.     

A Single Methylene Group in Oligoalkylamine‐Based Cationic Polymers and Lipids Promotes Enhanced mRNA Delivery

The development of chemically modified mRNA holds great promise as a new class of biologic therapeutics. However, the intracellular delivery and endosomal escape of mRNA encapsulated in nanoparticles has not been systematically investigated. Here, we synthesized a diverse set of cationic polymers and lipids from a series of oligoalkylamines and subsequently characterized their mRNA delivery capability. Notably, a structure with an alternating alkyl chain length between amines showed the highest transfection efficiency, which was linked to a high buffering capacity in a narrow range of pH 6.2 to 6.5. Variation in only one methylene group resulted in enhanced mRNA delivery to both the murine liver as well as porcine lungs after systemic or aerosol administration, respectively. These findings reveal a novel fundamental structure–activity relationship for the delivery of mRNA that is independent of the class of mRNA carrier and define a promising new path of exploration in the field of mRNA therapeutics.     

Leaching test for calcined kaolinite and kaolinite/TiO<Subscript>2</Subscript> photoactive composite

Kaolinite is a suitable material for fixing TiO₂ nanoparticles in a composite form. The kaolinite/TiO₂ composite has promising photoactive properties which are as important as is the possible impact of the composite on the environment. Accordingly, the stability of the kaolinite/TiO₂ composite dried at 105°C (KTI1) and calcined at 600 °C (KTI6) and the stability of the original kaolinite treated at various temperatures (105–800 °C) were studied by the leaching test in accordance with European standard BS EN 12457-2:2002 (British Standards Institution, 2002). The stability was evaluated on the basis of elements leached from the materials to extraction agents. Atomic emission spectrometry with inductively coupled plasma was used for determining the concentration of elements. In order to better understand the process of calcination and the structure changes in the kaolinite/TiO₂ composite and calcined kaolinite, the materials were evaluated using X-ray powder diffraction and infrared spectroscopy with Fourier transformation. The processes of kaolinite dehydroxylation and metakaolinite formation were observed. Kaolinite is an appropriate carrier for composite preparation due to its stability even after its treatment at high temperatures. The experiments confirmed the TiO₂ nanoparticles to be very strongly bound to the kaolinite surface. On the other hand, the experiments demonstrated that the presence of TiO₂ on the kaolinite surface caused the release of Al in high concentrations to the final extracts, especially after kaolinite/TiO₂ composite calcination.     

1,2,4‐Triazole‐based N‐heterocyclic carbene complexes of gold(I): synthesis,characterization and biological activity

Two gold(I) complexes of the (NHC)AuX type bearing a triazole‐based N‐heterocyclic carbene (NHC) ligand (1‐tert‐butyl‐4‐(4‐methylphenyl)‐3‐phenyl‐1H‐1,2,4‐triazol‐4‐ium‐5‐ylidene) and various halide ligands (X = Br, I) were synthesized and characterized in solution using NMR spectroscopy as well as in the solid state using X‐ray diffraction techniques. The cytotoxic properties of both compounds and the precursor, (NHC)AuCl, were screened against a panel of human tumour cell lines including liver cancer (HepG2), cervical cancer (HeLa S3) and leukaemia (CCRF‐CEM, HL‐60) and compared to cisplatin and auranofin. It was found that the activities of the chloro and bromo derivatives were generally superior to that of cisplatin and slightly less effective compared to auranofin, except for HepG2 cells where auranofin was not as effective. In addition, the ability to induce membrane phosphatidyl serine externalization as a hallmark of apoptosis in CCRF‐CEM leukaemic cells was investigated. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrochemical conversion of dinitrogen to ammonia mediated by a complex of fullerene C60 and gamma-cyclodextrin

We report on an electrochemical conversion of N2 to NH3 at ambient pressure and 60 degrees C, which is mediated by reduced C(60) inside the molecular cavity of gamma-cyclodextrin.     

Capillary electrophoresis mass spectrometry coupling with immobilized enzyme electrospray capillaries

Open tubular capillary enzyme reactors were studied for rapid protein digestion and possible on-line integration into a CE/ESI/MS system. The need to minimize the time of the analyte molecules to diffuse towards the surface immobilized enzyme and to maximize the surface-to-volume (S/V) ratio of the open tubular reactors dictated the use of very narrow bore capillaries. Extremely small protein amounts (atto-femtomoles loaded) could be digested with enzymes immobilized directly on the inside wall of a 10 microm I.D. capillary. Covalently immobilized L-1-tosylamido-2-phenylethyl chloromethyl ketone (TPCK)-trypsin and pepsin A were tested for the surface immobilization. The enzymatic activity was characterized in the flow-through mode with on-line coupling to electrospray ionization-time of flight-mass spectrometer (ESI/TOF-MS) under a range of protein concentrations, buffer pH's, temperatures and reaction times. The optimized reactors were tested as the nanospray needles for fast identification of proteins using CE-ESI/TOF-MS.     

Relationships between 31P chemical shift tensors and conformation of nucleic acid backbone: a DFT study

Density functional theory (DFT) has been applied to study the conformational dependence of 31P chemical shift tensors in B-DNA. The gg and gt conformations of backbone phosphate groups representing BI- and BII-DNA have been examined. Calculations have been carried out on static models of dimethyl phosphate (dmp) and dinucleoside-3',5'-monophosphate with bases replaced by hydrogen atoms in vacuo as well as in an explicit solvent. Trends in 31P chemical shift anisotropy (CSA) tensors with respect to the backbone torsion angles alpha, zeta, beta, and epsilon are presented. Although these trends do not change qualitatively upon solvation, quantitative changes result in the reduction of the chemical shift anisotropy. For alpha and zeta in the range from 270 degrees to 330 degrees and from 240 degrees to 300 degrees , respectively, the delta22 and delta33 principal components vary within as much as 30 ppm, showing a marked dependence on backbone conformation. The calculated 31P chemical shift tensor principal axes deviate from the axes of O-P-O bond angles by at most 5 degrees . For solvent models, our results are in a good agreement with experimental estimates of relative gg and gt isotropic chemical shifts. Solvation also brings the theoretical deltaiso of the gg conformation closer to the experimental gg data of barium diethyl phosphate.     

Short monolithic columns--a breakthrough in purification and fast quantification of tomato mosaic virus

Drawbacks of conventional virus purification methods have led to the development of new, mostly chromatography-based methods. Short monolithic columns are stationary phases intended for purification of large molecules. In this work efficient chromatographic purification of tomato mosaic virus (ToMV) from plant material is described. Based on short monolithic column, the purification process was shortened from 5 days to 2 hours. High viral purity was achieved and recovery of chromatographic step was up to 90%. In addition, these columns enabled preliminary quantification of the virus in just a few minutes, much faster than other quantification methods (e.g. enzyme-linked immunosorbent assay or real-time polymerase chain reaction) which take 1-2 days. These results demonstrate the potential of short monolith column technology for purification and analysis of different viruses.