A New Chemometric Strategy in Electrochemical Method Optimization for the Quantification of Cefdinir in Tablets,Effervescent Tablets and Suspension Samples

A new voltammetric method, based on the use of single‐use pencil graphite electrode, was developed for the quantitative determination of cefdinir by square wave voltammetry. Chemometric optimization strategy was used to select the suitable values for three experimental parameters (pH of the supporting electrolyte, frequency and square wave amplitude) by applying a 3³ full factorial design model. The optimal voltammetric conditions were found to be pH 5.0 for supporting electrolyte (Britton‐Robinson buffer), 43 mV for square wave amplitude and 108 Hz for frequency. Square wave voltammograms of calibration, validation and unknown samples were recorded between 0.0–1400 mV under the optimized voltammetric conditions. Linear regression equation was computed in the linear working range of 0.5–20 μg/mL by using the relationship between the concentration and peak current at 600 mV. The optimized voltammetric method was validated by assessing the analysis results of validation samples. Then the proposed method was applied for the quantitative determination of cefdinir in three different pharmaceutical preparations, namely film‐coated tablets, effervescent tablets and powder for oral suspension. It was concluded that the proposed voltammetric method was suitable for the quantitative analysis of commercial pharmaceutical preparations containing cefdinir.     

Spectrum and Eigenfunctions of the Lattice Hyperbolic Ruijsenaars–Schneider System with Exponential Morse Term

We place the hyperbolic quantum Ruijsenaars–Schneider system with an exponential Morse term on a lattice and diagonalize the resulting n-particle model by means of multivariate continuous dual q-Hahn polynomials that arise as a parameter reduction of the Macdonald–Koornwinder polynomials. This allows to compute the n-particle scattering operator, to identify the bispectral dual system, and to confirm the quantum integrability in a Hilbert space setup.     

New Cardenolides from Biotransformation of Gitoxigenin by the Endophytic Fungus Alternaria eureka 1E1BL1: Characterization and Cytotoxic Activities

Microbial biotransformation is an important tool in drug discovery and for metabolism studies. To expand our bioactive natural product library via modification and to identify possible mammalian metabolites, a cytotoxic cardenolide (gitoxigenin) was biotransformed using the endophytic fungus Alternaria eureka 1E1BL1. Initially, oleandrin was isolated from the dried leaves of Nerium oleander L. and subjected to an acid-catalysed hydrolysis to obtain the substrate gitoxigenin (yield; ~25%). After 21 days of incubation, five new cardenolides 1, 3, 4, 6, and 8 and three previously- identified compounds 2, 5 and 7 were isolated using chromatographic methods. Structural elucidations were accomplished through 1D/2D NMR, HR-ESI-MS and FT-IR analysis. A. eureka catalyzed oxygenation, oxidation, epimerization and dimethyl acetal formation reactions on the substrate. Cytotoxicity of the metabolites were evaluated using MTT cell viability method, whereas doxorubicin and oleandrin were used as positive controls. Biotransformation products displayed less cytotoxicity than the substrate. The new metabolite 8 exhibited the highest activity with IC₅₀ values of 8.25, 1.95 and 3.4 µM against A549, PANC-1 and MIA PaCa-2 cells, respectively, without causing toxicity on healthy cell lines (MRC-5 and HEK-293) up to concentration of 10 µM. Our results suggest that A. eureka is an effective biocatalyst for modifying cardenolide-type secondary metabolites.     

Electron paramagnetic resonance study of irradiated tetramethyl-4-piperidion

The electron paramagnetic resonance of single crystals of tetramethyl-4-piperidion (TMP; C₉H₁₉NO) has been observed and analysed for different orientations of the crystal in the magnetic field, after being damaged at 300 K by γ-irradiation. The crystals have been investigated between 100 and 450 K. The spectra were found to be temperature dependent. The irradiation of TMP by γ-rays produces radicals at the nitrogen atoms in the molecule. The principal values of the hyperfine coupling tensor of the unpaired electron and the principal values of the g-tensor were determined. The results were found to be in good agreement with the existing literature data and theoretical predictions.     

An electron paramagnetic resonance study on irradiated triphenylphosphinselenid single crystal

The single crystals of triphenylphosphinselenid [C₁₈H₁₅PSe] were produced by slow evaporation of concentrated ethyl acetate solutions. These single crystals were exposed to ⁶⁰Co gamma (γ) rays with a dose speed of 0.980 kGy/h at the room temperature for 72 h. The free radical over the sample was observed using electron paramagnetic resonance (EPR)–X band spectrometer. The EPR spectra were recorded between 120 and 400 K. Furthermore, the sample irradiated was rotated in steps of 10° and analyzed for different orientations of the crystal in the magnetic field. Only one radical structure was determined on the molecule. The hyperfine constants of the sample were found to be anisotropic. The average values of these constants and value of g were calculated as following: g=2.007656, a_Se=37.47 G, a_P=27.44 G, a_Ha=17.28 G, and a_Hb=18.16 G.     

Fractional-continuous wavelet transforms and ultra-performance liquid chromatography for the multicomponent analysis of a ternary mixture containing thiamine, pyridoxine, and lidocaine in ampules

New chemometric approaches based on the application of partial least squares (PLS) and principal component regression (PCR) algorithms with fractional wavelet transform (FWT) and continuous wavelet transform (CWT) are proposed for the spectrophotometric multicomponent determination of thiamine hydrochloride (B1), pyridoxine hydrochloride (B6), and lidocaine hydrochloride (LID) in ampules without any separation step. In this study PLS and PCR techniques were applied to the raw spectral data, FWT-coefficients, and FWT-CWT-coefficients. These calibration models were labeled as Raw-PLS and Raw-PCR, FWT-PLS and FWT-PCR, and FWT-CWT-PLS and FWT-CWT-PCR, respectively. A new ultra-performance liquid chromatographic (UPLC) method was developed for the comparison of the results obtained by applying the chemometric calibration methods. Chromatographic separation and determination of B1, B6, and LID in ampules were performed on an Acquity UPLC BEH C18 column (50x2.1 mm id, 1.7 pm particle size) using gradient elution with a mobile phase consisting of methanol and 0.01 M HCI at a constant flow rate of 0.6 mL/min. These combined chemometric calibrations and UPLC were validated by analyzing various ternary mixtures, B1, B6, and LID. The proposed chemometric approaches (signal processing-multivariate calibrations) and UPLC method were applied to the quantitative multicomponent analysis of marketed ampules containing the vitamins B1 and B6 with LID.     

Determination of the Complexing Constants by the Aid of 13C Dipole-Dipole Relaxation Time Measurements. Part. III. Complexing of 15-Crown-5 and 18-Crown-6 with Na+,K+ and Ca2+ in DHOX

The association constants, K_a of KI, Nal and CaCl₂ complexing with 1,4,7,10,13-pentaoxacyclopentadecane and 1,4,7,10,13,16-hexaoxacycloocta-decane in DHO were determined by the aid of ¹³C dipole-dipole relaxation time measurements.

The mole fraction of the complexed ligand, P_C were obtained by the use of the equation of 1/T^obs ₁ - 1/T₁₀ = P_C (1/T^O ₁ - 1/T₁₀) where the T₁₀ and T^o ₁ are the relaxation times of free and complexed macrocyclic ethers respectively.

K_a values obtained from the above given equation depending on the cation concentration, [A⁺ _O] typically reflected the relation between the cationic radius and cyclic ether ring size.     

Fixed point theory for cyclic generalized {(\varphi-\phi)}-contraction mappings

Fixed point results are presented for cyclic generalized ${(\phi-\varphi)}$ -contraction mappings on complete metric spaces (X, d). Our results extend previous results given by ?iri?, Moradi and Khojasteh, and Karap?nar.