Simultaneous spectrophotometric determination of phenanthridine, phenanthridinone and phenanthridine N-oxide using multivariate calibration methods

Phenanthridine-pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

Two novel conjugate molecules were designed: pyrene and phenanthridine-amino acid units with a different linker length between the aromatic fragments. Molecular modelling combined with spectrophotometric experiments revealed that in neutral and acidic buffered water solutions conjugates predominantly exist in intramolecularly stacked conformations because of the π-π stacking interaction between pyrene and phenanthridine moieties. The investigated systems exhibited a pH-dependent excimer formation that is significantly red-shifted relative to the pyrene and phenanthridine fluorescence. While the conjugate with a short linker showed negligible spectrophotometric changes due to the polynucleotide addition, the conjugate with a longer and more flexible linker exhibited a micromolar and submicromolar binding affinity for ds-polynucleotides and inactivated a mutant of dipeptidyl peptidase enzyme E451A. Confocal microscopy revealed that the conjugate with the longer linker entered the HeLa cell membranes and blue fluorescence was visualized as the dye accumulated in the cell membrane.

UV-VIS spectrophotometric-assisted chemometric calibration models for simultaneous determination of thiamine and pyridoxine vitamins in powdered infant formula

Thiamine and pyridoxine, which are hydrophilic B vitamins, are compounds that play an important role in many biochemical events for the health of infants and adults. Recently, because of the complexity of food and pharmaceutical composition, chemometric models are preferred to obtain relevant information from multivariate measured data. The aim of this study was to determine the simultaneous quantitative analysis of thiamine and pyridoxine in powdered infant formula and pharmaceutical formulations by the UV-visible spectrophotometric method coupled with chemometric calibration models (partial least squares (PLS) and principal component regression (PCR)). These vitamins were extracted by addition of trichloroacetic acid (precipitation of proteins) after samples of powdered infant formula was dissolved in Milli-Q water. Factorial design was used to prepare the calibration (25 samples) and validation (8 samples) sets containing mixture of thiamine and pyridoxine within their linear range (2.5-25 μg/mL). Spectra of obtained mixtures and samples were recorded between wavelengths of 200-360 nm with the intervals Δλ=1 nm. In regression models created by using PLS and PCR algorithm, the results had acceptable recovery 98.14% for both compounds. These chemometric models predict the quantification of both, thiamine and pyridoxine in powdered infant formula samples via interpreting the UV-Vis spectrum. The average thiamine and pyridoxine contents of powdered infant formula samples were found to be 5.02±0.065 μg/g and 4.32±0.086 μg/g for PLS model and 4.98±0.078 μg/g and 4.03±0.091 μg/g for PCR model, respectively.

Simultaneous monitoring of photocatalysis of three pharmaceuticals by immobilized TiO2 nanoparticles: chemometric assessment, intermediates identification and ecotoxicological evaluation

In this study, the photocatalytic degradation of a mixture of three pharmaceuticals, Metronidazole (MET), Atenolol (ATL) and Chlorpromazine (CPR), was quantified simultaneously during the UV/TiO2 process. The investigated TiO2 was Millennium PC-500 immobilized on ceramic plates by sol-gel based method. The partial least squares modeling was successfully applied for the multivariate calibration of the spectrophotometric data. The central composite design was applied to model and optimize the UV/TiO2 process. Predicted values of removal efficiency were found to be in good agreement with experimental values for MET, ATL and CPR (R(2)=0.947 and Adj-R(2)=0.906, R(2)=0.977 and Adj-R(2)=0.960 and R(2)=0.982 and Adj-R(2)=0.969, respectively). The optimum initial concentration of pharmaceuticals, reaction time and UV light intensity was found to be 10 mg L(-1), 150 min and 38.45 W m(-2), respectively. The main degradation intermediates of pharmaceuticals produced in this process were identified by GC-MS technique. The chronic ecotoxicity of pharmaceuticals was evaluated using aquatic species Spirodela polyrrhiza prior to and after photocatalysis. The TOC results (90% removal after 16 h) and ecotoxicological experiments revealed that the photocatalysis process could effectively mineralize and reduce the ecotoxicity of the pharmaceuticals from their aqueous solutions.