Anna Krause

Application of spectroscopic methods for identification (FT-IR, Raman spectroscopy) and determination (UV, EPR) of quercetin-3-O-rutinoside. Experimental and DFT based approach.

Vibrational (FT-IR, Raman) and electronic (UV, EPR) spectral measurements were performed for an analysis of rutin (quercetin-3-O-rutinoside) obtained from Rutaofficinalis. The identification of rutin was done with the use of FT-IR and Raman spectra. Those experimental spectra were determined with the support of theoretical calculations based on a DFT method with the B3LYP hybrid functional and 6-31G(d,p) basis set. The application of UV and EPR spectra was found to be a suitable analytical approach to the evaluation of changes in rutin exposed to certain physicochemical factors. Differences in absorbance observed in direct UV spectra were used to monitor changes in the concentration of rutin in degraded samples. Spectra of electron paramagnetic resonance allowed studying the process of free-radical quenching in rutin following its exposure to light. The molecular electrostatic potential (MEP) and frontier molecular orbitals (LUMO-HOMO) were also determined in order to predict structural changes and reactive sites in rutin.

Quantitative structure-retention relationship model for the determination of naratriptan hydrochloride and its impurities based on artificial neural networks coupled with genetic algorithm

Mathematical modeling of Quantitative Structure - Property Relationships met great interest in fields of in silico drug design and more recently, pharmaceutical analysis. In our approach we proposed automated method of creation Quantitative Structure-Retention Relationship (QSRR) for analysis of triptans, selective serotonin 5-HT1 receptor agonists used for the treatment of acute headache. The method was created using hybrid machine learning approach, namely Genetic algorithm (GA) coupled with artificial neutral networks (ANN). Performance of proposed hybrid GA-ANN model was evaluated with predicting relative retention times of naratriptan hydrochloride impurities. Several ANN types were coupled with GA and tested: single-layer ANN (SL-ANN), double-layer ANN (D-ANN) and higher order architectures: pi-sigma ANN (PS-ANN) and sigma-pi-sigma ANN (SPS-ANN). Partial Least Squares (PLS) method was used as a reference. The separation of naratriptan hydrochloride and its related products (impurities and degradation products) was obtained by developing a gradient high-performance liquid chromatography method with diode-array detector (HPLC-DAD). Degradation products during acid-basic hydrolysis were identified with an electrospray ionization tandem mass spectrometry (Q-TOF-MS/MS) detector. Independent data for outer validation of QSRR model was obtained from the determination of related products of sumatriptan succinate via an HPLC-DAD method. Accuracy of QSRR was measured by inner-validation on naratriptan data and outer validation on sumatriptan succinate samples. The best performing model were PS-ANN and SPS-ANN with mean errors of 8% (Q2=0.87) and 15% (Q2=0.77) on an inner-validation data set, respectively. Validation on similar samples from an outer validation data set of sumatriptan succinate impurities gave mean errors of 18% (R2pred=0.64) and 17% (R2pred=0.63) for the PS-ANN and SPS-ANN models, respectively.

Spectrophotometric Methods as Solutions to Pharmaceutical Analysis of β-Lactam Antibiotics

Following the discovery of the first analog of penicillin by A. Fleming (1929), the ┚-lactam antibiotics are still a developing group of chemotherapeutics and are used in treatment of majority of diseases with bacterial etiology. ┚-lactam antibiotics have a broad spectrum of antibacterial activity, favourable pharmacokinetic parameters and low side effects. In ┚lactam therapy two main problems are still current. The increasing resistance of some bacterial strains which implicates necessity to combine the therapy with inhibitors of ┚lactamases and other chemotherapeutics. The second problem of therapy of ┚-lactam antibiotics is their significant instability [1-3]. The analogs from that group are easily degraded in aqueous solutions and in solid state. They are a special group of drugs because parallel to losing the antibacterial efficiency, the strong allergic properties can also appear as a results of their degradation. Therefore in terms of quality control, the stability of ┚-lactam antibiotics in solutions was widely studied. The evaluation of stability concerned also the studies of their metabolites and intravenous solutions after preparations of pharmaceutical dosage forms. Moreover, the evaluation of concentration changes during storage of substance in solid state was also conducted. As problem of the instability of some ┚-lactam analogs has been solved their oral administration is possible. An intake of oral formulations is connected with appearance of excipients, which can influence rate of degradation and cause formation of different degradation products.

Acid-base catalysis of N-[(morpholine)methylene]daunorubicin.

The stability of N-[(morpholine)methylene]-daunorubicin hydrochloride (MMD) was investigated in the pH range 0.44−13.54, at 313, 308, 303 and 298 K. The degradation of MMD as a result of hydrolysis is a pseudo-first-order reaction described by the following equation: ln c = ln c0 – kobs. t. In the solutions of hydrochloric acid, sodium hydroxide, borate, acetate and phosphate buffers, kobs = kpH because general acid-base catalysis was not observed. Specific acid-base catalysis of MMD comprises the following reactions: hydrolysis of the protonated molecules of MMD catalyzed by hydrogen ions (k1) and spontaneous hydrolysis of MMD molecules other than the protonated ones (k2) under the influence of water. The total rate of the reaction is equal to the sum of partial reactions: kpH = k1 • aH+ • f1 + k2 • f2 where: k1 is the second-order rate constant (mol−1 l s−1) of the specific hydrogen ion-catalyzed degradation of the protonated molecules of MMD; k2 is the pseudo-first-order rate constant (s−1) of the water-catalyzed degradation of MMD molecules other than the protonated ones, f1 – f2 are fractions of the compound. MMD is the most stable at approx. pH 2.5.

Enhanced pharmacological efficacy of sumatriptan due to modification of its physicochemical properties by inclusion in selected cyclodextrins

The study focused on the pharmacological action of sumatriptan, in particular its antiallodynic and antihyperalgesic properties, as an effect of cyclodextrinic inclusion of sumatriptan, resulting in changes of its physicochemical qualities such as dissolution and permeability through artificial biological membranes, which had previously been examined in vitro in a gastro-intestinal model. The inclusion of sumatriptan into β-cyclodextrin and 2-hydroxylpropylo-β-cyclodextrin by kneading was confirmed with the use of spectral (fourier-transform infrared spectroscopy (FT-IR); solid state nuclear magnetic resonance spectroscopy with magic angle spinning condition, 1H and 13C MAS NMR) and thermal (differential scanning calorimetry (DSC)) methods. A precise indication of the domains of sumatriptan responsible for its interaction with cyclodextrin cavities was possible due to a theoretical approach to the analysis of experimental spectra. A high-performance liquid chromatography with a diode-array detector method (HPLC-DAD) was employed to determine changes in the concentration of sumatriptan during dissolution and permeability experiments. The inclusion of sumatriptan in complex with cyclodextrins was found to significantly modify its dissolution profiles by increasing the concentration of sumatriptan in complexed form in an acceptor solution compared to in its free form. Following complexation, sumatriptan manifested an enhanced ability to permeate through artificial biological membranes in a gastro-intestinal model for both cyclodextrins at all pH values. As a consequence of the greater permeability of sumatriptan and its increased dissolution from the complexes, an improved pharmacological response was observed when cyclodextrin complexes were applied.

The Analysis of the Physicochemical Properties of Benzocaine Polymorphs

The study was a pioneering attempt to assess the influence of the structural polymorphism (forms I, II, III) of benzocaine on its solubility, apparent solubility, and chemical stability, which are vital parameters for preformulation and formulation work. The impact of differences in the solubility of selected polymorphs of benzocaine on their permeability through artificial biological membranes (PAMPA system) was evaluated. The polymorphs of benzocaine were obtained by means of techniques commonly used for the preparation of various pharmaceutical dosage forms: ball milling, micro milling, and cryogenic grinding, which allowed for the appearance or preservation of form III, the initial conformation of benzocaine. Ball milling resulted in the conversion of form III to I, whereas micro milling yielded form II. As a result of cryogenic grinding, form III of benzocaine was preserved. The identification of all polymorphic forms of benzocaine was confirmed via X-ray powder diffraction (PXRD) supported by FT-IR spectroscopy coupled with density functional theory (DFT) calculations. The differences in solubility, dissolution, and permeability through artificial biological membranes resulting from the polymorphic forms of benzocaine were established by using chromatographic determinations. Accelerated stability tests indicated that all polymorphic forms were chemically stable at a required level.