Alicja Nowaczyk

Quantitative structure–retention relationships models for prediction of high performance liquid chromatography retention time of small molecules: Endogenous metabolites and banned compounds

Quantitative structure-retention relationship (QSRR) is a technique capable of improving the identification of analytes by predicting their retention time on a liquid chromatography column (LC) and/or their properties. This approach is particularly useful when LC is coupled with a high-resolution mass spectrometry (HRMS) platform. The main aim of the present study was to develop and describe appropriate QSRR models that provide usable predictive capability, allowing false positive identification to be removed during the interpretation of metabolomics data, while additionally increasing confidence of experimental results in doping control area. For this purpose, a dataset consisting of 146 drugs, metabolites and banned compounds from World Anti-Doping Agency (WADA) lists, was used. A QSRR study was carried out separately on high quality retention data determined by reversed-phase (RP-LC-HRMS) and hydrophilic interaction chromatography (HILIC-LC-HRMS) systems, employing a single protocol for each system. Multiple linear regression (MLR) was applied to construct the linear QSRR models based on a variety of theoretical molecular descriptors. The regression equations included a set of three descriptors for each model: ALogP, BELe6, R2p and ALogP(2), FDI, BLTA96, were used in the analysis of reversed-phase and HILIC column models, respectively. Statistically significant QSRR models (squared correlation coefficient for model fitting, R(2)=0.95 for RP and R(2)=0.84 for HILIC) indicate a strong correlation between retention time and the molecular descriptors. An evaluation of the best correlation models, performed by validation of each model using three tests (leave-one-out, leave-many-out, external tests), demonstrated the reliability of the models. This paper provides a practical and effective method for analytical chemists working with LC/HRMS platforms to improve predictive confidence of studies that seek to identify small molecules.

New alkyl-phosphate bonded stationary phases for liquid chromatographic separation of biologically active compounds

A new type of bonded stationary phase for liquid chromatography, with the properties of immobilized artificial membranes, has been synthesized. Alkyl-phosphate adsorbents were obtained by modification of aminopropyl silica gel. The structures of the synthesized materials were confirmed by use of instrumental techniques—elemental analysis, infrared spectroscopy (FTIR), and 13 C and 29Si CP/MAS NMR. Analysis revealed that the adsorbents mimic the phospholipids present in natural cell membranes. The new synthesized alkyl-phosphate stationary phases may be used for liquid chromatographic separation of biologically active compounds of different polarity.

Design, synthesis and pharmacological evaluation of new 1-[3-(4-arylpiperazin-1-yl)-2-hydroxy-propyl]-3,3-diphenylpyrrolidin-2-one derivatives with antiarrhythmic, antihypertensive, and α-adrenolytic activity

A series of novel arylpiperazines bearing a 3,3-diphenylpyrrolidin-2-one fragment were synthesized and evaluated for their binding affinity for alpha(1)- and alpha(2)-adrenoceptors (ARs), as well as their antiarrhythmic, and antihypertensive activities. The highest affinity for the alpha(1)-AR was displayed by 1-{3-[4-(2-ethoxy-phenyl)-piperazin-1-yl]-2-hydroxy-propyl}-3,3-diphenylpyrrolidin-2-one (7), which binds with a pK(i)=7.28. The highest affinity for the alpha(2)-AR was shown by 1-{3-[4-(2-methoxy-phenyl)-piperazin-1-yl]-2-hydroxy-propyl}-3,3-diphenylpyrrolidin-2-one (5), which binds with a pK(i)=6.68. Compound 7 was additionally evaluated in in vitro functional tests for its affinity for alpha(1B)- and alpha(1D)-AR, which gave pA(2) alpha(1B)=6.55 and pA(2) alpha(1D)=7.26. Among the compounds tested, compound 7 also had the highest prophylactic antiarrhythmic activity in adrenaline-induced arrhythmia in anaesthetized rats. Its ED(50) value was 1.1mg/kg (i.v.). The compounds significantly decreased systolic and diastolic pressure in normotensive anaesthetized rats at doses of 2.5-5.0mg/kg (i.v.) and their hypotensive effects lasted for longer than 1h. It was found that the introduction of two phenyl ring substituents into the 3rd position of the pyrrolidin-2-one fragment gave compounds with affinity for both alpha(1)- and alpha(2)-AR. The substitution of the 2nd position in the phenyl piperazinyl fragment of the molecule was crucial for activity. To determine detailed information concerning the structure-activity relationship, a preliminary molecular modeling study was undertaken.

Artificial neural networks in prediction of antifungal activity of a series of pyridine derivatives against Candida albicans.

Quantitative structure-activity relationships (QSAR) studies of antifungal activity against Candida albicans of a large series of new pyridine derivatives were conducted with the use of artificial neural networks (ANNs). The application of ANNs has been provided with respect to the prediction of antimicrobial potency of new pyridine derivatives based on their structural descriptors generated by calculation chemistry. Antifungal activity against C. albicans has been related to a number of physicochemical and structural parameters of the pyridine derivatives investigated. The activity was expressed as logarithm of the reciprocal of the minimal inhibitory concentrations, log 1/MIC. Molecular descriptors of agents were obtained from structure fragment reference databases and by quantum-chemical calculations combined with molecular modeling. A high correlation resulted between the ANN predicted antifungal activity, log 1/MIC(pred), and that one from biological experiments, log 1/MIC(exp), for the data used in the testing set of pyridine was obtained with correlation coefficient, R, on the level of 0.9112.

Modeling solvation on the chemically modified silica surfaces

A detailed molecular-level description of the retention mechanism in RP-HPLC is a point of great interest to analytical chemists. For this purpose, the solvent adsorption on the octadecyl stationary-bonded phase was investigated. Preferential adsorption of solvents from the acetonitrile-water mobile phase was modeled on the silica surface with one, two, three and four organic ligands, which represents a series of non-end-capped-bonded phases with different coverage density of bonded ligands. As a result of the computer simulation, the increase of adsorbed acetonitrile around bonded ligands is observed. The number of water molecules near the modeled surface is observed as well. The results are in agreement with experimental measurement of acetonitrile excess adsorption isotherms on the series of in-house made stationary-bonded phase.

Artificial neural networks analysis used to evaluate the molecular interactions between selected drugs and human α1-acid glycoprotein

Quantitative structure-retention relationships (QSRR) were proposed for alpha(1)-acid glycoprotein (AGP) column using physicochemical molecular descriptors of the selected drugs and interacting with that column. The set of 52 structurally diverse drug compounds, with experimentally derived logarithms of retention factors (log k) values was considered. Thirty-six physicochemical property descriptors were calculated by standard molecular modeling and used to establish QSRR and predict the retention data by artificial neural network (ANN). The QSRR indicated that heat of formation (HF), Moriguchi n-octanol-water partition coefficient (M log P) and the energy of the highest occupied molecular orbital (HOMO) are the most important for interactions between drugs and AGP. The proposed ANN model based on selected molecular descriptors showed a high degree of correlation between log k observed and computed. The final model possessed a 36-5-1 architecture and correlation coefficients for learning, validating and testing sets equaled 0.975, 0.950 and 0.972, respectively.

Antiarrhythmic and antioxidant activity of novel pyrrolidin-2-one derivatives with adrenolytic properties

A series of novel pyrrolidin-2-one derivatives (17 compounds) with adrenolytic properties was evaluated for antiarrhythmic, electrocardiographic and antioxidant activity. Some of them displayed antiarrhythmic activity in barium chloride-induced arrhythmia and in the rat coronary artery ligation-reperfusion model, and slightly decreased the heart rate, prolonged P–Q, Q–T intervals and QRS complex. Among them, compound EP-40 (1-[2-hydroxy-3-[4-[(2-hydroxyphenyl)piperazin-1-yl]propyl]pyrrolidin-2-one showed excellent antiarrhythmic activity. This compound had significantly antioxidant effect, too. The present results suggest that the antiarrhythmic effect of compound EP-40 is related to their adrenolytic and antioxidant properties. A biological activity prediction using the PASS software shows that compound EP-35 and EP-40 can be characterized by antiischemic activity; whereas, compound EP-68, EP-70, EP-71 could be good tachycardia agents.

Selective determination of cocaine and its metabolite benzoylecgonine in environmental samples by newly developed sorbent materials

Sewage epidemiology, as compared to crime statistics, health, medical reports or population surveys, is becoming the most objective and realistic approach to estimate drug consumption and trends in local communities. In this study we proposed newly synthesized sorbent materials for selective extraction of cocaine and benzoylecgonine from wastewater samples. The molecular modeling calculations were conducted to provide the choice of proper template and functional monomer for synthesis of extraction materials. The physicochemical properties of synthesized sorbents were studied using various techniques. The newly developed sorbent materials were applied for selective extraction of cocaine and benzoylecgonine from wastewater samples collected from different wastewater treatment plants in Poland. The obtained recoveries values in wastewater samples were 83.6(±7.1)% and 72.1(±4.8)%, for cocaine and benzoylecgonine, respectively. The newly developed sorbents comprise an alternative to conventional ones, which are not entirely suitable for highly efficient purification of environmental samples due to the presence of contaminants.

QSAR studies on a number of pyrrolidin-2-one antiarrhythmic arylpiperazinyls

The activity of a number of 1-[3-(4-arylpiperazin-1-yl)propyl]pyrrolidin-2-one antiarrhythmic (AA) agents was described using the quantitative structure–activity relationship model by applying it to 33 compounds. The molecular descriptors of the AA activity were obtained by quantum chemical calculations combined with molecular modeling calculations. The resulting model explains up to 91% of the variance and it was successfully validated by four tests (LOO, LMO, external test, and Y-scrambling test). Statistical analysis shows that the AA activity of the studied compounds depends mainly on the PCR and JGI4 descriptors.

Potential role of selected antiepileptics used in neuropathic pain as human GABA transporter isoform 1 (GAT1) inhibitors - molecular docking and pharmacodynamic studies.

&NA; The chemical interaction of nine antiepileptic drugs (tiagabine, gabapentin, pregabalin, lamotrigine, zonisamide, valproic acid, valpromide, vigabatrin, progabide) and two endogenous metabolites (4‐aminobutanoic acid, 4‐hydroxybutanoic acid) with a model of human GABA transporter 1 (hGAT1) is described using the molecular docking method. To establish the role of hGAT1 in chronic pain, tiagabine, a selective hGAT1 inhibitor, was assessed in the in vivo experiments for its antiallodynic properties in two mouse models of neuropathic pain. Docking analyses performed in this study provided the complex binding energies, specific hydrogen bond components, and hydrogen bond properties such as energies, distances and angles. The data of the docking studies strongly support the assumption that the antiepileptic and analgesic actions of the studied drugs can be at least in part related to the strength of their chemical interactions with hGAT1. In vivo experiments with tiagabine confirmed the involvement of hGAT1 in the regulation of the mechanical nociceptive threshold in neuropathic pain. Graphical abstract Figure. No caption available.