Примена на електродните механизми на површинско-активни системи во аналитика на лекови – теоретска и експериментална студија во услови на квадратно-бранова волтаметрија

Волтаметриските анализи за студирање на електродните механизми на површинско-активни системи претставуваат електрохемиски методи со кои можат да се разработат соодветни аналитички методи, како и да се добијат релевантни параметри за квантитативно определување на голем број лекови, како и за интеракциите што можат да настанат помеѓу два лека. Притоа, доколку постојат интеракции помеѓу два дефинирани лека, со примена на теоретски методи, можат да се опрeделат кинетички и термодинамички параметри што се во корелација со брзината на интеракциите, како и со стабилноста на евентуалните комплeкси што настануваат при интеракција на дефинираните лекови. Во рамките на докторската работа се разработени поголем број на теоретски модели на површинско-активни лекови што се поврзани со хемиски рамнотежи, каде електронскиот трансфер се случува во еден или во два последователни чекори. Дел од резултатите од теоретските модели се тестирани со експериментални системи на површинско-активни моделни супстанци. Резултатите од теоретските и експерименталните испитувања се од корист во дизајнирањето на нови електрохемиски методи во аналитиката на лекови, како и за дизајнирање на соодветни експериментални методи преку кои ќе можат да се анализираат квантитативно голем број лекови, но и да се определат релевантни кинетички и термодинамички параметри од интеракциите помеѓу дефинирани лекови

Multistep Surface Electrode Mechanism Coupled with Preceding Chemical Reaction-Theoretical Analysis in Square-Wave Voltammetry

In this theoretical work, we present for the first time voltammetric results of a surface multistep electron transfer mechanism that is associated with a preceding chemical reaction that is linked to the first electron transfer step. The mathematical model of this so-called “surface CEE mechanism” is solved under conditions of square-wave voltammetry. We present relevant set of results portraying the influence of kinetics and thermodynamics of chemical step to the features of simulated voltammograms. In respect to the potential difference at which both electrode processes occur, we consider two different situations. In the first scenario, both peaks are separated for at least |150 mV|, while in the second case both peaks occur at same potential. Under conditions when both peaks are separated for at least |150 mV|, the first process can be described with the voltammetric features of a surface CE mechanism, while the second peak gets attributes of a simple surface electrode reaction. When both peaks take place at same potential, we elaborate an elegant methodology to achieve separation of both overlapped peaks. This can be done by modifying the concentration of the substrate “Y” in electrochemical cell that is involved in the preceding chemical reaction. The results of this work can be of big assistance to experimentalists working in the field of voltammetry of metal complexes and drug-drug interaction

Multistep Surface Electrode Mechanism Coupled with Preceding Chemical Reaction-Theoretical Analysis in Square-Wave Voltammetry

In this theoretical work, we present for the first time voltammetric results of a surface multistep electron transfer mechanism that is associated with a preceding chemical reaction that is linked to the first electron transfer step. The mathematical model of this so-called “surface CEE mechanism” is solved under conditions of square-wave voltammetry. We present relevant set of results portraying the influence of kinetics and thermodynamics of chemical step to the features of simulated voltammograms. In respect to the potential difference at which both electrode processes occur, we consider two different situations. In the first scenario, both peaks are separated for at least |150 mV|, while in the second case both peaks occur at same potential. Under conditions when both peaks are separated for at least |150 mV|, the first process can be described with the voltammetric features of a surface CE mechanism, while the second peak gets attributes of a simple surface electrode reaction. When both peaks take place at same potential, we elaborate an elegant methodology to achieve separation of both overlapped peaks. This can be done by modifying the concentration of the substrate “Y” in electrochemical cell that is involved in the preceding chemical reaction. The results of this work can be of big assistance to experimentalists working in the field of voltammetry of metal complexes and drug-drug interaction

Theory of Square-wave Voltammetry of Two-step Surface Electrode Mechanisms Associated with Chemical Equilibria

Two-step electrode mechanisms that are associated with chemical equilibria are considered theoretically under conditions of square-wave voltammetry. The mechanisms designated as "surface EE", "surface ECE", "surface EECrev" and "surface EECatalytic" mechanisms are often encountered in experimental chemistry of many drugs and redox enzymes containing ions of transient metals as co-factors, or quinone-moieties, as well. We present large set of representative results that reveal specific features met at all considered mechanisms. We also propose set of simple methodologies to get access to kinetic and thermodynamic parameters relevant to electron transfer step, and to associated chemical reactions, as well. The work is of outmost importance to understand many aspects of enzyme-substrate interactions, but also the nature of drug-drug interactions of lipophilic and hydrophilic drugs

Vitamins E and C exert protective roles in hydrogen peroxide-induced DNA damage in human peripheral blood mononuclear cells

Hydrogen peroxide (H2O2) exerts strong oxidative, cytotoxic, and genotoxic effects, whereas vitamins C and E are potent non-enzymatic antioxidants. This study aimed to demonstrate the ameliorative effects of vitamins C and E, individually or in combination, on H2O2-induced DNA damage using the alkaline Comet Assay with silver nitrate staining and visual scoring. Trypan blue exclusion assay was used to determine the cytotoxicity of the treatments, whereas alkaline Comet Assay with silver nitrate staining was used to quantify DNA damage. DNA damage was assessed by the method of visual comet scoring and expressed in arbitrary units. Human peripheral blood mononuclear cells (PBMCs) were pretreated with 100 µM vitamin C and E for 30 min, individually or in combination, followed by a treatment with 100 µM H2O2 for 30 min. Untreated cells were used as a negative control, whereas cells treated with 100 µM H2O2 only were used as a positive control. We observed a considerable H2O2-induced DNA damage in the positive control, which was reduced in vitamin-pretreated cells. The combination of vitamins C and E led to the greatest amelioration of DNA damage. In our hands, Comet Assay with silver nitrate staining and visual scoring represents a rapid and reliable method to investigate the protective effects of vitamins C and E on H2O2-induced DNA damage

Systematic bioinformatic analyses of nutrigenomic modifications by polyphenols associated with cardiometabolic health in humans: Evidence from targeted nutrigenomic studies

Cardiometabolic disorders are among the leading causes of mortality in the human population. Dietary polyphenols exert beneficial effects on cardiometabolic health in humans. Molecular mechanisms, however, are not completely understood. Aiming to conduct in-depth integrative bioinformatic analyses to elucidate molecular mechanisms underlying the protective effects of polyphenols on cardiometabolic health, we first conducted a systematic literature search to identify human intervention studies with polyphenols that demonstrate improvement of cardiometabolic risk factors in parallel with significant nutrigenomic effects. Applying the predefined inclusion criteria, we identified 58 differentially expressed genes at mRNA level and 5 miRNAs, analyzed in peripheral blood cells with RT-PCR methods. Subsequent integrative bioinformatic analyses demonstrated that polyphenols modulate genes that are mainly involved in the processes such as inflammation, lipid metabolism, and endothelial function. We also identified 37 transcription factors that are involved in the regulation of polyphenol modulated genes, including RELA/NFKB1, STAT1, JUN, or SIRT1. Integrative bioinformatic analysis of mRNA and miRNA-target pathways demonstrated several common enriched pathways that include MAPK signaling pathway, TNF signaling pathway, PI3K-Akt signaling pathway, focal adhesion, or PPAR signaling pathway. These bioinformatic analyses represent a valuable source of information for the identification of molecular mechanisms underlying the beneficial health effects of polyphenols and potential target genes for future nutrigenetic studies

Theoretical study of activity of redox enzymes with protein-film square-wave voltammetry

In this presentation we focus on several theoretical models in protein-film voltammetry under conditions of square-wave voltammetry. While we present novel theoretical models on surface ECreversible, EECirreversible, EECreversible and ECatalytic(reversible) systems, we reveal new diagnostic criteria to recognize the considered redox mechanisms. We also present novel methodologies to determine kinetic and thermodynamic parameters relevant to system considered. Models are seen as a cornerstone for developing biochemical sensors for detection of various substrates and medicaments

The Power of Voltammetry

Majority of the chemical processes taking place in our Universe have a “redox” origin (redox=reduction-oxidation). The exchange of a charge (electrons of ions) between two neighbouring systems that are in contact can lead to a flow of electrical current. Almost a century ago, an instrumental technique had been developed capable to study the redox processes of various substances. The basic principles of this electroanalytical technique, named as “polarography”, had been established by Jaroslaw Heyrovsky, who was awarded with Nobel Prize of chemistry in 1959 for his invention. In the last 70 years, we witnessed a very fast development of large number electroanalytical techniques evolving from Heyrovsky’s polarography. Voltammetric techniques are, indeed, the most advanced members in the family of electroanalytical techniques. Voltammetry involves application of a time-dependent potential as a driving force, while the measuring output is the corresponding electrical current that flows between the working and reference electrode. In the last 60 years we saw great number of rigorous theoretical and mathematical models describing various mechanistic pathways of many important systems. Moreover, reliable voltammmetric methods have been developed to access the thermodynamics and kinetics of charge transfer in many important systems. Nowadays, the voltammetry is almost an inevitable toll in every physical, chemical, pharmaceutical, biological, metallurgical and environmental laboratory. Designed initially to study the processes of corrosion, voltammetry evolved in a very powerful instrumental technique that can be intensively used to get insight into the drug-drug interactions, the ion transfer across biological membranes, the processes of metal-ligand complex formation, the enzyme-substrate reactions, the polymerization reactions, in the electro-synthesis, further in designing bio-fuel cells, in studying the chemical features of nano-materials, and many more. What impresses by this technique is the velocity of obtaining relevant chemical information, the simplicity of the experimental set-up, and the very low costs of the instrumentation. In this lecture we refer to some of the greatest achievements of voltammetry in last 30 years. References: 1. A. J. Bard, G. Inzelt, F. Scholz, Electrochemical Dictionary, Springer, 2012. 2. A. J. Bard, L. R. Faulkner, Electrochemical Methods, Fundamentals and Applications, Willey, 2001

Примена на квадратно-бранова волтаметрија во аналитика на лекови на површинско-активни системи-Пилот Проект

Квадратно-брановата волтаметрија е електрохемиска техника што интензивно се применува во хемијата, фармацијата и физиологијата во последните 20тина години. Во рамките на овој пилот-проект, прикажани се резултати од неколку теоретските модели за површински реакции поврзани со хемиски рамнотежи, што се адекватни модели за студирање на интеракциите помеѓу различни типови на лекови. Покрај тоа, дадени се експериментални примени преку кои може да се испитуваат кинетичките (брзината на интеракциите помеѓу лекови) и термодинамичките параметри (константите на стабилност на два лекови што стапуваат во хемиска интеракција). Резултатите од овој пилот проект се дел од четири трудови што се публикувани во списанија со фактор на влијание во 2019 и 2020 година

Electrochemical analysis of the properties of benzene-1,2,4-triol

1,2,4-benzenetriol is an aromatic chemical compound used in direct hair colouring products at a maximum use concentration of 3.0%. In plants it can be found as a product of the degradation of some organic compounds, while in humans it can be detected after poisoning with benzene because it is a metabolite of the biotransformation of benzene. In the human organism, 1,2,4-benzenetriol causes harmful effects such as DNA damage and there is possibility that 1,2,4-benzenetriol-induced DNA damage is one of the primary reactions in carcinogenesis induced by benzene. In nature, this compound is found in coffee extracts inhibiting the anti-hypertensive effect of chlorogenic acid. Hydroxyhydroquinone or 1,2,4-benzenetriol (BT) detected in the beverages has a structure that coincides with the water-soluble form of a sesame lignan, sesamol and further studies are required to confirm the importance of the cellular antioxidant activity of BT. Materials and methods: In this study we examined the electrochemical properties of 1,2,4-benzenetriol by using cyclic voltammetry and square-wave voltammetry. Cyclic voltammetry (CV) is widely used for the study of redox processes, for understanding the reaction mechanisms, and for obtaining stability of reaction products. To perform this study, we used a three-electrode system, graphite rod was used as a working electrode, the reference electrode was silver / silver chloride (Ag / AgCl), while the auxiliary electrode was Pt-electrode. Results: The electrochemical response of the aqueous solution of 1,2,4-benzenetriol at different pH (3 to 9) depends mainly on pH. The calculated diffusion coefficient indicates that the process of diffusion of this substance is relatively low. The complexes between benzenetriol the Fe2+ and Mg2+ ions are the type 1:1 (one ligand and one metal ion are complexed). The values of the stability constants show that the complex of magnesium ions and benzenetriol is weak, while the complex with iron ions is moderately stable complex. In strong alkaline environment there is a chemical transformation and it is assumed that the new compound has four OH groups. For examination of the anti-oxidative potential we compared the native 1,2,4-benzenetriol, re-titrated benzentriol and vitamin C using ABTS. It has been confirmed that the tetra-hydroxy compound has the highest antioxidant potential. Conclusion: The results obtained of the study will help in further investigations of antioxidant properties of 1,2,4-benzenetriol and the potential use of this compound as an antioxidant. Keywords: 1,2,4-benzentriol, Anti-oxidative potential, Cyclic voltammetry, Complexes with metal ions