JournalTOCs

Acta Chimica Slovaca
Number of Followers: 4

This is an Open Access Journal

Open Access journal
ISSN (Print) 1337-978X - ISSN (Online) 1339-3065
Published by Sciendo

[389 journals]

DFT studies of camptothecins cytotoxicity IV — active and inactive
forms of irinotecan
- Abstract: Structures of irinotecan (CPT-11) in neutral lactone, neutral carboxyl, and anionic carboxylate forms in singlet ground states and of their complexes with Cu(II) in doublet ground states are optimized using B3LYP/6-311G* treatment. Metal ion affinities (MIA), Cu charges and Laplacians of Cu-ligand bond critical points of possible CPT active sites are evaluated. The formation of Cu(II) complexes with the anionic carboxylate ligand leads to the release of CO2 that can cause a decrease in the concentration of the active lactone form due to equilibria between all forms of the drug. MIA values and electron density transfer to Cu increase in the sequence lactone < neutral carboxyl < anionic carboxylate. Both neutral forms of irinotecan exhibit lower MIA values than those of camptothecin, unlike the anionic carboxylate form.
  PubDate: Thu, 30 Mar 2023 00:00:00 GMT
Modeling of transport properties of binary mixtures including ionic
liquids based on their experimental estimation
- Abstract: Transport properties of selected imidazolium ionic liquids (1-ethyl-3-methylimidazolium acetate, [emim][ac], and 1-butyl-3-methylimidazolium trifluoromethanesulfonate, [bmim][triflate]) as well as of binary mixtures of these ILs with water and ethanol were estimated experimentally. Density data were obtained within the temperature range of 293.15—333.15 K and used for the excess molar volume calculations. For the binary mixtures comprising selected ionic liquids and water/ethanol, partial molar volumes of mixture components were computed and the excess molar volume variation with the mixture composition was correlated using the Redlich-Kister equation. Dependence of viscosity on the binary mixture composition and temperature was described using the Jouyban-Acree model. These data form a base for the assessment of OPEX connected with transportation of mixtures containing these ionic liquids.
  PubDate: Thu, 08 Dec 2022 00:00:00 GMT
Analytical methods for pesticide residues determination in propolis and
propolis-based products
- Abstract: As a result of massive bee deaths in recent years, beekeeping is raising concerns about the presence of pesticides in propolis which is considered as a safe product. The paper is focused on the analysis of bee propolis and propolis-based products using various chromatographic techniques using mass spectrometry detection predominantly. An important part of the work is an overview concerning methods of sample preparation, extraction, and purification of extracts, followed by separation and detection techniques. Positive findings of contaminants and their concentrations in propolis samples and propolis products were evaluated. Sorption based techniques such as matrix solid phase dispersion and solvent-based extraction techniques are frequently applied for propolis analysis in connection with chromatographic techniques. Liquid-based extractions, such as the QuEChERS extraction technique (Quick, Easy, Cheap, Effective, Rugged, Safe), combine extraction by solvent with several ways of extract cleaning using combinations of salts and sorbents, primary secondary amine, MgSO4, NaCl, graphitized carbon, EMR-lipid, florisil, or octadecylsilane-modified silica gel. Other extraction techniques were reviewed. The most significant problem to be considered in pesticides detection is the topic of matrix effects, which have to be solved for each sample analysis with special care.
  PubDate: Tue, 11 Oct 2022 00:00:00 GMT
Impact of molecular chain length on polarizabilities of model acenes and
oligomers
- Abstract: A systematic quantum chemical study of model linear oligomers and their ring-fused (condensed) analogues based on six-membered and five-membered aromatic units is presented. Static electric polarizabilities were calculated for optimal geometries. The dependence of electronic and vibrational polarizability contributions on the molecular size was discussed and polymer limits were estimated. The presence of a diradical electronic structure in fused six-membered compounds significantly increases the polarizability values.
  PubDate: Tue, 11 Oct 2022 00:00:00 GMT
Detoxification and adaptation mechanisms of to antifungal agents
- Abstract: Filamentous fungi are crucial for recycling of organic material in nature. In natural habitats, they cope with many stress factors and therefore their adaptation ability to various conditions is very high. Trichoderma sp., fungi used in agriculture as biocontrol agent, are exposed to a variety of toxic molecules including pesticides and fungicides. They have to fight with toxic molecules using stress adaptation mechanisms known as the stress response. Adaptation of fungi to stress, especially to chemical stress, is not well studied in environmental fungal strains. Moreover, the adaptation process presents a risk of resistance mechanism induction to antifungal agents. Such resistant strains could be spread in the environment. This work aims to contribute to the knowledge of the adaptation process spread throughout the fungal kingdom. Transcriptional response of ABC transporters, the main detoxification efflux pumps of subfamily B and G in presence of antifungal agents, is shown. On the other hand, as azoles are the most commonly used antifungal structures in clinical practice and agriculture, changes in important fungal ergosterol biosynthesis genes as a result of their exposure to various azoles structure are highlighted.
  PubDate: Thu, 15 Sep 2022 00:00:00 GMT
Thermodynamic characterization of acid cryolite systems
- Abstract: Measuring of the electromotive force in molten system is used to characterize thermodynamic properties of the system at equilibrium. Values of the electromotive force are very important for the determination of activity and standard electrode potential. Investigation of the electromotive force of Al + TiB2 and Al-Al cell was the main aim of this work leading to the characterization of acid cryolite systems. The measurements were realized using a molten aluminum electrode and the electromotive force of an electrochemical cell was investigated in electrolytes at various molar ratios (NaF/AlF3) at equilibrium. Thermodynamic properties were measured in acid cryolite melts at three different temperatures: 800 °C, 900 °C, and 1000 °C, for all experiments.
  PubDate: Thu, 15 Sep 2022 00:00:00 GMT
The role of deep eutectic solvents in the production of cellulose
nanomaterials from biomass
- Abstract: In recent years, the demand for environment-friendly products has been on an increasing trend among researchers and industry for sustainable development. Deep eutectic solvents are green solvents which, due to their properties (biodegradability, recyclability, low cost, availability, easy preparation, low toxicity, chemical and thermal stability), can be used in various fields such as polymer chemistry, which includes nanocellulose isolation and polysaccharides processing. Several studies have illustrated the effectiveness of using deep eutectic solvents instead of the conventional reaction system to produce and disperse nanomaterials. This work summarizes the use of deep eutectic solvents in the isolation of cellulosic nanomaterials from different types of biomass. Deep eutectic solvents demonstrate high effectiveness in swelling lignocellulosic biomass and producing cellulose nanomaterials. Overall, deep eutectics solvents represent an innovative and effective pretreatment process for the fractionation of raw cellulose-containing fibres to promote subsequent isolation of nanomaterials made from cellulose.
  PubDate: Tue, 23 Aug 2022 00:00:00 GMT
DFT studies of camptothecins cytotoxicity III: camptothecin, irinotecan
and SN-38
- Abstract: Geometries of camptothecin, irinotecan, SN-38, and of their hypothetical Cu(II) complexes were optimized at the B3LYP/6-311G* level of theory. Their electron structure, evaluated in terms of Mulliken population analysis and Quantum Theory of Atoms-in-Molecule, was subsequently related to in vitro cytotoxicity. Electron density transfer from the relevant active sites to Cu decreases in the sequence irinotecan > SN-38 > camptothecin. The absolute values of their metal-ligand interaction energies exhibit the same trend. Discrepancy with the least relative in vitro cytotoxicity of irinotecan can be explained by differences in its pharmacokinetics.
  PubDate: Tue, 23 Aug 2022 00:00:00 GMT
Simultaneous detection of purine metabolites by membrane modified
electrochemical sensors
- Abstract: Purine metabolites are important for metabolic and cellular processes. Deregulation of purinergic signaling leads to pathological accumulation of purine degradation products in extracellular fluids and indicates various diseases. In clinical diagnosis at early stages of related diseases, accurate detection of Uric acid and Xanthine is of high importance. Electrochemical methods are fast, simple, sensitive, more convenient, and cost-effective compared to other analytical methods used in purine metabolites signaling. Electrochemical sensors are able to detect more compounds simultaneously. Modification of a glassy carbon electrode sensor with external protective membranes was used in this study to avoid unwanted signal interferences from analyte matrices. Polyvinyl alcohol, Chitosan, and Nafion membranes were selected for sensor modification to compare the electro-neutral, positive and negative charged setting of the Xanthine and Uric acid detection. All three membrane modified sensors showed adequate stability in the phosphate buffer solution after 5 min of incubation and are thus suitable for simultaneous detection of purine metabolites. The best results in anodic peak current response values were observed using the Nafion membrane modified glassy carbon electrode sensor. The approach reported here can be useful for the detection of purine metabolites from various matrices at early stages of clinical diagnosis.
  PubDate: Tue, 23 Aug 2022 00:00:00 GMT
Nanotextiles — materials suitable for respiratory tract protection but a
source of nano- and microplastic particles in the environment
- Abstract: The paper deals with the formation of nanomaterials (nanoparticles and nanofibers) in the manufacture and use of respiratory protective equipment. It focuses mainly on processes leading to the release of nanoplastics into the workplace and the environment. Based on selected properties of materials used for the manufacture of protective equipment, their stability in the environment is revealed. The paper demonstrates the impact on the environment considering semichronic phytotoxicity of nanoplastics.
  PubDate: Mon, 16 May 2022 00:00:00 GMT
Thermochemistry of antioxidant action of isoflavones and their
deprotonated forms in aqueous solution: hydrogen or electron transfer'
- Abstract: Isoflavones possessing several weak acidic hydroxyl groups can undergo successive deprotonations in aqueous solutions. Therefore, their antioxidant properties cannot be ascribed only to the neutral forms but also to corresponding phenoxide anions. It was already confirmed that isoflavones prefer the formation of dianions in aqueous solution. For eight isoflavones and their preferred (poly)deprotonated forms, thermochemistry of hydrogen atom transfer and electron abstraction was studied in terms of corresponding reaction enthalpies, i.e., O—H bond dissociation enthalpies and ionization potentials. Our results clearly indicate that the increase in negative charge causes significant drop in ionization potential and bond dissociation enthalpy. On the other hand, proton affinities show the opposite trend. Thus, it is unfeasible to find a generally valid trend for dianions — corresponding reaction enthalpies strongly depend on the structure of isoflavone, especially on the number/positions of OH groups.
  PubDate: Mon, 16 May 2022 00:00:00 GMT
Pre-treatment of lignocellulosic materials by enzymatic mixture to enhance
biogas production
- Abstract: The aim of this study was to evaluate the effect of an enzymatic mixture on the increase of biogas production from lignocellulosic materials as rapeseed straw, maize waste, and wheat straw. For efficient application of the enzymatic mixture, conditions of its use were optimized regarding 50 °C, pH 7 and an enzyme dose of 0.25 % w/v. Biogas potential test confirmed positive effect of the enzymatic mixture on anaerobic digestion of already thermally and alkali pre-treated lignocellulosic materials, as significantly higher biogas production was observed after the enzymatic mixture addition for all monitored substrates. Addition of the enzymatic mixture to the most used substrate at biogas plants — maize silage, had also positive effect on biogas production during the biogas potential test. This fact was not proven during long-term operations of the reactors as the values of total cumulative biogas productions for the whole monitored period from reactors for anaerobic digestion of maize silage with and without addition of enzymatic mixture did not differ significantly.
  PubDate: Mon, 16 May 2022 00:00:00 GMT
Binary mixtures containing imidazolium ionic liquids: properties
measurement
- Abstract: Densities and transport properties (dynamic viscosity) of pure imidazolium ionic liquids 1-butyl-3-methylimidazolium acetate and 1-butyl-3-methylimidazolium dicyanamide and their binary mixtures with water and ethanol were measured within the temperature range of 293.15—333.15 K. Obtained experimental data were used to calculate excess molar volume and viscosity deviation. For the chosen binary mixtures, variations of excess molar volume, partial molar volumes of mixture components and of the viscosity deviation with the binary mixture composition were correlated using the Redlich-Kister equation. In addition, variation of viscosity with the binary mixture composition and temperature was fitted using the Jouyban-Acree model.
  PubDate: Thu, 24 Mar 2022 00:00:00 GMT
On the energetics of radical adduct formation of OH with phenol analogs
and aniline
- Abstract: Theoretical studies on aniline, phenol, benzenethiol, benzeneselenol, and their corresponding adducts with hydroxyl radical in possible positions on a hydrocarbon ring are presented. Bond dissociation enthalpies, related to radical scavenging of primary antioxidants, were calculated using the M06–2X/6–311+G** method. Calculated data were compared with available experimental data. Preferable homolytic bond dissociation of the presented molecules with OH• through functional groups X—OH followed by the m–OH ones has been confirmed. The highest antioxidant activity among the investigated positions is predicted for benzeneselenol. Also, the formation of non-covalent van der Waals structures has been shown as important in radical scavenging.
  PubDate: Thu, 24 Mar 2022 00:00:00 GMT
Ceylon cinnamon and clove essential oils as promising free radical
scavengers for skin care products
- Abstract: Due to adverse effects of free radicals on human skin and increasing consumer demand for natural ingredients, essential oils from basil, Ceylon cinnamon bark, clove, juniper, lavender, oregano, rosemary, tea tree, thyme, and ylang-ylang were assessed for their antiradical activity. The oils were evaluated in the concentration range of 5—0.1 mg·mL−1, in which the three reference synthetic antioxidants are most often added to mass-produced cosmetics. Among all examined samples, C. cinnamon oil at a concentration of 5 mg·mL−1 showed the strongest DPPH radical scavenging activity (0.41 mg·mL−1 IC50), followed by clove oil, BHA, α-tocopherol, and BHT (0.82, 0.84, 0.88 and 0.93 mg·mL−1 IC50), respectively. At the same concentration, the reduction power of C. cinnamon oil was higher (1.64 mg·mL−1 Trolox Eq.) than that of α-tocopherol and BHT (1.42 and 0.80 mmol·L−1 Trolox Eq., respectively) but lower than that of BHA (1.81 mmol·L–1 Trolox Eq.). Antiradical activity of the other eight essential oils was low or negligible. C. cinnamon oil and clove oil are promising antiradical agents for skin care but according to our GC-MS analysis, these oils contain 0.29 % of cinnamaldehyde, 0.03 % of linalool, 0.02 % of D-limonene, and 0.02 % of eugenol or 0.41 % of eugenol and 0.002 % of linalool, respectively, which are monitored contact allergens in cosmetics. Such a product is not be suitable for consumers allergic to these substances but for the vast majority of consumers it does not pose a risk in terms of allergic manifestations.
  PubDate: Thu, 24 Mar 2022 00:00:00 GMT
Determination of phosphate in water by flow coulometry
- Abstract: In this work, the possibility of flow coulometry application as coulometric titration was studied. The method was used to analyze phosphates in wastewater samples. The principle of the determination consisted in the formation of molybdophosphate and its subsequent one-electron electrolytic reduction. The present method is applicable under optimal conditions in the concentration range of 1.5 × 10−6 to 5.5 × 10−5 mol/dm3. Detection limit of the method is 3.42 × 10−7 mol/dm3. Mineralization step has been proved a problem in total phosphate content determination. If mineralization was not carried out, only inorganic soluble phosphates were determined. It is a new method characterized by its simplicity of instrumentation and handling, which is a prerequisite for its further use in the field of trace analysis.
  PubDate: Mon, 29 Jun 2020 00:00:00 GMT
Determination of carotenoids in flowers and food supplements by HPLC-DAD
- Abstract: Marigold flowers (Tagetes patula and Calendula officinalis) were chosen for analysis because they are the most often used source of lutein and its isomer zeaxanthin for the production of food supplements on the Czech market. Direct extraction and extraction with alkaline hydrolysis were compared to detect free or bound carotenoids. For carotenoid separation, C18 and C30 columns were used. A new method for determination of carotenoid content in food supplements in form of capsules has been developed and validated. All matrices were analysed by high-performance liquid chromatography with diode array detection (HPLC-DAD). It has been found that alkaline hydrolysis is required for both Marigold flowers and food supplements to release lutein from ester bonds to fatty acids. In Calendula officinalis lutein in the concentration of 807—1472 mg·kg−1 of dry matter was detected. Tagetes patula has been identified as a better lutein source with the content of 5906—8677 mg·kg−1 of dry matter. It has been found that the content of lutein and zeaxanthin in commercial food supplements (Lutein Complex Premium and Occutein Brillant) is consistent with the declared quantity. Linearity of the HPLC-DAD method ranged from 0.1—20 μg·mL−1 with the limit of quantification (LOQ) of 1.7 mg·kg−1 for lutein in Marigold flowers and 200 mg·kg−1 in food supplements. Repeatability was 2.3 % for lutein in all tested matrices.
  PubDate: Mon, 29 Jun 2020 00:00:00 GMT
Carbon family nanomaterials — new applications and technologies
- Abstract: Research on carbon-based nanomaterials (CBNMs) and their development is one of the major scientific disciplines of the last century. This is mainly because of their unique properties which can lead to improvements in industrial technology or new medical applications. Therefore, it is necessary to examine their properties such as shape, size, chemical composition, density, toxicity, etc. This article focuses on the general characteristics of nanomaterials (NMs) and their behavior when entering the environment (water and soil). In addition, it presents individual members of the graphene family including porous ecological carbon (biochar). The article mainly deals with the new potential technologies of CBNMs considering their possible toxic and genotoxic effects. This review also highlights the latest developments in the application of self-propelled micromotors for green chemistry applications. Finally, it points to the potential biomedical applications of CBNMs.
  PubDate: Mon, 29 Jun 2020 00:00:00 GMT
Inclination to self-ignition and analysis of gaseous products of wood
chips heating
- Abstract: This paper focuses on the assessment of the inclination to self-ignition of various types of wood chips according to the methodology of European standard EN 15188. The study also assesses the effect of heating temperatures on the composition and quantity of gaseous products of heating. Gases were analysed using an infrared spectrometer with Fourier transformation. From the measured results it was found that the inclination to self-ignition differs for various samples of wood chips. The paper discusses certain parameters assumed to affect the inclination of biomass to self-ignite. When assessing the effect of temperature on the composition of gaseous products, a sample of forest wood chips heated at temperatures from 50 to 150 °C resulted in the following gaseous products: carbon dioxide, carbon monoxide, water and aliphatic hydrocarbons; their concentrations increase with the increasing temperature. Carbon oxides have been proposed as indicators of the state of stored materials self-heating. Observations presented in this paper can be used as data for elaborating safety instructions for storage of fuels based on solid biomass.
  PubDate: Mon, 29 Jun 2020 00:00:00 GMT
Apiin-induction of -apiosidase production by sp. strains
- Abstract: β-Apiosidase is a rare glycosidase applied in winemaking for flavour enhancement. This enzyme is involved in the release of volatile terpenes by hydrolysis of their odourless glycosidic precursors. It is found as a minor component in commercial pectinase/cellulase preparations. Microbial production of β-apiosidase by two Aspergillus sp. strains was investigated. Apiin-induced production of this extracellular glycosidase was confirmed only during the cultivation of Aspergillus niger CBS 554.65 but the high productivity value reported in the work of Dupin et al. (1992) J. Agric. Food Chem. 40(10): 1886—1891 could not be reproduced. The achieved productivity was by far not satisfactory considering the apiin cost. Commercial enzyme preparations with β-apiosidase side-activity thus remain a better alternative as the enzyme source for biocatalytic applications.
  PubDate: Mon, 29 Jun 2020 00:00:00 GMT