Institute of Chemistry

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Pharmacokinetics of different selenium supplements in healthy individuals and patients with autoimmune thyroiditis after oral administration
(Society of Chemists and Technologists of Macedonia, 2025-06-24)
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Stafilov, Trajče
Selenium is essential for the function of key selenoproteins such as glutathione peroxidase, thiore-doxin reductase, and iodothyronine deiodinase, which have antioxidant properties and support thyroid hormone metabolism. Due to the low selenium content in European soils – particularly in the Southeast-ern regions, supplementation is often recommended, especially for conditions like Hashimoto's thyroidi-tis. However, careful consideration of selenium dosage and pharmacokinetics is crucial, as the margin be-tween essential and toxic levels is very narrow. The aim of this study was to investigate the pharmacoki-netics of selenium absorption and plasma concentration following oral administration of various selenium doses and chemical forms, both in the short and long term, in healthy individuals and patients with auto-immune thyroiditis. Selenium concentrations in blood plasma were measured using electrothermal atomic absorption spectrometry (ETAAS). The study found that L-selenomethionine is absorbed more efficiently than inorganic sodium selenite, with peak plasma concentrations reached and sustained within 6 – 8 hours. Selenium levels remained elevated 48 hours after ingestion compared to baseline. At a daily dose of 200 μg of selenium as L-selenomethionine, plasma selenium concentrations increased by approximate-ly 30 %, and by about 25 % at 100 μg/day, relative to the initial value. Long-term studies showed that plasma selenium concentrations rose significantly after the first month of supplementation, with a slower increase in subsequent months. After supplementation ended, selenium levels declined rapidly. Interest-ingly, no significant differences in selenium absorption or excretion were observed between patients with Hashimoto's thyroiditis and healthy controls.
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Lipoxygenase Inhibitory Activity and Prostate Cancer Cytotoxicity of In Situ- and In Vitro-Cultivated Balkan Endemic Sideritis scardica Griseb
(MDPI AG, 2025-10-25)
Danova, Kalina
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Stoyanova, Elena
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Alipieva, Kalina
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Sideritis scardica Griseb., a Balkan endemic species traditionally used for respiratory conditions and wound-healing, was investigated for its 15-lipoxygenase (15-LOX) inhibitory and cytotoxic activities in relation to its phenolic composition. Aerial parts from the wild-collected and in vitro-cultivated plant were successively extracted with hexane, chloroform, and methanol and the methanol extract was further fractionated into ethyl acetate, butanol, and water fractions. This study presents the first combined evaluation of LOX inhibition and cytotoxicity against prostate cell lines WPMY-1 (normal epithelial fibroblast/myofibroblast), PC-3 (epithelial adenocarcinoma, Grade IV), and LNCaP (epithelial carcinoma) and detailed phytochemical profiles of wild-collected and in vitro-cultivated S. scardica. The phytochemical analysis revealed distinct profiles: increased LOX-inhibition activity was related to a higher phenylethanoid/flavone glycoside ratio, while PC cytotoxicity was rather related to flavone glycoside domination in the plant preparations. The cytotoxic effect of the in vitro-obtained preparations was characterized by a marked selectivity when comparing their effects on WPMY-1, PC-3 and LNCaP cells. To our knowledge, this is the first report linking phenylethanoid/flavone glycoside profiles of in situ and in vitro S. scardica plants with dual LOX-inhibitory and anti-prostate cancer activities, supporting the plant’s potential as a sustainable source of bioactive compounds.
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LC-HRMS and NMR study of the esterification products of ibuprofen with solketal: Formation, isolation and identification
(Society of Chemists and Technologists of Macedonia, 2025-12-24)
Jakimovska Pokupec, Viktorija
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Popova, Milena
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Bankova, Vassya
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Ibuprofen is a widely used non-steroidal anti-inflammatory drug dispensed in tablets, capsules, suspensions, oral solutions, creams, and gels. Ibuprofen's poor water solubility and gastrointestinal side-effects present ongoing formulation challenges. Alcoholic excipients are often employed to enhance solubility and minimise adverse effects. Solketal (1,2-isopropylidene glycerol), a ketal produced by the condensation of glycerol with acetone, offers further versatility as an excipient due to its free hydroxyl group, which enables esterification reactions with acidic active pharmaceutical ingredients like ibuprofen. Introducing any excipient, especially in direct contact with the active pharmaceutical ingredient, necessitates careful evaluation of potential drug–excipient interactions, as these can alter the drug's physicochemical properties and impact clinical performance. Chromatographic techniques coupled with mass spectrometry and nuclear magnetic resonance spectroscopy remain essential for identifying and characterising related and degradation products in pre-formulation studies. In this study, we investigated the esterification of ibuprofen with solketal to identify possible interaction products. Two major compounds were isolated and thoroughly characterised by MS and NMR, confirming their chemical structures: 1-mono-glycerol ester of ibuprofen and ibuprofen-solketal-ester, which contained a 1,3-dioxolane ring. This finding highlights the importance of comprehensive analytical evaluation of drug–excipient interactions during formulation development, as these can affect drug stability and performance.
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Evaluating green and sustainable chemistry education through students’ interventions
(Society of Chemists and Technologists of Macedonia, 2025-05-28)
Nikolovski, Daniel
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This study explores the integration of green and sustainable chemistry into educational curricula and its impact on students' knowledge, motivation, and perceptions. The research aimed to evaluate whether activities centered on green and sustainable chemistry improve students' academic performance and foster awareness of sustainability concepts. Conducted between April and June 2024 in three primary schools in N. Macedonia, the study involved 211 8th grade students, divided into a control group and an experimental group. While the control group followed standard les-sons, the experimental group participated in specific activities integrated into the topic "Introduction to Organic Chemistry." A mixed-methods approach was employed, combining quantitative tools such as the conceptual knowledge test and the activity perception questionnaire, alongside qualitative methods like focus groups and semi-structured inter-views. The conceptual knowledge test assessed students' academic achievements, while the activity perception questionnaire evaluated their perceptions of the activities. The results showed no significant difference in academic performance between the two groups. However, the activity perception questionnaire revealed that students in the experimental group found the activities engaging, valuable, and effective in enhancing their understanding of green and sustainable chemistry concepts. Qualitative data further indicated a preference for interactive learning methods like re-search, games, and experiments, which fostered greater motivation and collaboration among students. This study under-scores the importance of integrating green and sustainable chemistry into curricula to promote environmental awareness and sustainable practices. These findings provide insights into effective teaching strategies and support the inclusion of green and sustainable chemistry in educational policies to equip students for global environmental challenges.
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Unmasking the Aliphatic Repertoire: New Polyunsaturated Metabolites in Bupleurum falcatum sensu lato Provide Chemotaxonomic Insights
(MDPI AG, 2025-05-10)
Nešić, Milica D.
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Nešić, Milan S.
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Raca, Irena Lj.
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Radulović, Niko S.
Bupleurum falcatum (Apiaceae) sensu lato includes multiple infraspecific taxa with longstanding taxonomic ambiguities, often resulting from incomplete morphological and chemical characterizations. Herein, diethyl ether extracts were analyzed from four Balkan populations that were tentatively identified as B. falcatum subsp. falcatum (syn. B. falcatum) and B. falcatum subsp. cernuum (syn. B. sibthorpianum). Comprehensive chro-matography and spectroscopic techniques (GC-MS and 1D/2D NMR) enabled the iso-lation of several newly identified aliphatic polyunsaturated esters, including com-pounds bearing uncommon conjugated tetraene and triyne backbones. These novel structures differ from canonical falcarinol derivatives by lacking the usual 3-hydroxylation, suggesting a divergent branch in the crepenynate pathway. The chemical profiles of each sample correlated closely with leaf morphology and infra-specific designations: for example, the Galičica Mt. population of B. falcatum featured a unique newly detected heptadecadientriyne, while the populations from Šar Planina and Suva Planina displayed distinct polyunsaturated repertoires. Extracts from B. sibthorpianum likewise contained stereoisomeric compounds that highlight metabolic divergence. Collectively, these findings demonstrate significant chemotypic variation within the Bupleurum falcatum complex and provide the first account of less-polar sec-ondary metabolites, including newly discovered polyunsaturated metabolites. Future research integrating molecular markers and bioactivity assays may elucidate how these specialized metabolites contribute to both the taxonomy and pharmacological potential of these understudied taxa.
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Molecular Hydrogen Acts as a Hydrogen Bond Proton Acceptor: From Protonated Betaine Tagging to the Weakest Hydrogen Bond
(American Chemical Society, 2024-05-23)
Achevski, Blagoj
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Pejov, Ljupcho
In an attempt to gain further insights into the intermolecular interactions implied by Rizzo’s group’s cautionary tale related to molecular tagging in infrared multiple photon dissociation (IRMPD) spectroscopy with molecular messengers [Masson, A. et al.. J. Chem. Phys. 2015, 143, 104313], in the present study, we provide an in-depth analysis of the noncovalent interaction between the molecular hydrogen and protonated betaine molecule in the gas phase. We aim to shed some new light on the fundamental issues concerning the wide diapason of hydrogen-bonding-type intermolecular interactions, with a wide variety of proton acceptors. We demonstrate that in the course of tagging the protonated betaine with molecular hydrogen from the OH group side, it is the σ bond of molecular hydrogen that plays the role of hydrogen-bonding proton acceptor. The tagging thus induces a small yet significant red shift of the protonated betaine O−H stretching mode. We investigate the performance of a wide range of density functional theory (DFT) functionals for the calculation of anharmonic vibrational frequency shifts of the studied system, which are essential for the correct interpretation of the experimental IRMPD data. For an accurate prediction of the OH stretching frequency shifts, specifically designed functionals such as Handy’s group HCTH/407 should be applied. The empirical dispersion correction enhances the systematic overestimation of the anharmonic frequency shift, characteristic of the most widely used DFT functionals. Combining the full-wave function approach with the charge field perturbation and natural bond orbital (NBO) deletion analyses, we demonstrate that the frequency shift in the OH-tagged structure is governed by the σHH → σ*OH intermolecular charge transfer. This interaction stabilizes the OH-tagged dimer as well, in contrast to the dipole−quadrupole electrostatic interaction energy term. Topological analysis of the electron density reveals the presence of an intermolecular bond critical point with a positive value of the density Laplacian very close to the lower limit for hydrogen bonds. NCI analyses demonstrate that the OH···H2 interaction is weaker than the intramolecular CH···O one within the protonated betaine molecule, with the through of reduced density gradient appearing at less negative sign(λ2)·ρ values. Analyzing the O−H stretching vibrational potential with the second-generation absolutely localized molecular orbitals energy decomposition analysis (ALMO-EDA 2) revealed that in the case of betaineH(+) tagged from the OH group side, the permanent electrostatics (ΔEelec), polarization (ΔEpol), and charge-transfer (ΔEct) contributions to the total intermolecular interaction energy contribute favorably to the weak hydrogen bond formation and to the red shift of the fundamental O−H stretching frequency, the ΔEct contribution being the most significant in the last context. The Pauli repulsion term, on the other hand, favors an O−H stretching frequency blue shift as a consequence of the vibrational confinement effects.
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3D self-assembled polar vs. non-polar NiO nanoparticles nanoengineered from turbostratic Ni3(OH)4(NO3)2 and ordered β-Ni(OH)2 intermediates
(Royal Society of Chemistry, 2024-11-07)
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Eid, Arej
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Lari, Leonardo
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Althumali, Ahmad
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Šiller, Lidija
A surfactant-free ammonia and carbamide precursor-modulated engineering of self-assembled flowerlike 3D NiO nanostructures based on ordered β-Ni(OH)2 and turbostratic Ni3(OH)4(NO3)2 nanoplate structured intermediates is reported. By employing complementary structural and spectroscopic techniques, fundamental insights into structural and chemical transformations from intermediates to NiO nanoparticles (NPs) are provided. FTIR, Raman and DSC analyses show that the transformation of intermediates to NiO NPs involves subsequent loss of NO3− and OH− species through a double-step phase transformation at 306 and 326 °C corresponding to the loss of free interlayer ions and H2O species, respectively, followed by the loss of chemically bonded OH− and NO3− ions. Transformation to NiO NPs via the ammonia route proceeds as single-phase transition, accompanied with a loss of OH− species at 298 °C. The full transformation to NiO NPs of both intermediates is achieved at 350 °C through annealing in the air atmosphere. Ammonia-derived NPs maintain nanoflower morphology by self-assembling into nanoplates, which is enabled by H2O-mediated adhesion on the NiO NPs’ {100} neutral surfaces. Structural transformations of turbostratic Ni3(OH)4(NO3)2 nanoplates result in the formation of NiO NPs dominantly shaped by inert polar OH-terminated (111) atomic planes, leading to the loss of the initial self assembled 3D structure. DFT calculations support these observations, confirming that H2O adsorbs dissociatively on polar {111} surfaces, while only physisorption is energetically feasible on {100} surfaces. NiO NPs obtained via two different routes have overall different properties: carbamide-derived NPs are 3 times larger (15.5 vs. 5.4 nm), possess a larger band gap (3.6 vs. 3.2 eV) and are more Ni deficient. The intensity ratio of surface optical (SO) modes to transversal and longitudinal optical modes is ∼40 times higher in the NiO NPs obtained from β-Ni(OH)2 compared to Ni3(OH)4(NO3)2-derived NPs. The SO phonon lifetime is an order of magnitude shorter in NiO obtained from β-Ni(OH)2, reflecting a much smaller NP size. The choice of a precursor defines the size, morphology, crystallographic surface orientations and band gap of the NiO NPs, with Ni deficiency providing pathways for utilizing them as p-type materials, allowing for the precise nanoengineering of polar and neutral surface-dominated NiO NPs, which is of exceptional importance for use in catalysis.
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Facile Synthesis of Cu<sub>x</sub>S Electrocatalysts for CO<sub>2</sub> Conversion into Formate and Study of Relations Between Cu and S with the Selectivity
(Wiley, 2024-10-25)
Stojkovikj, Sasho
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El‐Nagar, Gumaa A.
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Gupta, Siddharth
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Koleva, Violeta
<jats:title>Abstract</jats:title><jats:p>The conversion of CO<jats:sub>2</jats:sub> into formate (HCOO<jats:sup>−</jats:sup>), a techno‐economically feasible product, can be achieved using earth‐abundant Cu<jats:sub>x</jats:sub>S electrocatalysts, but questions remain regarding how catalyst structure, composition, and reaction environment influence product selectivity. A novel synthesis method based on electrodeposition of Cu foam and its subsequent sulfidation via immersion in sulfur saturated toluene solution resulted in Cu<jats:sub>x</jats:sub>S foams. Catalytic activity studies found that HCOO<jats:sup>−</jats:sup> selectivity is dependent on electrochemical activation at higher overpotentials. To understand the effects of activation, determine the active forms of the catalysts, and identify the role of sulfur, the electrodes are carefully characterized as well as gaseous and sulfur dissolved in electrolyte. This included study of the effects of intentional addition of solution sulfur species, identification of the sulfur loss, determination of the electrode composition and relating sulfur speciation to observed product selectivity. It is found that residual sulfur stabilizes Cu<jats:sup>+</jats:sup> during electrolysis at potentials favoring HCOO<jats:sup>−</jats:sup> production, in contrast to pristine Cu that undergoes complete reduction and shows poor HCOO<jats:sup>−</jats:sup> selectivity. Sulfur in both the catalyst and dissolved in electrolyte are of dynamic nature, and surface residues of SO<jats:sub>4</jats:sub><jats:sup>2−</jats:sup> species are identified in all activated catalysts which correspond with enhanced HCOO<jats:sup>−</jats:sup> production.</jats:p>
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Establishment, evaluation, and application of a gas chromatography–mass spectrometry method for quantification of volatile organic compounds in ambient air using anisole as an internal standard
(SHTM, UKIM, 2024)
Sofronievska, Ivona
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Upcycling of plastic waste into multi-walled carbon nanotubes as efficient organic dye adsorbent
(Slovenian Chemical Society, 2025-03-03)
Bogoeva-Gaceva, Gordana
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Sokolovska, Meri
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Kovačič, Sebastijan
Multi-walled CNTs with an average diameter of about 80 nm, a length of several micrometers and surface area (SBET) of 100 m2 g-1 were obtained by pyrolysis of low-density polyethylene waste. The potential of the resulting MWCNTs material to purify water containing organic dyes was tested with Bezaktiv Blau HE-RM (BB) and Bezaktiv Rot S-3B (BR) reactive dyes. 200 mg L-1 MWCNT material was used to follow the adsorption of 30 mg L-1, 40 mg L-1, 50 mg L-1 and 60 mg L-1 BB and BR at pH 3 and a temperature of ~25 oC. The results have shown that this material has a high potential as a sorbent, and its adsorption capacity of 257 mg g-1 (for Bezaktiv Blau HE-RM) and 213 mg g-1 (for Bezaktiv Rot) is close to some commercial MWCNTs and functionalized MWCNT-based adsorbents. The adsorption process was very fast, reaching 80-90 % of the dye removal in 10-15 minutes, and the equilibrium time was reached in 40-60 minutes. The adsorption isotherm showed that the Langmuir model was more suitable than the Freundlich model for describing the adsorption properties of the pollutants.

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