Browsing by Author "Kaloyanov N."
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Item Antioxidant capacity of 1,10-phenanthroline, 5-amino-1,10-phenanthroline and their Pd-Complexes(2017-01-01) Neykov M.; Kaloyanov N.; Mihailova B.; Goshev I.The present study describes the antioxidant activity of 1,10-phenanthroline, 5-amino-1,10-phenanthroline and their Pd complexes: Pd(5-NH2-phen)2(NO3)2 and Pd(phen)(NO3)2(H2O). It is evaluated in situ using HORAC (Hydroxyl Radical Averting Capacity) and ORAC (Oxygen Radical Absorbance Capacity) methods. The best antioxidant activity determined by HORAC method refers to Pd(5-NH2-phen)2(NO3)2. It is followed by that of 5-amino-1,10-phenanthroline and Pd(phen)2(NO3)2(H2O). The application of ORAC method shows that the best antioxidant activity is attributed to Pd(5- NH2-phen)2(NO3)2. It is followed by that of Pd(phen)2(NO3)2(H2O) and 5-amino-1,10-phenanthroline. The comparison of all results obtained leads to the conclusion that the Pd complex of 5-amino-1,10-phenanthroline shows the best antioxidant activity because of the presence of an amino group.Item COMPARATIVE STUDY OF POLYPHENOLIC COMPOSITION AND REDUCING PROPERTIES OF EXTRACTS OF CANNABIS SATIVA L., CANNABIS INDICA AND CANNABIS HYBRID(2024-01-01) Vetskov N.; Kaloyanov N.; Hinkov I.; Diankov S.; Pashova K.; Gerasimova V.; Funeva-Peycheva M.; Yankovska-Stefanova T.; Garbev A.Cannabis Sativa L., Cannabis Indica and Cannabis Hybrid are widespread plant species that find legal use in many countries around the world. The first of them has found considerable application in medicine, cosmetics, building construction, textile and food industries. Cannabis Indica and Cannabis Hybrid are used as raw materials for the extraction of oils that are used as pain relievers as well as for recreation purposes. The aim of the present study is to compare the polyphenolic composition of extracts from the three types of plants, by the maceration method of dry green leaf mass consisting of inflorescences and leaves. Ethanol (99.9 %) is used as an extractant, and the duration of the maceration process is seven days, at room temperature and stirring. The polyphenol composition is determined using HPLC-DAD method. The following polyphenol composition is found in extracts of Cannabis Sativa L.: epigallocatechin, rutin, myricetin, quercetin and kaempferol. On the other hand, quercetin and kaempferol are detected in the Cannabis Indica samples, while epigallocatechin, quercetin and kaempferol are present in the hybrid sort. In addition, green synthesis of silver nanoparticles by using sunlight or microwave irradiation was carried out to evaluate the reduction properties of three cannabis extracts. The least quantity of silver nanoparticles was obtained in the presence of Cannabis Sativa L. extracts. From the other two species of cannabis, microwave irradiation produces more silver nanoparticles, with smaller sizes, while exposure to direct sunlight produces fewer particles, but with larger sizes.Item Efficiency of transparent structures in Trombe walls(2018-01-01) Kaloyanov N.; Stankov B.; Tomov G.; Penkova N.The Trombe wall is a passive solar design solution suitable for buildings in temperate and warm climates. The transparent units, which constitute the external boundary of the structure, are among the most important factors for its energy performance. This paper presents an analysis of the energy performance of unvented Trombe walls using two of the most commonly encountered types of glazing - single glass and double insulting glass units (IGU). The analyses are based on physical measurements obtained at a test site and numerical simulations of the heat transfer processes in the system. In addition to the energy performance assessment, a thermal load analysis is performed for the more efficient solution, i.e., the double glazed unit, to predict the influence of the occurring heat transfer processes on the mechanical behavior and reliability of the construction.Item METHANE PRODUCTION FROM COW MANURE IN THE PRESENCE OF Bi(III) COMPLEX OF SULFAMIC ACID(2024-01-01) Tzanova A.; Kaloyanov N.; Ruskova K.; Zahariev A.The present study examines the process of biomethanization of cow manure in an anaerobic environment, in the presence of small amounts of Bi(III) complex of sulfamic acid. Since this complex has good antimicrobial activity, the purpose of adding the complex is to determine its effect on biogas and methane production. The reference samples (cow manure only) and mixtures of cow manure + 10 mg and cow manure + 20 mg of bismuth complex with a composition [Bi6O4(OH)4](NH2SO3)6 are subjected to biodegradation under the following conditions – duration of 33 days, nitrogen atmosphere and temperature of 34.5 ± 1°C. During the process, the volume of biogas and the percentage content of methane in biogas are measured in 2 - 3 days as well. The analyses performed reveal that until the 10th day, the amount of biogas produced increases constantly and is comparable both for the control samples and for the mixtures. Further, until the end of the experiment, a significant and constant increase in the volume of biogas produced by the mixtures is observed compared to the control samples. Regarding the percentage of methane produced by the reference samples and the mixtures, comparable relative amounts are found by the 7th day. From the 8th day to the 33rd day, the percentage of methane released by the mixtures is visibly greater than that by the reference samples.Item Modelling and numerical simulation of the transport phenomena in water thermal energy storage tanks(2021-11-22) Kaloyanov N.; Tsecov R.; Penkova N.Mathematical model for numerical simulation of the transient heat transfer and fluid flows in water thermal energy storage tanks is developed. The model allows analysis of the thermal fields in the accumulators at different schemes and modes of charging and discharging. It was verified and validated based on experimentally obtained information about the temperature stratification at charging of a thermal accumulator at a laboratory solar system. The proposed approach for numerical study of the thermal energy storage is convenient for parametrical estimation and improvement of the efficiency of the thermal systems.Item Neuroprotection in non-transgenic and transgenic mouse models of Alzheimer's disease by positive modulation of σ 1 receptors(2019-06-01) Maurice T.; Volle J.N.; Strehaiano M.; Crouzier L.; Pereira C.; Kaloyanov N.; Virieux D.; Pirat J.L.The sigma-1 (σ 1 ) receptor is an endoplasmic reticulum (ER) chaperone protein, enriched in mitochondria-associated membranes. Its activation triggers physiological responses to ER stress and modulate Ca 2+ mobilization in mitochondria. Small σ 1 agonist molecules activate the protein and act behaviorally as antidepressant, anti-amnesic and neuroprotective agents. Recently, several chemically unrelated molecules were shown to be σ 1 receptor positive modulators (PMs), with some of them a clear demonstration of their allostericity. We here examined whether a σ 1 PM also shows neuroprotective potentials in pharmacological and genetic models of Alzheimer's disease (AD). For this aim, we describe (±)-2-(3-chlorophenyl)-3,3,5,5-tetramethyl-2-oxo-[1,4,2]-oxazaphosphinane (OZP002) as a novel σ 1 PM. OZP002 does not bind σ 1 sites but induces σ 1 effects in vivo and boosts σ 1 agonist activity. OZP002 was antidepressant in the forced swim test and its effect was blocked by the σ 1 antagonist NE-100 or in σ 1 receptor knockout mice. It potentiated the antidepressant effect of the σ 1 agonist igmesine. In mice tested for Y-maze alternation or passive avoidance, OZP002 prevented scopolamine-induced learning deficits, in a NE-100 sensitive manner. Pre-administered IP before an ICV injection of amyloid Aβ 25-35 peptide, a pharmacological model of Alzheimer's disease, OZP002 prevented the learning deficits induced by the peptide after one week in the Y-maze, passive avoidance and novel object tests. Biochemical analyses of the mouse hippocampi showed that OZP002 significantly decreased Aβ 25-35 -induced increases in reactive oxygen species, lipid peroxidation, and increases in Bax, TNFα and IL-6 levels. Immunohistochemically, OZP002 prevented Aβ 25-35 -induced reactive astrogliosis and microgliosis in the hippocampus. It also alleviated Aβ 25-35 -induced decreases in synaptophysin level and choline acetyltransferase activity. Moreover, chronically administered in APPswe mice during 2 months, OZP002 prevented learning deficits (in all tests plus place learning in the water-maze) and increased biochemical markers. This study shows that σ 1 PM with high neuropotective potential can be identified, combining pharmacological efficacy, selectivity and therapeutic safety, and identifies a novel promising compound, OZP002.Item Self-Assembled Molecular Complexes of 1,10-Phenanthroline and 2-Aminobenzimidazoles: Synthesis, Structure Investigations, and Cytotoxic Properties(2024-02-01) Anichina K.; Kaloyanov N.; Zasheva D.; Rusew R.; Nikolova R.; Yancheva D.; Bakov V.; Georgiev N.Three new molecular complexes (phen)3(2-amino-Bz)2(H+)(BF4−)·3H2O 5, (phen)3(2-amino-5(6)-methyl-Bz)2(H+)(BF4−)·H2O 6, and (phen)(1-methyl-2-amino-Bz)(H+)(BF4−) 7, were prepared by self-assembly of 1,10-phenanthroline (phen) and various substituted 2-aminobenzimidazoles. Confirmation of their structures was established through spectroscopic methods and elemental analysis. The X-ray diffraction analysis revealed that the crystal structure of 7 is stabilized by the formation of hydrogen bonds and short contacts. In addition, the molecular geometry and electron structure of molecules 5 and 6 were theoretically evaluated using density functional theory (DFT) methods. According to the DFT B3LYP/6-311+G* calculations, the protonated benzimidazole (Bz) units act as NH hydrogen bond donors, binding two phenanthrolines and a BF4− ion. Non-protonated Bz unit form hydrogen bonds with the N-atoms of a third molecule phen. The molecular assembly is held together by π-π stacking between benzimidazole and phenanthroline rings, allowing for N-atoms to associate with water molecules. The complexes were tested in vitro for their tumor cell growth inhibitory effects on prostate (PC3), breast (MDA-MB-231 and MCF-7), and cervical (HeLa) cancer cell lines using MTT-dye reduction assay. The in vitro cytotoxicity analysis and spectrophotometric investigation in the presence of ct-DNA, showed that self-assembled molecules 5–7 are promising DNA-binding anticancer agents warranting further in-depth exploration.Item Synthesis and biological activity of novel heavy metal complexes of 5-amino-1, 10-phenanthroline and 1,10-phenanthroline(2012-08-01) Kaloyanov N.; Neykov M.; Wesselinova D.; Dimitrov G.Novel heavy metal complexes: Sr(5-NH 2-phen) 4(NO 3)(OH)(H 2O) 2 (1) (synthesized via a static self-assembly process) and Sn(phen) (NO 3)(OH)(H 2O) (2), Sn(5-NH 2-phen)(OH)(Cl)(H 2O) (3), Pb(5-NH 2-phen)(NO 3) 2(H 2O) (4) (obtained via metal competitive reactions under mild conditions) were reported. The coordination compounds were characterized by elemental analysis, FTIR-spectroscopy and FAB-mass spectrometry. Their cytotoxicity was measured by MTS-test towards human tumour (MDA-MB-231, HT-29, HeLa, HepG2) and non-tumour diploid (Lep-3) cell lines. The most pronounced cytotoxic effect on all cancer lines showed 1 and 4 at their high concentrations as well as 1 at its lower ones (≤ 4×10 -2 mg). Therefore, strontium complex of 5-amino-o-phenanthroline (1) exhibited the widest antitumour spectrum activity, having no toxicity to non-tumour cells at quantities ≤ 4×10 -2 mg. The computed EC 50 values of 1-4 against MDA-MB-231, HT-29, HeLa, HepG2 varied from 1.40×10 -3 to 6.31×10 -6 M. Towards Lep-3 substances 2-4 showed IC 50 7.52×10 -4 - 0.44 M. Substance 1 possess EC 50=1. 26×10 -7 M to the non-tumour cells. © Versita Sp. z o.o.Item Synthesis of new complex [Bi6O6(OH)2](ClC6H4SO3)4and investigation of its thermal decomposition(2023-05-01) Kaloyanov N.; Zahariev A.; Parvanova V.; Avdeev G.; Girginov C.A new [Bi6O6(OH)2](ClC6H4SO3)4complex is synthesized through a reaction of Bi2O3 with aqueous 4-chlorobenzenesulfonic acid at elevated temperature. The product composition is elucidated by elemental analysis, ICP-OES and FTIR techniques. By means of XRD analysis, the compound s indexation, monoclinic P2(3) space group and unit cell parameters: A=31.25(3) A, b=19.78(1) A, c=8.795(8) A, γ = 94.33(4)o as well as a cell volume = 5424.21 A3 are determined. Based on DTA-TG technique, three specific temperatures aimed at studying product s thermal decomposition are determined. The compositions of solid residues after isothermal heating are proved following the XRD and FTIR data.