Browsing by Author "Anastassova N."
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Item Evaluation of the combined activity of benzimidazole arylhydrazones as new anti-Parkinsonian agents: Monoamine oxidase-B inhibition, neuroprotection and oxidative stress modulation(2021-11-01) Anastassova N.; Aluani D.; Kostadinov A.; Rangelov M.; Todorova N.; Hristova-Avakumova N.; Argirova M.; Lumov N.; Kondeva-Burdina M.; Tzankova V.; Yancheva D.Neuroprotective drugs and selective monoamine oxidase inhibitors can slow down the progression and improve symptoms of Parkinson's disease (PD). Since there is an implication of oxidative stress in the pathophysiological mechanisms of the disease, the compounds possessing an ability to reduce the oxidative stress are prime candidates for neuroprotection. Thereby our current study is focused on the development of new multi-target PD drugs capable of inhibiting the activity of monoamine oxidase-B while exerting neuroprotective and antioxidant properties. A small series of benzimidazole derivatives containing hydroxy and methoxy arylhydrazone fragments has been synthesized and the neurotoxicity of the compounds has been evaluated in vitro on neuroblastoma SH-SY5Y cells and on isolated rat brain synaptosomes by measuring the cell viability and the levels of reduced glutathione and a good safety profile has been shown. The 2-hydroxy-4-methoxy substituted arylhydrazone 7 was the least toxic on neuronal SH-SY5Y cells and showed the lowest neurotoxicity in rat brain synaptosomes. The neuroprotective properties of the test compounds were further assessed using two models: H2O2-induced oxidative stress on SH-SY5Y cells and 6-hydroxydopamine-induced neurotoxicity in rat brain synaptosomes. Compound 7 showed more pronounced neuroprotective activity on SH-SY5Y cells, compared to the referent melatonin and rasagiline. It also preserved the synaptosomal viability and the reduced glutathione levels; the effects were stronger than those of rasagiline and comparable to melatonin. All the tested compounds were capable to inhibit human monoamine oxidase-B enzyme to a significant extent, however, compound 7 exerted the most prominent inhibitory activity, similar to selegiline and rasagiline. The carried out molecular docking studies revealed that the activity is related to the appropriate molecular structure enabling the ligand to enter deeper in the narrow and highly lipophylic active site pocket of the human monoamine oxidase-B and has a favoring interaction with the key amino acid residues Tyr326 and Cys172. Since much scientific evidence points out the implication of iron dyshomeostasis in PD, the compounds were tested to reduce the ferrous iron induced oxidative molecular damage on biologically important molecules in an in vitro lecithin containing model system. All the investigated compounds denoted protection effect, stronger than the one of the referent melatonin. In order to support the assignments of the significant neuroprotective and antioxidant pharmacological activities, the radical-scavenging mechanisms of the most promising compound 7 were evaluated using DFT methods. It was found that the most probable free radicals scavenging mechanism in nonpolar phase is the hydrogen atom transfer from the amide group of compound 7, while in polar medium the process is expected to occur by a proton transfer. The current study outlines a perspective leading structure, bearing the potential for a new anti-PD drug. All performed procedures were approved by the Institutional Animal Care Committee of the Medical University of Sofia (Bulgarian Agency for Food Safety with Permission № 190, approved on February 6, 2020).Item Evaluation of the combined activity of benzimidazole arylhydrazones as new anti-Parkinsonian agents: Monoamine oxidase-B inhibition, neuroprotection and oxidative stress modulation(2021-11-01) Anastassova N.; Aluani D.; Kostadinov A.; Rangelov M.; Todorova N.; Hristova-Avakumova N.; Argirova M.; Lumov N.; Kondeva-Burdina M.; Tzankova V.; Yancheva D.Neuroprotective drugs and selective monoamine oxidase inhibitors can slow down the progression and improve symptoms of Parkinson's disease (PD). Since there is an implication of oxidative stress in the pathophysiological mechanisms of the disease, the compounds possessing an ability to reduce the oxidative stress are prime candidates for neuroprotection. Thereby our current study is focused on the development of new multi-target PD drugs capable of inhibiting the activity of monoamine oxidase-B while exerting neuroprotective and antioxidant properties. A small series of benzimidazole derivatives containing hydroxy and methoxy arylhydrazone fragments has been synthesized and the neurotoxicity of the compounds has been evaluated in vitro on neuroblastoma SH-SY5Y cells and on isolated rat brain synaptosomes by measuring the cell viability and the levels of reduced glutathione and a good safety profile has been shown. The 2-hydroxy-4-methoxy substituted arylhydrazone 7 was the least toxic on neuronal SH-SY5Y cells and showed the lowest neurotoxicity in rat brain synaptosomes. The neuroprotective properties of the test compounds were further assessed using two models: H2O2-induced oxidative stress on SH-SY5Y cells and 6-hydroxydopamine-induced neurotoxicity in rat brain synaptosomes. Compound 7 showed more pronounced neuroprotective activity on SH-SY5Y cells, compared to the referent melatonin and rasagiline. It also preserved the synaptosomal viability and the reduced glutathione levels; the effects were stronger than those of rasagiline and comparable to melatonin. All the tested compounds were capable to inhibit human monoamine oxidase-B enzyme to a significant extent, however, compound 7 exerted the most prominent inhibitory activity, similar to selegiline and rasagiline. The carried out molecular docking studies revealed that the activity is related to the appropriate molecular structure enabling the ligand to enter deeper in the narrow and highly lipophylic active site pocket of the human monoamine oxidase-B and has a favoring interaction with the key amino acid residues Tyr326 and Cys172. Since much scientific evidence points out the implication of iron dyshomeostasis in PD, the compounds were tested to reduce the ferrous iron induced oxidative molecular damage on biologically important molecules in an in vitro lecithin containing model system. All the investigated compounds denoted protection effect, stronger than the one of the referent melatonin. In order to support the assignments of the significant neuroprotective and antioxidant pharmacological activities, the radical-scavenging mechanisms of the most promising compound 7 were evaluated using DFT methods. It was found that the most probable free radicals scavenging mechanism in nonpolar phase is the hydrogen atom transfer from the amide group of compound 7, while in polar medium the process is expected to occur by a proton transfer. The current study outlines a perspective leading structure, bearing the potential for a new anti-PD drug. All performed procedures were approved by the Institutional Animal Care Committee of the Medical University of Sofia (Bulgarian Agency for Food Safety with Permission № 190, approved on February 6, 2020).Item Hepatotoxicity and antioxidant activity of some new N,N′-disubstituted benzimidazole-2-thiones, radical scavenging mechanism and structure-activity relationship(2018-03-01) Anastassova N.; Mavrova A.; Yancheva D.; Kondeva-Burdina M.; Tzankova V.; Stoyanov S.; Shivachev B.; Nikolova R.A new method for the synthesis of 1,3-disubstituted benzimidazole derivatives was developed using aza-Michael addition. The target compounds were synthesized in good yields and purity and tested on isolated hepatocytes for their toxicity and antioxidant activity. The antioxidant properties of the substances with lowest toxicity were evaluated using oxidative stress induced by tert-butyl hydroperoxide (tert-BOOH). Some of them as methyl 3-[3-(3-methoxy-3-oxopropyl)-5-benzoyl-2-thioxo-2,3-dihydro-1H-benzimidazol-1-yl]propanoate 10 and 1,3-bis[3-(hydrazinooxy)-3-oxopropyl]-5-benzoyl-1,3-dihydro-2H-benzimidazole-2-thione 15 exhibited statistically significant cytoprotective and antioxidant effects which were similar to those of quercetin. In order to estimate the influence of the structure on the biological properties, structural characterization of the studied compounds was performed by X-ray diffraction analysis and DFT methods. On the basis of the calculated reaction enthalpies of hydrogen atom abstraction (HAT mechanism) and single-electron transfer (SET mechanism) the mechanisms of the antioxidant action of the tested compounds were studied. Subsequently it was established that the HAT mechanism governs the radical scavenging of 10 and 15 in the lipid phase, while the SET mechanism is preferred in water medium for 10 and competitive to HAT for 15.Item In vitro Assessment of the Lipid Peroxidation of N,N'-Disubstituted Benzimidazole-2-Thiones: Hydrazides vs Esters(2022-01-01) Lazarević J.; Zvezdanović J.; Anastassova N.; Mavrova A.T.; Yancheva D.; Šmelcerović A.Introduction: Oxidative stress and resulting lipid peroxidation are involved in numerous pathological conditions. For this reason, the role of antioxidants attracts attention and the radical-scavenging capacity of many natural and synthetic supplements and drugs has been extensively evaluated. Material and methods: In the present study, seven N,N'-disubstituted benzimidazole-2-thiones with ester (1 - 4) and hydrazide (5 - 7) side chains were investigated for in vitro antioxidant activity using lipid peroxidation method. Results: Among the assayed compounds, three hydrazides, 1,3-bis[3-(hydrazinooxy)-3-oxopropyl]-1,3- dihydro-2H-benzimidazole-2-thione (5), 1,3-bis[3-(hydrazinooxy)-3-oxopropyl]-5-methyl-1,3-dihydro-2Hbenzimidazole- 2-thione (6) and 1,3-bis[3-(hydrazinooxy)-3-oxopropyl]-5-benzoyl-1,3-dihydro-2Hbenzimidazole- 2-thione (7) showed good antioxidant properties (IC50 < 100 μM), with the best lipid peroxidation inhibition values (IC50) shown for compound 5 (64 ± 10 μM) and compound 6 (73 ± 29 μM). Conclusion: Indicated hydrazide structures may constitute a sort of molecular basis, a promising starting point for the development of compounds for the prevention and treatment of diseases resulting from oxidative damage.Item New Indole-3-Propionic Acid and 5-Methoxy-Indole Carboxylic Acid Derived Hydrazone Hybrids as Multifunctional Neuroprotectors(2023-04-01) Anastassova N.; Stefanova D.; Hristova-Avakumova N.; Georgieva I.; Kondeva-Burdina M.; Rangelov M.; Todorova N.; Tzoneva R.; Yancheva D.In light of the known neuroprotective properties of indole compounds and the promising potential of hydrazone derivatives, two series of aldehyde-heterocyclic hybrids combining those pharmacophores were synthesized as new multifunctional neuroprotectors. The obtained derivatives of indole-3-propionic acid (IPA) and 5-methoxy-indole carboxylic acid (5MICA) had good safety profiles: Hemolytic effects < 5% (200 μM) and IC50 > 150 µM were found in the majority of the SH-SY5Y and bEnd3 cell lines. The 2,3-dihydroxy, 2-hydroxy-4-methoxy, and syringaldehyde derivatives of 5MICA exhibited the strongest neuroprotection against H2O2-induced oxidative stress in SH-SY5Y cells and 6-OHDA-induced neurotoxicity in rat-brain synaptosomes. All the compounds suppressed the iron-induced lipid peroxidation. The hydroxyl derivatives were also the most active in terms of deoxyribose-degradation inhibition, whereas the 3,4-dihydroxy derivatives were able to decrease the superoxide-anion generation. Both series of compounds showed an increased inhibition of hMAO-B, with greater expression detected in the 5MICA hybrids. The in vitro BBB model with the bEnd3 cell line showed that some compounds increased the permeability of the endothelial monolayer while maintaining the tight junctions. The combined results demonstrated that the derivatives of IPA and 5MICA showed strong neuroprotective, antioxidant, MAO-B inhibitory activity and could be considered as prospective multifunctional compounds for the treatment of neurodegenerative disorders.Item Spectroscopic and thermodynamic characterization of the interaction of a new synthesized antitumor drug candidate 2H4MBBH with human serum albumin(2024-01-01) Abarova S.; Stoitchkova K.; Tzonev S.; Argirova M.; Yancheva D.; Anastassova N.; Tenchov B.In the present work we studied the interactions of a newly synthesized drug candidate, 2-(2-hydroxy-4-methoxyben-zylidene)-1-(1H-benzimidazol-2-yl)hydrazine (2H4MBBH), with human serum albumin (HSA) by fluorescence spectroscopy. 2H4MBBH-HSA binding parameters were assessed by fluorescence quenching strategy. As made clear by the concentration data, 2H4MBBH unequivocally quenched the instrinsic HSA fluorescence. The calculated Stern-Volmer quenching constant Ksv, the Ka of 2H4MBBH-HSA complexes, as well as the thermodynamic parameters ΔH°, ΔS° and ΔG°, showed that the H-bonding forces play major part in the interaction of 2H4MBBH with HSA. These calculations point to a quenching component based on 2H4MBBH-HSA static complex formation rather than energetic collisions.Item Study on the Neuroprotective, Radical‐Scavenging and MAO‐B Inhibiting Properties of New Benzimidazole Arylhydrazones as Potential Multi‐Target Drugs for the Treatment of Parkinson’s Disease(2022-05-01) Anastassova N.; Aluani D.; Hristova‐avakumova N.; Tzankova V.; Kondeva‐burdina M.; Rangelov M.; Todorova N.; Yancheva D.Oxidative stress is a key contributing factor in the complex degenerating cascade in Par-kinson’s disease. The inhibition of MAO‐B affords higher dopamine bioavailability and stops ROS formation. The incorporation of hydroxy and methoxy groups in the arylhydrazone moiety of a new series of 1,3‐disubstituted benzimidazole‐2‐thiones could increase the neuroprotective activity. In vitro safety evaluation on SH‐SY5Y cells and rat brain synaptosomes showed a strong safety profile. Antioxidant and neuroprotective effects were evaluated in H2O2‐induced oxidative stress on SH‐ SY5Y cells and in a model of 6‐OHDA‐induced neurotoxicity in rat brain synaptosomes, where the dihydroxy compounds 3h and 3i demonstrated the most robust neuroprotective and antioxidant activity, more pronounced than the reference melatonin and rasagiline. Statistically significant MAO‐B inhibitory effects were exerted by some of the compounds where again the catecholic compound 3h was the most potent inhibitor similar to selegiline and rasagiline. The most potent anti-oxidant effect in the ferrous iron induced lipid peroxidation assay was observed for the three cate-chols—3h and 3j, 3q. The catecholic compound 3h showed scavenging capability against superox-ide radicals and antioxidant effect in the iron/deoxyribose system. The study outlines a perspective multifunctional compound with the best safety profile, neuroprotective, antioxidant and MAO‐B inhibiting properties.Item SYNTHESIS OF NEW TRIAZOLE AND THIADIAZOLE DERIVATIVES OF THE N,N’-DISUBSTITUTED BENZIMIDAZOLE-2-THIONE AND EVALUATION OF THEIR ANTITUMOR POTENTIAL(2022-01-01) Anastassova N.; Georgieva I.; Milanova V.; Tzoneva R.; Radev K.; Yancheva D.; Mavrova A.In the present study series of triazole-, thiadiazoleand thiosemicarbazone-benzimidazole hybrid compounds were synthesized as potential anti-cancer agents. In order to determine their antitumor potential and cytotoxic effect (via MTT assay) lung adenocarcinoma (A549) and breast cancer (MDA-MB-231) cell lines were examined. For detection of apoptosis induced by drug treatment, DAPI staining was performed in order to observe the apoptotic alterations in cell nuclei. It was found that the thiadiazole derivative 12 leads to the occurrence of micronuclei, suggesting genotoxic effect. Furthermore, a wound healing assay was performed in order to test whether any changes in cell motility occurred upon treatment with the newly synthesized hybrids, since both cell lines are examples of highly invasive tumours. The cell motility of MDA-MB-231 was impeded mostly by compound 12 (15 % of wound closure) and in A549 compound 9 reduced cell motility by 46 % compared to the control. The obtained results suggest that compound 12 possesses a promising anticancer effect.Item Two 5-Methoxyindole Carboxylic Acid-Derived Hydrazones of Neuropharmacological Interest: Synthesis, Crystal Structure, and Chemiluminescent Study of Radical Scavenging Properties(2024-05-01) Anastassova N.; Hristova-Avakumova N.; Rusew R.; Shivachev B.; Yancheva D.Given the importance of molecular structure in pharmacological activity and interaction with biological receptors, we conducted a study on the 3,4-dihydroxybenzaldehyde hydrazone derivative of 5-methoxy-indole carboxylic acid (5MICA) and a newly synthesised analogue bearing a 2-methoxy-4-hydroxyphenyl ring using single-crystal X-ray diffraction. We studied the ability of the two compounds to scavenge hypochlorite ions using luminol-enhanced chemiluminescence and their potential to modulate oxidative damage induced by iron on the biologically significant molecules lecithin and deoxyribose in order to evaluate possible antioxidant and prooxidant effects. The X-ray study revealed highly conserved geometry and limited rotation and deformation freedom of the respective indole and phenyl fragments. Interestingly, a conformational difference between the two independent molecules in the asymmetric unit of 3b was found. The X-ray study revealed a combination of hydrogen bonding interactions, short contacts, and π–π stacking stabilizing the specific three-dimensional packing of the molecules of 3a and 3b in the crystal structures. The three-dimensional packing of the molecules of 3b produced a zigzag layering projected along the c-axis. Both compounds effectively decreased luminol-dependent chemiluminescence in model systems with KO2-produced superoxide. They displayed opposite effects when applied in a xanthine/xanthine oxidase system. The hydrazones of 5MICA do not trigger a prooxidant effect or subsequent toxicity under conditions of iron-induced oxidative stress. The 3,4-dihydroxy-substituted derivative demonstrated excellent radical scavenging properties in all model systems, making it the lead compound for the development of compounds with combined neuroprotective and antioxidant properties.