Browsing by Author "Tan, Oya Unsal"

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    Investigation of anti-cholinesterase and anti-amyloidogenic activities of beta-lactam antibiotics
    (2022) Ozer, Eda Ozturan; Mirza, Hasan Cenk; Tan, Oya Unsal; Turkoglu, Suna; 0000-0002-8853-3893; 0000-0003-4805-1918; F-1232-2015; AAJ-2243-2021
    Objectives: Neuroinflammation is an important factor in the pathogenesis of neurodegenerative disesases. The following study aimed to clarify the effects of beta-lactam antibiotics to the cholinergic system, on acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) activities, considering the structural differences of antibiotics, to evaluate the underlying mechanism of effects provided by protein-antibiotic interactions, and to clarify possible effects of the antibiotics on the aggregation of A beta-peptides. Methods: The inhibition/activation mechanisms for each antibiotic were examined kinetically by Ellman method. Destabilization effects of them on amyloid peptide fibrillation were examined and protein-ligand interactions were evaluated with most potent antibiotics by molecular docking studies. Results: The most powerful inhibitions were detected by the inhibition studies of AChE with ceftazidime (CAZ) and BuChE with amoxicillin (AMX). CAZ was exhibited dose-related dual effect on AChE activity. CAZ was actually the dose-related modifier of AChE. At higher concentrations, CAZ was a nonessential activator of AChE. Molecular docking studies have been confirmed by kinetic studies. Interested beta-lactam antibiotics did not prevent fibrillation rate as rifampicin. Conclusion: Inhibition/activation behaviours of studied beta-lactam antibiotics on both cholinesterases may suggest that cholinergic transmission is one of the crucially important components of the beta-lactam antibiotics-induced central nervous system adverse reactions.
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    The structural diversity of ginsenosides affects their cholinesterase inhibitory potential
    (2020) Ozer, Eda Ozturan; Tan, Oya Unsal; Turkoglu, Suna; 0000-0003-4805-1918; 0000-0001-6543-4043; AAJ-2243-2021; AAK-3000-2021
    Background/Objective: Ginsenosides, the major active components of the ginseng, are known to have various effects on nervous systems. The present study aimed to clarify the inhibition potentials of ginsenosides Rb1, Rc, Re and Rg1 on acetylcholinesterase (AChE) and butrylcholinesterase (BChE) activities, and to evaluate the underlying mechanisms of inhibitions provided by protein-ligand interactions considering their probable candidates of prodrug. Materials and methods: The inhibitory mechanisms of ginsenosides related with their structural diversity were analyzed kinetically and protein-ligand interactions for both enzymes were evaluated with most potent ginsenosides, by molecular docking studies. Results: Ginsenosides Re and Rg1, with sugar moieties attached to the C-6 and C-20 positions of core structure were found to possess the most powerful inhibitory effect on AChE and BChE activities. Molecular docking studies have been confirmed by kinetic studies. Ginsenosides having a direct interaction with amino acid residues belonging to the catalytic triad revealed the most powerful inhibition with lowest enzyme-inhibitor dissociation constant (Ki) values. Conclusions: Ginsenosides Re and Rgl, either alone or in a specific combination, may provide beneficial effects on neurodegenerative pathologies in therapeutic terms.