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    Anticholinesterase and Antioxidant Activities of Natural Abietane Diterpenoids with Molecular Docking Studies
    (Bentham Science Publ Ltd, 2020) Topcu, Gulacti; Akdemir, Atilla; Kolak, Ufuk; Ozturk, Mehmet; Boga, Mehmet; Bahadori, Fatemeh; Cakmar, Seda Damla Hatipoglu
    Background: Alzheimer's Disease (AD) is one of the most prevalent causes of dementia in the world, and no drugs available that can provide a complete cure. Cholinergic neurons of the cerebral cortex of AD patients are lost due to increased activity of cholinesterase enzymes. Objective: Acetylcholinesterase (AChE) and Butyrylcholinesterase (BuChE) are the two major classes of cholinesterases in the mammalian brain. The involvement of oxidative stress in the progression of AD is known. Thus, the objective of this study is to determine strong ChE inhibitors with anti-oxidant activity. Methods: In this study, 41 abietane diterpenoids have been assayed for antioxidant and anticholinesterase (both for AChE and BuChE) properties in vitro, which were previously isolated from Salvia species, and structurally determined by spectroscopic methods, particularly intensive 1D- and 2D-NMR and mass experiments. Molecular modeling studies were performed to rationalize the in vitro ChE inhibitory activity of several abietane diterpenoids compared with galantamine. Results: Thirteen out of the tested 41 abietane diterpenoids exhibited at least 50% inhibition on either AChE or BuChE. The strongest inhibitory activity was obtained for Bractealine against BuChE (3.43 mu M) and AChE (33.21 mu M) while the most selective ligand was found to be Hypargenin E against BuChE enzyme (6.93 mu M). A full correlation was not found between anticholinesterase and antioxidant activities. The results obtained from molecular modelling studies of Hypargenin E and Bractealine on AChE and BuChE were found to be in accordance with the in vitro anti-cholinesterase activity tests. Conclusion: Abietane diterpenoids are promising molecules for the treatment of mild-moderate AD.
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    Antioxidant and Anticholinesterase Activities of Some Dialkylamino Substituted 3-Hydroxyflavone Derivatives
    (Bentham Science Publ Ltd, 2017) Culhaoglu, Burcu; Capan, Asli; Boga, Mehmet; Ozturk, Mehmet; Ozturk, Turan; Topcu, Gulacti
    Background: Flavones, are a class of naturally occuring polyphenolic compounds which have 2-phenylchromen-4-one structure. Various studies showed that flavones have several pharmacological activities such as antioxidant, anti-inflammatory, antimicrobial, cytotoxic, antitumour and antiallergic. In the present study, 3-hydroxyflavones also called flavonols, posessing 4'-dialkylamino moiety were synthesized, and their antioxidant and anticholinesterase activities were investigated by comparison with unmodified 3-hydroxflavone. Method: For investigation of antioxidant potential, radical scavenging assays (DPPH., ABTS(+)-, O-2(-)) were used along with CUPRAC and lipid peroxidation inhibitory assays, as well as anticholinesterase activity by Ellman method. Results: The best results were obtained for 4'-N, N-dimethyl flavonol (1) in both antioxidant and anticholinesterase activity tests, possibly due to its least steric hinderance effect. It exhibited remarkable DPPH free radical scavenging activity (2.43 perpendicular to 0,09 mu g/mL) competing with a standard compound quercetin (2.10 +/- 0,10 mu g/mL). Moreover, the other tested flavonols also showed high antioxidant activities. Compounds 5 and 6 exhibited close IC50 values to those of compound 1. Conclusion: Antioxidant activity test results were found to be well correlated with anticholinesterase activity test results indicating possible role of antioxidant compounds in the treatment of Alzheimer's disease.
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    Antioxidant, anticholinesterase, and antimicrobial activities and fatty acid constituents of Achillea cappadocica Hausskn. et Bornm.
    (Tubitak Scientific & Technological Research Council Turkey, 2014) Ertas, Abdulselam; Boga, Mehmet; Hasimi, Nesrin; Yesil, Yeter; Goren, Ahmet Ceyhan; Topcu, Gulacti; Kolak, Ufuk
    This study was the first fatty acid analysis and biological activity report on an endemic Achillea species, Achillea cappadocica Hausskn. et Bornm. The major compounds in the fatty acid were identified as oleic (34.7%), palmitic (23.1%), and linoleic acids (20.6%). The methanol and water extracts indicated higher ABTS cation radical scavenging activity than that of alpha-tocopherol and BHT at 100 mu g/mL. The acetone extract showed 70.62% inhibitory activity against butyrylcholinesterase at 200 mu g/mL. The acetone and methanol extracts exhibited moderate antimicrobial activity.
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    Bioguided Isolation of Secondary Metabolites fromSalvia cerino-pruinosa Rech. f. var. cerino-pruinosa
    (2021) Kolak, Ufuk; Ertas, Abdulselam; Firat, Mehmet; Cakirca, Hatice; Topcu, Gulacti; Yener, Ismail; Akdeniz, Mehmet
    In the current study, the ethanol extracts prepared from the aerial parts and roots of an endemicspecies, Salvia cerino-pruinosa Rech. f. var. cerino-pruinosa were fractionated on silica gel columns and testedfor determination of their antioxidant activity using DPPH free radical and ABTS cation radical scavenging, andcupric reducing antioxidant capacity (CUPRAC) test assays. Twenty known secondary metabolites were isolatedfrom the active antioxidant fractions; rosmarinic acid (1), chlorogenic acid (2), caffeic acid (3), 4- hydroxybenzoic acid (4), benzoic acid (5), luteolin 7-O-glucoside (6), bis-(2-ethylhexyl)benzene-1,2- dicarboxylate (7), salvianolic acid A (8), salvianolic acid B (9), 7-acetylroyleanone (10), 6,7-dehydroroyleanone(11), ferruginol (12), inuroyleanol (13), 12-hydroxy-6,7-secoabieta-8,11,13-triene-6,7-dial (14), ursolic acid(15), oleanolic acid (16), taraxasterol (17), lupenone (18), ?-sitosterol (19), and stigmasterol (20). Rosmarinicacid, which was obtained from the aerial parts, was found to be the best antioxidant compound among theisolated secondary metabolites in DPPH free radical and ABTS cation radical scavenging, and CUPRAC assays(IC50: 1.20±0.04 ?g/mL, IC50: 1.74±0.06 ?g/mL, A0.5: 1.22±0.02 ?g/mL, respectively). Chlorogenic and caffeicacids, luteolin 7-O-glucoside, salvianolic acids A and B, and inuroyleanol exhibited also high antioxidantactivity in the mentioned assays.
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    Inhibition of Amyloid Aggregation Using Optimized Nano-Encapsulated Formulations of Plant Extracts with High Metal Chelator Activities
    (Bentham Science Publ Ltd, 2020) Kazdal, Fatma; Bahadori, Fatemeh; Celik, Burak; Ertas, Abdulselam; Topcu, Gulacti
    Background: The role of Fe+2, Cu+2 and Zn+2 in facilitating aggregation of Amyloid beta (A beta) and consequently, the progression of Alzheimer's disease (AD) is well established. Objective: Development of non-toxic metal chelators is an emerging era in the treatment of AD, in which complete success has not been fully achieved. The purpose of this study was to determine plant extracts with high metal chelator and to encapsulate them in nano-micellar systems with the ability to pass through the Blood Brain Barrier (BBB). Methods: Extracts of 36 different Anatolian plants were prepared, total phenolic and flavonoid contents were determined, and the extracts with high content were examined for their Fe+2, Cu+2 and Zn+2 chelating activities. Apolipoprotein E4 (Apo E) decorated nano-formulations of active extracts were prepared using Poly (Lactide-co-Glycolide) (PLGA) (final product ApoEPLGA) to provide BBB penetrating property. Results: Verbascum jlavidum aqueous extract was found as the most active sample, incubation of which, with A beta before and after metal-induced aggregation, resulted in successful inhibition of aggregate formation, while re-solubilization of pre-formed aggregates was not effectively achieved. The same results were obtained using ApoEPLGA. Conclusion: An optimized metal chelator nano-formulation with BBB penetrating ability was prepared and presented for further in vivo studies.
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    Novel Terpenoids with Potential Anti-Alzheimer Activity from Nepeta obtusicrena
    (Acg Publications, 2016) Yilmaz, Anil; Boga, Mehmet; Topcu, Gulacti
    Dichloromethane extract of Nepeta obtusicrena Boiss. Et Kotschy Ex Hedge afforded two novel terpenoids, a diterpenoid and a triterpenoid in addition to two known triterpenoids, oleanolic acid and ursolic acid. Purification of the diterpenoid was carried out by HPLC, and its structure was elucidated as 14a-acetoxy-6-oxo-abieta-7-ene, and structure of the triterpenoid was elucidated as 2 alpha, 3 beta, 19 alpha, 24-tetrahydroxy-11-oxo-olean-12-ene. Both of the novel terpenes were obtained from nature for the first time and named as obtusicrenone and nemrutolone, respectively. Anticholinesterase (anti-Alzheimer) and antioxidant activities [DPPH free radical scavenging activity, ABTS cation radical scavenging activity, lipid peroxidation inhibitory activity, CUPRAC (Cupric Reducing Antioxidant Capacity)] of the dichloromethane and methanol extracts and the isolated four terpenoids were investigated. Both of the extracts and the isolated four terpenoids exhibited high anticholinesterase activity, particularly against acetylcholinesterase (AChE) enzyme. None of the samples tested showed high antioxidant activity.