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    Alkaloid profiling in Galanthus gracilis Celak. from western Turkey by GC/MS
    (Istanbul Univ, Fac Pharmacy, 2018) Karakoyun, Cigdem
    Galanthus L. is generally acknowledged as a valuable biological source due to its Amaryllidaceae alkaloids with unusual chemical structures and a wide variety of biological activities. Among these alkaloids, galanthamine is the first example of their practical application in medicine as a potent and selective inhibitor of the enzyme acetylcholinesterase, and already present on the market as a therapeutic agent for Alzheimer's disease. Lycorine is the main Amaryllidaceae alkaloid deeply investigated for its biological activity for many years. In this study the alkaloidal profile of G. gracilis collected from western Aegean (Alankiyi/Bayindir) will be illustrated for the first time. GC-MS profiling was carried out on the crude alkaloidal extract obtained from dried and powdered plant material. 11 alkaloids were detected by GC-MS, including graciline, demethylhomolycorine and tazettine as the major ones.
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    A Brief Up-to-Date Overview of Amaryllidaceae Alkaloids: Phytochemical Studies of Narcissus tazetta subsp. tazetta L., Collected in Turkey
    (Sage Publications Inc, 2019) Karakoyun, Cigdem; Masi, Marco; Cimmino, Alessio; Onur, Mustafa Ali; Somer, Nehir Unver; Kornienko, Alexander; Evidente, Antonio
    A brief up-to-date overview on the isolation, and chemical and biological characterization of new and known alkaloids from different Amaryllidaceae species, including Brunsvigia, Crinum, Cyrtanthus, Narcissus, and Nerine genera, was reported. Furthermore, the isolation and chemical characterization of alkaloids extracted from bulbs of Narcissus tazetta subsp. tazetta L. collected from Mula, Turkey were described.
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    Five new cardenolides transformed from oleandrin and nerigoside by Alternaria eureka 1E1BL1 and Phaeosphaeria sp. 1E4CS-1 and their cytotoxic activities
    (Elsevier, 2021) Karakoyun, Cigdem; Kucuksolak, Melis; Bilgi, Eyup; Dogan, Gamze; Comlekci, Yigit Ege; Bedir, Erdal
    Biotransformation of oleandrin (1) and nerigoside (2) by endophytic fungi; Alternaria eureka 1E1BL1 and Phaeospheria sp. 1E4CS-1, has led to the isolation of five new metabolites (3, 5, 6, 7 and 8) together with a known compound (4). The structures of the biotransformation products were elucidated by 1D-, 2D NMR and HR-MS. Phaeospheria sp. mainly provided monooxygenation reactions on the A and B rings, whereas A. eureka afforded both monooxygenated and desacetylated derivatives of the substrates. Cytotoxic activity of the compounds was tested against a non-cancerous (HEK-293) and four cancer (PANC-1, MIA PaCa-2, DU 145 and A549) cell lines by MTT cell viability assay. All compounds were less cytotoxic than oleandrin, which had IC50 values ranging between 2.7 and 41.9 nM. Two of the monohydroxylated metabolites, viz. 7(beta)-hydroxy oleandrin (3) and 1(beta)-hydroxy oleandrin (7), were also potent with IC50 values from 18.45 to 39.0 nM, while desacetylated + monohydroxylated, or dihydroxylated products had much lower cytotoxicity. Additionally, the lesser activity of 2 and its metabolite (6) possessing diginose as sugar residue inferred that oleandrose moiety is important for the toxicity of oleandrin as well as hydrophobicity of the steroid core.
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    New Cardenolides from Biotransformation of Gitoxigenin by the Endophytic Fungus Alternaria eureka 1E1BL1: Characterization and Cytotoxic Activities
    (Mdpi, 2021) Bedir, Erdal; Karakoyun, Cigdem; Dogan, Gamze; Kuru, Gulten; Kucuksolak, Melis; Yusufoglu, Hasan
    Microbial biotransformation is an important tool in drug discovery and for metabolism studies. To expand our bioactive natural product library via modification and to identify possible mammalian metabolites, a cytotoxic cardenolide (gitoxigenin) was biotransformed using the endophytic fungus Alternaria eureka 1E1BL1. Initially, oleandrin was isolated from the dried leaves of Nerium oleander L. and subjected to an acid-catalysed hydrolysis to obtain the substrate gitoxigenin (yield; similar to 25%). After 21 days of incubation, five new cardenolides 1, 3, 4, 6, and 8 and three previously- identified compounds 2, 5 and 7 were isolated using chromatographic methods. Structural elucidations were accomplished through 1D/2D NMR, HR-ESI-MS and FT-IR analysis. A. eureka catalyzed oxygenation, oxidation, epimerization and dimethyl acetal formation reactions on the substrate. Cytotoxicity of the metabolites were evaluated using MTT cell viability method, whereas doxorubicin and oleandrin were used as positive controls. Biotransformation products displayed less cytotoxicity than the substrate. The new metabolite 8 exhibited the highest activity with IC50 values of 8.25, 1.95 and 3.4 mu M against A549, PANC-1 and MIA PaCa-2 cells, respectively, without causing toxicity on healthy cell lines (MRC-5 and HEK-293) up to concentration of 10 mu M. Our results suggest that A. eureka is an effective biocatalyst for modifying cardenolide-type secondary metabolites.
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    Screening of cytotoxicity and DNA topoisomerase Ha inhibitory activity of Turkish Onosma species
    (Tubitak Scientific & Technical Research Council Turkey, 2021) Guzel, Ozge; Duman, Seda; Yilmaz, Sinem; Karakoyun, Cigdem; Kul, Demet; Pirhan, Ademi Fahri; Bedir, Erdal
    Onosma L., the largest genus of Boraginaceae, is represented by 105 species in Turkey with an endemism rate of 52%. Phytochemical studies indicate that Boraginaceae plants mainly comprise naphthoquinones with a wide range of biological activities including anticancer, antiinflammatory, wound healing, and antioxidant effects. However, few taxa of the genus Onosma have been investigated in detail for their bioactivities. Considering the high rate of endemism and an inadequate number of bioactivity screening studies in literature, we aimed to evaluate the cytotoxic effects and topoisomerase inhibitory activities of some Onosma species growing in southwestern Turkey. Here, we describe a comprehensive cytotoxic activity screening study on petroleum ether, dichloromethane, and methanol extracts of the roots of 20 identified and one unidentified Onosma taxa. The MTT cell viability assay has been performed to investigate the cytotoxicity of the extracts against seven cancer cell lines (MCF-7, HeLa > Hep G2, A549, Capan-1, HCC-1937, and DU-145) and a noncancerous cell line (MRC-5), while doxorubicin was served as a positive standard. The petroleum ether extracts of O. aksoyii Aytac&Turkmen, O. isaurica Boiss. and Heldr., O. taurica Pallas ex Willd. var. taurica and O. alborosea Fisch. & C.A. Mey subsp. alborosea var. alborosea were determined as the most active ones based on their IC50 values. DNA topoisomerase Ila inhibition assay was conducted on the petroleum ether and dichloromethane extracts of these four active species, and almost all tested extracts demonstrated strong inhibition on the enzyme at a concentration of 0.1 mg/mL. Our cytotoxicity screening results were consistent with the findings of the topoisomerase Ila inhibition test. This study advocates the significant role of Onosma species in the field of anticancer drug discovery.
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    Simultaneous quantitative analysis of biologically important Amaryllidaceae alkaloids in Narcissus tazetta L. subsp. tazetta by HPLC/PDA
    (Marmara Univ, 2019) Karakoyun, Cigdem; Unver-Somer, Nehir
    The present study was conducted for the quantitative determination of biologically active Amaryllidaceae alkaloids, galanthamine and lycorine, in the bulbs and aerial parts of a subspecies naturally growing in Turkey namely, Narcissus tazetta L. subsp. tazetta collected from Mugla/Turkey. A reverse phase high performance liquid chromatographic method using an isocratic system consisting of trifluoroacetic acid:water:acetonitrile (0.01:90:10) with a flow rate of 1 mL/min was carried out. Photodiode array detection was employed to determine the UV-visible spectral characteristics of the alkaloids. Determination of acetylcholinesterase and butyrylcholinesterase inhibitory activities of different parts of mentioned subspecies were accomplished using a microplate assay modified from Ellman's method. This is the first report of the galanthamine content of Narcissus tazetta subsp. tazetta of Turkish origin. 0.0051% and 0.0055% galanthamine was detected in the bulbs and aerial parts of the plant, respectively. Also, lycorine was determined as 0.0250% in the bulbs and 0.0672 % in the aerial parts.
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    Synthesis of albumin nanoparticles in a water-miscible ionic liquid system, and their applications for chlorambucil delivery to cancer cells
    (Elsevier, 2022) Akdogan, Yasar; Sozer, Sumeyra Cigdem; Akyol, Cansu; Basol, Merve; Karakoyun, Cigdem; Cakan-Akdogan, Gulcin
    Serum albumin has been a preferred protein to generate biodegradable and non-toxic nanoparticles (NPs) for drug delivery applications. Different methods applied for the preparation of serum albumin NPs mostly used organic solvents. Here, we prepared serum albumin NPs in an ionic liquid (IL) system. ILs are considered to be green and designer solvents with unique properties that can replace organic solvents in the synthesis of albumin NPs. Bovine serum albumin (BSA) proteins dissolved in water were trans-formed into BSA NPs in a water/ TritonTMX (TX-100), 1-butanol/1-butyl-3-methylimidazolium trifluo-romethanesulfonate (BmimCF3SO3) microemulsion-like system by using a high-speed homogenizer and crosslinker glutaraldehyde. The obtained BSA NPs have been used in drug loading and release studies with a hydrophobic anticancer drug chlorambucil (Chl). Drug loading increased as increasing the ratio of Chl incubated with BSA NPs. Monitoring the drug release by UV-Vis spectroscopy revealed a burst release at first 4 h, but two-thirds of drugs stayed with NPs upon diffusion method. On the other hand, cellular uptake of Chl loaded BSA NPs caused a significant MCF7 breast cancer cell death, whereas free Chl and unloaded BSA NPs did not have a significant effect on the cell viability. Furthermore, in vivo toxicity assessment of BSA NPs obtained in the IL system was conducted in the zebrafish animal model. It showed that zebrafish body is able to eliminate BSA NPs without any toxic side effects and encapsulation of Chl into NPs reduced the toxicity of free Chl. In summary, we showed that BSA NPs with size smaller than 200 nm could be prepared in BmimCF3SO3 mediated system. They can be used for Chl loading (up to 6.9 wt%) with a sustainable release and they induce significant cell death in Chl sensitive cancer cells up to 45% in 24 h. These results indicate that BSA NPs could be prepared alternatively in IL systems and used in drug delivery studies.(c) 2022 Elsevier B.V. All rights reserved.