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Öğe 7?,8?-Dihydroobolactone, a typanocidal ?-pyrone from the rainforest tree Cryptocarya obovata(Pergamon-Elsevier Science Ltd, 2010) Davis, Rohan A.; Demirkiran, Ozlem; Sykes, Melissa L.; Avery, Vicky M.; Suraweera, Lekha; Fechner, Gregory A.; Quinn, Ronald J.Mass-directed isolation of the CH(2)Cl(2)/MeOH extract from the leaves of Cryptocarya obovata resulted in the purification of a new trypanocidal alpha-pyrone, 7',8'-dihydroobolactone ( 1). The chemical structure of 1 was determined by 1D/2D NMR, MS and CD data analysis. 7',8'-Dihydroobolactone was shown to inhibit Trypanosoma brucei brucei with an IC(50) of 2.8 mu M. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Antioxidant and Tyrosinase Inhibitory Activities of Flavonoids from Trifolium nigrescens Subsp petrisavi(Amer Chemical Soc, 2013) Demirkiran, Ozlem; Sabudak, Temine; Ozturk, Mehmet; Topcu, GulactiTrifolium nigrescens was researched for its chemical constituents for the first time. Bioassay-guided isolation of the EtOAc extract from the leaves of T. nigrescens resulted in the purification of a new biflavone, 4',5,5 '',7,7 ''-pentahydroxy-3',3'-dimethoxy-3-O-beta-D-glucosyl-3 '',4'-O-biflavone (1) along with eleven known compounds consisting of three phenolics (2-4), and eight flavonoid glycosides (5-12). Their structures were determined by extensive ID and 2D NMR, and MS data analyses. The isolated compounds were evaluated for their antioxidant activity and inhibitory activity on mushroom tyrosinase. Highly potent inhibitions Were found by compounds 7 (IC50 = 0.38 mM), 8 (IC50 = 0.19 mM), and 12 (IC50 = 0.26 mM) when compared with standard tyrosinase inhibitors kojic acid (IC50 = 0.67 mM) and L-mimosine (IC50 = 0.64 mM). The antioxidative effect of the isolated compounds and the extracts were determined by using, beta-carotene-linoleic acid, DPPH center dot scavenging, ABTS(+center dot) scavenging, superoxide scavenging, and CUPRAC assays. The experimental findings indicated that all the compounds demonstrated activity in all antioxidant activity tests employed except for the compounds 2-6. Compounds 2-6 showed moderate activity only in ABTS(+center dot) scavenging assay. The new compound 1 exhibited better activity than standard alpha-tocopherol in DPPH center dot scavenging, and ABTS(+center dot) scavenging assays. The results show that T. nigrescens can be regarded as a potential source of antioxidant compounds and tyrosinase inhibitors of significance in both the pharmaceutical and food industries.Öğe Cellular reactive oxygen species inhibitory constituents of Hypericum thasium Griseb(Pergamon-Elsevier Science Ltd, 2009) Demirkiran, Ozlem; Mesaik, M. Ahmed; Beynek, Hayrettin; Abbaskhan, Ahmed; Choudhary, M. IqbalThe phytochemical investigation of the ethyl acetate extract of Hypericum thasium has led to the characterization of four benzophenone derivatives 1-4, a known benzophenone 5 and four known flavonoids, quercetin (6), quercitrin (7), isoquercetin (8), and 3, 8-biapigenin (9). Lucigenin- and luminal-based chemiluminescence assays were employed to monitor the inhibitory activity of these compounds towards the production of reactive oxygen species (ROS) by human polymorphoneutrophils (PMNs). The assay results showed that benzophenones 1 and 3 are extracellular inhibitors of ROS production, while flavonoids 6, 8, and 9 can modulate intracellular ROS production. (C) 2008 Elsevier Ltd. All rights reserved.Öğe Cytotoxic meroterpenoids from brown alga Stypopodium schimperi (Kutzing) Verlaque & Boudouresque with comprehensive molecular docking & dynamics and ADME studies(Elsevier Sci Ltd, 2024) Demirkiran, Ozlem; Erol, Ebru; Senol, Halil; Kesdi, Irem Meryem; Toraman, Gulbahar Ozge Alim; Okudan, Emine Sukran; Topcu, GuelactiIn this study, five known meroterpenoids sargaol (1), flabellinone (2), stypodiol (3), atomarianone A (4), atomarianone B (5), and a known steroid fucosterol (6) were isolated from brown alga Stypopodium schimperi. Their structures were elucidated by 1D- and 2D NMR and mass spectroscopic analyses. Isolated compounds were tested against human healthy fibroblast cells (CCD-1079Sk), and two different types of human breast cancer cell lines (MDA-MB-231 and MCF-7). They were also investigated by molecular docking studies on estrogen receptor alpha (ER alpha), human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptors 1 and 2 (VEGFR1 and VEGFR2), cyclin-dependent kinases 2, 4 and 6 (CDK2/4/6) proteins. Molecular dynamics simulations were carried out to determine their ligand-protein stability and binding affinity. The four isolates (1-3, 6) showed strong cytotoxic activity in vitro against both cancer cell lines, particularly the aggressive MDA-MB-231 cell line, which was verified by in silico screening. Fucosterol was found to be the most selective compound against cancer cell lines, particularly the aggressive MDA-MB-231 cell line with a selectivity index (SI>16). The ADME prediction was also carried out and all the isolate compounds showed drug likeness. As a result, stypodiol and fucosterol were found to be the most potent compounds against both cancer cell lines by in vitro and in silico studies.Öğe Immunosupressive Phenolic Constituents from Hypericum montbretii Spach.(Acg Publications, 2013) Demirkiran, Ozlem; Mesaik, M. Ahmad; Beynek, Hayrettin; Abbaskhan, Ahmed; Choudhary, M. IqbalThe MeOH extract of aerial parts of H. monbretii Spach. have yielded quercetin (1), kaempferol (2), quercitrin (3), hyperin (4), myricitrin (5), rutin (6), I 3 II 8 '' biapigenin (7), methyl chlorogenate (8), 5-O-p-coumaroylquinic acid (9), and chlorogenic acid (5-O-caffeoyl quinic acid) (10), mangiferin (11), and shikimic acid (12). Three compounds 1, 2 and 4 were found to have an immunomodulating inhibitory activity on the oxidative burst response of human neutrophils, as well on mouse peritoneal macrophages. Effects of compounds on whole blood phagocytes activity was found to be with IC50 ranging between 8.0-12.2 mu g/mL. Only compounds 1, and 2 were found to interfere with T-cell proliferation, and IL-2 release in PHA activated peripheral blood mononuclear cells system. To the best of our knowledge, this is the first report of phytochemical and biological activity study on H. montbretii Spach.Öğe Isolation and characterisation of secondary metabolites from Trifolium vesiculosum Savi and their antiproliferative activities(Taylor & Francis Ltd, 2023) Cevik, Dicle; Aru, Basak; Karagoz, Sanem; Gurizi, Niyazi; Demirkiran, OzlemOne unreported flavonol namely morin-7-O-methyl ether (1) along with seven known compounds were isolated from the aerial parts of Trifolium vesiculosum Savi which were elucidated by using extensive spectroscopic methods such as 1D and 2D NMR and HR-MS. According to the cell viability assay (MTS) on the purified compounds (1-8), quercetin-3-O-(6''-trans-p-coumaroyl)-& beta;-galactoside (4) revealed remarkable antiproliferative activity most particularly against breast cancer cells (IC50 = 2.90 & PLUSMN; 0.25 & mu;M in HCC1937 and 7.98 & PLUSMN; 0.57 & mu;M in MCF7) while moderate inhibitory activity (IC50 = 17.96 & PLUSMN; 0.51-51.70 & PLUSMN; 2.69 & mu;M) on prostate, colorectal and liver cancer cell viability was observed. Further mechanistic examinations (Annexin V/PI staining, DNA content and detection of reactive oxygen species analyses) showed that compound 4 significantly induced apoptosis, enhanced mitochondrial reactive oxygen species (ROS) accumulation, and caused cell cycle arrest in cancer cells by increasing accumulation of cells at G(0)/G(1) and/or G(2)/M phases of the cell cycle.Öğe Kalkipyrone B, a marine cyanobacterial ?-pyrone possessing cytotoxic and anti-fungal activities(Pergamon-Elsevier Science Ltd, 2016) Bertin, Matthew J.; Demirkiran, Ozlem; Navarro, Gabriel; Moss, Nathan A.; Lee, John; Goldgof, Gregory M.; Vigil, EdgarBioassay-guided fractionation of two marine cyanobacterial extracts using the H-460 human lung cancer cell line and the OVC-5 human ovarian cancer cell line led to the isolation of three related alpha-methoxy-beta, beta'-dimethyl-gamma-pyrones each containing a modified alkyl chain, one of which was identified as the previously reported kalkipyrone and designated kalkipyrone A. The second compound was an analog designated kalkipyrone B. The third was identified as the recently reported yoshinone A, also isolated from a marine cyanobacterium. Kalkipyrone A and B were obtained from a field-collection of the cyanobacterium Leptolyngbya sp. from Fagasa Bay, American Samoa, while yoshinone A was isolated from a field-collection of cyanobacteria (cf. Schizothrix sp.) from Panama. One-dimensional and twodimensional NMR experiments were used to determine the overall structures and relative configurations of the kalkipyrones, and the absolute configuration of kalkipyrone B was determined by H-1 NMR analysis of diastereomeric Mosher's esters. Kalkipyrone A showed good cytotoxicity to H-460 human lung cancer cells (EC50 = 0.9 mu M), while kalkipyrone B and yoshinone A were less active (EC50 = 9.0 mu M and >10 mu M, respectively). Both kalkipyrone A and B showed moderate toxicity to Saccharomyces cerevisiae ABC16-Monster strain (IC50 = 14.6 and 13.4 mu M, respectively), whereas yoshinone A was of low toxicity to this yeast strain (IC50 = 63.8 mu M). (C) 2015 Elsevier Ltd. All rights reserved.Öğe Lignans From Taxus Species(Springer, 2007) Topcu, Gulacti; Demirkiran, OzlemLignans are widely distributed in nature and exhibit various activities, including antitumor, antiviral, hepatoprotective, antioxidant, antiulcer, antiallergen, antiplatelet and antiosteoporotic activities. So far, Taxus species have received a great deal of interest in regard to their taxane diterpenes rather than their lignans. This chapter will review lignan biosynthesis and recent strategies in the synthesis of lignans and provide an overview of isolation and structural elucidation studies of all Taxus lignans, along with their biological activities. About 50 lignans, including neolignans and a few terpenolignans, isolated from eight Taxus species, are presented herein. Recent studies on the activities of lignans, particularly Taxus lignans, are outlined.Öğe Phenolic compounds from Trifolium echinatum Bieb. and investigation of their tyrosinase inhibitory and antioxidant activities(Pergamon-Elsevier Science Ltd, 2013) Sabudak, Temine; Demirkiran, Ozlem; Ozturk, Mehmet; Topcu, GulactiTwo bischromones, 3,3'-dimethoxy-2'-oxychromone (1), 3,3'-dihydroxy-2,2'-oxychromone (2) and a biflavone, 5,7,4',5 '',3''',4''''-hexahydroxy-3 ''-O-beta-glucosyl-3',7 ''-O-biflavone (3) have been isolated from whole plant of Trifolium echinatum Bieb. together with five known fiavonoids. The structures of the compounds were elucidated by 1D and 2D NMR analysis as well as HRESIMS. The isolated compounds were investigated for their antioxidant activity and tyrosinase inhibitory activity. Highly potent inhibition was found for compounds 1 (IC50 = 0.41 mM), 5 (IC50 = 0.47 mM) and 8 (IC50 = 0.45 mM) compared to those of standard tyrosinase inhibitors kojic acid (IC50= 0.67 mM) and L-mimosine (IC50 = 0.64 mM). The antioxidative effect of the extracts was determined by using beta-carotene-linoleic acid, DPPH. scavenging, ABTS(+-) scavenging, and CUPRAC assays. The experimental findings indicated that the compounds 2 and 8 were found to be active in radical scavenging and CUPRAC assays. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Portobelamides A and B and Caciqueamide, Cytotoxic Peptidic Natural Products from a Caldora sp. Marine Cyanobacterium(Amer Chemical Soc, 2021) Demirkiran, Ozlem; Almaliti, Jehad; Leao, Tiago; Navarro, Gabriel; Byrum, Tara; Valeriote, Frederick A.; Gerwick, LenaThree new compounds, portobelamides A and B (1 and 2), 3-amino-2-methyl-7-octynoic acid (AMOYA) and hydroxyisovaleric acid (Hiva) containing cyclic depsipeptides, and one long chain lipopeptide caciqueamide (3), were isolated from a field-collection of a Caldora sp. marine cyanobacterium obtained from Panama as part of the Panama International Cooperative Biodiversity Group Program. Their planar structures were elucidated through analysis of 2D NMR and MS data, especially high resolution (HR) MS2/MS3 fragmentation methods. The absolute configurations of compounds 1 and 2 were deduced by traditional hydrolysis, derivative formation, and chromatographic analyses compared with standards. Portobelamide A (1) showed good cytotoxicity against H-460 human lung cancer cells (33% survival at 0.9 mu M).Öğe Structure elucidation of two new unusual monoterpene glycosides from Euphorbia decipiens, by 1D and 2D NMR experiments(Wiley-Blackwell, 2011) Demirkiran, Ozlem; Topcu, Gulacti; Hussain, Javid; Ahmad, Viqar Uddin; Choudhary, M. IqbalTwo new unusual monoterpene glycosides, (Z)-3,6-dimethyl-3-(beta-D-O-glucosylmethylene)cyclohept-4-ene-1-one (1) and 3,6-dimethyl-3-(beta-D-O-glucosylmethylene) cycloheptanone (2) have been isolated along with five known compounds, 3-hydroxy-4-methoxybenzoic acid, 6,7-dihydroxycoumarin, luteolin, apigenin 5-O-alpha l-L-rhamnoside, and pinocembrin-7-O-rutinoside from ethyl acetate extract of Euphorbia decipiens. The structures of the isolated compounds were elucidated by extensive 1D- and 2D-NMR, and mass spectroscopic analyses. Copyright (C) 2011 John Wiley & Sons, Ltd.Öğe Three new benzophenone glycosides with MAO-A inhibitory activity from Hypericum thasium Griseb.(Elsevier Science Bv, 2012) Demirkiran, OzlemPurification of n-BuOH fraction from 80% ethanol extract of Hypericum thasium Griseb. resulted in the isolation of three new compounds 3',4,5'-trihydroxy-6-methoxy-2-O-alpha-L-arabinosylbenzophenone (1), 3',4,5',6-tetrahydroxy-2-O-alpha-L-arabinosylbenzophenone (2), and 3',4-dihydroxy-5'-methoxy-2-O-alpha-L-arabinosyl-6-O-beta-D-xylosylbenzophenone (3) along with a known flavonoid glycoside quercetin-3-O-alpha-L-arabinofuranoside (4). The structures of the new compounds were elucidated by 1D and 2D NMR analysis as well as HRESIMS. The isolated compounds (1-4), as well as quercetin, and kaempferol previously isolated from EtOAc fraction were screened against MAO-A inhibitory activity. When tested against the MAO-A quercetin and kaempferol displayed IC50 values of 19.6, and 17.5 mu M, respectively. The IC50 values for MAO-A inhibition by compounds (1-4) were 310.3, 111.2, 726.0, and 534.1 mu M, respectively. Standard inhibitor (clorgyline) exhibited MAO-A inhibition with an IC50 value of 0.5 mu M. (C) 2012 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.Öğe Two New Phenylpropanoid Glycosides from the Leaves and Flowers of Erica arborea(Wiley-V C H Verlag Gmbh, 2010) Demirkiran, Ozlem; Topcu, Guelacti; Bahadori, Fatemeh; Ay, Mehmet; Nazemiyeh, Hossein; Choudhary, IqbalTwo new phenylpropanoid glucosides, 1,2-erythro-1-(3,4,5-trimethoxyphenyl)-2-(beta-D-glucopyranosyloxy)propan-1,3-diol (1) and 7,8-threo-2',8-epoxysyringylglycerol-7-O-alpha-D-glucopyranoside (ericarboside; 2) have been isolated together with four known compounds 2',7-epoxysyringylglycerol-8-O-beta-D-glucopyranoside (ficuscarpanoside B; 3), benzylrutinoside (hydrangeifolin; 4), phenethylrutinoside (5), and caffeic acid from the BuOH soluble part of the MeOH extract of the leaves and flowers of E. arborea L. Final purification of the compounds was achieved on a reversed-phase HPLC. Their structures have been elucidated by extensive 1D- and 2D-NMR, and mass spectroscopic techniques.Öğe Tyrosinase Inhibitory Activity of Chemical Constituents of Euphorbia macrostegia(Springer, 2014) Demirkiran, Ozlem; Topcu, Gulacti; Azarpira, Ali; Choudhary, M. IqbalThe chloroform extract of the aerial parts of E. macrostegia has yielded a new compound, 2-(4-hydroxyphenyl)-ethylhentriacontanoate (1), along with hentriacontan-1-ol (2), lupenone (3), cycloart-22-ene-3,25-diol (4), 3,3',4'-tri-O-methylellagic acid (5), cleomiscosin (6), and glucoclioniasterol (stigmast-5-en-3-O-beta-glucopyranoside) (7), and from the ethyl acetate extract of aerial parts of the plant isoquercetin (8), quercetin-3-O-alpha-arabinofuranoside (avicularin) (9), and rutin (10) have been isolated. Compounds 1-10 were tested for their tyrosinase inhibitory activity, and 2 exhibited an IC50 value of 71.4 mu M, almost comparable to standard kojic acid (IC50 58.2 mu M). Compounds 1-4 also showed good activity with IC50 values of 77.2, 78.6, 71.4, and 77.5 mu M, respectively.Öğe Xanthones in Hypericum: Synthesis and Biological Activities(Springer, 2007) Demirkiran, OzlemThere has been an increasing interest in the genus Hypericum, because it is a source of a variety of compounds with different biological activities. Xanthones are one of these compounds within Hypericum species. Recently, growing attention has been given to these heterocyclic compounds containing oxygen because of their many interesting pharmacological and biological properties, such as monoamine oxidase inhibition and antioxidant, antifungal, cytotoxic, and hepatoprotective activities.
