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GÖREN, AHMET CEYHAN

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AHMET CEYHAN

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GÖREN

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2010 - 20191092020 - 202225
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Now showing 1 - 10 of 134
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    Publication
    Sage (Salvia pilifera): determination of its polyphenol contents, anticholinergic, antidiabetic and antioxidant activities
    (2019-09-01) GÜLÇİN, İlhami; Tel, Ahmet Zafer; GÖREN, AHMET CEYHAN; Taslimi, Parham; Alwasel, Saleh H.; GÖREN, AHMET CEYHAN
    In this work, we determined for the first time the Salvia pilifera Montbret & Aucher ex Bentham as an important source for natural products with antioxidant and antidiabetic potentials. In this context, methanol (MESP) and water (WESP) extracts were prepared from aerial parts of S. pilifera. Also, it was evaluated for antioxidant profile by eight distinguishes bioanalytical methods and inhibition effects against enzymes linked to different diseases, namely butyrylcholinesterase (BChE), acetylcholinesterase (AChE), alpha-glycosidase and alpha-amylase. Also, the polyphenolic compositions of MESP and WESP were evaluated by high performance liquid chromatography and tandem mass spectrometry (LC-MS/MS). Fourteen phenolics were identified in the evaporated MESP and thirteen phenolic compounds were identified in the lyophilized WESP. Also, we performed the antioxidant properties of both extracts. In order to estimate the capacity of MESP and WESP to act as antioxidants, 1,1-diphenyl-2-picryl-hydrazyl radicals (DPPH center dot), 2,2 --azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals (ABTS(center dot+)) and N,N-dimethyl-p-phenylenediamine radicals (DMPD center dot+), scavenging activities, ferric ions (Fe3+), Fe3+-TPTZ and cupric ions (Cu2+) reducing assays were studied. MESP and WESP were found as potent effective DPPH center dot (IC50: 7.05 and 8.56 mu g/mL), ABTS(center dot+) (IC50: 3.52 and 4.76 mu g/mL) and DMPD center dot+ (IC50: 28.92 and 30.95 mu g/mL) scavenging effects. On the other hand, MESP and WESP showed the potent inhibition effects against AChE (IC50: 94.93 and 138.61 mu g/mL), BChE (IC50: 60.05 and 99.13 mu g/mL), alpha-glycosidase (IC50: 23.28 and 36.47 mu g/mL) and alpha-amylase (IC50: 46.21 and 97.67 mu g/mL) enzymes. This study will be an innovative and guider for further studies for antioxidant properties for industrial or medicinal plants.
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    Determination of sulfonamides in milk by ID-LC-MS/MS
    (2018-01-01T00:00:00Z) Unsal, Isin Aydin; Tasan, Murat; GOKCEN, Taner; Goren, AHMET CEYHAN; GÖREN, AHMET CEYHAN
    In this study, an ID-LC-MS method was developed and validated for the determination of 14 sulfonamides in milk samples. Recovery results were found to be in the range of 91%-114% for milk samples. The relative measurement uncertainty was between 7.5%-12.7%. Validated method was performed on milk samples obtained from market and street vendors. The amount of sulfonamides in the analyzed samples was found to be below the legal limits (Sulfamethazine: 6.46 +/- 0.76 ng/g and sulfisoxazole: 7.3 +/- 0.71 ng/g).
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    Towards tributyltin quantification in natural water at the Environmental Quality Standard level required by the Water Framework Directive
    (2016-11-01T00:00:00Z) ALASONATI, Enrica; Fettig, Ina; RICHTER, Janine; PHILIPP, Rosemarie; MILACIC, Radmila; SCANCAR, Janez; ZULIANI, Tea; TUNC, Murat; BILSEL, Mine; Goren, AHMET CEYHAN; FISICARO, Paola; GÖREN, AHMET CEYHAN
    The European Union (EU) has included tributyltin (TBT) and its compounds in the list of priority water pollutants. Quality standards demanded by the EU Water Framework Directive (WFD) require determination of TBT at so low concentration level that chemical analysis is still difficult and further research is needed to improve the sensitivity, the accuracy and the precision of existing methodologies. Within the frame of a joint research project -Traceable measurements for monitoring critical pollutants under the European Water Framework Directive- in the European Metrology Research Programme (EMRP), four metrological and designated institutes have developed a primary method to quantify TBT in natural water using liquid-liquid extraction (LLE) and species-specific isotope dilution mass spectrometry (SSIDMS). The procedure has been validated at the Environmental Quality Standard (EQS) level (0.2 ng L-1 as cation) and at the WFD-required limit of quantification (LOQ) (0.06 ng L-1 as cation). The LOQ of the methodology was 0.06 ng L-1 and the average measurement uncertainty at the LOQ was 36%, which agreed with WFD requirements. The analytical difficulties of the method, namely the presence of TBT in blanks and the sources of measurement uncertainties, as well as the interlaboratory comparison results are discussed in detail. (C) 2016 Elsevier B.V. All rights reserved.
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    Development and validation of a generic method for quantification of collagen in food supplement tablets using liquid chromatography coupled with time-of-flight mass spectrometry
    (2015-03-01T00:00:00Z) VATANSEVER, Bilgin; SENAL, Merve Oztug; AKGOZ, Muslum; Goren, AHMET CEYHAN; GÖREN, AHMET CEYHAN
    A generic method for the quantification of type II collagen in protein-based dietary supplements is described. This quantitative analysis was conducted using liquid chromatography-electrospray ionization-time-of-flight mass spectrometry (LC-ESI-TOF MS). Compared to classical methods with the use of isotope-labeled standards, our method includes, for the first time, the quantification of hydroxyproline using histidine as an internal standard. Separation of the analytes was performed on a Phenomenex Synergi 4 mu m Fusion-RP 80 C-0 column (150 x 2.0 mm, 4.0 mu m) with a mobile phase made of 10 mM ammonium formate in water (A) and 10 mM ammonium formate in methanol (B). The assay was fully validated according to FDA guidelines, and the method exhibited sufficient specificity, accuracy, and precision. Intra- and inter-batch accuracy, determined as a deviation between nominal and measured values, ranged from -4.8 to 9.1% and from 0.9 to 6.4 %, respectively. All analytes (hydroxyproline and histidine) at three concentration levels showed extraction recoveries from 89 to 98 %. The method was successfully applied to protein-based dietary supplements of the pharmaceutical industry.
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    Potential reference measurement procedures for PBDE in surface water at levels required by the EU Water Frame Directive
    (2016-05-15T00:00:00Z) SWART, Claudia; GANTOIS, Fanny; PETROV, Panayot; ENTWISLE, John; GOENAGA-INFANTE, Heidi; NOUSIAINEN, Marjaana; BILSEL, Mine; BINICI, Burcu; GONZALEZ-GAGO, Adriana; PROEFROCK, Daniel; Goren, AHMET CEYHAN; GÖREN, AHMET CEYHAN
    Polybrominated diphenylethers (PBDE), used as flame retardants, are named as priority substances in the Directive 2000/60/EC of the European parliament and of the council establishing a framework for Community action in the field of water policy. An annual average environmental quality standard (EQS) for inland surface waters of 0.0005 mu g/L (0.0002 mu g/L for other surface waters) for PBDE congeners involved in the technical penta-PBDE mixtures containing PBDE with five bromine atoms has been established. The directives focus especially on the congeners PBDE 28, 47, 99, 100, 153 and 154 contained in the penta-PBDE mixture. Up to now, no reference measurement procedures have been established reaching the limits of quantification (LOQs) and the associated uncertainties as defined in the directives with results traceable to the SI. Within a recent European project on metrology, different approaches for the traceable quantification of PBDE, based on liquid/liquid or solid phase extraction followed by the detection with gas chromatography coupled to either inductively coupled plasma mass spectrometry or triple quadrupole mass spectrometry, were investigated and the related LOQs and expanded uncertainties of the results were compared. A complete uncertainty budget for each method was estimated according to the Guide to the Expression of Uncertainty in Measurement (GUM). All presented analytical procedures can serve as reference measurement procedures regarding the LOQs and their associated expanded uncertainties for monitoring the six priority PBDEs named above. LOQs as low as 0.026 ng/kg with an associated expanded uncertainty of 0.002 ng/kg could be achieved (C) 2016 The Authors. Published by Elsevier B.V.
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    CCQM-K132: low-polarity analytes in a biological matrix: vitamin D metabolites in human serum
    (2017-01-01T00:00:00Z) Wise, Stephen A.; Tai, Susan S-C; Duewer, David L.; Bedner, Mary; Camara, Johanna E.; Lippa, Katrice A.; Qinde, Liu; Kang, Dukjin; Kim, Byungjoo; Quan, Can; GÖREN, AHMET CEYHAN
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    Sambulin A and B, non-glycosidic iridoids from Sambucus ebulus, exert significant in vitro anti-inflammatory activity in LPS-induced RAW 264.7 macrophages via inhibition of MAPKs-s phosphorylation
    (2017-07-12T00:00:00Z) Balkan, Irem Atay; Akulke, Ayca Zeynep Ilter; Bagatur, Yesim; Telci, Dilek; Goren, AHMET CEYHAN; Kirmizibekmez, Hasan; Yesilada, Erdem; GÖREN, AHMET CEYHAN
    Ethnopharmacological relevance: The leaves of Sambucus ebulus L. (Adoxaceae) are widely used in Turkish folk medicine particularly against inflammatory disorders. The fresh leaves after wilted over fire or the poultices prepared are directly applied externally to heal burns, edema, eczema, urticarial and abscess. Two iridoids were recently isolated (sambulin A, sambulin B) from the leaves of S. ebulus.
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    Antidiabetic, anticholinergic and antioxidant activities of aerial parts of shaggy bindweed (Convulvulus betonicifolia Miller subsp.) - profiling of phenolic compounds by LC-HRMS
    (2021-05-01T00:00:00Z) Bingol, Zeynebe; Kızıltaş, Hatice; GÖREN, AHMET CEYHAN; Kose, Leyla Polat; Topal, Meryem; DURMAZ, LOKMAN; Gulcin, İlhami; Alwasel, Saleh H.; GÖREN, AHMET CEYHAN
    In order to evaluate the antioxidant activity of evaporated ethanolic extract (EESB) and lyophilized water extract (WESB) of Shaggy bindweed (Convulvulus betonicifolia Mill. Subs), some putative antioxidant methods such as DPPH. scavenging activity, ABTS(center dot)(-) scavenging effect, ferric ions (Fe3+) reduction method, cupric ions (Cu2+) reducing capacity, and ferrous ions (Fe2+) binding activities were separately performed. Also, ascorbic acid, alpha-tocopherol and BHT were used as the standard compounds. Additionally, some phenolic compounds that responsible for antioxidant abilities of EESB and WESB were screened by liquid chromatography-high resolution mass spectrometry (LC-HRMS). At the same concentration, EESB and WESB demonstrated effective antioxidant abilities when compared to standards. In addition, EESB demonstrated IC50 values of 1.946 mu g/mL against acetylcholinesterase (AChE), 0.815 mu g/mL against alpha-glycosidase and 0.675 mu g/mL against alpha-amylase enzymes.
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    CCQM-K140: carbon stable isotope ratio delta values in honey
    (2017-01-01T00:00:00Z) Dunn, P. J. H.; Goenaga-Infante, H.; Goren, A. C.; Simsek, A.; Bilsel, M.; Ogrinc, N.; Armishaw, P.; Hai, L.; GÖREN, AHMET CEYHAN
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    Validation of a GC-IDMS method for the metrologically traceable quantification of selected FAMEs in biodiesel
    (2015-10-01T00:00:00Z) MORALES, Valle; Goren, AHMET CEYHAN; HELD, Andrea; BILSEL, Mine; GUNDUZ, Simay; YILMAZ, Hasibe; GÖREN, AHMET CEYHAN
    Current methods for the analysis of fatty acid methyl esters (FAMEs) in rapeseed oil-based biodiesel refer to operationally defined measurands, which is a practical solution for routine analysis. In this paper, a new method for the SI-traceable quantification of selected FAMEs in biodiesel and its validation are described. This method has the potential to be a reference method for applications requiring structurally defined measurands and traceability to the SI as it allows direct comparisons to well-characterised calibrants through the use of isotopically labelled analogues of the analytes as well as establishing a full uncertainty budget. The method is based on gas chromatography-isotope dilution mass spectrometry. Its performance is demonstrated through its implementation and validation in two independent laboratories and is shown to provide reliable and traceable results for selected FAMEs in biodiesel test samples.