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DEMİR, CEVDET

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DEMİR

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CEVDET

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2014 - 201922020 - 20211
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    Publication
    Optimization and validation of ultrasensitive GC-MS/MS method to measure oxidatively induced DNA damage products and role of antioxidants in oxidation mechanism
    (Elsevier, 2021-04-08) Aybastıer, Önder; Demir, Cevdet; AYBASTIER, ÖNDER; DEMİR, CEVDET; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; 0000-0002-0380-1992; 0000-0002-9381-0410; X-4621-2018; DTQ-5753-2022
    Oxidation of DNA due to exposure to reactive oxygen species (ROS) is a major source of DNA damage. ROS induced damage to DNA plays an important role in some diseases such as various cancers, aging and neurodegenerative diseases. The detection of DNA oxidation products plays a major role in assessing the mutagenicity potential of specific exposure. The GC-MS/MS method was developed for the ultrasensitive determination of individual DNA damage products. The validation results revealed that the proposed method was reliable and sensitive. Multiple response surface methodology (MRSM) was used to optimize derivatization conditions of oxidatively DNA base damage products before GC-MS/MS analysis. The optimum derivatization conditions were determined as 40 min for derivatization time, 120 degrees C for derivatization temperature and 1.4 for BSTFA/pyridine ratio under nitrogen atmosphere. The effects of thymol, carvacrol and thymoquinone as antioxidants were investigated on oxidative DNA damage. The determination of the oxidatively induced DNA damage products was performed after adding DNA and antioxidants with different concentrations under oxidative stress. Eighteen DNA base damage products were analyzed simultaneously using GC-MS/MS. This study showed a significant decrease in the amount of DNA base damage products when the antioxidants were present in the medium.
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    Investigation of antioxidant ability of grape seeds extract to prevent oxidatively induced dna damage by gas chromatography-tandem mass spectrometry
    (2018) Aybastier, Önder; Dawbaa, Sam; Demir, Cevdet; AYBASTIER, ÖNDER; Dawbaa, Sam; DEMİR, CEVDET; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü; 0000-0003-1508-0181; 0000-0002-9381-0410; 0000-0002-0380-1992; 0000-0001-7001-0739; AFR-1890-2022; ABA-2005-2020; KRQ-0516-2024; X-4621-2018
    Phenolic compounds have been studied elaborately for their efficacy to improve health and to protect against a wide variety of diseases. Herein this study, different analysis methods were implemented to evaluate the antioxidant properties of catechin and cyanidin using their standard substances and as they found in the grape seeds extracts. Total phenol contents were 107.39 +/- 8.94 mg GAE/g dw of grape seeds for grape seed extract (GSE) and 218.32 +/- 10.66 mg GAE/g dw of grape seeds for acid-hydrolyzed grape seed extract (AcGSE). The extracts were analyzed by HPLC-DAD system and the results showed the presence of catechin, gallic acid, chlorogenic acid and ellagic acid in the processed methanolic extract and cyanidin, gallic acid and ellagic acid in the processed acidified methanolic extract. The protective abilities of catechin and cyanidin were tested against the oxidation of DNA. The results showed that cyanidin has better protection of DNA against oxidation than catechin. GSE and AcGSE were revealed to inhibit the oxidatively induced DNA damage. GSE decreased about 57% of damage caused by the Fenton control sample. This study could show new aspects of the antioxidant profiles of cyanidin and catechin.
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    Publication
    Olea europaea leaf extract improves the treatment response of GBM stem cells by modulating miRNA expression
    (E-century Publishing Corp, 2014-01-01) Tezcan, Gülçin; Tunca, Berrin; Bekar, Ahmet; Budak, Ferah; Şahin, Saliha; Çeçener, Gülşah; Egeli, Ünal; Taşkapılıoğlu, Mevlut Özgür; Kocaeli, Hasan; Tolunay, Şahsine; Malyer, Hulusi; Demir, Cevdet; Tümen, Gülendam; TEZCAN, GÜLÇİN; TUNCA, BERRİN; BEKAR, AHMET; BUDAK, FERAH; ŞAHİN, SALİHA; ÇEÇENER, GÜLŞAH; EGELİ, ÜNAL; TAŞKAPILIOĞLU, MEVLÜT ÖZGÜR; KOCAELİ, HASAN; TOLUNAY, ŞAHSİNE; MALYER, HULUSİ; DEMİR, CEVDET; Tümen, Gülendam; Uludağ Üniversitesi/Tıp Fakültesi/Beyin Cerrahi Kliniği; Uludağ Üniversitesi/Tıp Fakültesi/Mikrobiyoloji Bölümü; Uludağ Üniversitesi/Tıp Fakültesi/Patholoji Bölümü; 0000-0002-5956-8755; 0000-0002-1619-6680; 0000-0001-7625-9148; 0000-0002-3820-424X; 0000-0001-7904-883X; 0000-0001-5472-9065; 0000-0002-9381-0410; ABA-2005-2020; F-8554-2017; ABX-9081-2022; AFR-1890-2022; F-4657-2014; AAH-3843-2020; AAI-1612-2021; ABI-6078-2020; IZP-9398-2023; AAW-5254-2020; AAP-9988-2020; AAH-2892-2021; ABB-8161-2020; AAH-1420-2021; ABI-6078-2020
    The stem-like cells of Glioblastoma multiforme (GBM) tumors (GSCs) are one of the important determinants of recurrence and drug resistance. The aims of the current study were to evaluate the anticancer effect of Olea europaea leaf extract (OLE) on GBM cell lines, the association between OLE and TMZ responses, and the effect of OLE and the OLE-TMZ combination in GSCs and to clarify the molecular mechanism of this effect on the expression of miRNAs related to cell death. The anti-proliferative activity of OLE and the effect of the OLE-TMZ combination were tested in the T98G, U-138MG and U-87MG GBM cell lines using WST-1 assay. The mechanism of cell death was analyzed with Annexin V/FITC and TUNEL assays. The effects of OLE on the expression levels of miR-181b, miR-153, miR-145 and miR-137 and potential mRNA targets were analyzed in GSCs using RT-qPCR. OLE exhibited anti-proliferative effects via apoptosis and necrosis in the GBM cell lines. In addition, OLE significantly induced the expression of miR-153, miR-145, and miR-137 and decreased the expression of the target genes of these miRNAs in GSCs (p < 0.05). OLE causes cell death in GBM cells with different TMZ responses, and this effect is synergistically increased when the cells are treated with a combination of OLE and TMZ. This is the first study to indicate that OLE may interfere with the pluripotency of GSCs by modulating miRNA expression. Further studies are required, but we suggest that OLE may have a potential for advanced therapeutic cancer drug studies in GBM.