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    Antioxidant and cytotoxic properties of some new dipeptide-indole conjugates
    (Wiley, 2023) Gonul, Zeynep; Ozturk, Dilara Altay; Kucukbay, Fatumetuzzehra; Tekin, Suat; Tekin, Zehra; Kucukbay, Hasan
    In this study, 10 new indole-dipeptide conjugates were synthesized, and their anticancer activity was determined against on A2780 (ovarian cancer cell line) and MCF-7 (breast cancer cell line) cells. Among compounds, 5 and 10 showed better activity against A2780 cell lines than the standard drug docatexel at 0.1 and 1 mu M concentrations, while only compound 5 showed better activity than docatexel, the MCF-7 cell line at 0.1 and 1 mu M concentrations. The antioxidant potencies of the compounds were low in both the DPPH and iron reducing power methods tested when compared to standard antioxidants used in this work.
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    Evaluation of phytochemical contents and antioxidant activity of pomegranate flower
    (2020) Tekin, Zehra; Küçükbay, F. Zehra
    Abstract: Pomegranate is one of the most abundant fruits consumed in Turkey. This study aimed to determine the content of total phenolic, total flavonoid, and antioxidant activity of Punica granatum L. flower in different extracts. Antioxidant activities of different extracts were determined 2,2-diphenyl-1- picrylhydrazyl (DPPH•) radical scavenging, reducing power, and metal chelating methods. The results showed that the total phenolic content for the extracts ranged from 14.82 to 90.86 mg gallic acid equivalents (GAE) / g extract. The contents of flavonoids were found to range from 7.35 to 500.00 mg quercetin equivalents (QUE)/ g extract. All pomegranate flower extracts displayed remarkable antioxidant activity according to DPPH and reducing power assays. Especially the methanolic extract of pomegranate flower possesses significant scavenging activity against DPPH• (85.80 %), as well as the largest contents of flavonoids and phenolic compounds. The antioxidant capacity of the methanolic extract was also greater than those of BHT and ?-tocopherol in DPPH and reducing power assays. The results demonstrated that the antioxidant activity of extracts of Punica granatum L. flower might, at least in part, have high content of flavonoids and other phenolics.
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    Pomegranate leaves, buds, and flowers: phytochemical, antioxidant, and comparative solvent analyzes
    (Kemerovo State Univ, 2025) Tekin, Zehra; Kucukbay, Fatumetuzzehra
    Punica granatum L. possesses significant nutritional and medicinal potential. Its pharmacological activities have been investigated, but no comparative evaluation has been reported regarding the effect of different extraction solvents on the phytochemical content and antioxidant activity of its leaf, bud, and flower extracts. This research involved seven various solvents, namely methanol, ethanol, water, acidified methanol, acidified ethanol, acidified water, and hexane. A set of experiments made it possible to define the effect of each of these solvents on the contents of phenolics, flavonoids, flavanols, flavonols, anthocyanins, and tannins, as well as on the antioxidant activity of pomegranate leaf, bud and flower tissues. The research objective was to identify the optimal solvent for the most effective extraction of the abovementioned functional compounds. The antioxidant activity tests involved DPPH free radical scavenging, metal chelating, iron (III) reducing power, and CUPRAC assays. The aqueous extract of P. granatum leaves demonstrated the highest total phenolic content (192.57 mg GAE/g extract) while the greatest flavonoid content belonged to the acidified methanol extract of P. granatum buds (73.93 mg RE/g extract). The HPLC analysis detected such significant phenolic compounds as punicalagin in buds and flowers, as well as gallic acid in leaves. All the extracts showed good antioxidant activity; however, the bud extracts had a better antioxidant profile than the extracts from leaves and flowers. The pomegranate leaf, bud, and flower extracts demonstrated excellent phytochemical and antioxidant properties, which makes it possible to recommend these plant tissues as raw materials to be used in pharmaceutical, food, nutraceutical, and cosmetic industries.
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    Preparation, DFT calculations, docking studies, antioxidant, and anticancer properties of new pyrazole and pyridine derivatives
    (Wiley, 2022) Zebbiche, Zineddine; Sekerci, Guldeniz; Boulebd, Houssem; Kucukbay, Fatumetuzzehra; Tekin, Suat; Tekin, Zehra; Kucukbay, Hasan
    Seven novel pyrazole derivatives (4a-g) and four novel starting compounds incorporating substituted pyridine moieties were synthesized successfully. Cell viability assay for the tested compounds was performed, and the inhibitory concentrationlogarithmic 50 (LogIC(50)) values of the compounds were calculated after a 24-h treatment. Four of the examined compounds (3d, 3g, 4f, and 4g) showed comparable cytotoxic activity against CaCo-2 compared to the standard drug docetaxel at 0.1 and 1 mu M concentrations. Although the LogIC(50) of docetaxel was -0.678 mu M for CaCo-2 cells at 24 h, the LogIC(50) values of compounds were -0.794, -0.567, -0.657, and -0.498 respectively. Five of the compounds (2d, 2g, 3d, 3g and 4e) showed comparable cytotoxic activity against MCF-7 at 0.1 mu M concentration compared to docetaxel (p < 0.05). Docking studies revealed the compounds have a good affinity to the active site of the human topoisomerase II beta enzyme. The antioxidant capacities of all compounds were determined using both 1,1-diphenyl-2-picrylhydrazyl and metal chelation methods. Although the compounds did not show significant antioxidant activity, relatively effective are compounds 3c, 3d, and 3g, which are hydrazine derivatives with approximately 50% antioxidant activity of standard antioxidants at concentrations of 62.5 and 125 mu g/ml.
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    Synthesis of new 7-amino-3,4-dihydroquinolin-2(1H)-one-peptide derivatives and their carbonic anhydrase enzyme inhibition, antioxidant, and cytotoxic activities
    (Wiley-V C H Verlag Gmbh, 2021) Kucukbay, Hasan; Gonul, Zeynep; Kucukbay, Fatumetuzzehra Zehra; Tekin, Zehra; Angeli, Andrea; Bartolucci, Gianluca; Supuran, Claudiu T.
    Six new monopeptides, seven new dipeptides, and two deprotected monopeptide dihydroquinolinone conjugates were prepared by the benzothiazole-mediated method and their structures were confirmed by nuclear magnetic resonance, mass, infrared spectroscopy, and elemental analysis methods. The human carbonic anhydrase (hCA) I and hCA II enzyme inhibition activities of the compounds were determined using the stopped-flow instrument. The synthesized peptide-dihydroquinolinone conjugates 2, 3, 6, 10, 13, and 15 showed inhibition against the hCA II enzyme in the range of 15.7-65.7 mu M. However, none of the compounds showed inhibition of hCA I at a concentration of 100 mu M. The antioxidant activities of the compounds were also examined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method at concentrations of 12.5-125 mu g/ml, but when compared with the standard antioxidant compounds alpha-tocopherol and butylated hydroxyanisole (BHA), weak antioxidant activities were detected. The cytotoxic effects of four compounds against the A549 and BEAS-2B cell lines were also investigated. Among the compounds studied, compound 7 was found to be most effective, with the IC50 values on the A549 cells for 48 and 72 h being 26.87 and 9.979 mu g/ml, respectively, and the IC50 values on the BEAS-2B cells being >100 mu g/ml. None of the tested compounds showed antimicrobial activity in the concentration range (800-1.56 mu g/ml) studied.