Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 4Citation - Scopus: 5Antioxidant and Antimicrobial Activities of Plants Grown in the Mediterranean Region(John Wiley and Sons Inc., 2022) Kaçar, D.; Bayraktar, Oğuz; Erdem, C.; Alamri, A.S.; Galanakis, C.M.Background: The main objective of this research was to identify plant species with possible bioactivities based on their total phenol content, antioxidant, and antimicrobial properties. Therefore, different parts of 42 plant species grown in the Mediterranean region were extracted with aqueous ethanol solutions to prepare extracts with antioxidant and antimicrobial activities, mainly resulting from their total phenol contents. No detailed laboratory data on the flora of this area exists regarding their total phenol contents and total antioxidant activities. Results: Yields of extraction for each plant material were determined. Extracts were characterized based on their total phenol contents, total antioxidant (both hydrophilic and lipophilic), and antimicrobial activities using Folin–Ciocalteu, Photochemiluminescence, disc diffusion, and microdilution methods, respectively. The extract of Hypericum empetrifolium had the relatively highest total water-soluble and lipid-soluble antioxidant activities. Sarcopoterium spinosum extract had relatively high total phenol content. Preliminary screening study was conducted with the disc diffusion method to evaluate the extracts' antimicrobial activities. 26 out of 42 plant species showed significant antimicrobial activities against the growth of microorganisms. Microdilution assays were performed to evaluate the most active plant species with their minimum inhibition concentrations. H. empetrifolium, Pistacia terebinthus, Arbutus unedo, and Cistus parviflorus were the most antimicrobial plant species among those investigated. CONCLUSION: The new potential sources for the isolation of bioactive natural compounds from specific plant species could be possible with the help of this present screening study. Isolated bioactive natural compounds can be utilized as raw materials in cosmetics, nutraceuticals, food supplements, and pharmaceutical industries. © 2022 Society of Chemical Industry.Conference Object Hidrofobik İlaç Taşıyıcısı Olarak Akrilik Yıldız Blok Kopolimerler(Institute of Electrical and Electronics Engineers Inc., 2009) Genç, Gözde; Batıgün, Ayşegül; Bayraktar, Oğuz; Altıntaş, Özcan; Tunca, Ümit; Hizal, GürkanAmphiphilic poly(methyl methacrylate)-b-poly(acrylic acid) (PMMA-b-PAA) copolymers with 4 and 6 arms were synthesized by Atomic Transfer Radical Polymerization (ATRP). The polymers were characterized by GPC, H-NMR and FTIR analysis. Polymer samples synthesized at various molecular weights between 18-80 kDa were investigated in terms of maximum loading capacity and critical micelle concentration by fluorescence spectroscopy. 4 arm PMMA-b-PAA (MW 30 kDa) was loaded with hydrophobic model drug indomethacin with an extremely high drug loading efficiency (22.5% drug content). Drug loaded polymer formed a stable and biodegradable complex in aqueous medium.Conference Object Citation - Scopus: 4Trans-resveratrol’ün Kitosan Mikroküreler İçerisindeki Kararlılığı(Institute of Electrical and Electronics Engineers Inc., 2009) Altıok, Duygu; Altıok, Evren; Bayraktar, Oğuz; Tıhmınlıoğlu, Fundatrans-Resveratrol, (3,5,4?-trihydroxy-trans-stilbene), a phenolic compound present in some plant species, have been shown to posses antioxidative, anticarcinogenic and antitumour properties. However, under UV light, it turns into -cis form and looses its bioactivity.This study aims to increase the stability of trans-resveratrol by loading it into chitosan microspheres. Within this context, the trans-resveratrol loaded chitosan microspheres was produced by spray drying and then the resultant microspheres were characterized. The particle size and the surface morphology of resultant microspheres were investigated by scanning electron microscope (SEM) and the thermal properties were determined by thermogravimetry analyser(TGA). The stability of free and that of inside the microspheres was determined by high performance liquid chromatography (HPLC). It was found that the stability of trans-resveratrol incorporated into chitosan microspheres kept constant. ©2009 IEEE.Article Citation - Scopus: 7Oxidation of Oregano Essential Oil Using Zeolite-Encapsulated Cr(salpn) Complex(SCIBULCOM, 2017) Bayraktar, Oğuz; Yerkesikli, Alev GüneşFlexible ligand (H2salpn, N,N´-bis(salicylidene)propane-1,3-diamine) was used to form complex with Cr(III) metal ion inside the cages of NaY-zeolite. The encapsulation of Cr(salpn) complex was confirmed with Fourier transform infrared (FT-IR). The encapsulated Cr(salpn) complex catalysed the liquid-phase oxidation of both carvacrol and thymol in the presence of hydrogen peroxide. The conversion range was found be between 35–39% for the oxidation of both carvacrol and thymol. A high yield of thymoquinone (TQ) was obtained along with other side-products such as, thymohydroquinone (THQ) and benzoquinones (BQ). Oxidation of carvacrol and thymol provided a TQ yield of 31.2 and 34.5%, respectively. Oxidation reaction did not occur in the absence of a catalyst. The Cr(salpn)-NaY catalyst was catalytically active with an acceptable leaching performance. Oxidation of oregano essential oil having carvacrol as major compound caused the formation of an essential oil rich in TQ. The carvacrol present in the oregano essential oil was converted into mainly TQ with 33.6% yield and 70% total conversion as a result of the side-products namely BQ, THQ, and several undefined products. © 2017 Scibulcom Ltd. All Rights Reserved.Article Citation - WoS: 5Citation - Scopus: 8A Research on the Production of Silk Sericin Powders by Using Spray Drying Method(Ege Üniversitesi, 2009) Genç, Gözde; Bayraktar, Oğuz; Başal, GüldemetSericin protein is usually discarded as a waste in silk industry. Production of silk sericin powders, which can be incorporated into fibers used in textile industry, by spray drying method will enable value-added utilization of waste sericin. in this study aqueous sericin solutions were used as raw material for the production of dry powders using a lab-scale spray dryer. A linear regression analyses were employed, in addition to experimental design at two levels with three factors for the analysis of three responses: moisture content, particle type and agglomeration degree. The process factors were the drying air temperature (120°C and 160°C), the feed rate (1.25x10-4 and 2.5x10-4 dms -), and the concentration of sericin solutions of 10% and 30% (w/w) fed to the spray dryer. The three responses were analyzed statistically to determine the effective parameters and it was concluded that moisture content depended on three factors-drying air temperature being the dominant parameter. Particle size and shape depended mainly on feed rate and agglomeration depended on the moisture content of the product.Conference Object Citation - WoS: 4Citation - Scopus: 4Antioxidative and Antimicrobial Screening of 19 Commercial Essential Oils in Turkey(International Society for Horticultural Science, 2009) Bulut, Çisem; Altıok, Evren; Bayraktar, Oğuz; Ülkü, SemraPlant oils have been used for wide variety purposes for many years in Turkey. These essential oils have usage in many areas such as perfumery, cosmetic, food flavoring and folkloric medicine. In the study, 19 commercial essential oils were studied by means of antibacterial and antioxidant capacity. Antibacterial test was performed against S. aureus, S. epidermidis, K. pneumoniae and E. coli using standard disc diffusion method. Penicillin, gentamicin and vancomycin discs were also included. Inhibition zones (mm) were recorded to indicate antibacterial property. Penicillin (44 mm) and vancomycin (14 mm) could inhibit only S. aureus. Except essential oils of Juniperus nana (Ardiç), Ocimum basilicum (Feslegen), Urtica dioica (Isirgan), Foeniculum vulgare (Rezene) ressential oils indicated antimicrobial activity against some of the test microorganims. The most active essential oil was found as Thymus serpyllum (Kekik). It indicated highest inhibition zones for other microorganisms among others. Antioxidant capacities were measured using photochemiluminescence (PCL) method. The highest antioxidant activity was measured for Dianthus caryophyllus (Karanfil) as 547.781 103 ug trolox/mL of oil. It was followed by Thymus serpyllum (Kekik), Lilium candidum (Zambak) and Matricaria chamomilla (Papatya). Especially, Thymus serpyllum and Dianthus caryophyllus have significant antimicrobial and antioxidant capacity therefore it could be suggested for further investigations and applications.Book Part Citation - WoS: 30Citation - Scopus: 41Nanocarriers for Plant-Derived Natural Compounds(Elsevier Ltd., 2017) Bayraktar, Oğuz; Erdoğan, İpek; Köse, Merve D.; Kalmaz, GülcanNatural products constitute a large fraction in drug discovery processes. The term includes compounds from plants, microorganisms, and animals. Most of the natural products are secondary metabolites derived from plants, which are low in amounts and difficult to isolate. Another issue is the preservation of their bioactivity during process and storage as well as degradation in the gastrointestinal system before reaching circulation. Advances in nanotechnology offer nanoparticles, nanocapsules, and conjugates, which are devoted to site-specific, time-controlled delivery of bioactive agents. Nanoencapsulated systems have the advantage of high drug encapsulation efficiency because of optimized drug solubility in the core, low polymer content compared to other nanoparticulated systems such as nanospheres, drug polymeric shell protection against degradation factors, and the reduction of tissue irritation caused by the polymeric shell. This chapter will discuss nanoencapsulation methods and advances in carrier systems for plant-derived natural compounds.Article Citation - WoS: 47Citation - Scopus: 54Olive Leaf Extracts Protect Cardiomyocytes Against 4-Hydroxynonenal Toxicity in Vitro: Comparison With Oleuropein, Hydroxytyrosol, and Quercetin(Georg Thieme Verlag, 2014) Bali, Elif Burcu; Ergin, Volkan; Rackova, Lucia; Bayraktar, Oğuz; Küçükboyacı, Nurgün; Karasu, ÇimenOlive (Olea europaea) leaf, an important traditional herbal medicine, displays cardioprotection that may be related to the cellular redox modulating effects of its polyphenolic constituents. This study was undertaken to investigate the protective effect of the ethanolic and methanolic extracts of olive leaves compared to the effects of oleuropein, hydroxytyrosol, and quercetin as a positive standard in a carbonyl compound (4-hydroxynonenal)- induced model of oxidative damage to rat cardiomyocytes (H9c2). Cell viability was detected by the MTT assay; reactive oxygen species production was assessed by the 2′,7′-dichlorodihydrofluorescein diacetate method, and the mitochondrial membrane potential was determined using a JC-1 dye kit. Phospho-Hsp27 (Ser82), phospho-MAPKAPK-2 (Thr334), phospho-c-Jun (Ser73), cleaved-caspase-3 (cl-CASP3) (Asp175), and phospho-SAPK/JNK (Thr183/Tyr185) were measured by Western blotting. The ethanolic and methanolic extracts of olive leaves inhibited 4-hydroxynonenal-induced apoptosis, characterized by increased reactive oxygen species production, impaired viability (LD50: 25 μM), mitochondrial dysfunction, and activation of pro-apoptotic cl-CASP3. The ethanolic and methanolic extracts of olive leaves also inhibited 4-hydroxynonenal-induced phosphorylation of stress-activated transcription factors, and the effects of extracts on p-SAPK/JNK, p-Hsp27, and p-MAPKAPK-2 were found to be concentration-dependent and comparable with oleuropein, hydroxytyrosol, and quercetin. While the methanolic extract downregulated 4-hydroxynonenal-induced p-MAPKAPK-2 and p-c-Jun more than the ethanolic extract, it exerted a less inhibitory effect than the ethanolic extract on 4-hydroxynonenal-induced p-SAPK/JNK and p-Hsp27. cl-CASP3 and p-Hsp27 were attenuated, especially by quercetin. Experiments showed a predominant reactive oxygen species inhibitory and mitochondrial protecting ability at a concentration of 1-10 μg/mL of each extract, oleuropein, hydroxytyrosol, and quercetin. The ethanolic extract of olive leaves, which contains larger amounts of oleuropein, hydroxytyrosol, verbascoside, luteolin, and quercetin (by HPLC) than the methanolic one, has more protecting ability on cardiomyocyte viability than the methanolic extract or each phenolic compound against 4-hydroxynonenal-induced carbonyl stress and toxicity.Article Citation - WoS: 4Citation - Scopus: 5Adsorption/Desorption and Biofunctional Properties of Oleuropein Loaded on Different Types of Silk Fibroin Matrices(The Society of Chemists and Techonogists of Macedonia, 2017) Bayraktar, Oğuz; Balta, Ali Bora; Başal Bayraktar, GüldemetThe objective of this study was to investigate the adsorption/desorption behavior of oleuropein on different types of silk fibroin matrices including silk fibroin microfibers (MF), regenerated silk fibroin (RSF), and silk fibroin nanofibers (NF). Nanofibers with an average diameter of ranging between 24 and 326 nm were successfully prepared using the electrospinning technique. The effects of the silk fibroin concentration, the voltage applied and the distance between needle tip and collector plate on the morphol-ogy of the NF were investigated. The adsorption capacities of MF, RSF and NF were determined as 104.92, 163.07 and 228.34 mg oleuropein per gram of material, respectively. The percentage of initially adsorbed oleuropein that was desorbed was 86.08, 91.29 and 96.67% for MF, RSF and NF, respectively. NF and RSF discs loaded with oleuropein were subjected to disc diffusion assays to determine their antibacterial activity against test microorganisms Staphylococcus epidermidis (Gram +) and Esche-richia coli (Gram -). The results showed that both biomaterials possessed antibacterial properties after loading with oleuropein. Wound scratch assays using oleuropein released from NF revealed an enhance-ment of cell migration, indicating a wound healing property of the material. In conclusion, the NF can be utilized as a biofunctional polymeric material with better perfor-mance for the adsorption and desorption of oleuropein compared with MF and RSF.Article Citation - WoS: 30Citation - Scopus: 35Bioactive Sheath/Core Nanofibers Containing Olive Leaf Extract(John Wiley and Sons Inc., 2016) Doğan, Gamze; Başal, Güldemet; Bayraktar, Oğuz; Özyıldız, Figen; Uzel, Ataç; Erdoğan, İpekThis study aimed at producing silk fibroin (SF)/hyaluronic acid (HA) and olive leaf extract (OLE) nanofibers with sheath/core morphology by coaxial electrospinning method, determining their antimicrobial properties, and examining release profiles of OLE from these coaxial nanofibers. Optimum electrospinning process and solution parameters were determined to obtain uniform and bead-free coaxial nanofibers. Scanning electron microscopy and transmission electron microscopy (TEM) were used to characterize the morphology of the nanofibers. The antimicrobial activities of nanofibers were tested according to AATCC test method 100. Total phenolic content and total antioxidant activity were tested using in vitro batch release system. The quality and quantity of released components of OLE were determined by high-performance liquid chromatography. The changes in nanofibers were examined by Fourier-transform infrared spectroscopy. Uniform and bead-free nanofibers were produced successfully. TEM images confirmed the coaxial structure. OLE-loaded nanofibers demonstrated almost perfect antibacterial activities against both of gram-negative and gram-positive bacteria. Antifungal activity against C. albicans was rather poor. After a release period of 1 month, it was observed that ∼70-95% of the OLE was released from nanofibers and it was still bioactive. Overall results indicate that the resultant shell/core nanofibers have a great potential to be used as biomaterials.