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Öğe ANTIOXIDANT ACTIVITY, SOME NUTRITIONAL AND COLOUR PROPERTIES OF VACUUM DRIED STRAWBERRY TREE (ARBUTUS UNEDO L.) FRUITE(Termedia Publishing House Ltd, 2011) Orak, H. Hulya; Aktas, Turkan; Yagar, Hulya; Isbilir, S. Selen; Ekinci, Neslihan; Sahin, Fusun H.Background. The strawberry tree (Arbutus unedo L.) fruit contains a higher amount of nutrients and bioactive compounds than many other cultivated species, however, the edible use of this fruit is currently not widespread. In this study, the influences of vacuum drying have been investigated in terms of changing of some nutritional characteristics, antioxidant properties, and colour. Material and methods. Fruits were collected from Canakkale province in Turkey and next vacuum dried. Ethyl oleate and water blanching pre-treatments were applied to fruits before drying. Ascorbic acid, reducing sugar, minerals, colour, total phenolic content, DPPH radical scavenging activity, beta-carotene bleaching activity and HMF formation were determined. Results. The EO pretreatment shortened the drying time more than WB and gives a higher beta-carotene bleaching activity, lower HMF and higher yellowness and brightness of external colour characteristics. Conclusions. In this research, the effects of vacuum drying process on the colour, antioxidant activity and nutritional characteristics of fruit have been determined and it has been concluded that the strawberry tree fruit is assessable in food industry by drying due to rich nutritional components, antioxidant activity and attractive colour of the fruit.Öğe Assessment of in vitro Antioxidant and Antidiabetic Capacities of Medlar (Mespilus germanica)(Univ Agr Sci & Veterinary Med Cluj-Napoca, 2019) Isbilir, Sebnem Selen; Kabala, Sevilay Inal; Yagar, HulyaThe objective of the current study was to evaluate the antioxidant activity and enzyme inhibitory effect of different parts of medlar including fruit, leaf and flower bud by using various in vitro methods, and also determination of total phenolic and flavonoid content in the samples. Ethanol extracts of medlar parts were prepared and their antioxidant activities were determined using 1,1-diphenyl-2-picryl-hydrazil (DPPH center dot) scavenging and beta-carotene bleaching methods. The leaf extract showed the strongest antioxidant activity. DPPH radical scavenging activity was in the order of BHA > leaf > bud > fruit. This ordering was the same for beta-carotene bleaching activity, tocopherol > leaf > bud > fruit. The highest total phenolic (60.3 +/- 1.69 mg GAE g(-1) extract) and flavonoid (14.77 +/- 1.15 mg QE g(-1 )extract) content were determined in leaf extract. For possible antidiabetic effects of extracts, alpha-amylase and alpha-glucosidase inhibitory activities were investigated, the bud extract showed the highest inhibition activities among the all extracts.Öğe Comparison of antioxidant activities of juice, peel, and seed of pomegranate (Punica granatum L.) and inter-relationships with total phenolic, Tannin, anthocyanin, and flavonoid contents(Korean Society Food Science & Technology-Kosfost, 2012) Orak, Hakime Hulya; Yagar, Hulya; Isbilir, Sebnem SelenIn this study, the antioxidant activities of juice, peel, and seed parts of pomegranate were investigated by using DPPH scavenging activity, beta-carotene bleaching method, reducing power, and metal chelating activity. Sample of pomegranates which are named Punica granatum L. cv. Hicaznar, genotype 19-121, genotype 17-67, and genotype 19-66 obtained from BATEM (West Mediterranean Agricultural Research Institute) in Anlalya. The EC50 values of DPPH scavenging activities in peel extracts (PE) had 23.4-fold higher than the juice extracts (JE), and the seed extracts (SE) had 2.3-fold higher than JE. The reducing power in peel extracts was found to be 4.7-fold higher than SE and 10.5-fold higher than the JE. The highest metal chelating capacity (37.22%) was determined in peel, while the lowest (7.151%) in seed. Generally, in peel, the total polyphenol, flavonoid, tannin contents, and in juice, the total polyphenol, anthocyanin, tannin contents, and acidity significantly affected to antioxidant activities.Öğe Comparison of Polyphenol Oxidases Prepared From Different Parts of Artichoke (Cynara Scolymus L.)(Taylor & Francis Inc, 2011) Tuncay, Didem; Yagar, HulyaArtichoke polyphenol oxidases (PPOs) were obtained by (NH4)2SO4 precipitation using ascorbic acid, polyvinylpyrrolidone, and Triton X-100. The PPO content of artichoke head (AHPPO) was 8820 units (mg protein)-1 as compared with 3370 units (mg protein)-1 in artichoke leaves-and-stem (ALSPPO) by using catechol as a substrate. The substrates of both AHPPO and ALSPPO are o-diphenols, such as catechol, pyrogallol, and L-DOPA. Optimum pH and temperature of both PPOs were determined. AHPPO had higher thermal stability than ALSPPO. Also, Tm (the midpoint of thermal inactivation) and t1/2 (half-life) values were determined. Km and Vmax of both PPOs were observed to be similar. Twelve inhibitors were tested and their I50 values were determined. The most effective inhibitors were found to be potassium cyanide, ascorbic acid, L-cysteine, and thiourea. Sodiumdodecylsulfate, urea, and cupric sulfate caused an increase about 20-30% in the PPO activity.Öğe Comparison of some biochemical properties of artichoke polyphenol oxidase entrapped in alginate-carrageenan and alginate gels(Informa Healthcare, 2014) Yagar, Hulya; Kocaturk, SelinPolyphenol oxidase (PPO, EC.1.14.18.1) isolated from artichoke (Cynara scolymus) was entrapped within alginate and alginate+ carrageenan beads, and the catecholase and cresolase activities of both entrapped enzymes were determined. Some properties of these immobilized enzymes such as optimum pH and temperature, kinetic parameters (K-m and V-max), thermal, and storage stability were determined and compared to each other. The highest catecholase activity was observed in alginate gel (370 U/g bead) while the highest cresolase activity was in alginate+ carrageenan gel (90 U/g bead). For catecholase and cresolase activities, optimum pHs of alginate and alginate+ carrageenan beads were determined to be 7.0 and 4.0, respectively. Optimum temperatures for catecholase activity were determined to be 40 degrees C for both entrapped enzymes. These values for cresolase activity were 30 degrees C and 20 degrees C, respectively. Immobilized artichoke PPOs greatly preserved their thermal stability which exists anyway. The catalytic efficiency value (V-max/K-m) of the alginate beads is approximately high as two-and-a-half folds of that of alginate+kappa-carrageenan beads for cresolase activity. These values were very close for catecholase activity. Immobilized beads saved their both activities after 30 days of storage at 4 degrees C.Öğe Comparison off some properties of free and immobilized ?-amylase by Aspergillus sclerotiorum in calcium alginate gel beads(Taylor & Francis Inc, 2008) Yagar, Hulya; Ertan, Figen; Balkan, BilalSome properties of immobilized a-amylase by Aspergillus sclerotiorum within calcium alginate gel beads were investigated and compared with soluble enzyme. Optimum pH and temperature were found to be 5.0 and 40 degrees C, respectively, for both soluble and immobilized enzymes. The immobilized enzyme had a better Km value, but k(cat)/K-m values were the same for both enzymes. Entrapment within calcium alginate gel beads improved, remarkably, the thermal and storage stability of a-amylase. The half life values of immobilized enzyme and soluble enzyme at 60 degrees C were 164.2, and 26.2 min, respectively. The midpoint of thermal inactivation (T-m) shifted from 56 degrees C (for soluble enzyme) to 65.4 degrees C for immobilized enzyme. The percentages of soluble starch hydrolysis for soluble and immobilized alpha-amylase were determined to be 97.5 and 92.2% for 60 min, respectively.Öğe DETERMINATION OF ANTIOXIDANT ACTIVITIES OF STRAWBERRY TREE (Arbutus unedo L.) FLOWERS AND FRUITS AT DIFFERENT RIPENING STAGES(Wydawnictwo Akad Rolniczej W Lublinie, 2012) Isbilir, Sebnem Selen; Orak, Hakime Hulya; Yagar, Hulya; Ekinci, NeslihanIn this study, the antioxidant activities of Strawberry tree (Arbutus unedo L.) flowers at flowering period and fruits during ripening period were investigated, along with some ripening characteristics such as color, reducing sugar and acidity. Antioxidant activity characteristics were investigated using by the methods of DPPH (1,1-Diphenyl-2-picryl-hydrazyl) scavenging activity, beta-carotene bleaching, reducing power, metal chelating capacity, superoxide anion scavenging and hydrogen peroxide scavenging activity in water, ethanol and methanol extracts. The total phenolic content of flowers in water extracts was found to be 232.38 +/- 7.19 mg GAE . g(-1) extract, and the DPPH activity was 81.3 +/- 0.49% at 50 mu g.ml(-1) concentration. In the ripening stages, the fully red fruits were determined higher antioxidant capacity than green and yellow fruits, except H2O2 scavenging activity which was highest in green fruit. In correlation study, the highest relationship was found between total phenolic content with reducing power (r(2) = 0.987**, P < 0.01), while the lowest with H2O2 scavenging activity (r(2) = 0.519*, P < 0.05).Öğe Determination of antioxidant properties of lyophilized olive leaf water extracts obtained from 21 different cultivars(Korean Society Food Science & Technology-Kosfost, 2012) Orak, Hakime Hulya; Isbilir, Sebnem Selen; Yagar, HulyaThe objective of this study was to compare the antioxidant activities of lyophilized olive leaf water extracts (OLWExtracts) from 21 different olive tree cultivars. The highest total phenolic content (102.69 +/- 1.63 mu g GAE/mg extract) was found in cultivar 'Esek Zeytini' and the lowest content (78.52 +/- 2.18 mu g GAE/mg extract) was in 'Uslu'. The highest total flavonoid content (12.47 +/- 0.12 mu g QE/mg extract) obtained from 'Frantoio'. According to EC50 values, 'Domat' have the highest DPPH scavenging activity (EC50 =59 mu g/mL), reducing power (EC50 =180 mu g/mL), and superoxide radical scavenging capacity (EC50=44 mu g/mL). While, 'Ascolana' showed the highest metal chelating capacity (EC50=163 mu g/mL), 'Memecik' showed the highest hydrogen peroxide (H2O2) scavenging capacity. Research results exhibited that OLWExtracts are comparable to synthetic antioxidants. The correlation study showed that while total phenolic content correlated with DPPH scavenging activity and reducing power (p < 0.01), total flavonoid content correlated with metal chelating and superoxide radical scavenging capacity (p < 0.05).Öğe Entrapment of laurel lipase in chitosan hydrogel beads(Taylor & Francis Ltd, 2017) Yagar, Hulya; Balkan, UgurLaurel seed lipase was entrapped within chitosan beads with ionotropic gelatin method using tripolyphosphate (TPP) as multivalent covalent counter ion. Immobilization yield was 78%. First, optimum immobilization conditions were determined, and morphology of chitosan beads was characterized by scanning electron microscopy. Optimum pH and temperature were evaluated as 6.0 and 40 degrees C, respectively. The immobilized beads saved about 55% of its activities at 60 degrees while saved about 32% at 70 degrees C for 30min. V-max/K-m values were determined as 31.75 and 2.87 using olive oil as substrate for immobilized beads and free enzyme, respectively. Immobilized beads showed the activities during 30 days at+4 degrees C.Öğe Evaluation of Antioxidant and Antimicrobial Potential of Strawberry Tree (Arbutus Unedo L.) Leaf(Korean Society Food Science & Technology-Kosfost, 2011) Orak, Hakime Hulya; Yagar, Hulya; Isbilir, Sebnem Selen; Demirci, Ahmet Sukru; Gumus, Tuncay; Ekinci, NeslihanIn present study, antioxidant and antimicrobial activities of strawberry tree (Arbutus unedo L.) leaves were investigated. Antioxidant activity was determined by methods of DPPH scavenging, beta-carotene bleaching, reducing power, metal chelating, superoxide anion scavenging, and hydrogen peroxide scavenging activity. Total phenolic content were determined to be 197.16 +/- 1.43 mg GAE/g extract in aqueous extract. The EC50 value of methanolic extracts was found to be 0.423 mg/mL. The extracts of leaves showed nearly 1/4 metal chelating capacity of standard EDTA, high reducing power, superoxide anion scavenging, and hydrogen peroxide scavenging activities. While the strawberry tree leaves exhibited antibacterial activity against Staphylococcus aureus, there was no inhibitory effect against Escherichia coli and Salmonella enteritidis. The strawberry tree leaves exhibited antifungal effect against 2 aflatoxigenic molds namely Aspergillus parasiticus NRRL 2999 and NRRL 465. These results suggest that the strawberry tree leaves may be used as an antioxidant source for pharmaceutical application, nutraceutical and functional food industries.Öğe A new biosensor for osteoporosis detection(Taylor & Francis Inc, 2019) Kabala, Sevilay Inal; Yagar, Hulya; Ozcan, Hakki MevlutOsteoporosis is a disease that is characterized by deterioration of bone tissue and increased risk of fracture as it leads to a decrease in bone mineral density, which is an important public health problem. Today, bone mineral density is measured by radiological techniques. Alternative techniques are needed because of the disadvantages such as excessive radiation intake, the cost of radiological techniques, and the necessity for specialist personnel for the devices. The quantitative determination of biochemical markers that play a role in bone mineralization may be a good alternative for the osteoporosis diagnosis and especially in the follow-up of treatment. In this study, a specific and sensitive immunological biosensor, which quantitatively determines the osteocalcin molecule, has been developed to be used in the early osteoporosis diagnosis and to evaluate the response to the drug treatment. Anti-osteocalcin antibody was immobilized onto gold electrode surface via covalent immobilization method by using 6-mercaptohexanol, 1,4-butanedioldiglycidyl ether, ethanolamine, and glutaraldehyde. Immobilization steps and biosensor characterization were specified by cyclic voltammetry and electrochemical impedance spectroscopy. The detection time and range of Ocn biosensor were determined as 45 min and 10-60 pg mu L-1 Ocn concentration, respectively. The Ocn biosensor was successfully applied in artificial serum samples spiked with Ocn.Öğe A new ITO-based A?42 biosensor for early detection of Alzheimer's disease(Elsevier Science Sa, 2023) Altay, Dilek Nur; Yagar, Hulya; Ozcan, Hakki MevlutIn this study, a novel label-free impedimetric immunosensor was fabricated for rapid, selective, and sensitive quantitative analysis of A & beta;42 protein for use in the diagnosis of Alzheimer's disease. The immunosensor was fabricated using inexpensive and disposable indium tin oxide polyethylene terephthalate (ITO-PET) electrodes. After the electrodes were modified with 3-glycidoxypropyldimethoxymethylsilane (GPDMMS), the antibody specific to the A & beta;42 protein (anti-A & beta;42) was immobilized. The affinity interaction between anti-A & beta;42 and A & beta;42 in the immobilization steps in immunosensor fabrication and in the quantitation of A & beta;42 were analyzed using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) techniques. Additionally, the morphological changes occurring on the electrode surface during each immobilization step were imaged using scanning electron microscopy (SEM). The linear detection range of the immunosensor was determined as 1-100 pg/mL with the limit of detection value of 0.37 pg/mL. Analytical properties of the biosensor, including reproducibility, repeatability, storage stability, selectivity, and regeneration were investigated. The kinetic behavior of antibody-antigen complex formation was determined for the first time using single frequency impedance (SFI) analysis on an A & beta;42 biosensor. The potential for use of the immunosensor in clinical studies was demonstrated by analysis of A & beta;42 in commercially purchased human serum.Öğe Optimization of ?-amylase immobilization in calcium alginate beads(Taylor & Francis Inc, 2007) Ertan, Figen; Yagar, Hulya; Balkan, Bilalalpha-Amylase enzyme was produced by Aspergillus sclerotiorum under SSF conditions, and immobilized in calcium alginate beads. Effects of immobilization conditions, such as alginate concentration, CaCl2 concentration, amount of loading enzyme, bead size, and amount of beads, on enzymatic activity were investigated. Optimum alginate and CaCl2 concentration were found to be 3% (w/v). Using a loading enzyme concentration of 140 U mL(-1), and bead (diameter 3 mm) amount of 0.5 g, maximum enzyme activity was observed. Beads prepared at optimum immobilization conditions were suitable for up to 7 repeated uses, losing only 35% of their initial activity. Among the various starches tested, the highest enzyme activity (96.2%) was determined in soluble potato starch hydrolysis for 120 min at 40 degrees C.Öğe Optimization of Polyphenol Oxidase Immobilization in Copper Alginate Beads(Informa Healthcare, 2010) Kocaturk, Selin; Yagar, HulyaPolyphenol oxidase (PPO, EC 1.14.18.1) was isolated from artichoke head (Cynara scolymus L.) by using 0.1 M Tris-HCl buffer (pH 7.0), concentrated by (NH4)(2)SO4 precipitation, and immobilized in copper-alginate beads. Immobilization yield was determined to be 70%. The cresolase and catecholase activities of enzyme immobilized at optimum immobilization conditions were found to be 13.3 and 670 U g beads minÖğe Some biochemical properties of lipase from bay laurel (Laurus nobilis L.) seeds(Wiley, 2008) Isbilir, Sebnem Selen; Ozcan, Hakki M.; Yagar, HulyaLipase was isolated from bay laurel (Laurus nobilis L.) seeds, some biochemical properties were determined. The bay laurel oil was used as the substrate in all experiments. The pH optimum was found to be 8.0 in the presence of this substrate. The temperature optimum was 50 degrees C. The specific activity of the lipase was found to be 296 U mg protein(-1) in optimal conditions. The enzyme activity is quite stable in the range of pH 7.0-10. The enzyme was stable for 1 h at its optimum temperature, and retained about 68% of activity at 60 degrees C during this time. K-m and V-max values were determined as 0.975 g and 1.298 U mg protein(-1), respectively. Also, storage stability and metal effect on lipolytic activity were investigated. Enzyme activity was maintained for 9, 12, and 42 days at room temperature, 4 and -20 degrees C, respectively. Ca2+, Co2+, Cu2+, Fe2+, and Mg2+ lightly enhanced bay laurel lipase activity.