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Öğe ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES OF WHITE, GREEN AND BLACK TEA EXTRACTS(Akademiai Kiado Zrt, 2013) Orak, H. H.; Yagar, H.; Isbilir, S. S.; Demirci, A. S.; Gumus, T.In the present study, the antioxidant and antimicrobial activities of three tea (Camellia sinensis) types (white tea WT, green tea - GT, and black tea - BT) were compared and the relationships between total phenolic, tannin and flavonoid contents were determined. Regardless of the assays used, the highest total phenolic content (313.3 +/- 1.41 mu g GAE/mg extract), total flavonoid (16.98 +/- 0.27 mu g QE/mg extract) and total tannin content (266.79 +/- 2.59 mu g TAE/mg extract) were determined in green tea extract, which also demonstrated the highest antioxidant capacity. Black tea extract showed the lowest phenolic content and antioxidant capacity. The EC50 value of DPPH scavenging activity was in the order of: ascorbic acid >GT>BHA>WT>BT>BHT. While the tea extracts exhibited antibacterial activity against Staphylococcus aureus, no inhibitory effects were observed against Escherichia coli and Salmonella enteritidis. All extracts exhibited antifungal activity against two aflatoxigenic moulds Aspergillus parasiticus NRRL 2999 and NRRL 465. The antibacterial activity of tea extracts decreased in the following order: GT>WT>BT DPPH scavenging activity strongly correlated with total phenolic content, reducing power, antimicrobial activity against S. aureus, A. parasiticus NRRL 2999, A. parasiticus NRRL 465 (P<0.05). These data suggest that green tea extract is more effective than white and black tea extracts as a potential source of natural antioxidants.Öğe Decolorization of Reactive Blue-19 textile dye by Boletus edulis laccase immobilized onto rice husks(Springer, 2020) Tuncay, D.; Yagar, H.Reactive Blue-19 is one of the most important synthetic dyes, which is used in the different industrial processes, especially for textile industry. Due to its fused aromatic structure, it is regarded as a toxic organic pollutant in wastewater. In the present study, the decolorization activity of Boletus edulis laccase immobilized onto rice husks for Reactive Blue-19 was examined. Boletus edulis, an edible mushroom, was used as a laccase source for the first time. Laccase was immobilized onto the rice husks which are inexpensive support having lignocellulose structure by using a simple method. The operating conditions of immobilized laccase were optimized for dye decolorization, and the decolorization activity of immobilized laccase was determined to be 91% for Reactive Blue-19 with initial concentration of 100 mg/L kept in 0.1 M of citrate phosphate buffer solution (pH 3.5) for 1 h at 25 degrees C. The decolorization of Reactive Blue-19 catalyzed by immobilized laccase was monitored by ultraviolet-visible spectroscopy analysis. The results of reusing studies showed that immobilized laccase retains approximately 50% of its initial decolorization activity after 9 cycles. Also, the effects of some auxiliary chemicals and metal ions found in textile wastewaters were investigated for decolorization process. In the reaction medium, containing 10 mM Fe2+ and 10 mM Tween 80, the decolorization activity decreased to 76% and 80.8%, respectively. The remarkable decolorization activity of immobilized laccase showed that it has a high potential for the treatment of textile wastewaters.Öğe Effects of hot air and freeze drying methods on antioxidant activity, colour and some nutritional characteristics of strawberry tree (Arbutus unedo L) fruit(Sage Publications Ltd, 2012) Orak, H. H.; Aktas, T.; Yagar, H.; Isbilir, S. Selen; Ekinci, N.; Sahin, F. HasturkAntioxidant activity, colour and some nutritional properties of hot air and freeze-dried strawberry tree (Arbutus unedo L.) fruits were investigated. Additionally, the effects of two pre-treatments, namely ethyl oleate and water blanching, were compared in terms of drying characteristics. For determination of antioxidant activities in ethanol extracts, two different analytical methods were used: 1,1-diphenyl-2-picrylhydrazyl scavenging activity and beta-carotene bleaching activity. As a result, the ethyl oleate pre-treatment shortened the drying time by hot air method and gave a higher 1,1-diphenyl-2-picrylhydrazyl scavenging activity (82.16 +/- 0.34%), total phenolic content (7.62 +/- 1.09 mu g GAE/g extract), ascorbic acid content (236.93 +/- 20.14 mg/100 g), besides hydromethylfurfural was not observed. Freeze- dried fruits exhibited higher ascorbic acid content (368.63 +/- 17.16 mg/100 g) than those fresh fruits (231.33 +/- 19.51 mg/100 g) and nearly 1,1-diphenyl-2- picrylhydrazyl activity (93.52 +/- 0.41 %) to fresh fruits (94.03 +/- 1.18%). Colour characteristics, sugar content and mineral contents of fruits were significantly affected by pre-treatments and drying methods (p < 0.05). It is concluded that the drying of strawberry tree fruits should bring a valuable and attractive foodstuff to food industry due to the rich nutritional components, antioxidant activity and colour. Another conclusion from this study is that the freeze-drying is the best drying method to keep the nutritional value, antioxidant activity and sensory properties of fruits.Öğe MAO Inhibitory Activity of Xanthones from Dichloromethane Extract of Polygala supina(Georg Thieme Verlag Kg, 2011) Esen, H.; Demirkiran, O.; Yagar, H.; Topcu, G.[Abstract Not Available]
