Browsing by Author "Özkan O.E."

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Chemical contents and antifungal activity of some durable wood extractives vs. Pleurotus ostreatus
(2015-01-01) Ates S.; Gür M.; Özkan O.E.; Akça M.; Olgun Ç.; Güder A.
The total phenolic content (TPC), total flavonoid content (TFC), phenolic compounds, and antifungal activity of olive (Olea europaea var. sylvestris) and juniper (Juniperus foetidissima) sapwood and heartwood extractives were examined. The extractives were obtained using methanol solvents. The different compounds in extractives were identified and quantified. The antifungal activities of different parts of the olive and juniper wood extractives were determined in vitro. Pleurotus ostreatus mycelium was used for the antifungal activity experiment. Extractive compounds obtained from olive and juniper woods were found to be effective, natural antifungal agents.
Coating performances of crimean juniper (juniperus excelsa M. Bieb.) wood
(2019-01-01) Öncel M.; Vurdu H.; Kaymakçi A.; Özkan O.E.; Aydogan H.
The purpose of this study is to determine the varnish layer hardness and varnish adhesion strength of the varnished Crimean juniper (Juniperus excelsa M. Bieb.) wood growing naturally in the Kastamonu region of Turkey. Test samples were varnished with UV-resistant polyurethane alkyd resin high gloss varnish (PAV) and water-based acrylic resin gloss varnish (WBAV). The varnish adhesion strength test was carried out by using universal testing machine. The varnish layer hardness was measured by using König pendulum hardness tester. Additionally, the colour properties were measured by spectrophotometer equipment that used the L*a*b* colour space. The adhesion strength of the polyurethane varnish and the water-based varnish were determined 2.81 MPa and 2.25 MPa respectively. Surface hardness value for water-based varnish and polyurethane varnish were determined 71 and 25 oscillation respectively. Detecting the performance of polyurethane and water-based varnish applications for the Crimean juniper wood will provide guidance in which type of varnish will be better for finishing. As a result, in varnish applications of the wood, it is recommended that water-based acrylic varnish should be applied when surface hardness is required. In addition, polyurethane alkyd varnish should be applied when better surface adhesion strength is desired.
DNA protection, antioxidant, antibacterial and enzyme inhibition activities of heartwood and sapwood extracts from juniper and olive woods
(2015-08-21) Özkan O.E.; Zengin G.; Akça M.; Baloʇlu M.C.; Olgun Ç.; Altuner E.M.; Ateş S.; Aktümsek A.; Vurdu H.
In this study, DNA protective, antioxidant, antibacterial and enzyme inhibiting properties of methanol extracts obtained from juniper and olive heartwood and sapwood were determined. These extracts were tested by five antioxidant methods (DPPH scavenging, FRAP, CUPRAC, metal chelating and phosphomolybdenum). Generally, heartwood extracts of both species are more efficient for DPPH radical scavenging activity, cupric ion reducing activity, ferric reducing antioxidant power and metal chelating activity than sapwood extracts. When compared to heartwood extracts, sapwood extracts have larger inhibition zone in disk diffusion test. In addition, all extracts showed high antibacterial activity against Staphylococcus aureus. DNA protection of both extracts had a capacity to inhibit the DNA damage arisen from Fenton's reagent. The highest DNA protective activity was observed in juniper sapwood extract with 84%. Furthermore, other extracts also indicated more than 60% of DNA protective activity. Olive wood extracts displayed the strongest enzyme inhibition activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Although juniper heartwood extracts showed highest anti-amylase, anti-glucosidase and anti-tyrosinase effects, they had no ability for inhibition BChE. The methanol extracts of olive samples demonstrated the most antioxidant activity (DPPH, CUPRAC and FRAP). In addition, juniper samples showed the highest anti-amylase, anti-tyrosinase, metal chelating and DNA protective activity. According to these results, the extracts of juniper and olive wood can be considered as a source of natural bio active agents for dietary, pharmacological and medicinal applications. This research will also serve as a base for future studies about biological activities of wood extracts.
Effect of Freezing Temperature on Impact Bending Strength and Shore-D Hardness of Some Wood Species
(2022-01-01) Özkan O.E.
Wood is exposed to variable environmental conditions during its use. Low temperature is one of the most important environmental factors affecting the behavior of wood in use. Contrary to other mechanical properties, there are not enough studies on how the impact bending strength is affected during freezing of wood. This study evaluated the effect of various freezing temperatures (-20,-40,-78.5, and-196 °C) on the impact bending strengths of beech (Fagus orientalis Lipsky), Scotch pine (Pinus sylvestris L.), fir (Abies nordmanniana subsp. bornmulleriana), and spruce (Picea orientalis L.) wood in comparison with non-frozen wood (+20 °C). During the freezing, the impact bending strength generally increased in softwood species but decreased in hardwood. The highest drop in impact bending strength value of-30.6% was found at-196 °C for beech wood. For this reason, precautions should be taken when using beech wood at ultra-low temperatures, due to substantial decreases in impact bending strength values. The good impact bending strength properties of the softwood while frozen allows application in low temperature environments.
Effect of Freezing Temperature on Impact Bending Strength and Shore-D Hardness of Some Wood Species
(2022-01-01) Özkan O.E.; Ozkan, OE
Wood is exposed to variable environmental conditions during its use. Low temperature is one of the most important environmental factors affecting the behavior of wood in use. Contrary to other mechanical properties, there are not enough studies on how the impact bending strength is affected during freezing of wood. This study evaluated the effect of various freezing temperatures (-20,-40,-78.5, and-196 °C) on the impact bending strengths of beech (Fagus orientalis Lipsky), Scotch pine (Pinus sylvestris L.), fir (Abies nordmanniana subsp. bornmulleriana), and spruce (Picea orientalis L.) wood in comparison with non-frozen wood (+20 °C). During the freezing, the impact bending strength generally increased in softwood species but decreased in hardwood. The highest drop in impact bending strength value of-30.6% was found at-196 °C for beech wood. For this reason, precautions should be taken when using beech wood at ultra-low temperatures, due to substantial decreases in impact bending strength values. The good impact bending strength properties of the softwood while frozen allows application in low temperature environments.
Effect of post-heat treatment on fire retardant treated wood properties
(2022-07-01) Özkan O.E.; Temiz A.; Tor Ö.; Vurdu H.
In this study, Anatolian black pine (Pinus nigra subsp. pallasiana) was treated with fire retardants of 10, 20, and 30% aqueous solutions composed of di-ammonium phosphate (DAP), borax, boric acid, and glucose to determine the effectiveness of these chemicals in preventing the spread of fire. The treated wood was subjected to post-heat treatment at 120, 150, and 180 °C for 1 h to examine the effects of the post-heat treatment on pH changes, anti-swelling efficiency, water absorption, mechanical strength, accelerated weathering, leaching resistance, thermogravimetric analysis (TGA), UL-94 vertical burning test and crystallinity index. The post-heat treatment of fire-retardant treated wood reduced water intake and increased dimensional stability, while also improving mechanical and thermal properties in general. DAP/glucose complexes promote phosphorus fixation in wood and reduce leaching, resulting in long-term fire protection of wood in service. Because of these improvements in the post-heat treated wood by impregnated fire retardant, it can potentially be used as a reliable engineering material in a wide range of structural applications.
Effects of cryogenic temperature on some mechanical properties of beech (Fagus orientalis Lipsky) wood
(2021-03-01) Özkan O.E.; Ozkan, OE
It is important to know the changes in the mechanical properties of wood during freezing for engineering calculations of the wood material to be used in cold environments. Although this is important, the mechanical properties of wood at temperatures below − 100 °C have rarely been studied. In this study, the effects of cryogenic temperature (− 196 °C) on the bending strength, modulus of elasticity in bending and compression strength parallel to the grain of oven-dried and air-dried beech wood was investigated. As a result of the experiment, the mechanical strength properties of the wood increased during freezing. The increase in bending strength and modulus of elasticity values were higher in air-dried wood than those in oven-dried wood. However, the increase in compression strength values was determined at the same rates as 61% for air-dried and oven-dried wood. This increase in mechanical strength properties of wood during freezing could be explained by freezing of water in the wood, hardening of wood cell walls, decreasing intermolecular distance, increasing intermolecular force and stabilization of crystalline structure.
Effects of cryogenic temperature on some mechanical properties of beech (Fagus orientalis Lipsky) wood
(2021-03-01) Özkan O.E.
It is important to know the changes in the mechanical properties of wood during freezing for engineering calculations of the wood material to be used in cold environments. Although this is important, the mechanical properties of wood at temperatures below − 100 °C have rarely been studied. In this study, the effects of cryogenic temperature (− 196 °C) on the bending strength, modulus of elasticity in bending and compression strength parallel to the grain of oven-dried and air-dried beech wood was investigated. As a result of the experiment, the mechanical strength properties of the wood increased during freezing. The increase in bending strength and modulus of elasticity values were higher in air-dried wood than those in oven-dried wood. However, the increase in compression strength values was determined at the same rates as 61% for air-dried and oven-dried wood. This increase in mechanical strength properties of wood during freezing could be explained by freezing of water in the wood, hardening of wood cell walls, decreasing intermolecular distance, increasing intermolecular force and stabilization of crystalline structure.
New 1,3,4-thiadiazole compounds including pyrazine moiety: Synthesis, structural properties and antimicrobial features
(2017-07-05) Gür M.; Şener N.; Muğlu H.; Çavuş M.S.; Özkan O.E.; Kandemirli F.; Şener İ.
In the study, some new 1,3,4-thiadiazole compounds were synthesized and we have reported identification of the structures by using UV-Vis, FT-IR, 1H NMR, 13C NMR and Mass spectroscopic methods. Antimicrobial activities of the compounds against three microorganisms, namely, Candida albicans ATCC 26555, Staphylococcus aureus ATCC 9144, and Escherichia coli ATCC 25922 were investigated by using disk diffusion method. These thiadiazoles exhibited an antimicrobial activity against Staphylococcus aureus and Candida albicans. The experimental data was supported by the quantum chemical calculations. Density functional theory (DFT) calculations were carried out to obtain the ground state optimized geometries of the molecules using the B3LYP, M06 and PBE1PBE methods with 3–21 g, 4–31 g, 6–311++g(2d,2p), cc-pvtz and cc-pvqz basis sets in the different combinations. Frontier molecular orbitals (FMOs) energies, band gap energies and some chemical reactivity parameters were calculated by using the aforementioned methods and basis sets, and the results were also compared with the experimental UV-Vis data.
Some Important Plants for Epilepsy Treatment: Antioxidant Activity and Flavonoid Compositions
(2018-12-01) Gür M.; Güder A.; Verep D.; Güney K.; Özkan O.E.; Seki N.; Kandemirli F.
Epilepsy, a disorder of the brain, is a major health problem that the widespread availability and use of herbal medicines raise the potential for adverse effects in the epilepsy population. Although many synthetic antiepileptic drugs are available in operation, their efficiency does not verify with the all population suffering from this disorder because of the major restrictions such as side effects and the drug interactions in its clinical utility. This paper is concerned with antioxidant activity, total phenolic and flavonoid contents and flavonoid composition of the 14 plants for three different solvents (water, ethanol and hexane). For this reason, FRAP, DPPH free radical scavenging, metal-chelate and H2O2 scavenging activities were investigated. In addition, total phenolic and flavonoid contents of extracts were determined via spectroscopic techniques. Lastly, composition of catechin, epicatechin, rutin, naringin, myricetin, luteolin, naringenin and apigenin was found with normal-phase HPLC in the obtained extracts. Extracts of fourteen plants taxa foreseen in having antioxidant and antiepileptic features were obtained with soxhlet extraction using different solvents, i.e., water, ethanol and hexane in this study. The extracts of 14 plant taxa were acquired: French lavender (Lavandula stoechas L.—inflorescence), Valerian (Valeriana officinalis L.—herb), Syrian rue (Peganum harmala L.—seeds), Liquorice (Glycyrrhiza glabra L.—roots), Boxwood (Buxus sempervirens L.—leaves), Chicory (Cichorium intybus L.—herb), Marjoram (Origanum majorana L.—leaves), Lemon balm (Melissa officinalis L.—leaves), Prickly juniper (Juniperus oxycedrus L.—fruits), Wild camomile (Anthemis cotula L.—flowers), Oats (Avena sativa L.—herb), Coriander (Coriandrum sativum L.—seeds), Flax (Linum usitatissimum L.—seeds) and Marijuana (Cannabis sativa L.—seeds)”. The antioxidant capacities of plant extracts were assayed with four different assays including FRAP, metal chelating, H2O2, DPPH scavenging because the antioxidant capacity cannot be fully described by a single method. The determined flavonoid amounts are between 3.85 and 694-47 (catechin), 2.70 and 2045.49 (epicatechin), 0.12 and 47.11 (rutin), 0.02 and 24.99 (naringin), 0.80 and 153.19 (myricetin), 0.03 and 7.80 (luteolin), 0.02 and 4.75 (naringenin) and 0.38 and 2.73 (apigenin) as µg g−1 plant. These plant materials and their flavonoid components via gamma-aminobutyric acid (GABA) and GABAA receptors can be therapeutical due to their different mechanism on treatment of epilepsy.
Synthesis and characterization of 1,3,4-thiadiazole compounds derived from 4-phenoxybutyric acid for antimicrobial activities
(2018-12-15) Muğlu H.; Şener N.; Mohammad Emsaed H.A.; Özkınalı S.; Özkan O.E.; Gür M.
New 1,3,4-thiadiazole compounds were synthesized through the cyclization reaction of 4-phenoxybutyric acid and N-phenylthiosemicarbazide derivatives with phosphorous oxychloride. The structures of 1,3,4-thiadiazole compounds (I–XII) were clarified using spectroscopic methods such as FT-IR, 1H NMR, and 13C NMR. Moreover, their antibacterial activities were tested against gram negative bacteria (Salmonella enteritidis, Salmonella typhimurium, Enterobacter aerogenes, Salmonella infantis, Salmonella kentucky, Escherichia coli) and gram positive bacteria (Staphylococcus aureus, Bacillus subtilis, Enterococcus durans) using a disk diffusion method. An antifungal activity experiment was further carried out against Candida albicans using the disk diffusion method. While these compounds presented antibacterial activity against S. aureus, they did not show antimicrobial activity against gram negative (E. coli, E. aerogenes, S. kentucky, S. enteritidis, S. typhimurium, S. infantis) and gram positive (B. subtilis) bacteria, and the fungi C. albicans.
Synthesis and characterization of some new 1,3,4-thiadiazole compounds derived from 3,4-(Methylenedioxy)cinnamic acid and their antimicrobial activities
(2019-01-01) Muğlu H.; Gür M.; Hsin M.A.M.B.; Şener N.; Özkınalı S.; Özkan O.E.; Şener İ.
Some new 1,3,4-thiadiazole compounds derived from 3,4-(methylenedioxy)cinnamic acid were synthesized in this study. Their structures were determined using UV-Vis, IR,1H-NMR, and13C-NMR spectroscopy. Moreover, the antibacterial activities of the new 1,3,4-thiadiazole derivatives were tested against Gram positive (Enterococcus durans, Bacillus subtilis, and Staphylococcus aureus) and gram negative (Salmonella typhimurium, Escherichia coli, Salmonella enteritidis, Salmonella in-fantis, Salmonella kentucky, Enterobacter aerogenes) bacteria using the disk diffusion method. Furthermore, their antifungal activity was tested against Candida albicans using the disk diffusion method. Some of the synthesized compounds (V, VII, XIII, and XIV) showed antibacterial activity against S. aureus. Also, one synthesized compound (VIII) showed antibacterial activity against E. coli, exhibiting 8 and 9 mm inhibition zones using 50 and 80 µL. One compound (IX) showed antibacterial activity against E. aerogenes, exhibiting a 12 mm inhibition zone using 80 µL. One compound (XIII) showed antibacterial activity against S. kentucky, exhibiting an inhibition zone of about 9 mm using 80 µL. Also, one compound (VII) showed antibacterial activity against E. durans, exhibiting 7, 7, and 8 mm inhibition zones using 30, 50, and 80 µL. None of the compounds (I-XV) showed antifungal activity against C. albicans. These results showed that some of the synthesized compounds could be used as antibacterial agents.
Synthesis and Characterization of Some New Heteroaromatic Compounds Having Chirality Adjacent to a 1,3,4-Thiadiazole Moiety and Their Antimicrobial Activities
(2017-11-01) Gür M.; Şener N.; Kaştaş Ç.A.; Özkan O.E.; Muğlu H.; Elmaswari M.A.M.
Through a cyclization reaction of 2-phenylbutyric acid with N-phenylthiosemicarbazide and POCl3, novel 1,3,4-thiadiazole derivatives were synthesized. Their structures were confirmed using IR, 1H NMR, and 13C NMR spectroscopies and elemental analysis. The antibacterial activities of the obtained 1,3,4-thiadiazole derivatives were tested against Gram-negative bacteria (Salmonella enteritidis, Salmonella typhimurium, Enterobacter aerogenes, Salmonella infantis, Salmonella kentucky, and Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, and Enterococcus durans) using a disk diffusion method. Moreover, an antifungal activity experiment was performed against Candida albicans using the disk diffusion method. It was observed that the synthesized 1,3,4-thiadiazole derivatives exhibited effective antimicrobial activity against S. aureus, E. coli, and C. albicans. Based on these results, the 1,3,4-thiadiazole derivatives can be considered as a source of bioactive agents for pharmacological and medicinal applications.