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Articles by Mehmet Guvenc
Total Records ( 6 ) for Mehmet Guvenc
  Okkes Yilmaz , Serhat Keser , Mehmet Tuzcu , Mehmet Guvenc , Buket Cetintas , Sevgi Irtegun , Hakki Tastan and Kazim Sahin
  Glutathione is a tripeptide ubiquitously distributed in living cells, which play an important role in the intracellular protective mechanism against oxidative stress. There are many methods for glutathione analysis including spectrophotometric, fluorometric and bioluminometric assays, often applied to HPLC. In this study, an improved and modified method to measure reduced and oxidized glutathione (GSH and GSSG, respectively) concentrations in animal tissues has been developed. In the study, quail and rat tissue samples were homogenized with the mixture of 10 mM ETDA and 50 mM NaClO4 0.1% H3PO4 buffer. Proteins were precipitated by the addition 5% metaphosphoric acid. 50 mM NaClO4 0.1% H3PO4 was used as mobile phase and Discovery RP-Amide C16 was used as HPLC column. Glutathione molecules were separated at 215 nm by the UV detector. GSH molecule was eluded between 2.3 and 3 min and GSSG molecule was eluted between 3.5 and 4.5 min from the column. It was observed that in low level of glutathione molecules was detected by this process. Recovery rates of GSH and GSSG were 99.32 and 90.29%, respectively. In conclusion, this method is speed, sensitive and achieved since, it doesn’t need forward derivatization process in contrast to many HPLC methods used for glutathione analysis.
  Ayse Dilek Ozsahin , Mehmet Guvenc , Okkes Yilmaz , Abdullah Aslan and Mehmet Tuzcu
  Molasses contains a variety of ions, vitamins and sugar, it is considered as a good source of nutrient. In this study, we aimed to investigate the effects of molasses samples (produced from 2 different crop supplies) on the Saccharomyces cerevisiae FMC-16 culture. For this purpose, control yeast cell cultures that contained mulberry and grape molasses were prepared. In the control group, glucose was used as a source for sugar and in the other group, molasses samples were used. In our result, it was found that the α-tocoferol decreased in the grape molasses group. Ergesterol decreased in the group to which, mulberry molasses was added, when compared to the control group. Linoleic acid increased in the groups, in which molasses was added when compared to the control group. Palmitic acid ascended in mulberry molasses culture media but decreased in the grape molasses media. Palmitoleic acid decreased in the grape molasses group and oleic acid, a decrease in both molasses media was observed when compared to the control group. Consequently, it was found that molasses samples added to the development media of Saccharomyces cerevisiae FMC-16 instead of glucose caused differences on the synthesis of some vitamins and fatty acids.
  Mehmet Tuzcu , Sevgi Irtegun , Okkes Yilmaz , Mehmet Guvenc , Orhan Erman and Kazim Sahin
  The aim of this research was to examine the effects of (+)-catechin on the levels of Malondialdehyde (MDA), homocysteine, vitamin C, cholesterol, GSH, GSSG and lipophilic vitamins in serum and erythrocytes of old and ovariectomized rats after exposure to the carcinogen potassium bromate. Female Wistar rats (n = 30) were randomly divided into 3 groups. The 1st group was used as a control, the 2nd group was treated with KBrO3 and 3rd group received C + KBrO3. Rats in the KBrO3 and C + KBrO3 groups were injected intraperitoneally with a single dose of KBrO3 (80 mg kg-1) in physiological saline. After 2 days, those in the C + KBrO3 group were intraperitoneally injected with catechin (30 mg kg-1) 4 times week-1. Physiological saline was injected into the control group rats. The results indicate that the serum cholesterol level in the KBrO3 group was higher than in the other 2 groups (p<0.01). MDA level was lower in the C + KBrO3 group than the others (p<0.001). The amount of α-tocopherol increased in the KBrO3 treated groups (p<0.05, p<0.01). Vitamins C and D2 levels were higher in the KBrO3 and C + KBrO3 groups than the control group (p<0.001). In erythrocytes, the cholesterol level decreased in the KBrO3 group and the vitamin D3 level decreased in the C + KBrO3 group (p<0.005). MDA level in the KBrO3 group was higher than the control and C + KBrO3 group (p<0.05). GSH, GSSG and α-tocopherol levels were lower in erythrocytes from the KBrO3 and C + KBrO3 groups than the control group (p<0.001). The GSH/GSSG ratio was high in the KBrO3 group; there was no difference between the control and C + KBrO3 groups. In conclusion, it can be said that administration of catechin decreased MDA in the serum and erythrocytes of old and ovariectomized Wistar rats and prevented the decrease of erythrocyte cholesterol.
  Okkes Yilmaz , Mehmet Guvenc , Buket Cetintas , Mehmet Tuzcu , Alpaslan Dayangac and Kazim Sahin
  Dietary soy isoflavones reduce hepatic 3-hydroxy-3-methylglutaryl CoA reductase and Delta six desaturase activities and isoflavone metabolites from diet may act as scavengers of reactive oxygen species. Since, dietary intake of soy isoflavones has been associated with reduced lipid perxidation, we investigated the effects of soy isoflavone supplementation on the cholesterol and fatty acid levels of muscle and liver tissue in Japanese quails (Coturnix coturnix japonica). One hundred and twenty quail (5 month old) were assigned to three experimental groups consisting of 10 birds in each group. Birds were fed either a basal diet or a basal diet supplemented with 200 or 800 mg of soy isoflavones/kg of diet. The animals were sacrificed after 10 month and the tissue samples werecollecetd and analyzed in HPLC and GC equipments. Muscle and liver fatty acid composition, palmitic acid (16:0), palmitoleic acid (16:1, n-9), oleic acid (18:1, n-9), linoleic (18:2, n-6) and linolenic acids (18:3, n-3) increased (p<0.001), whereas, stearic acid (18:0) (p<0.001) eicosatrienoic (20:3, n-6), arachidonic (20:4, n-6) and eicosapentaenoic acids (20:5, n-3) docosahexaenoic acid level (226, n-3) concentrations decreased with soy isoflavone supplementation. Liver and muscle cholesterol concentrations decreased decreased with soy isoflavone supplementation (p<0.001). As a result, administration of isoflavones was seen to elevate the amount of monounsaturated fatty acids in both muscle and liver tissues, while, reducing the amount of polyunsaturated fatty acids. This suggests that isoflavones influence the liver enzymes taking part in the lipid metabolism.
  Yusuf Ozkan , Okkes Yilmaz , Mehmet Tuzcu , Gulsen Murat , Mehmet Guvenc , Ali Ihsan ozturk and Kazim Sahin
  In this study, the effects of dietary taurine (2-amino ethane sulphonic acid) (TAUR) and Gamma Amino Butyric Acid (GABA) on the levels of reduced glutathione (GSH), lipid and fatty acid composition in liver tissues of 3 and 8 months female wistar rats was evaluated. The rats (n = 48) were randomly assigned to 8 treatment groups consisting of 6 rats each. The rats (both 3 and 8 month old) were fed a basal diet (Control) or basal diet plus taurine given by drinking water (500 mg kg-1) (TAUR groups) or basal diet plus GABA given by drinking water (500 mg kg-1) (GABA) or basal diet plus the combinations of GABA and TAUR given by drinking water (500 + 500 mg kg-1) (GABA+TAUR groups). In 3 month old rats, the lipid level in GABA and GABA+TAUR groups was higher than control group (p<0.01). GSH level was high in the TAUR group (p<0.05). While, the lipid level increased in GABA group of 8 month old rats, its level decreased in TAUR group (p<0.05). The level of GSH in GABA, TAUR and GABA+TAUR groups was lower than control group (p<0.01). Oleic acid level (18:1, n-9) was high in TAUR group (p<0.05) and linoleic acid level (18:2, n-6) GABA and GABA+TAUR groups was higher than control group (p<0.01) in 3 month old rats. However, arachidonic acid level (20:4, n-6) in supplemented groups was lower than control group (p<0.01). While, the saturated fatty acid level increased in the supplemented groups, unsaturated fatty acid decreased in the same groups (p<0.05). In 8 month old rats, palmitic acid level (16:0) increased in supplemented groups (p 0.05), but stearic acid level decreased in the same groups. The levels of oleic and linoleic acids were high in GABA and GABA+TAUR groups. Arachidonic and docosahexaenoic acid levels in GABA and GABA+TAUR groups were lower than control group (p<0.01). The level of saturated fatty acid level was high in the GABA and TAUR groups, but the unsaturated fatty acid was low in the same groups (p<0.05). In conclusion, present study showed that the products of 6 desaturation pathway such as arachidonic acid was decreased by the GABA and taurine in 3 and 8 months old of female rats. Conversely, the products of steroil CoA desaturase were increased by dietary taurine treatment.
  Mehmet Guvenc , Mehmet Tuzcu and Okkes Yilmaz
  Fig. is a fibrous plant, which contains organic acids, provitamin A and vitamin C. It is widely consumed in both fresh and dried form in Turkey. In this study, we aimed to establish the fatty acid and lipophilic vitamin components of the fruits of the Ficus carica variety found in the province of Adiyaman, Turkey. For the analysis of the fig fruit of the Ficus carica variety, the whole fruit, the skin and the flesh were analyzed separately using High Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC). As a result of the analysis, on examining the fig fruit as a whole, several vitamins with lipophilic properties were identified. Upon analyzing different sections of the fruit, it was observed that the skin and the flesh had different vitamin and fatty acid contents. The fig fruit was found to be rich in terms of fatty acids as well as vitamin content. Primarily, it was identified that in addition to the non-essential fatty acids such as palmitic (16:0), stearic (18:0) and oleic (18:1 n-9) fatty acids, it also contained a significant level of essential fatty acids such as linoleic acid (18:2 n-6) and linolenic acid (18:3 n-3). In conclusion, the fig fruit was confirmed to have important nutrients in terms of human nutrition rather than just a fibrous food.
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