Ahmet Colak

Proximate composition and selected mineral content of commercially important fish species from the black sea

Proximate composition, selected mineral (Zn, Fe, Cd, As, Hg, Pb, Ni, Cu) content and fatty acid profiles were determined in some widely consumed fish species obtained from the Black Sea. All fish species analysed individually were fairly high in protein (14·1–25·1%) and lipid (7·4–18·4%). Moisture and ash content varied within a narrow range. The mineral content was highly variable. The most abundant microelements in fish were Zn and Fe followed by Cu, and the remaining elements were present in amounts below toxic levels. Eight fatty acids (16: 0, 16:1, n-7, 18: 0, 18:1 n-9, 18: 2 n-6, 20:1 n-9, 20: 5 n-3, 22: 6 n-3) represented more than 60% of the fatty acid content. Saturated fatty acids ranged from 25·8 to 45·1%. Anchovy and whiting contained almost 35% of polyunsaturated fatty acids. The percentage of docosahexaenoic acid (DHA) exceeded that of eicosapentaenoic acid (EPA) in almost all the fish species examined, and the actual content of these acids has shown that sprat, whiting, garfish, red mullet, shad and sea bream provide the recommended daily intake of 1 g of EPA+DHA with reasonable amounts of fillet. These results indicate that biological differences existing in fish species can influence the values to be set for the standards and composition.

DNA binding, antioxidant and antimicrobial activities of homo- and heteronuclear copper(II) and nickel(II) complexes with new oxime-type ligands.

Some homo- and heteronuclear Cu(II) and Ni(II) complexes of new oxime-type ligands were tested against several pathogenic microorganisms to assess their antimicrobial potentials. The antimicrobial activities of complexes were evaluated in terms of minimum inhibitory concentration (MIC; μg/μL) and it was observed that the complexes possess moderate antimicrobial properties. The binding of the complexes with DNA were also investigated by using UV-Vis spectroscopy. It was seen that three of the complexes could bind to DNA through an intercalative mode while the other complexes could have other mechanisms. Furthermore, the antioxidant efficiencies of the metal complexes were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavening activities. Due to the observed IC(50) values, they are potential drugs to eliminate the radicals.

Oxidative cleavage of DNA by homo- and heteronuclear Cu(II)-Mn(II) complexes of an oxime-type ligand

Novel homodinuclear Cu(II) (K1), heterodinuclear Cu(II)-Mn(II) (K2) and homotrinuclear Cu(II) (K3) complexes with a novel oxime-type ligand have been prepared and their nucleolytic activities on pCYTEXP were established by neutral agarose gel electrophoresis. The analyses of the cleavage products obtained electrophoretically indicate that although the examined complexes induces very similar conformational changes on supercoiled DNA by converting supercoiled form to nicked form than linear form in a sequential manner as the complex concentration or reaction period is increased, K3 is less effective than the two others. The oxime complexes were nucleolytically active at physiological pH values but the activities of K1 or K2 were diminished by increasing the pH of the reaction mixture. In contrast, K3 makes dominantly single strand nicking by producing nicked circles on DNA at almost all the applied pH values. Metal complex induced DNA cleavage was also tested for inhibition by various radical scavengers as superoxide dismutase (SOD), azide, thiourea and potassium iodide. The antioxidants inhibited the nucleolytic acitivities of the oxime complexes but SOD afforded no protection indicating that the nucleolytic mechanism involves of copper and/or manganese complex-mediated reactive oxygen species such as hydroxyl radicals being responsible for the oxidative DNA cleavage.

Copper(II)–manganese(II) complexes of 3,3′-(1,3-propanediyldiimine)bis-(3-methyl-2-butanone)dioxime with superoxide dismutase-like activity

Novel mononuclear [Cu(HPnAO)H2O]ClO4(2), homodinuclear [Cu(PnAO)Cu(phen)(H2O)2](ClO4)2(3), homotrinuclear [Cu3(PnAO)2(H2O)2](ClO4)2(4) and heterodinuclear [Cu(PnAO)Mn(phen)2(H2O)](ClO4)2(5) complexes have been prepared from 3,3′-(1,3-propanediyldiimine)bis-(3-methyl-2-butanone)dioxime (H2PnAO) and characterized by elemental analyses, magnetic moments, i.r., u.v.–vis., and by mass spectral studies. The geometry of the metal chelates is discussed with the help of magnetic and spectroscopic measurements. I.r. spectra show that the ligand acts in a tetradentate manner and coordinates through the (C=N) and (N—H) groups. The elemental analyses, stoichiometry and the spectroscopic data of the complexes indicate that the copper(II) ions are coordinated by the ligand dianion. The heterodinuclear complex (5) displays in vitro ability to scavenge superoxide radicals produced by the xanthine–xanthine oxidase (XXO) system, using nitroblue tetrazolium as an indicator. The complex also supports aerobic growth of Escherichia coli (sodA−sodB−) in vivo in minimal media, indicating that complex (5) is a speculative potent SOD-mimic.

Fatty acid and amino acid compositions of selected wild-edible mushrooms consumed in Turkey

The fatty acid and amino acid compositions of 11 mushroom species commonly consumed were collected from the East Black Sea region of Turkey and analyzed. All species were characterized by a high content of linoleic acid (C18:2n-6) and glutamic acid. The highest content of linoleic acid (78.0%) and glutamic acid (29.4 μg/mg dry weight [d.w.]) was found in Agaricus arvensis and the lowest in Cantharellus tubaeformis, 19.8% and 10.9 μg/mg d.w., respectively. The average content of amino acids for all species was 148 μg/mg d.w. Overall, these results demonstrate that the 11 different kinds of wild edible mushrooms gathered from the region represent substantial sources of fatty acids and amino acids that are essential in the diet of humans. Quality of the mushroom protein compares favorably with the FAO/WHO Standard. The present study demonstrates that macrofungi from the East Black Sea region (Turkey) are a good source of many nutrients essential to human well-being.

Purification and characterization of an extremely stable glucose isomerase from Geobacillus thermodenitrificans TH2.

The D-glucose/D-xylose isomerase was purified from a thermophilic bacterium, Geobacillus thermodenitrificans TH2, by precipitating with heat shock and using Q-Sepharose ion exchange column chromatography, and then characterized. The purified enzyme had a single band having molecular weight of 49 kDa on SDS-PAGE. In the presence of D-glucose as a substrate, the optimum temperature and pH of the enzyme were found to be 80°C and 7.5, respectively. The purified xylose isomerase of G. thermodenitrificans TH2 was extremely stable at pH 7.5 after 96 h incubation at 4°C and 50°C. When the thermal stability profile was analyzed, it was determined that the purified enzyme was extremely stable during incubation periods of 4 months and 4 days at 4°C and 50°C, respectively. The Km and Vmax values of the purified xylose isomerase from G. thermodenitrificans TH2 were calculated as 32 mM and 4.68 μmol/min per mg of protein, respectively. Additionally, it was detected that some metal ions affected the enzyme activity at different ratios. The enzyme was active and stable at high temperatures and nearly neutral pHs which are desirable for the usage in the food and ethanol industry.

Characterization of polyphenol oxidase during three ripening stages of an eggplant (Solanum melongena L.) fruit: a local type in northeast Anatolia

Abstract Objective: A relatively new cultivar of eggplant, Solanum melongena L. ‘Kadife’ is widely consumed in Turkey because of its economic availability and good nutritional qualities. However, the high polyphenol content of eggplant renders it susceptible to unattractive oxidative browning catalyzed by polyphenol oxides (PPOs). Therefore, the main aim of this study was to characterize PPO in this eggplant cultivar at three stages of its development. Methods: In this study, we determined substrate specificity, optimum pH and temperature, and optimum substrate concentration of the partial purified eggplant fruits PPO during ripening. Results: L-DOPA was proved to be the preferred PPO substrate in all three stages of ripening. Optimum activity was observed at pH 7.0 for PPO in extracts of ripening and overly-ripe eggplant, while activity in extracts of immature eggplant exhibited a broad pH optimum between, pH 5.0 and 7.0. In general, at all ripening stages, PPO was most active at 30°C and was most sensitive to inhibition by sodium metabisulphite and ascorbic acid. The metal ions (Hg2+, Mn2+, Fe3+ and Co2+) mostly inhibited PPO activities. Conclusion: These data regarding the properties of PPO should enhance understanding of the browning reaction in eggplant and lead to the development of techniques for controlling this undesirable process. Özet Amaç: Kısmen yeni bir patlıcan çeşidi olan Solanum melongena L. ‘Kadife’, ekonomik uygunluğu ve iyi besin kalitesinden dolayı Türkiye’de yaygın olarak tüketilir. Bununla birlikte, patlıcanın yüksek polifenol içeriği, bu meyveyi polifenol oksidaz (PFO) tarafından katalizlenen istenmeyen oksidatif esmerleşmeye karşı duyarlı kılar. Dolayısıyla, bu çalışmanın temel amacı, gelişiminin üç safhasında bu patlıcan kültivarındaki PFO’yu karakterize etmektir. Metod: Bu çalışmada, olgunlaşma boyunca patlıcan meyvelerinden elde edilen kısmi saflaştırılmış PFO’nun substrat özgünlüğünü, optimum pH ve sıcaklığını, ve optimum substrat konsantrasyonunu belirledik. Bulgular: Olgunlaşmanın her üç safhasında, L-DOPA’nın tercih edilen PFO substratı olduğu ortaya konuldu. Olgunlaşmamış patlıcan özütlerinde optimum pH 5.0 ile 7.0 arasında geniş bir aktivite gösterirken olgun ve aşırı olgun patlıcan özütlerindeki PFO aktivitesi için optimum pH’nın 7.0 olduğu gözlendi. Genel olarak, tüm olgunlaşma safhalarında, PFO, 30°C’de en aktiftir ve inhibitör olarak sodium metabisülfit ve askorbik aside oldukça duyarlıdır. Metal iyonları (Hg2+, Mn2+, Fe3+ ve Co2+) çoğunlukla PPO aktivitesini inhibe ettiler. Sonuç: PFO’nun özelliklerine ilişkin bu veriler, patlıcandaki esmerleşme reaksiyonunun anlaşılmasını arttırmalı ve istenilmeyen bu sürecin kontrolü için teknikler geliştirmeye öncülük etmelidir.

Effect of divalent metal ions on the microsomal aniline hydroxylase system of rainbow trout.

The ability of trout to metabolize aniline in vitro in the presence of some divalent metal ions was investigated in the liver microsomes of rainbow trout, Salmo gairdneri. Trout liver microsomes were highly capable of catalyzing aniline hydroxylation to p-aminophenol with a specific activity of 0.068 nmoles/ min per mg of microsomal protein in potassium phosphate buffer, pH 7.4 at 25 degrees C. The activity of the aniline hydroxylase system was competitively inhibited by Hg+2, Ni+2, Cd+2, and Zn+2, while Cu+2 and Fe+3 seemed to inhibit the activity noncompetitively at 1 mM aniline concentrations. IC50 values at fixed aniline concentration were estimated to be 0.45 mM for Hg+2, Ni+2, and Cd+2, 1.8 mM for Zn+2 and Fe+3, and 1.3 mM for Cu+2. Eadie-Hofstee plots gave identical Vmax values of approximately 0.046 nmol/min per mg of protein while K(m) values were increased in the presence of Hg+2, Ni+2, Cd+2, and Zn+2, indicating competitive inhibition. Both K(m) and Vmax values were affected by Fe+3 and Cu+2, suggesting noncompetitive inhibition. Ki values extracted from the Dixon plots were determined to be 0.23, 0.43, and 0.65 mM for Hg+2, Ni+2, and Cd+2, respectively, providing the most effective inhibition on the aniline hydroxylase system among studied metal ions. The Ki values were much higher in the presence of others. The results indicate a selective inhibition of the aniline hydroxylase system of trout liver microsomes by divalent metal ions.

Dephytinization of food stuffs by phytase of Geobacillus sp. TF16 immobilized in chitosan and calcium-alginate

ABSTRACT In this work, Geobacillus sp. TF16 phytase was separately immobilized in chitosan and Ca-alginate with the efficiency of 38% and 42%, respectively. These enzymes exhibited broad substrate specificity. Maximal relative phytase activity was measured at pH 5.0 and 95°C and pH 3.0 and 75°C for chitosan and Ca-alginate, respectively. The enzymes were highly stable in a wide pH and temperature range. Values of Km and Vmax were determined as 2.38 mM and 3401.36 U/mg protein for chitosan, and 7.5 mM and 5011.12 U/mg protein for Ca-alginate. The immobilized enzymes showed higher resistance to proteolysis. After 4 h incubation, hydrolysis capacities of chitosan- and Ca-alginate immobilized enzymes for soymilk phytate were calculated as 24% and 33%, respectively. The chitosan- and Ca-alginate immobilized phytases conserved its original activity after 8 and 6 cycles of reuse, respectively. The features of the enzymes were very attractive and they might be useful for some industrial applications.

Synthesis of 1,2,4-triazole-5-on derivatives and determination of carbonic anhydrase II isoenzyme inhibition effects

Carbonic anhydrase (CA) II plays major roles in pH regulation of body, protection of electrolyte balance, transportation of water and some metabolic pathways. Therefore, CA II inhibitors are very important molecules for drug design and have many pharmacological applications. CA II as a target molecule is also important for eliminating some pathological conditions such as glaucoma, cancer, epilepsy, ulcer and obesity. In this study, some 1,2,4-triazole derivatives were synthesized and CA II inhibition potentials of these molecules were examined. It has been found that molecule 7c was the most potent inhibitor with the lowest IC50 value at micromolar level among the examined molecules. The inhibition in the range of 18.41-64.97% was seen in the presence of newly synthesized molecules at their reachable maximum concentration in the reaction mixtures. Kinetic studies showed that the inhibition mechanism of compound 7c on carbonic anhydrase activity was reversible and uncompetitive. Molecular docking studies also indicated that compound 7c could bind to the active site of the enzyme by weakly interacting with especially Gln102, Leu240, Ala241 and Trp243. ADME properties of these newly synthesized (3a-e, 6, 7a-e) were also studied and showed good oral drug candidate like properties.