Ozkan Danis

Antioxidative and Lipid Lowering Effects of 7,8-Dihydroxy-3-(4-methylphenyl) Coumarin in Hyperlipidemic Rats

In this study, 7,8-dihydroxy-3-(4-methylphenyl) coumarin (DHMPC), a new coumarin derivative, was tested for the first time to determine whether it had any antioxidant and lipid lowering effects. Hypercholesterolemia was induced by feeding rats with a high cholesterol diet for 17 days. The lipid lowering and antioxidant effects of DHMPC were compared with those of hesperidin (CAS 520-26-3) and rutin (CAS 153-18-4), which have been pharmacologically determined as potential lipid lowering and antioxidant agents. DHMPC significantly decreased total cholesterol levels but not as efficient as hesperidin. When the ratios of high density lipoprotein-cholesterol (HDL-cholesterol) to total cholesterol were evaluated, the most significant changes were observed in DHMPC and rutin treatments. The results of serum triglyceride levels indicate that DHMPC and hesperidin did not significantly decrease triglyceride level when compared to rutin group but prevented it to rise. Serum malondialdehyde (MDA) levels increased as expected in high cholesterol diet groups but no significant decrease was observed for serum MDA levels in all treated groups. In contrast to serum MDA levels, liver homogenates MDA levels decreased in all treated groups but a considerable decrease was not observed for DHMPC treated group. Liver homogenates glutathione (GSH) levels drastically decreased in hyperlipidemic group and increased in all treated groups. As a conclusion DHMPC displayed both antioxidant and lipid lowering effects and can be a candidate drug for further studies.

Production of cellulase by immobilized whole cells of Haloarcula

Halophilic Archaea are adapted to a life in the extreme conditions and some of them are capable of growth on cellulosic waste as carbon and energy source by producing cellulase enzyme. The production of cellulase using free and immobilized cells of halophilic archaeal strain Haloarcula 2TK2 isolated from Tuzkoy Salt Mine and capable of producing cellulose was studied. The cells were cultured in a liquid medium containing 2.5 M NaCl to obtain the maximum cellulase activity and immobilized on agarose or polyacrylamide or alginate. Optimal salt dependence of free and immobilized cells of Haloarcula 2TK2 was established and the effects of pH and temperature were investigated. Immobilization to Na-alginate enhanced the enzymatic activity of the Haloarchaeal cells when compared to free cells and other polymeric supports. From the results obtained it is reasonable to infer that decomposition of plant polymers into simpler end products does occur at high salinities and cellulase producing haloarchael cells may be potentially utilized for the treatment of hypersaline waste water to remove cellulose.

Synthesis of selected 3- and 4-arylcoumarin derivatives and evaluation as potent antioxidants

A series of hydroxyl-, methoxy-, and acetoxy-substituted 3- and 4-arylcoumarins were synthesized. All title compounds were screened for their antioxidant capacity, ability to scavenge the 1,1-diphenyl-1-picrylhydrazyl (DPPH) radical, and ability to chelate iron ions. Furthermore, all derivatives were assessed using molecular properties prediction and drug likeness using Molinspiration. It was found that all studied derivatives were potential candidates for further research, as they complied with Lipinski’s rule of five for drug likeness. 3- or 4-arylcoumarins that possess two hydroxyl groups in ortho position, such as 4h, 5b, h, and 6a, had remarkable half-maximal effective concentration (EC50) for radical scavenging, with better performance than known antioxidants in DPPH and metal-chelating assays. In addition, the cupric-reducing antioxidant capacity and ferric-reducing antioxidant power of the synthesized compounds were investigated for antioxidant activity. Among them, 5g, h and 6a, b showed significantly better Trolox equivalent antioxidant capacity (TEAC) than standard compounds. The results demonstrate that the compounds with dihydroxyl groups at 6- and 7-positions of the benzopyrone ring of the arylcoumarin structure are the most active of the series as antioxidants. On the basis of these findings, these new coumarin derivatives are potential therapeutic candidates for pathogenesis of many diseases characterized by free-radical overproduction.

In Vitro Inhibition of Human Placental Glutathione S‐Transferase by 3‐Arylcoumarin Derivatives

Glutathione S‐transferases (EC: 2.5.1.18, GSTs) are phase II detoxification enzymes that catalyze the conjugation of various electrophilic compounds to glutathione (GSH), thus usually producing less reactive and more water soluble compounds. However, there is evidence that elevated expression of GSTs, especially GSTP1, is involved in the resistance of tumor cells against chemotherapeutic agents. In this study, we synthesized and investigated the inhibitory effects of differently substituted 3‐arylcoumarin derivatives on human placental GST, identified as GSTP1‐1, using 1‐chloro‐2,4‐dinitrobenzene as a substrate. A known potent inhibitor of GST, ethacrynic acid was used as a positive control. Among the tested compounds, 6,7‐dihydroxy substituted coumarin derivatives exhibited the highest inhibitory activity (IC50 = 13.50–20.83 μM). These results suggest that 6,7‐dihydroxy‐3‐arylcoumarins may represent a new promising scaffold to discover potent GST inhibitors.

Comprehensive structural analysis of the open and closed conformations of Theileria annulata enolase by molecular modelling and docking

Theileria annulata is an apicomplexan parasite which is responsible for tropical theileriosis in cattle. Due to resistance of T. annulata against commonly used antitheilerial drug, new drug candidates should be identified urgently. Enolase might be a druggable protein candidate which has an important role in glycolysis, and could also be related to several cellular functions as a moonlight protein. In this study; we have described three-dimensional models of open and closed conformations of T. annulata enolase by homology modeling method for the first time with the comprehensive domain, active site and docking analyses. Our results show that the enolase has similar folding patterns within enolase superfamily with conserved catalytic loops and active site residues. We have described specific insertions, possible plasminogen binding sites, electrostatic potential surfaces and positively charged pockets as druggable regions in T. annulata enolase.

QSAR models for antioxidant activity of new coumarin derivatives

This study presents 37 new antioxidant coumarin derivatives and strategies for structural modification to improve their antioxidant activities, the main ferric-reducing antioxidant power (FRAP) assay used to evaluate their antioxidant properties and the generation of validated quantitative structure–activity (antioxidant activity) relationship (QSAR) models. In an attempt to generate QSAR models, structures of all coumarin derivatives in the data set were fully optimized by semi-empirical PM6 method using SPARTAN 10 software. Descriptors were calculated by DRAGON 6.0 software. Multiple linear regression (MLR) models were developed with different training/test set combinations using QSARINS 2.2.1 software. Robustness, reliability and predictive power of the models were tested by internal and external validations. Applicability domain of the best two-descriptor model (nTR = 30; r2 = 0.924; RMSETR = 0.213; nTEST = 7; r2ext = 0.887; RMSEext = 0.255; CCCext = 0.939) was determined. Descriptors appeared in the model revealed that complexity, H-bond donor and lipophilic character are important parameters in describing the antioxidant activity. Apart from the compounds in the data set, we also designed 31 new antioxidant coumarin derivatives and predicted their antioxidant activity using the best two-descriptor model. Most of these compounds are promising antioxidants

Preparation, characterization, and in vitro evaluation of isoniazid and rifampicin‐loaded archaeosomes

The ability of Archaea to adapt their membrane lipid compositions to extreme environments has brought in archaeosomes into consideration for the development of drug delivery systems overcoming the physical, biological blockades that the body exhibits against drug therapies. In this study, we prepared unilamellar archaeosomes, from the polar lipid fraction extracted from Haloarcula 2TK2 strain, and explored its potential as a drug delivery vehicle. Rifampicin and isoniazid which are conventional drugs in tuberculosis medication were loaded separately and together in the same archaeosome formulation for the benefits of the combined therapy. Particle size and zeta potential of archaeosomes were measured by photon correlation spectroscopy, and the morphology was assessed by with an atomic force microscope. Encapsulation efficiency and loading capacities of the drugs were determined, and in vitro drug releases were monitored spectrophotometrically. Our study demonstrates that rifampicin and isoniazid could be successfully loaded separately and together in archaeosomes with reasonable drug‐loading and desired vesicle‐specific characters. Both of the drugs had greater affinity for archaeosomes than a conventional liposome formulation. The results imply that archaeosomes prepared from extremely halophilic archaeon were compatible with the liposomes for the development of stable and sustained release of antituberculosis drugs.

Polyhydroxyalkanoates Production from Renewable and Waste Materials Using Extremophiles/Recombinant Microbes

Polyhydroxyalkanoates (PHAs) are biodegradable polyesters produced by various species of Bacteria and Archaea as reserves of energy and carbon in nutrient poor environments. Being biodegradable and biocompatible, PHAs have found many industrial and medical applications as attractive bio-based alternatives to petroleum-based polymers. To compete with petroleum-based polymers and garner a bigger market share, cost-effective PHA production processes are needed. Therefore, renewable, cheap, sustainable, and readily available carbon sources from industrial wastes and agricultural by-products should be considered in PHA production.

A study of Bos taurus muscle specific enolase; biochemical characterization, homology modelling and investigation of molecular interaction using molecular docking and dynamics simulations

Tropical theileriosis caused by Theileria annulata obligate parasite that infect ruminant animals, including Bos taurus. The disease results massive economic losses in livestock production worldwide. Here we describe cloning, expression and both biochemical and structural characterization of beta enolase from Bos taurus in vitro and in silico. The interconversion of 2‑phosphoglycerate to phosphoenolpyruvate was catalyzed by enolase is a metalloenzyme in glycolytic pathway and gluconeogenesis. Enolase from Bos taurus was cloned, expressed and the protein was purified at 95% purity using cobalt column by affinity chromatography. The optimum enzymatic activity was calculated at pH 6.5. For the first time in the literature, the kinetic parameters of the enzyme, Vmax and Km, were measured as 0.1141 mM/min and 0.514 mM, respectively. Besides, Bos taurus enolase 3-dimensional structure was built by homology modelling to be used in silico analyses. The interactions of the enzyme-substrate complex were elucidated by molecular dynamics simulations for 100 ns. These interactions were found to be the same as experimentally determined interactions in yeast. These results would enable further structure based drug design studies with the biochemical characterization of the host organism Bos taurus enolase enzyme in vitro and the elucidation of behavior of enzyme-substrate complex in silico.

Proteomic changes in the cortex membrane fraction of genetic absence epilepsy rats from Strasbourg

Epilepsy is a serious neurodegenerative disorder with a high incidence and a variety of presentations and causes. Studies on brain from various animal models including chronic models: Genetic Absence Epilepsy Rats from Strasbourg (GAERS) are very useful for understanding the fundamental mechanisms associated with human epilepsy. Individual regions of the brain have different protein composition in different conditions. Therefore, proteomic analyses of the brain compartments are preferred for the development of new therapeutic targets in different pathophysiological conditions like neurodegenerative disorders. In this study, we describe a proteomic profiling of membrane fraction of cortex tissue from epileptic GAERS and non-epileptic Wistar rat brain by two-dimensional gel electrophoresis coupled with matrix-assisted laser desorption/ionization mass spectroscopy. Comparing the optical density of spots between groups, we found that one protein expression was significantly down-regulated (guanine nucleotide-binding protein G(I)/G(S)/G(T) subunit beta-1) and one protein expression was significantly up-regulated (14-3-3 protein epsilon isoform) in GAERS group. Our results indicate that these proteins might have played a significant role in epilepsy and may be considered as valuable therapeutic targets in the absence of epilepsy.