Ahmet Gültek

Caffeic acid phenethyl ester prevents intestinal reperfusion injury in rats

BACKGROUND/PURPOSE Ischemia-reperfusion injury is encountered frequently in conditions that diminish intestinal blood flow. Caffeic acid phenethyl ester (CAPE), which is a specific component of the honeybee hive product propolis, exhibits potential antioxidant properties. This experimental study was designed to determine the effect of CAPE on ischemia-reperfusion injury in rat intestine. METHODS Fifty rats were divided into 5 groups; sham (SH), saline ischemia (SI), saline reperfusion (SR), CAPE ischemia (CI), and CAPE reperfusion (CR). Either CAPE, 10 micromol/kg, or saline was administered intraperitoneally 30 minutes before ischemia. Intestinal ischemia for 30 minutes and reperfusion for 60 minutes were applied. Ileum specimens were obtained to determine the tissue levels of malondialdehyde, superoxide dismutase, catalase, and histological changes. RESULTS Malondialdehyde levels in the CR group did not increase after reperfusion when compared with the CI group. However, statistically significant differences were observed between the SR and SI groups. Additional mucosal injury in the CR group when compared with the CI group was not observed. Whereas, there was a statistically significant increase in mucosal injury in the SR group. Reperfusion did not cause further injuries through both biochemical and histological parameters in the CR group. CONCLUSIONS Results of this study showed that prophylactic administration of CAPE in ischemic condition prevents reperfusion injuries by eliminating oxygen radicals and inhibiting polymorphonuclear leukocyte infiltration. CAPE may be useful in combating the diseases of oxidative stress.

Caffeic acid phenethyl ester to inhibit posterior capsule opacification in rabbits

Purpose: To assess whether caffeic acid phenethyl ester (CAPE) prevents posterior capsule opacification (PCO) by suppressing the transformation of the lens epithelial cells. Setting: Departments of Ophthalmology, Chemistry, and Pathology, Turgut Ozal Medical Center, University of Inonu, Malatya, Turkey. Methods: Twenty pigmented island rabbits having phacoemulsification in their right eyes were randomized into two groups. In Group 1, 10 Fig/ml of CAPE was added to the anterior chamber irrigating solution and a 1 % solution of CAPE was injected subconjunctivally for 3 weeks postoperatively. The irrigating solution in Group 2 (control) did not include CAPE. The development of PCO was assessed weekly and its density was graded by slitlamp biomicroscopy. Histologic analysis was performed 3 months after surgery. Results: Group 1 had clear capsules or minor PCO. Group 2 developed more severe PCO or complete opacification. The difference between the two groups was statistically significant (P = .04). Conclusion: These preliminary results indicate that CAPE is effective in suppressing PCO in pigmented rabbits and may be beneficial in clinical use in humans because it has no documented harmful effects on normal cells.

The grafting of Rhodamine B onto sol-gel derived mesoporous silicas

Amorphous meseporous silica, silica foams and silica nanotubes have been prepared by the controlled hydrolysis of tetraethoxysilane in various environments. A self-similar structure was obtained in all cases. Rhodamine B was post grafted onto the meseporous silica foam which has been modified with γ-glycidyloxypropyl trimethoxysilane. The grafting and post grafting efficiency of γ-glycidyloxypropyl trimethoxysilane as well as the post grafting efficiency of Rhodamine B on meseporous silica foam were studied, respectively. Basic physicochemical properties of the modified particles are given. When the hybrid pigments were exposed to UV radiation pulses, the emission of the hybrid pigments was increased.

Effect of caffeic acid phenethyl ester on corneal neovascularization in rats

Purpose. Caffeic acid phenethyl ester (CAPE), a biologically active component of propolis from honeybee hives, has potent antiinflammatory and antioxidant properties. We aimed to evaluate the ability of topically applied CAPE in comparison with known steroidal (dexamethasone sodium phosphate) and nonsteroidal (indomethacin) topical agents to reduce corneal neovascularization (CNV) induced by silver nitrate cauterization in rats. Methods. Following silver nitrate cauterization on both eyes, male rats were randomly assigned to the study and control groups, each consisting of ten rats. The inhibitory effects of the test drugs against a placebo (isotonic saline) on CNV were tested and compared to each other using a previously described method in which extent of neovascularization and burn stimulus intensity were scored by a masked examiner. Briefly, burn stimulus intensity was scored from 0 to +3 according to the height of blister from corneal surface, and extent of neovascularization was recorded from 0 to +6 according to the distance from limbus to the end point of CNV toward the central corneal burn. Results. The mean burn stimulus score were not different among the groups (P = 0.807). Percent inhibition of CNV compared to the placebo control and its significance were 31.5 %, P = 0.011 for indomethacin; 56 %, P < 0.001 for dexamethasone; and 52 %, P < 0.001 for CAPE. Dexamethasone was significantly (P < 0.05) more effective than indomethacin in inhibition of neovascular growth. CAPE was found to be superior (P < 0.05) to indomethacin and almost as effective as (P > 0.05) dexamethasone in reducing CNV. Conclusion. Topically applied CAPE was demonstrated to have an inhibitory effect, comparable to that of topical dexamethasone, on CNV in this rat model. Antiinflammatory and antioxidant properties of CAPE may contribute to its suppression on CNV.

Preparation and characterization of a clay-polyvinylpyridinium matrix for the removal of bacterial cells from water

Polyvinylpyridinium salts were immobilized onto a clay matrix and were then tested for their antibacterial properties. The clay-polyvinylpyridinium matrix was prepared by the copolymerization of γ-methacryloxypropyltriethoxy silane bonded covalently to clay and 4-vinylpyridine and subsequent quaternization with benzyl halides. Suspension tests for antibacterial properties of the immobilized bactericide against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa demonstrated the high activity of the pyridinium salts that are bonded to the polyacrylate spacer. Advantageously, these insoluble clay-polymer bactericides could be applied without any contamination by the substrate.

Effect of caffeic acid phenethyl ester on survival of axial pattern flaps in rats with ischaemia–reperfusion injuries

Oxygen–derived free radicals have been implicated in the pathogenesis of tissue injury after ischaemia–reperfusion. Caffeic acid phenethyl ester (CAPE), an active ingredient of honeybee propolis, has been identified as having potent antioxidant and anti-inflammatory properties. We evaluated the ability of CAPE applied intraperitoneally in reducing tissue injury after ischaemia–reperfusion. To investigate whether treatment with CAPE modifies the concentrations of the endogenous indices of oxidant stress, we examined its effects on a model of flap ischaemia–reperfusion injury in rats. CAPE (10 µmol/kg) was given through the peritoneum before reperfusion. CAPE given intraperitoneally had an inhibitory effect on tissue injury after ischaemia–reperfusion comparable to that of a control group. The anti-inflammatory and antioxidant properties of CAPE may contribute to its suppression of tissue injury.

Synthesis and stimuli-responsive properties of the phenanthroline based metallo-supramolecular polymers

A series of functional metallo-supramolecular materials based on polyhedral oligomeric silsesquioxane (POSS) and phenanthroline ligand were prepared using a two-step approach. Firstly, using a phenanthroline ligand, an amino-functionalized transition metal complex was prepared by tin(II) chloride. In the second step, this metal complex was subsequently reacted with the octakis(3-chloropropyl)octasilsesquioxane, resulting for the metallosupramolecular polymers bearing POSS structure. All the synthesized compounds were fully characterized by spectroscopic analysis, thermal and electron microscopy techniques. Stimuli responsible properties of metallo-supramolecular materials were also investigated the reversibility upon external factors, such as electrochemical or the addition of competitive complexing ligands by electroanalytic techniques and UV–Vis spectroscopy. The electro- and chemo-responsive properties of the metallo-supramolecular materials were also improved. As a result, prepared phenanthroline-functionalized polyhedral silsesquioxane are good candidates for electronic, opto-electronic, and photovoltaic applications as a smart stimuli-responsive material.

Synthesis, characterization and thermal properties ofbentonite-polyacrylate sol–gel materials

A new type of material incorporating bentonite with an alkoxide, H 2 CC(CH 3 )COO(CH 2 ) 3 Si(OCH 3 ) 3 , has been prepared successfully using a sol–gel process. The structures and structural changes upon heating, of the bentonite and the sol–gel material were investigated by FTIR, XRD and DSC. Using the metal alkoxide and the corresponding clay mineral as precursors, the additive reaction followed by free radical polymerization resulted in a novel material in which polymer was attached covalently to silicate sheets of bentonite via hydroxy bonding.

Effects of coating with different ceromers on the impact strength, transverse strength and elastic modulus of polymethyl methacrylate

The aim of this study was to evaluate the mechanical properties of polymethyl methacrylate (PMMA) after coating with different ceromers. For transverse strength and modulus of elasticity tests, specimens of 65×10×2.5 mm dimensions were prepared (5 groups, n=10). For impact strength test, specimens of 60×7.5×4 mm dimensions were prepared (5 groups, n=10). Test group specimens were coated with one of four different types of ceromers, and specimens in the control group were not coated. After specimens were tested for transverse and impact strengths, the data were analyzed with Kruskal-Wallis and Conover post hoc tests (p<0.05). GLYMOTEOS-TiO2 and A174-TEOS significantly increased the transverse strength of PMMA. All ceromers caused a statistically significant increase in the elastic modulus of PMMA. While GLYMO-TEOS-ZrO2 significantly decreased the impact strength, the other ceromers did not cause any statistically significant difference in impact strength. Coating with ceromers substantially improved the mechanical properties of PMMA.