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Determination of Phenolic Acids by a Modified HPLC: Its Application to Various Plant Materials

Abstract The determination of certain phenolic acids employing a gradient HPLC method is described, in this study. The analysis was performed by using a gradient program with the two solvents system (A: methanol:water:formic acid (10∶88∶2 v/v); B: methanol:water:formic acid (90:8:2 v/v)). The flow rate of 1 mL · min−1, injection volume of 10 µL was used and signals were detected at 280 nm. Propylparaben was a suitable compound as an internal standard for this system. The method was validated and highly repeatable (between RSD values of 0.35–1.65) and linear results were obtained. The LOD and LOQ values of the phenolic acids are in the range of (2.58×10−6−9.69×10−6 M) and (7.83×10−6−2.93×10−5 M), respectively. The applicability of the method was tested by using some plant source materials, and the phenolic acid contents were successfully determined via well‐defined peaks. Therefore, the progressed method is suggested for the quantification of phenolic acids in food industry and laboratories.

Passage of vasoactive intestinal peptide across the blood–brain barrier

We investigated the ability of vasoactive intestinal peptide (VIP) to cross the blood-brain barrier (BBB), the interface between the peripheral circulation and central nervous system (CNS). VIP labeled with 131I (I-VIP) and injected intravenously into mice was taken up by brain as determined by multiple-time regression analysis. Excess unlabeled VIP was unable to impede the entry of I-VIP, indicating that passage is by nonsaturable transmembrane diffusion. High pressure liquid chromatography (HPLC) showed the radioactivity entering the brain to be intact I-VIP. After intracerebroventricular (i.c.v.) injection, I-VIP was sequestered by brain, slowing its efflux from the CNS. In summary, VIP crosses the BBB unidirectionally from blood to brain by transmembrane diffusion.

Vasoactive intestinal peptide inhibits degranulation and changes granular content of mast cells: a potential therapeutic strategy in controlling septic shock

Vasoactive intestinal peptide (VIP) has potent protective activity against sepsis and increases the survival rate of septic rats and mice. The present study was planned to evaluate the effect of VIP on mast cell activity, histamine and methylhistamine levels and oxidative stress in the liver and kidneys of septic rats. The effect of VIP was compared to that of nitric oxide synthesis inhibition, previously tested extensively in septic shock models, with doubtful benefit. The present study showed that endotoxic shock did not lead to oxidative stress in either liver or kidney of the rats. On the other hand, mast cells, based on their location, displayed functional heterogeneity to the septic insults. VIP possibly modulated the specific reactions of the tissues to mediators released from mast cells during septic shock. The most prominent effect of VIP as compared to nitric oxide synthesis inhibition was related to mast cells. In conclusion, the prevention of mast cell reactivity by VIP could be a potential therapeutic strategy in controlling septic shock.

Ovarian, uterine and brain mast cells in female rats: Cyclic changes and contribution to tissue histamine

Using histochemical techniques, we determined mast cell content in ovarian, uterine and brain tissues throughout the estrus cycle of the rat. In one series of experiments, 26 cycling female rats were used for the measurement of follicle stimulating hormone (FSH) in plasma and evaluation of mast cells in the tissues. In a second series, cycling female rats were used for the determination of tissue histamine. The number, degranulation pattern and staining characteristics of mast cells changed synchronously in rat ovarian, uterine and brain tissues during the estrus cycle. A great majority of mast cells in tissues were stained by Alcian blue at proestrus and metestrus. Safranin-stained mast cells were abundant in all tissues during estrus and diestrus. Alcian blue-stained mast cells contribute to the change of tissues histamine level. In ovarian tissue, histamine level increased significantly at proestrus and metestrus. The lowest ovarian histamine level was determined at estrus, in which virtually all mast cells were stained by safranin only. Mast cells in ovarian, uterine and brain tissues seem to change their histamine content throughout the estrus cycle. Mast cells are absent from the thalamus during proestrus and are present in the hypothalamus only during the estrus phase. Plasma FSH concentrations (mlU ml-1) did not significantly change throughout the estrus cycle (proestrus: 0.81 +/- 0.11, estrus: 0.69 +/- 0.07, metestrus: 0.82 +/- 0.13, diestrus: 0.67 +/- 0.19).

The Protective Effect of Vasoactive Intestinal Peptide (VIP) on Stress‐Induced Gastric Ulceration in Rats

Abstract: The pathogenesis of cold‐restraint stress ulcer involves various factors and is not completely understood. Mast cell degranulation, increased gastric muscular contractility, diminished mucosal blood flow, release of several biogenic amines, activated polymorphonuclear leukocytes, and lipid peroxidation which results from toxic oxygen molecules were suggested to be related to the production of gastric damage by cold‐restraint stress. Recent evidence strongly indicates that VIP has a modulatory effect on tissue injury.

FIA of sildenafil citrate using UV-detection

A flow injection analysis (FIA) of sildenafil citrate (SLD) using UV detection is described in this study. The best solvent system was found to be consisting of 0.2 M phosphate buffer at pH 8 having 10% MeOH. A flow rate of 1 ml. min(-1) was pumped and active material was detected at 292 nm. The calibration equation was linear in the range of 1x10(-6)-5x10(-6) M. Limit of detection (LOD) and limit of quantitation (LOQ) were calculated to be 3x10(-7) and 8.9x10(-7) M with a R.S.D. 1.9 and 0.6% (n=7), respectively. The proposed method was applied to the determination of SLD in VIAGRA tablet, containing 50 mg active material. The results were compared with those obtained from UV-Spectrophotometry. The results showed that there is a good agreement between FIA method and the UV-Spectrophotometry. The validation studies were realised by the related applications and the results were evaluated statistically. According to the results, insignificant difference was observed between the methods.

Phenolic compounds and antioxidant activities of some Hypericum species: A comparative study with H. perforatum

This study was designed to determine the polyphenolic contents of the extracts and to evaluate the antioxidant activity of Hypericum origanifolium Willd. and H. montbretii Spach. (Guttiferae (Hypericaceae)), The possible composition activity relationship was investigated and the results were compared with that of H. perforatum L. Methanol, ethyl acetate, and water were used as solvents to produce extracts from flowers and leaves of the plants. The determination of phenolic acids in the Hypericum species was achieved by using a modified Reverse phase-High pressure liquid chromatography (RP-HPLC) method adopting an internal standard. It was observed that chlorogenic and caffeic acids were higher in all extracts. The highest values were found in ethyl acetate extracts for total phenolic content as gallic acid and for the flavonoids and flavonols as rutin equivalents (all measurements are mg/g), respectively. Hypericum extracts were evaluated for their radical scavenging activity by the 2,2-diphenyl-1-picryhydrazyl radical (DPPH) and their oxidative stability by the Rancimat method. Results were compared with Butyllated hidroxy toluene (BHT), a synthetic antioxidant, and with a reference plant, H. perforatum. A good correlation between antioxidant activity and total phenol content in the extracts was observed. In an antioxidant activity assay, the leaf extracts of H. origanifolium were found to be two or three times more active than those of BHT, H. perforatum, and H. montbretii leaves and flowers. In an antiradical activity assay, leaves and flowers of H. montbretii and leaves of H. origanifolium were the most active at the tested concentrations, exhibiting an activity comparable to that of the positive control BHT, but all of the extracts, with the exception of the leaves of H. montbretii, showed activity weaker than the leaves and flowers of H. perforatum, the reference plant.

Determination of amlodipine in pharmaceutical formulations by differential-pulse voltammetry with a glassy carbon electrode

A differential‐pulse voltammetric method was developed for the determination of amlodipine based on the oxidation of the dihydropyridine group on the surface of glassy carbon electrode under stationary and rotating conditions. The experiments were conducted in a supporting electrolyte consisting of 0.2 MKCl, 0.1 Mphosphate buffer, and 10 % (v/v) methanol during investigation of initial potential and pH effects. No adsorption effect was observed on using an initial potential of 0 mVand the supporting electrolyte solution at pH 5.5 under both stationary and rotating conditions. The factor affecting the voltammetric current was diffusional in the range of 200—1000 rpm for rotating, and 2—40 mV s−1 for stationary conditions up to a concentration of 0.04 mg mL−1 amlodipine. The limit of detection (LOD) and the limit of quantitative (LOQ) for the rotating and stationary techniques were found to be 0.004 and 0.0072 mg mL−1 (for S/N = 3.3) and LOQ 0.012 and 0.022 mg mL−1 (for S/N = 10), respectively. The proposed method was applied to the tablets containing amlodipine and according to the statistical evaluations acceptable results were obtained at the 95 % probability level.

The Polarographic Determination of Tenoxicam in the Pharmaceutical Preparations

Abstract In this study, the polarographic behaviour and the optimum polarographic conditions for the determination of TNX using DC (direct current), DP (differential pulse), SCAP (superimposed constant amplitude pulse) and SIAP (superimposed increasing amplitude pulse) polarographic techniques are described based on the reduction of enol group of the molecule on the dropping mercury electrode. The experiments were conducted in the aqueous supporting electrolyte solution containing 0.2 M KCl and 0.2 M buffer solution. Single waves were obtained at various pH values. The limiting currents were decreased and E1/2 values were linearly shifted to more negative potentials with an increase in the pH. The system was irreversible at both the acidic and the basic media and it was adsorptional in the acidic medium and diffusional at pH 10.8. The variation in the limiting current was found to be 0.86 μA/°C. Good relations were obtained for DC, DP, SCAP and SIAP polarographic techniques at pH 10.8. The determination o...

A validated method development for ketoprofen by a flow-injection analysis with UV-detection and its application to pharmaceutical formulations

A simple, sensitive and fast flow-injection analysis method with UV-detection method was developed for the determination of ketoprofen in pharmaceuticals. The standard and sample solutions were dissolved in a 10% ethanol which was suitable for this study. A flow-rate of 0.6 ml min(-1) was used and the analyte was monitored at 260 nm. Variables such as concentrations, flow rate of reagents and other flow injection parameters were optimized to produce the most sensitive and reproducible results. Linear calibration curves were obtained in the range of 1.6 x 10(-6) and 1.7 x 10(-4) M. Limit of detection and limit of quantification were 1.7 x 10(-6) M (S/N=3.3) and 5.3 x 10(-6) M (S/N=10), respectively. The method was applied successfully to the analysis of ketoprofen pharmaceutical tablets. The recoveries were 102.75% for peak area and 98.42% for peak height. The proposed method is fast, precise, sensitive and easy to use for the determination of ketoprofen in pharmaceuticals.