Current Drug Therapy (v.9, #4)

Metal Based Pharmacological Active Agents: Structural, Electrochemical, DNA Binding Studies and Antibacterial Properties by Harun Muslu, Derya Kılıcaslan, Mustafa Cesme, Aysegul Golcu, Sibel Ozkan (210-218).
The present study contain the synthesis of enoxacin (ENO) complexes with transition metals of Cu( II), Zn(II), Pt(II), Fe(III) and Ru(III). The structure of the complexes was verified on the basis of elemental analyses, IR, UV-Vis, NMR, mass, electrochemical and thermal spectral data .The electrochemical properties of all compounds were studied by cyclic voltammetry (CV) using a glassy carbon electrode (GCE). The interaction of metal complexes with calf thymus DNA (CT-DNA) was studied with UV spectroscopy. UV studies of the interaction of the compounds with DNA reveal that these complexes can bind to CT-DNA and the binding constants have been calculated. The antimicrobial and antifungal activity of the complexes have been studied against Gram-positive and Gram-negative microorganisms and fungi's and compared with the reference drug ENO. However, the zinc complex was found to be more potent versus four bacterial species than the bare drug ENO.

Poloxamer/Chitosan In Situ Gelling System for Ocular Delivery of Ofloxacin by Aysegul Karatas, Ahsen Boluk, Aslıhan Hilal Algan (219-225).
The objective of the present research was to develop a temperature triggered in situ gelling system for ophthalmic delivery of Ofloxacin (OFL) which is used in acute and subacute conjunctivitis of eye. For this purpose, Pluronic F127 (PF127) was used as in situ gelling agent in combination with Chitosan (CTS) as a natural, biodegradable and mucoadhesive hydrophilic copolymer. The formulations were prepared using PF127 alone and various concentrations in mixture with CTS. In situ gels were evaluated for clarity, pH, gelling temperature and the rheological behaviors. Desired characteristics were obtained in five of the formulations. Selected formulations were clear and in a pH range of 5.0-6.7. The gelation temperatures were between 30-34oC and found to exhibit pseudoplastic behavior. Gelation temperatures of the formulations increased with the decrease of concentration of PF127. Also the use of the pH 6 buffer as solvent in the formulations led to a reduction in the gelation temperature. For the selected formulations, 0.3% ofloxacin was added to in situ gelling system and release of ofloxacin was evaluated by dissolution study. Release of OFL decreased with the increase of PF127 concentration in the formulations. The slowest release was obtained by the mixture of 15% PF127 and 30mL CTS solution (1% CTS in water). The results demonstrated that the composition of PF127 and CTS can be a promising in situ gelling vehicle for ocular delivery of OFL.

Electroanalytical Determination of Benzoic, Oxalic and Glyoxylic Acids Using Platinum Electrode by M. Khodari, Gaber A. M. Mersal, Ahmed A. Abd El-Raady, Beshary El-Desuki (226-231).
Due to the importance of Benzoic, Oxalic and Glyoxylic acids, a voltammetric technique using platinum electrode was developed to identify the mentioned acids.
The electrochemical behavior of Benzoic, Oxalic and Glyoxylic acids was studied using cyclic voltammetric technique at platinum wire electrode in sodium nitrate as a supporting electrolyte. Benzoic acid gave an oxidation peak at +0.096 V while oxalic acid showed a well single oxidation peak at +1.05 V (vs. AgǀAgCl). Glyoxalic acid showed a reduction peak in the presence of hexacynoferrite K4[Fe2(CN)6] at +0.126V.
The effect of supporting electrolyte kind, pH solution, ionic strength and scan rate on the oxidation peak of Benzoic and oxalic acids or the reduction peak of glyoxylic acid were investigated. Linear sweep voltammetry was used for the electrochemical determination of these acids under the optimum experimental conditions . A concentration of 8x10-5 lower detection limit was obtained for benzoic acid and a value of 9x10-5 was detected for Oxalic and Glyoxylic acid. The effect of some metal ions, amino acids, urea and ascorbic acid as interferences was examined. The results showed that the effect ranged between -5.0 to+14.0 % on peak response. Benzoic, Oxalic and Glyoxylic acids were successfully determined in industrial waste water.

The ionization constant (pKa) in general is a chief parameter for evaluating and measuring the reaction estimates, biological effects and retention, biological conveyance and ambient consequences. Therefore, the fluorimetric parameters of some local anaesthetics such as dibucaine, procaine and tetracaine in certain percentages of acetonitrile-water and methanol-water mixtures were optimized and then the pH and solvent percentage effects on fluorimetric parameters were investigated. In the optimal excitation and emission wavelengths and solvent percentage, pKa values of these compounds have been determined by plotting the pH-fluorescence intensity graphs in each solvent media. Almost all ionic species of tetracaine and the acidic species of dibucaine and procaine were fluorescent, but the basic species of dibucaine and procaine were non-fluorescent. The pKa values of the local anaesthetics in methanol-water media were very similar to those in acetonitrile-water media. Moreover, the pKa values determined by the spectrofluorimetric method were very close to the values predicted by the SPARC on-line pKa calculator.

Influence of Polymer Molecular Weight on in-vitro Characteristics and Cytotoxicity of Fulvestrant Loaded Nanoparticles by Canan Hascicek, Ceyda T. Sengel-Turk, Mehmet Gumustas, Sibel A. Ozkan, Filiz Bakar, Net Das-Evcimen, Ayhan Savaser, Yalcin Ozkan (239-249).
The objective of this research was to fabricate a novel polymeric nanoparticulate system of Fulvestrant (FLV) and investigate the effect of polymer molecular weight variation on in vitro properties and also anti-proliferative potency of the carriers. Two different forms of polymerspoly( lactic-co-glycolic acid) (PLGA) were employed for the fabrication of polymeric nanoparticles (PNPs) by using a combination of diffusion-emulsification-salting out preparation procedure. In vitro evaluation of the PNPs was performed in terms of entrapment efficiency, particle size, surface charge, thermal behavior redispersibility ability, in vitro drug release profile, release mechanisms, stability and anti-proliferative activity. PNPs were obtained in the size range between 191.80 to 211.80 nm with a lower polydesipersity index. FLV release from the developed PNP formulations was more than a 45 days period. Zero order release was obtained with low molecular weight form of PLGA PNPs, while relatively high weights of PLGA PNPs followed square root of time (the Higuchi's pattern) dependent release. Additionally, stability studies showed that PNPs were stable at 4A°C for a six months period. In the experimental work, it was also observed that FLV, which was entrapped into the PNPs, displayed strong in vitro antiproliferative activity on MCF-7 human breast cancer cells for a 48 h period, when compared to free the form of FLV.
As a conclusion, the PNPs developed in this research may have the potential to deal with the major handicaps of the available IM form of FLV, and may be a new promising delivery preparation approach.

Design of Potentiometric Sensors Based on Interaction of Cyclodextrins with the Enantiomer of Interest by Raluca-Ioana Stefan-van Staden, Rahel Girmai Bokretsion, Jacobus Frederick van Staden, Hassan Y Aboul-Enein (250-255).
Five enantioselective sensors based on α-, β-, carboxymethyl-β-(as sodium salt), 2-hydroxyl-3-trimethylammoniopropyl -β-(as chloride salt) and γ-cyclodextrins were designed based on results of their molecular interaction with the S- and R-enantiomers of ketoprofen obtained using SPR (surface plasmon resonance) based sensors. SPR proved to be an excellent technique for selecting the best chiral selectors. The best sensor was the one based on β-cyclodextrin. Low detection limits (of 10-8 to 10-9 magnitude orders) were recorded with the enantioselective, potentiometric membrane electrodes.

Determination and Validation of the Antiviral Drugs Using Reverse Phase High Performance Liquid Chromatographic Method by Sevinc Kurbanoglu, Amir M. Ashrafi, Karel Vytras, Bengi Uslu, Sibel A. Ozkan (256-260).
A new, simple, rapid, accurate and reproducible reverse phase high performance liquid chromatographic method with UV detection was developed and used for the estimation of abacavir sulphate and fosamprenavir in bulk and in their pharmaceutical dosage forms. High performance liquid chromatography was carried out on a Waters Spherisorb ODSI (250x4.6mm with 5 μm particle size) column with a flow rate 1.0 mL.min-1 using a mobile phase consisting of methanol: phosphate buffer (80:20, v/v) containing 15mM phosphoric acid at pH 6.2. The detection was carried out at 275 nm and the run time was 5 min. For the sensitive determination of abacavir, fosamprenavir was used as an internal standard and for determination of fosamprenavir vice versa. Using these conditions, both antiviral drugs were analyzed simultaneously with the same method and same chromatographic conditions. The linearity was found to be in the range of 0.25-75 μg.min-1 and 0.50-75 μg.min-1 for abacavir and fosamprenavir, respectively. The retention times for fosamprenavir and abacavir were 2.48 and 4.04 min, respectively. The proposed method was validated according to ICH and USP guidelines and application of the method to tablet dosage forms were also performed.

Investigation of the Metal Bonding Properties of Fluoroquinolone Type Antibiotics Using Spectrofluorimetric Method by S. Beniz Gündüz, Sevil Çan, Sibel A. Özkan (261-269).
The metal bonding properties of fluoroquinolone type antibiotics, namely levofloxacin and ciprofloxacin, were investigated by using spectrofluorimetric method. Fluorescence quenching of levofloxacin (LEV) and ciprofloxacin (CIP) by Fe (III) has been studied. The optimal experimental conditions were determined. The excitation and emission wavelengths were λex= 390 nm and λem= 500 nm for the Fe (III)-LEV complex and λex= 370 nm and λem= 462 nm for the Fe(III)-CIP complex at pH 5.5 in water medium. The calibration curves were obtained from Stern- Volmer equation plotting to F0/F-[Fe+3] graphs and the linearity was found within the range of 0.056-0.56 μg.mL-1 for the Fe(III)-LEV complex and 0.56-5.58 µg.mL-1 for the Fe(III)-CIP complex under the optimal conditions. The detection limits (LOD) of the proposed method for the Fe(III)-LEV and Fe(III)-CIP complexes were 1.6 ng.mL-1 and 5.9 ng.mL-1 respectively and the quantitation limits (LOQ) of these complexes were found to be 5.3 ng.mL-1 and 19.7 ng.mL-1 respectively. The stochiometry of both complexes was also determined by using the continuous variation method and the molar ratio of Fe(III):Fluoroquinolone was calculated as 2:3. The interaction between the fluoroquinolones in tablet forms and Fe(III) in the vitamin-mineral combination tablet was investigated by applying this quenching method and obtained satisfactory results.

Optimization and Application of Imprinted Poly(AA-EGDMA) for Solid Phase Extraction of Ciprofloxacin in Artificial Urine by Luis D. Marestoni, Ademar Wong, Gustavo T. Feliciano, Mary R.R. Marchi, Cesar R.T. Tarley, Mariar del Pilar Taboada Sotomayo (270-276).
Ciprofloxacin is one of the most widely used antibiotics and knowledge of concentration in the urine is of great significance for pharmacokinetic and environmental studies. In this work, the Poly (Acrylic Acid – Ethylene Glycol Dimethacrylate) Molecularly Imprinted Polymer was optimized as a adsorbent in solid phase extraction (MISPE) for Ciprofloxacin. It is desirable because they are adsorbent materials highly selective to their template molecule. The MIP resulted in maximum sorption capacities of 282 μmol g-1 in batch studies and in μmol g-1 in the breakthrough curve studies. MISPE was applied in synthetic urine to test its viability. The limit of detection was 70 ng mL-1. The enrichment factor of the method was 5.32, and recovery in urine ranged from 94.2% to 120.8%. These results showed the applicability of this optimized MISPE.

Liquid Chromatographic, Spectrophotometric and Potentiometric pKa Determination of Ranitidine and Famotidine by Y. Dogan Daldal, Cansel Cakır, Hulya Yılmaz, Ebru Cubuk Demiralay, Sibel A. Ozkan, Guleren Alsancak (277-284).
The dissociation constant (pKa) is one of the most significant properties of a substance chemical moiety which has to be estimated with accuracy. Liquid chromatographic, spectrophotometric and potentiometric methods are often employed for determination of pKa values of compounds. This study describes the practice of these three methods to the determination of dissociation constant values of famotidine and ranitidine in acetonitrile-water binary mixtures. From these constants, aqueous dissociation constants of investigated substances were calculated by different approaches.
Moreover, estimation of aqueous pKa values ( wwpKa ) can also be predicted by computational
method (Marvin Sketch) on the basis of molecular structure. Results obtained from wwpKa values are compared with Marvin Sketch program and literature values.

The metal bonding properties of some ARA-II (Angiotensin II Receptor Antagonists) compounds, such as valsartan (VAL), were investigated by using spectrofluorimetric method. Fluorescence quenching of VAL by Cu(II) was studied and optimal experimental conditions were determined. The excitation and emission wavelengths were λex= 280 nm and λem= 436 nm for the Cu(II)-VAL complex in methanol medium. The calibration curve was obtained from Stern-Volmer equation plotting to F0/F-[Cu+2] graphs and the linearity was found within the range of 0.25-2.54 μ for the Cu(II)-VAL complex under optimal conditions. The detection limit (LOD) and the quantitation limits (LOQ) of the proposed method for this complex were 4.96 and 16.53 respectively. The stochiometry of this complex was also determined by using the continuous variation method and the molar ratio of Cu(II):VAL was calculated as 1:1. The interaction between the valsartan in tablet form and Cu(II) in the vitamin-mineral combination tablet was investigated by applying this quenching method and obtained satisfactory results.

Enhanced Bioavailability of Cinnarizine Using Solid Dispersion: In Vitro and In Vivo Evaluation by Muzeyyeu Demirel, Gulary Buyukkoroglu, Basar Sırmagul, Bahar S. Kalava, N. Ozturk, Yesemin Yazan (294-301).
The aim of this study was to modify the release and thus enhance the bioavailability of a calcium antagonist cinnarizine whose aqueouse solubility is low and half-life is short. For this purpose, solid dispersion system was chosen as the delivery system since it is a simple method at laboratory conditions and it is belived to increase the dissolution of the active agents. Eight formulations of solid dispersions were prepared using four different methods and two different vehicles, to investigate the effects of the preparation method and the vehicle used on the release of the active ingredient, cinnarizine. For the characterization of cinnarizine solid dispersions, cinnarizine amount, practical yield %, thermal, particle size distribution and X-ray diffraction analysis were performed. In vitro dissolution from hard cellulose capsules containing cinnarizine solid dispersions was compared to pure cinnarizine. Aqueous dispersions of pure cinnarizine and the formulation selected depending on the results of the in vitro analyses were applied to rabbits orally. As a conclusion of the in vitro-in vivo evaluations of solid dispersions planned to be developed for increasing cinnarizine absorption potential, it was determined that the dissolution could be modified and the bioavailability could be enhanced.