A simple and rapid high-performance liquid chromatography method for determining furosemide, hydrochlorothiazide, and phenol red: applicability to intestinal permeability studies

A simple reversed-phase high-performance liquid chromatography (HPLC) method with ultraviolet detection at 280 nm was developed for simultaneous quantitation of furosemide and hydrochlorothiazide along with phenol red as a nonabsorbable marker for in situ permeability studies in anaesthetized rats. A jejunal segment of approximately 10 cm was isolated and cannulated in both ends for inlet and outlet solution. The perfusate was collected every 10 min, and samples were analyzed using the developed method. The mobile phase was acetonitrile-water-triethylamine-glacial acetic acid (41.5 + 57.4 + 0.1 + 0.9, adjusted to pH 5.6) at a flow rate of 1 mL/min; the run time was 9 min. The calibration graphs were linear for all 3 compounds (r > 0.999) across the concentration range of 7.93-125 microg/mL for phenol red and 6.25-100 microg/mL for hydrochlorothiazide and furosemide. The limits of quantitation were 7.2, 8.9, and 6.8 microg/mL for furosemide, hydrochlorothiazide, and phenol red, respectively. The coefficients of variation for intraassay and interassay precision were less than or equal to 7.6%, and the accuracy was between 93.2-103.4%. Using the single pass intestinal perfusion technique and the suggested HPLC method for sample analysis, mean values of 0.25 x 10(-4) (+/-0.16) cm/s and 0.22 x 10(-4) (+/-0.13) cm/s were obtained for furosemide and hydrochlorothiazide, respectively.     

Synthesis of New β,β′-Diketodithioethers via Swern Oxidation and Study of Their Hydrazone Formation Rate

The synthesis of β,β′-diketodithioethers 4b–j from corresponding β,β′-dihydroxydithioethers 3b–j was carried out by a Swern oxidation using DMSO-oxalyl chloride as oxidizing agent. β,β′-Dihydroxydithioethers 3b–j were prepared by the reaction of two molar equivalents of epoxides 1b–j with dimercaptoethane 2 in the presence of a saturated aqueous solution of potassium carbonate. The reactivity behavior of imine formation of the β,β′-diketodithioethers 4b–j by 2,4-dinitrophenylhydrazine was also investigated, and a mechanism was proposed by using molecular orbital (MO) calculations. To confirm the proposed mechanism, the role of the thia function to activate hydrazone formation by measuring HOMO-LUMO energy levels was also demonstrated.     

Coated-wire copper(II)-selective electrode based on phenylglyoxal-α-monoxime ionophore

A copper(II) ion-selective electrode based on a recently synthesized 2-quinolyl-2-phenylglyoxal-2-oxime (phenylglyoxal-alpha-monoxime) has been developed. The PVC-based membrane containing phenylglyoxal-alpha-monoxime, dibutyl phthalate as plasticizer, and sodium tetraphenylborate as anion excluder and membrane modifier, was directly coated on the surface of a platinum-wire electrode. The response of the electrode was linear with a near-Nernstian slope of 28.2 mV decade(-1) within the Cu2+ ion concentration range 1x10(-6)-1x10(-1) mol x L(-1). The response time for the proposed electrode to achieve a 95% steady potential for Cu2+ concentrations ranging from 1x10(-1) to 1x10(-6) mol x L(-1) is between 10 and 50 s, and the electrode is suitable for use within the pH range of 3 to 6.5. The electrode has a detection limit of 5x10(-7) mol x L(-1) Cu2+ and its selectivity relative to several alkali, alkaline earth, transition, and heavy metal ions was good. The coated-wire electrode could be used for at least two months without a considerable alteration of its potential. Applications of the electrode for determination of copper in milk powder samples and as an indicator electrode for potentiometric titration of Cu2+ ion using EDTA are reported.     

Efficient synthesis of fluorescent rosamines: multifunctional platforms for cellular imaging

Substituted rosamines are efficiently prepared through a new organometallic addition to an imine-substituted xanthone as a novel primary amine equivalent. The synthesis reduces the number of synthetic steps to the targeted rosamines, for convenient and facile access to potential libraries of rosamine dyes. The prepared rosamine derivatives represent unique multifunctional platforms that possess radiolabeling capability and fluorescence. Rosamines have (i) useful non-specific binding properties in mammalian cells and plant root hair, and (ii) positive uptake or binding properties in microbial systems.     

Effect of engineered PLGA‐gelatin‐chitosan/PLGA‐gelatin/PLGA‐gelatin‐graphene three‐layer scaffold on adhesion/proliferation of HUVECs

A three‐layered fibrous scaffold composed of fibers of different diameters in each layer was fabricated in correspondence with the structure of the blood vessels. Effect of solution and electrospinning parameters on morphology and diameters of the fibers were investigated by scanning electron microscopy (SEM), for each layer. The SEM images showed that 18% poly (lactic‐co‐glycolic acid) (PLGA)‐gelatin‐chitosan in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP)/acid acetic solution resulted in bead‐free fibers for the outer layer. For the middle layer, 18% PLGA‐gelatin in HFIP at 13 kV with 13 cm needle to collector distance was chosen as the optimum condition. SEM imaging demonstrated that by increasing graphene content from 0.5 to 2 wt% in the inner layer (as an electrically conductive/platelet anti‐adhesion material), the fiber diameter decreased from 324.01 ± 58.90 to 288.59 ± 70.77 nm. The effect of gelatin crosslinking on the microstructure of the fibers was also examined. Shrinkage ratio decreased from 57 to below 21% upon crosslinking of the three‐layered scaffold in exposure to vapor of 50% glutaraldehyde solution for 2 hours. Mechanical test showed that tensile strength of the crosslinked three‐layer scaffold in the longitudinal direction was 2.90 MPa which is comparable to that of the vein and artery. The MTT [3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide] assay displayed cell viability of above 96% for the PLGA‐gelatin containing 2 wt% graphene. SEM analysis revealed that the addition of graphene to PLGA‐gelatin (up to 2%) causes a remarkable improvement in cell adhesion.     

Inhibition of Scale Formation Using Silica Nanoparticle

Because of the wide use of water injection for enhanced oil recovery in the oil fields in order to displace oil into the production well, many reservoirs experience scale deposition problems. Scale formation can cause the production path to be blocked and also cause significant reduction in productivity. One of the most common methods for preventing or lowering the amount of scale formation is applying the scale inhibitors. In this work, silica nanoparticles are used as a scale inhibitor. Conductivity is used as a property of the fluid to show the amount of ion in the solution, leading us to predict the amount of scale formed in the solution. An optimum amount of silica nanoparticles could reduce the rate of conductivity decreasing the solution and consequently lowering the scale deposition, which is the aim of this challenging subject in the oil industry.     

Synthesis and Pharmacological Evaluation of Some Novel Imidazo[2,1-b][1,3,4]thiadiazole Derivatives

Synthesis of bis‐1,3‐{6′‐arylimidazo[2,1‐b][1,3,4]thiadiazol‐2‐yl}‐1,2,2‐trimethylcyclopentane ( 3 ), bis‐1,3‐{thiadiazolo[2′,3′:2,1]imidazo[4,5‐b]quinoxalinyl}‐1,2,2‐trimethylcyclopentane ( 5 ) has been achieved by the reaction of bis‐(5′‐amino‐1′,3′,4′‐thiadiazolyl)‐1,2,2‐trimethylcyclopentane with α‐haloketones, 2,3‐dichloroquinoxaline respectively. Bromination of compound 3 furnished bis‐1,3‐{5′‐bromo‐6′‐arylimidazo[2,1‐b][1,3,4]thiadiazol‐2‐yl}‐1,2,2‐trimethylcyclopentane ( 4 ). The structural assignment of these compounds was supported by IR, ¹H NMR and elemental analysis data. The antimicrobial, anti‐inflammatory and antifungal activities of some of the compounds have also been evaluated.     

Silica-supported cobalt(II) tetrasulfophthalocyanine catalyzed aerobic oxidation of thiols to disulfides under neutral conditions

A very simple and mild reaction is described for the aerobic oxidative coupling of thiols to disulfides by silica-supported cobalt(II) tetrasulfophthalocyanine as the catalyst in non-aqueous media under neutral conditions at room temperature. The catalyst can be reused for the oxidative coupling of several thiols without any significant loss of catalytic activity. Correspondence: Ahmad Shaabani, Department of Chemistry, Shahid Beheshti University, P.O. Box 19396, 4716 Tehran, Iran.