Simultaneous spectrophotometric determination of metformin hydrochloride and glibenclamide in binary mixtures using combined discrete and continuous wavelet transforms

In this work, a combined discrete and continuous wavelet transform analysis was developed for simultaneous spectrophotometric determinations of metformin hydrochloride and glibenclamide, two antidiabetic drugs, in binary mixtures without any chemical pretreatment. Absorption spectra were subjected to the 4-level db4 discrete wavelet transform (DWT) for signal de-noising. Selected continuous wavelet transform (CWT) families (rbio3.1 with scaling factor, a = 80, and gaus2, a = 60) were applied on these de-noised signals. Finally, a zero-crossing technique was used for the construction of calibration curves for both drugs. The proposed method was validated by analyzing synthetic mixtures of the investigated drugs with various concentrations. The amount of metformin hydrochloride and glibenclamide were determined by using CWT amplitudes in zero-crossing points. The mean recovery values of metformin hydrochloride and glibenclamide were found between 98.6-102.0 and 97.9-102.4% for rbio3 and 98.3-101.2 and 97.1-101.4% for gaus2 families, respectively. The obtained results showed that the developed method is a simple, rapid and precise procedure for the simultaneous determination of metformin hydrochloride and glibenclamide in binary mixtures.     

Exploiting adsorption and desorption at solid–liquid interface for the fluorometric monitoring of glibenclamide in adulterated drinks

Nowadays, the use of a drug to modify a person's behavior with criminal intentions has become a growing public concern. In fact, stealthy drink spiking with certain drugs can cause the incapacitation of a potential victim of assault and in extreme cases can even lead to death. Belonging to the group of drugs used to commit drug-facilitated crimes is glibenclamide, which not only exhibits high sedation secondary effects but when subject to an overdose intake can lead to intense hypoglycemic episodes that could end with death. Suicide attempts and homicides through overdose with glibenclamide have already been reported.     

Selective separation and enrichment of glibenclamide in health foods using surface molecularly imprinted polymers prepared via dendritic grafting of magnetic nanoparticles

In this paper, the novel surface molecularly imprinted polymers based on dendritic‐grafting magnetic nanoparticles were developed to enrich and separate glibenclamide in health foods. The density functional theory method was used to give theoretical directions to the synthesis of molecularly imprinted polymers. The polymers were prepared by using magnetic nanoparticles as supporting materials, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross‐linker. The characteristics of magnetic nanoparticles and polymers were measured by transmission electron microscope and SEM, respectively. The enriching ability of molecularly imprinted polymers was measured by Freundlich Isotherm. The molecularly imprinted polymers were used as dispersive SPE materials to enrich, separate, and detect glibenclamide in health foods by HPLC. The average recoveries of glibenclamide in spiked health foods were 81.46–93.53% with the RSD < 4.07%.     

Synthesis, characterization and hypoglycemic activity of Zn(II), Cd(II) and Hg(II) complexes with glibenclamide

A series of group 12 elements for Zn(II), Cd(II), Hg(II) complexes of glibenclamide were synthesized and characterized using various spectroscopic techniques and magnetic moments. The complexes exhibited significant activity against gram-negative and gram-positive bacteria species. Zn(II) complex showed remarkable hypoglycemic activity whereas Cd(II) and Hg(II) complexes exhibited antibacterial activity.     

Voltammetric study of glibenclamide at carbon paste and Sephadex-modified carbon paste electrodes

The oxidative behaviour of the antidiabetic agent glibenclamide on a bare carbon paste electrode (CPE) and a Sephadex-modified carbon paste electrode (SMCPE) was explored by cyclic and differential pulse voltammetry (DPV). The analysis procedure consisted of an open circuit accumulation step in stirred sample solution of Britton-Robinson buffer (0.04 mol L^–1, pH 2.0). This was followed by medium exchange to a clean solution of Britton-Robinson buffer (0.04 mol L^–1, pH 5.0), and subsequently an anodic potential scan was effected to obtain the voltammetric peak. The glibenclamide oxidation peak current obtained by DPV was proportional to the concentration of the glibenclamide in the range of 1.0×10^–9 mol L^–1 to 5.0×10^–8 mol L^–1 for 180 s accumulation time, with a detection limit of 4.0×10^–10 mol L^–1. A method was developed for the determination of glibenclamide in formulation and spiked human serum. Moreover, the proposed procedure was used to estimate the serum concentrations after oral administration of a 5 mg tablet of glibenclamide to three diabetic subjects.     

Automatic miniaturized fluorometric flow system for chemical and toxicological control of glibenclamide

In this work, and for the first time, it was developed an automatic and fast screening miniaturized flow system for the toxicological control of glibenclamide in beverages, with application in forensic laboratory investigations, and also, for the chemical control of commercially available pharmaceutical formulations. The automatic system exploited the multipumping flow (MPFS) concept and allowed the implementation of a new glibenclamide determination method based on the fluorometric monitoring of the drug in acidic medium (λ_ex = 301 nm; λ_em = 404 nm), in the presence of an anionic surfactant (SDS), promoting an organized micellar medium to enhance the fluorometric measurements.The developed approach assured good recoveries in the analysis of five spiked alcoholic beverages. Additionally, a good agreement was verified when comparing the results obtained in the determination of glibenclamide in five commercial pharmaceutical formulations by the proposed method and by the pharmacopoeia reference procedure.     

Glibenclamide in serum: comparison of high-performance liquid chromatography using fluorescence detector and liquid chromatography/mass spectrometry with atmospheric-pressure chemical-ionization (APCI LC/MS)

Comparative studies of high-performance liquid chromatographic and liquid chromatographic/mass spectrometric methods for the quantitative determination of glibenclamide in patient serum are described. The 4-methylcyclohexyl analogue of glibenclamide [N-(4-(-5-chloro-2-methoxybenzamidoethyl)benzenesulfonyl-N-(4-methylcyclohexyl)-urea] is used as internal standard for both methods. After acidification of the sample, the analyte and internal standard are extracted with chloroform. For HPLC analysis, the glibenclamide and internal standard are derivatized to a highly fluorescent amine with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-chloride). The glibenclamide derivative is detected by a fluorescence detector. For APCI LC/MS assay, a derivatization of the analyte is not required and the compounds are measured by selected ion monitoring (SIM). The accuracy, precision, and recovery of the compared methods are presented and discussed.     

A molecular dynamics study on heat conduction characteristics in DPPC lipid bilayer

In this paper, nonequilibrium molecular dynamics simulations were performed on a single component 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine lipid bilayer in order to investigate the thermal conductivity and its anisotropy. To evaluate the thermal conductivity, we applied a constant heat flux to the lipid bilayer along and across the membrane with ambient water. The contribution of molecular interaction to the heat conduction was also evaluated. Along the bilayer plane, there is little transfer of thermal energy by the interaction between lipid molecules as compared with the interaction between water molecules. Across the bilayer plane, the local thermal conductivity depends on the constituents (i.e., water, head group, and tail group of lipid molecule) that occupy the domain. Although the intramolecular transfer of thermal energy in the tail groups of lipid molecules works efficiently to promote high local thermal conductivity in this region, the highest thermal resistance appears at the center of lipid bilayer where acyl chains of lipid molecules face each other due to a loss of covalent-bond and low number density. The overall thermal conductivities of the lipid bilayer in the directions parallel and perpendicular to the lipid membrane have been compared, and it was found that the thermal conductivity normal to the membrane is higher than that along the membrane, but it is still smaller than that of bulk water.     

Determination of glibenclamide and its two major metabolites in human serum and urine by column liquid chromatography

A simple reversed-phase liquid chromatographic method for the measurement of low concentrations of glibenclamide (glyburide) and its two major metabolites, 4-trans- and 3-cis-hydroxyglibenclamide, in human serum and urine has been developed. The compounds were extracted with n-hexane-dichloromethane (1:1). The UV detection wavelength was 203 nm. The minimum detectable serum level of glibenclamide was 1 ng ml (2 nM), and the relative standard deviation was 8.9% (n = 9). When maximum sensitivity was desired the metabolites were chromatographed separately. Metabolites in urine were measured by the same method after five-fold sample dilution. The utility of the method was tested on a healthy volunteer who ingested 3.5 mg of glibenclamide. The parent drug was present in the serum for at least 18 h, and the metabolites in the urine for at least 24 h.     

The structure of glibenclamide in the solid state

The structure of glibenclamide, 5‐chloro‐N‐(2‐{4‐[(cyclohexylamino)carbonyl] aminosulfonyl}phenyl) ethyl)‐2‐methoxybenzamide, an important antidiabetic drug, has been studied both in solution and in the solid state by a combination of NMR spectroscopy and theoretical calculations. The possibility that glibenclamide suffers a tautomerization under melting to afford a desmotrope was rejected. Copyright © 2012 John Wiley & Sons, Ltd.     

Physicochemical properties of the binary system glibenclamide and polyethylene glycol 4000

Solid dispersions of the antidiabetic drug glibenclamide and polyethylene glycol 4000 (macrogol 4000) were prepared by the melting method in order to increase the solubility of this poorly water-soluble compound. The temperature/composition phase diagram of the components was analyzed by hot-stage microscopy and differential scanning calorimetry, showing a monotectic. Polarized light hot stage microscopy and X-ray-powder diffraction confirmed, that glibenclamide is mainly present in a non-crystalline state after melting and solidifying of a 10% (w/w) mixture, which results in an enhanced solubility compared to physical mixtures. The solubility and dissolution rate of the drug increases clearly with decreasing drug/polymer ratio. Moreover, it was observed for the first time that a drug could crystallize as whiskers at the surface of aged solid dispersion particles. Besides relaxation phenomena, this crystallization mechanism may be responsible for a deterioration of liberation properties and bioavailability of solid dispersion based drug products with increasing storage time. This revised version was published online in July 2006 with corrections to the Cover Date.     

胶束电动毛细管色谱法测定消糖灵中的优降糖

 以甲氧苄氨嘧啶为内标,采用胶束电动毛细管色谱法分离测定了新药消糖灵中的优降糖。电泳条件：以25 mmol/L硼砂-30 mmol/L十二烷基硫酸钠（pH 9.0）为电泳介质,未涂层石英毛细管（50 μm i.d.×39.5 cm,有效分离长度34.8 cm）为分离通道,压力进样(68.95 kPa.s),17 kV恒压电泳（28 ℃）,检测波长228 nm。优降糖在14 min内与其他成分得到很好分离,且质量浓度为25 mg/L～275 mg/L时,优降糖可进行定量分析,加标回收率为(100.6±1.4)%。方法简便、快速,结果准确,重现性好,可用于优降糖复方制剂的质量控制。     

A triply-responsive supramolecular amphiphile fabricated by a thermal-responsive pillar[5]arene-based host–guest recognition motif

A novel molecular recognition motif was built between a neutral water soluble pillar[5]arene and decyltrimethylammonium bromide in water. Its thermal-controlled complexation with G1 in water was investigated. Furthermore, based on this new thermal responsive host–guest recognition motif, we further constructed a supramolecular amphiphile between this pillar[5]arene and a trimethylammonium bromide derivative containing an azobenzene group at the other end. This supramolecular amphiphile showed triply-responsiveness, that is, thermal responsiveness of the host–guest complex, photo-responsiveness of the azobenzene group and chemical-responsiveness by adding β-CD.     

Curative Effect of Catechin Isolated from Elaeagnus Umbellata Thunb. Berries for Diabetes and Related Complications in Streptozotocin-Induced Diabetic Rats Model

In this study, catechin (CTN) isolated from Elaeagnus umbellata was evaluated for in vitro antioxidant potential and inhibition of carbohydrate digestive enzymes (α-amylase and α-glucosidase). The compound was also tested for its in vivo antidiabetic potential using Sprague-Dawley rats as experimental animals. The effects of various doses of catechin in STZ (Streptozotocin) induced diabetic rats on fasting blood glucose level, body weight, lipid parameters, hepatic enzymes, and renal functions were evaluated using the reported protocols. The CTN exhibited the highest percent antioxidant for free radical scavenging activity against DPPH and ABTS free radicals, and inhibited the activity of carbohydrate digestive enzymes (with percent inhibition values: 79 ± 1.5% α-amylase and 80 ± 1.1% α-glucosidase). Administration CTN and standard glibenclamide significantly decreased the fasting blood glucose level and increased the body weight in STZ-induced diabetic rats. CTN significantly decreased the different lipid parameters, hepatic, and renal function enzyme levels along with Hb1c level in diabetic rats, while significantly increasing the high-density lipoprotein (HDL) level with values comparable to the standard glibenclamide. Further, the altered levels of glutathione and lipid peroxides of liver and kidney tissues were restored (by CTN) to levels similar to the control group. CTN significantly increased the antioxidant enzyme activities, total content of reduced glutathione, and reduced the malondialdehyde (MDA) level in rat liver and kidney tissues homogenates, and also corrected the histopathological abnormalities, suggesting its antioxidant potential.     

Supramolecular hydrogel formed by glucoheptonamide of l-lysine: simple preparation and excellent hydrogelation ability

We describe the simple preparation of new l-lysine derivatives with a gluconic or glucoheptonic group, their hydrogelation properties, and the thermal and mechanical properties of the supramolecular hydrogels. The l-lysine derivatives with a gluconic group have no hydrogelation ability, while the l-lysine-glucoheptonamide derivatives functioned as hydrogelators. Their hydrogelation abilities increased with the decreasing length of the spacer between the l-lysine segment and the glucoheptonic group. The compound, which has no spacer, formed a supramolecular hydrogel at 0.05 wt % in pure water. The thermal stability and high mechanical strength of the supramolecular hydrogels based on this compound significantly depended on the aqueous solutions. Electron microscopy and FTIR studies demonstrated that the hydrogelators created a three-dimensional network through hydrogen bonding and hydrophobic interactions in the supramolecular hydrogel. In addition, it was found that hydrophobic interactions played an important role in the thermal stability of the supramolecular hydrogel.     

Practical application of thermogravimetry in soil science

Properties and compositions of soils originating from different sources usually vary, depending largely on the conditions of soil forming processes and parent materials. Our previous investigations of soils from contrasting localities showed linear correlations between carbon dioxide produced by soil microorganisms and thermal mass losses of air-dried soils recorded using thermogravimetry. The correlations were observed at temperatures corresponding both to moisture evaporation and thermal degradation of soil organic matter. In this work, those soils were combined into one group and the correlation analysis was repeated using both linear and power functions. Whereas the linear dependency between respiration and water evaporation was confirmed; the connection between respiration and thermal decay of organic matter appeared to follow power function. These findings indicate the existence of fundamental unifying principles in soil forming processes, in terms of water binding and clay-dependent organic carbon sequestration, notwithstanding the fact, that soils develop under contrasting conditions. Additional soils were analyzed in order to test the applicability of obtained models for prediction of soil respiration using thermogravimetry. The results indicate a promising potential of this method mainly for soils originating from areas undisturbed by anthropogenic activity.     

Synthesis, characterization, flame retardance and thermal properties of halogen-free expandable graphite/PMMA composites prepared from sol-gel method

In this work, silane was grafted on expandable graphite via a free-radical reaction. The modified expandable graphite has an -OEt functional group which reacts with TEOS and PMMA that was modified via a sol-gel reaction using a coupling agent that contains silicon. Synergism between silicon flame retardant and expandable graphite increased the flame retardance of the materials. Expandable graphite was functionalized using a coupling agent to increase the interactive force between the organic and inorganic phases. It enhanced the thermal stability of the composites. SEM was adopted to observe the morphology of the composites, and the behavior associated with expansion after the materials had been burned is elucidated. LOI, TGA and IPDT were employed to calculate the flame retardance and thermal stability. The results indicate that the composites are halogen-free flame retardant organic/inorganic composites. Two methods for elucidating the kinetics of thermal degradation were utilized to measure the activation energy when the composites degraded in the high-temperature atmosphere.     

High-performance liquid chromatographic determination of glibenclamide in human plasma and urine

A selective and sensitive high-performance liquid chromatographic method for determination of intact glibenclamide in human plasma or urine has been developed. With glibornuride as internal standard, acid-buffered plasma or urine was extracted with benzene. The organic layer was evaporated and the residue was dissolved in equilibrated mobile phase (acetonitrile-phosphate buffer 0.01 M pH 3.5, 50:50). An aliquot of 20 microliters was chromatographed on a Spherisorb ODS reversed-phase column, and quantitation was achieved by monitoring the ultraviolet absorbance at 225 nm. The response was linear (0-1000 ng/ml) and the detection limit was 5-10 ng/ml in plasma or urine. The within-assay variation was less than or equal to 10%. No interferences from metabolites or endogenous constituents could be noted. The utility of the method was demonstrated by analysing glibenclamide in samples from diabetic subjects on therapeutic doses of the drug.     

Alternative mechanisms of thermal decomposition of <Emphasis Type="Italic">o</Emphasis>-nitrotoluene in the gas phase

The density functional theory methods were used to demonstrate that during the thermal decomposition of o-nitrotoluene, with the formation of 5-methylene-6-aci-nitrocyclohexa- 1,3-diene (aci-form) being the primary event, the rotation of the =N(O)OH group around the CN double bond in the aci-form is of key importance. The activation enthalpy is lower for this step than for the alternative process of H atom transfer between the O atoms in this group. This accounts for the competitive formation of the experimentally observed products of о-nitrotoluene thermal decomposition, namely, the hydroxyl radical and water. The activation barriers of the reactions were estimated over a broad temperature range, which indicated the possible contribution of о-nitrotoluene thermal decomposition and other alternative primary event mechanisms (nitro—nitrite rearrangement, bicyclization) to the efficient rate constant. The results account for the differences between the activation parameters experimentally determined at various temperatures by different authors.     

Normal- and Reversed-Phase Thin-Layer Chromatography of Seven Oral Antidiabetic Agents

JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of seven oral antidiabetic drugs -chlorpropamide, tolbutamide, glibenclamide, metformin, pioglitazone,...