Development of bis-thiobarbiturates as successful urease inhibitors and their molecular modeling studies

Bis-thiobarbiturate derivatives 1–15 have been synthesized, characterized by1 HNMR and EI-MS and screened for urease inhibition. All compounds showed various degree of urease inhibitory activity with IC_(50) values ranging 7.45 0.12 74.24 0.81 mmol/L while the standard thiourea behaved normally(IC_(50) = 21.10 0.12). Compounds 1(IC_(50) = 7.45 0.12 μmol/L), 9(IC_(50) = 18.17 1.03 μmol/L) and 13(IC_(50) = 8.61 0.45 μmol/L) showed excellent urease inhibitory activity in the series. Molecular modeling studies were performed to understand the binding site with the bimetallic nickel center of the enzyme.Structure-activity relationship has also been established for these compounds. This study identified bisthiobarbiturate as a novel class of urease inhibitors.     

Multi-residue analytical method for the determination of emerging pollutants in water by solid-phase extraction and liquid chromatography-tandem mass spectrometry

This paper describes the development and validation of a method for the simultaneous determination of 53 multi-class emerging organic pollutants in water samples using solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), using electrospray ionisation (ESI) in both positive and negative modes. Target compounds include acidic herbicides, UV filters, insect repellents, organophosphorous flame retardants, a bactericide, pharmaceuticals and metabolites. A single SPE consisting on the loading of 200-500 mL of sample adjusted to pH 7 on Oasis HLB 200mg cartridges and elution with methanol, permitted obtaining good recoveries: higher than 60% for tap, surface and wastewater in most cases. The 7 isotopically labelled internal standards effectively compensated losses during sample preparation and matrix effects at LC-MS/MS determination. The precision of the method, calculated as relative standard deviation (RSD) was below 15% for all compounds and all tested matrices. Detection limits (LODs) based on the confirmation, less intense, MRM (multiple reaction monitoring) transition and considering blanks varied between 0.3 and 30 ngL(-1). Finally, the developed method was applied to the determination of target analytes in various samples, including tap, surface and waste water. Among the tested emerging pollutants, 31 were found in wastewater in concentrations reaching up to 10 microgL(-1) in the case of ibuprofen. Also, 13 species were detected in tap water with concentrations up to 0.13 microgL(-1) for tri(chloropropyl) phosphate (TCPP).     

Chitosan Elicitation Impacts Flavonolignan Biosynthesis in Silybum marianum (L.) Gaertn Cell Suspension and Enhances Antioxidant and Anti-Inflammatory Activities of Cell Extracts

Silybum marianum (L.) Gaertn is a rich source of antioxidants and anti-inflammatory flavonolignans with great potential for use in pharmaceutical and cosmetic products. Its biotechnological production using in vitro culture system has been proposed. Chitosan is a well-known elicitor that strongly affects both secondary metabolites and biomass production by plants. The effect of chitosan on S. marianum cell suspension is not known yet. In the present study, suspension cultures of S. marianum were exploited for their in vitro potential to produce bioactive flavonolignans in the presence of chitosan. Established cell suspension cultures were maintained on the same hormonal media supplemented with 0.5 mg/L BAP (6-benzylaminopurine) and 1.0 mg/L NAA (α-naphthalene acetic acid) under photoperiod 16/8 h (light/dark) and exposed to various treatments of chitosan (ranging from 0.5 to 50.0 mg/L). The highest biomass production was observed for cell suspension treated with 5.0 mg/L chitosan, resulting in 123.3 ± 1.7 g/L fresh weight (FW) and 17.7 ± 0.5 g/L dry weight (DW) productions. All chitosan treatments resulted in an overall increase in the accumulation of total flavonoids (5.0 ± 0.1 mg/g DW for 5.0 mg/L chitosan), total phenolic compounds (11.0 ± 0.2 mg/g DW for 0.5 mg/L chitosan) and silymarin (9.9 ± 0.5 mg/g DW for 0.5 mg/L chitosan). In particular, higher accumulation levels of silybin B (6.3 ± 0.2 mg/g DW), silybin A (1.2 ± 0.1 mg/g DW) and silydianin (1.0 ± 0.0 mg/g DW) were recorded for 0.5 mg/L chitosan. The corresponding extracts displayed enhanced antioxidant and anti-inflammatory capacities: in particular, high ABTS antioxidant activity (741.5 ± 4.4 μM Trolox C equivalent antioxidant capacity) was recorded in extracts obtained in presence of 0.5 mg/L of chitosan, whereas highest inhibitions of cyclooxygenase 2 (COX-2, 30.5 ± 1.3 %), secretory phospholipase A2 (sPLA2, 33.9 ± 1.3 %) and 15-lipoxygenase (15-LOX-2, 31.6 ± 1.2 %) enzymes involved in inflammation process were measured in extracts obtained in the presence of 5.0 mg/L of chitosan. Taken together, these results highlight the high potential of the chitosan elicitation in the S. marianum cell suspension for enhanced production of antioxidant and anti-inflammatory silymarin-rich extracts.     

Direct determination of Ge in hot spring waters and coal fly ash samples by hydride generation-ETAAS

A method for Ge determination in hot spring water and acid extracts from coal fly ash samples involving hydride generation, trapping and atomisation of the hydride generated from Ir-treated graphite tubes (GTs) has been developed. Hydride was generated from hydrochloric acid medium using sodium tetrahydroborate. Several factors affecting the hydride generation, transport, trapping and atomisation efficiency were studied by using a Plackett-Burman design. Results obtained from Plackett-Burman designs suggest that trapping and atomisation temperatures are the significant factors involved on the procedure. The accuracy was studied using NIST-1633a (coal fly ash) reference material. The detection limit of the proposed method was 2.4 μg l⁻¹ and the characteristic mass of 233 pg was achieved. The Ge concentrations in fly ash and hot spring samples were between 6.25-132 μg g⁻¹ and 12.84-36.2 μg l⁻¹.     

Progress and Prospects on the Fabrication of Graphene-Based Nanostructures for Energy Storage,Energy Conversion and Biomedical Applications

Graphene, a two-dimensional (2D) layered material has attracted much attention from the scientific community due to its exceptional electrical, thermal, mechanical, biological and optical properties. Hence, numerous applications utilizing graphene-based materials could be conceived in next-generation electronics, chemical and biological sensing, energy conversion and storage, and beyond. The interaction between graphene surfaces with other materials plays a vital role in influencing its properties than other bulk materials. In this review, we outline the recent progress in the production of graphene and related 2D materials, and their uses in energy conversion (solar cells, fuel cells), energy storage (batteries, supercapacitors) and biomedical applications.     

Effect of postcasting heat‐treatment on the structure and properties of semicrystalline phase‐inversion poly(vinylidene fluoride) membranes

Microporous PVDF membranes were prepared by immersion‐precipitation in 1‐octanol of casting dopes dissolved at different temperatures, with dissolution temperature affecting strongly the membrane microstructure. The effect of postcoagulation thermal annealing, which is an additional thermal parameter, on membrane microstructure and properties is probed herein. Membranes obtained were annealed at temperatures up to 160 °C, which is close to the melting point of PVDF polymer. Annealing leads to a substantial modification of the nano‐scale fine structure of the membranes, while the overall‐microporous structure is preserved. At elevated annealing temperatures, nano‐grains, fibrils, and stick‐like crystalline entities gradually eclipse, while globules develop more robust connections based on wide bands of crystal elements. Probing by X‐ray diffraction and dynamic scanning calorimetry shows that crystallinity increases when annealing temperature and time are increased. As regards mechanical properties, the tensile strength of the membranes can be enhanced substantially, up to about 10 times, upon appropriate high temperature prolonged annealing. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1880–1893, 2009     

HPLC method for determination of diclofenac in human plasma and its application to a pharmacokinetic study in Turkey

A simple high-performance liquid chromatography (HPLC) method has been developed for determination of diclofenac in human plasma. The method was validated on Ace C(18) column using UV detection. The mobile phase consisted of 20 mM phosphate buffer (pH 7) containing 0.1% trifluoroacetic acid-acetonitrile (65:35, v/v). Calibration curve was linear between the concentration range of 75-4000 ng/mL. Intra- and inter-day precision values for diclofenac in plasma were less than 3.6, and accuracy (relative error) was better than 5.3%. The limits of detection and quantification of diclofenac were 25 and 75 ng/mL, respectively. Also, this assay was applied to determine the pharmacokinetic parameters of diclofenac in healthy Turkish volunteers who had been given 50 mg diclofenac.     

High order approximations of the eigenvalues of sturm-liouville problems with coupled self-adjoint boundary conditions

Sampling theory has been used to compute with great accuracy the eigenvalues of regular and singular Sturm-Liouville problems of Bessel Type. We shall consider in this paper the case of general coupled real or complex self-adjoint boundary conditions. We shall present few examples to illustrate the power of the method and compare our results with the ones obtained using the well-known Sleign2 package.