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Background: Malondialdehyde (MDA) is a commonly used biomarker of oxidative stress in clinical studies and has been measured in many pathological conditions during last decades. Different analytical methods have been reported for determination of MDA in biological samples in which MDA was adducted with thiobarbituric acid (TBA) to produce more sensitive chromophore and also convert it to a fluorescent compound. In spite of the routine applications of this derivatization and subsequent analysis of MDA in biomedical studies, its reliability, repeatability and reproducibility is questionable. The aim of this work is to investigate the effects of some factors on the repeatability of MDA determinations in standard solutions and also in plasma samples using spectroscopic method. Methods: MDA-TBA adduct is prepared in standard solutions and the effects of pH, temperature, reaction time, open, closed and reflux systems and the ratio of MDA and TBA is investigated by measuring the absorbance of the solution at 532 nm. These effects are also investigated in human plasma samples. Results: The best results are obtained at pH 2.5, temperature of 70 °C, reaction time of 150 minutes, reflux system and ratio of 2. Conclusion: Using the optimized conditions are resulted in better repeatability.

In this study, a highly active catalyst based on copper iodide nanoparticles supported on magnetic aminomethylpyridine functionalized cellulose has been synthesized and characterized. Its catalytic activity was investigated in the multicomponent synthesis of N-sulfonylamidines via an in situ generated sulfonyl ketenimine intermediate under solvent free conditions at room temperature. The desired products were obtained in good to excellent yields at short reaction times. Based on observed results, the synthesized catalyst was an efficient, magnetically separable, recyclable and green catalyst from a natural source.

Water activity measurements by the isopiestic method have been carried out on the aqueous ternary system of { l -serine + 1-(2-carboxyethyl)-3-methylimidazolium chloride[HOOCEMIM][Cl]} ionic liquid and the aqueous binary system of IL at T = 298.15 K and atmospheric pressure. The data obtained were used to calculate the vapor pressure and osmotic coefficient of solution as a function of concentration. The experimental results for the activity of water were accurately correlated with segment-based local composition models of modified NRTL and UNIQUAC. The fitting quality of the above models has been favorably compared with the NRTL and Wilson models. From these data, the corresponding activity coefficients have been calculated. For the same system, the solubility of the l -serine at various [HOOCEMIM][Cl] ionic liquid concentrations was measured at T = 298.15 K using the gravimetric method. A chemical model was employed to describe the dissociation equilibria of all amino acid species with hydrogen ions in water. Moreover, for l -serine, the chemical model indicated that the formation of cations is insignificant in the [HOOCEMIM][Cl] solution. Also the above local composition models were used to predict the solubility of l -serine in aqueous IL solutions. To provide information regarding (solute + solute) interactions, transfer Gibbs free energies (ΔGtr) of amino acid from water to aqueous IL solutions have been determined.

In this study, water activities for the ternary system of { l -serine + 1-carboxymethyl-3-methylimidazolium chloride [Cmmim][Cl] + H2O} and their corresponding binary aqueous solutions have been measured using an improved isopiestic method over the entire homogeneous mixing range at 298.15 K. For the same system, the solubility of the l -serine at various IL concentrations was measured at 298.15 K using gravimetric method. From the vapor–liquid equilibrium measurements, values of the vapor pressure, osmotic coefficient and activity coefficient of solutions were determined. The experimental data for the activity of water, collected in this work, were accurately correlated with segment-based local composition models of the NRTL, modified NRTL, Wilson and NRF-NRTL. The results showed that these models can accurately correlate the water activity data generated in this work. Also the above local composition models used to describe the solubility of amino acid in pure water and in aqueous IL solutions.

An efficient green chemistry method has been developed for the synthesis of 1-amidoalkyl-2-naphthol derivatives via a one-pot three-component condensation of 2-naphthol, aldehydes and amide in the presence of boric acid as a mild catalyst.

Aldoxime derivatives of 4H-pyran-4-ones 4-7a,b have been synthesized by the reaction of di(aminoxymethyl) pyranones 3a,b with aromatic aldehydes.

New podand and crown ether derivatives of 3,5-disubstituted 4 H -pyran-4-one( 8-11 ) were prepared by the nucleophilic substitution reaction of 3,5-bis(bromomethyl)-2,6-diphenyl-4 H -pyran-4-one with o -nitrophenol, 8-hydroxyquinoline, 2-hydroxymethylpyridine and triethyleneglycol, respectively. The yield of 3,5-bis[(2-formyl-phenoxy)methyl]-2,6-diphenyl-4 H -pyran-4-one has been improved by modification ofour previous method using NaOH instead of Et 3 N. Keywords: Crown ether, Podands, 4 H -pyran-4-one, Open-chain crown, Nucleophilicsubstitution. Introduction Synthetic podands are a family of linear multidentate ligands, which includes acyclic polyethers.They generally form complexes with smaller stability constants than those of correspondingmacrocyclic complexes and thus are usually regarded as poor ligands [2]. In contrast, manyexcellent podands are found in nature. For example, naturally occurring polyether antibiotics, suchas monsin and lasalocid, selectively bind several metal cations and effectively transport them across