Synthesis of 3-cyano-2-pyridone derivative and its utility in the synthesis of some heterocyclic compounds with expecting antimicrobial activity

New 2-pyridone derivatives bearing p-methoxyphenyl and p-bromophenyl substituents at C-4 and C-6 were prepared smoothly by the one-pot reaction in high yield, and in a comparatively short time, it reacted with phosphorous oxychloride to produce the corresponding chloro compound. The latter was reacted with several nitrogen nucleophiles such as sodium azide, hydrazine, acetohydrazide, and benzohydrazide to give tetrazolo, hydrazino, and triazolo derivatives, respectively. The reaction of hydrazino derivative with cyclopentanone, furan-2-carbaldehyde afforded the corresponding hydrazone derivatives. Cyclocondensation of the latter compounds with thioglycolic acid afforded the nicotinamide derivatives. 2-Pyridone reacted with ethyl chloroacetate to afford chloroacetate and ethyl acetate derivatives. Ethyl acetate-derivative reacted with hydrazine hydrate and gave the acetohydrazide derivative, it was condensed with p-anisaldehyde and gave the 4-methoxybenzylidene acetohydrazide derivative. Also, 2-pyridone reacted with chloroacetic acid and or benzoyl chloride, afforded the benzoate derivative and 2-((6-(4-bromophenyl)-3-cyano-4-(4-methoxyphenyl) pyridin-2-yl) oxy) acetic acid, respectively. Structures of the products were confirmed using spectroscopic data and elemental analyses. Antibacterial activity of the synthesized compounds was evaluated against Escherichia coli and Staphylococcus aureus.     

Synthesis and antitumor activity of some nitrogen heterocycles bearing pyrimidine moiety

Synthesis of novel pyrimidine derivatives 4-16 was accomplished by heterocyclization of polarized system, for example, Chalcone. Claisen-Schmidt condensation of 2-acetyl naphthalene with 4-(N, N-dimethylaminobenzaldehyde) afforded chalcone 3 , which was utilized for synthesis various pyrimidine derivatives by treatment with urea, thiourea, and guandine hydrochloride in ethanolic sodium hydroxide solution. The reactivity of the synthesized pyrimidine derivatives towards different nucleophilic and electrophilic reagent were examined. The constructions of the newly synthesized pyrimidine derivatives were elucidated from their spectral and elemental analysis. All the synthesized compounds were tested in vitro for their anticancer activities against HePG-2 and MCF-7 cell lines. Some of them posses a wide range of pharmacological activity. Finally, a molecular docking study was conducted to reveal the probable interaction with the dihydrofolate reductase (DHFR) active site.     

Measurement of methyl mercury (I) and mercury (II) in fish tissues and sediments by HPLC-ICPMS and HPLC-HGAAS

A procedure for the extraction and determination of methyl mercury and mercury (II) in fish muscle tissues and sediment samples is presented. The procedure involves extraction with 5% (v/v) 2-mercaptoethanol, separation and determination of mercury species by HPLC-ICPMS using a Perkin-Elmer 3 μm C8 (33 mm × 3 mm) column and a mobile phase 3 containing 0.5% (v/v) 2-mercaptoethanol and 5% (v/v) CH₃OH (pH 5.5) at a flow rate 1.5 ml min⁻¹ and a temperature of 25 °C. Calibration curves for methyl mercury (I) and mercury (II) standards were linear in the range of 0-100 μg l⁻¹ (r² = 0.9990 and r² = 0.9995 respectively). The lowest measurable mercury was 0.4 μg l⁻¹ which corresponds to 0.01 μg g⁻¹ in fish tissues and sediments. Methyl mercury concentrations measured in biological certified reference materials, NRCC DORM - 2 Dogfish muscle (4.4 ± 0.8 μg g⁻¹), NRCC Dolt - 3 Dogfish liver (1.55 ± 0.09 μg g⁻¹), NIST RM 50 Albacore Tuna (0.89 ± 0.08 μg g⁻¹) and IRMM IMEP-20 Tuna fish (3.6 ± 0.6 μg g⁻¹) were in agreement with the certified value (4.47 ± 0.32 μg g⁻¹, 1.59 ± 0.12 μg g⁻¹, 0.87 ± 0.03 μg g⁻¹, 4.24 ± 0.27 μg g⁻¹ respectively). For the sediment reference material ERM CC 580, a methyl mercury concentration of 0.070 ± 0.002 μg g⁻¹ was measured which corresponds to an extraction efficiency of 92 ± 3% of certified values (0.076 ± 0.04 μg g⁻¹) but within the range of published values (0.040-0.084 μg g⁻¹; mean ± s.d.: 0.073 ± 0.05 μg g⁻¹, n = 40) for this material. The extraction procedure for the fish tissues was also compared against an enzymatic extraction using Protease type XIV that has been previously published and similar results were obtained. The use of HPLC-HGAAS with a Phenomenox 5 μm Luna C18 (250 mm × 4.6 mm) column and a mobile phase containing 0.06 mol l⁻¹ ammonium acetate (Merck Pty Limited, Australia) in 5% (v/v) methanol and 0.1% (w/v) l-cysteine at 25 °C was evaluated as a complementary alternative to HPLC-ICPMS for the measurement of mercury species in fish tissues. The lowest measurable mercury concentration was 2 μg l⁻¹ and this corresponds to 0.1 μg g⁻¹ in fish tissues. Analysis of enzymatic extracts analysed by HPLC-HGAAS and HPLC-ICPMS gave equivalent results.     

Water-soluble derivatives of chitosan as a target delivery system of <Superscript>99m</Superscript>Tc to some organs in vivo for nuclear imaging and biodistribution

Carboxymethyl chitosan, (CMC), and N-lauryl-carboxymethyl chitosan (LCMC), have been prepared as water soluble derivatives of chitosan. These biodegradable chitosan derivatives were characterized and investigated for nuclear imaging and body distribution. They were labeled with ^99mTc to use them as targeted delivery to some organs in vivo for nuclear imaging and to follow their biodistribution within the body. The factors controlling the labeling efficiency have been investigated. The percent labeling yield was determined by using ascending paper chromatographic technique. In vivo biodistribution studies of radiolabeled chitosan derivatives were carried out in groups of female Wistar rats, the body distribution profile in rat was recorded by gamma scintigraphy and the biodistribution of ^99mTc-labeled compounds in each organ was calculated as a percentage of the injected dose per gram of tissue (%ID/g). It has been found that the biodistribution of the two compounds and the pattern of their liver uptake were markedly different. The present study demonstrates a high potential approach for liver imaging using ^99mTc-LCMC. An intriguing finding of this study was that the three samples were excreted rapidly via the kidneys because of the water-soluble nature of chitosan derivatives. This suggests that water-soluble chitosan derivatives are good polymeric carriers for radioactive element that overcomes accumulation in the body. Moreover, the easy and inexpensive availability of chitosan could be beneficial for applications in scintigraphic imaging.     

Development of validated stability-indicating chromatographic method for the determination of fexofenadine hydrochloride and its related impurities in pharmaceutical tablets

ABSTRACT: A simple reversed phase high performance liquid chromatographic method with diode array detector (HPLC-DAD) has been developed and subsequently validated for the determination of fexofenadine hydrochloride (FEX) and its related compounds; keto fexofenadine (Impurity A), meta isomer of fexofenadine (Impurity B), methyl ester of fexofenadine (Impurity C) in addition to the methyl ester of ketofexofenadine (Impurity D). The separation was based on the use of a Hypersil BDS C-18 analytical column (250 × 4.6 mm, i.d., 5 μm). The mobile phase consisted of a mixture of phosphate buffer containing 0.1 gm% of 1-octane sulphonic acid sodium salt monohydrate and 1% (v/v) of triethylamine, pH 2.7 and methanol (60:40, v/v). The separation was carried out at ambient temperature with a flow rate of 1.5 ml/min. Quantitation was achieved with UV detection at 215 nm using lisinopril as internal standard, with linear calibration curves at concentration ranges 0.1-50 μg/ml for FEX and its related compounds. The optimized conditions were used to develop a stability-indicating HPLC-DAD method for the quantitative determination of FEX and its related compounds in tablet dosage forms. The drugs were subjected to oxidation, hydrolysis, photolysis and heat to apply stress conditions. Complete separation was achieved for the parent compounds and all degradation products. The method was validated according to ICH guidelines in terms of accuracy, precision, robustness, limits of detection and quantitation and other aspects of analytical validation.     

GC-MS and GC-IRD studies on dimethoxyphenethylamines (DMPEA): regioisomers related to 2,5-DMPEA

A series of regioisomeric dimethoxyphenethylamines have a mass spectra essentially equivalent to the drug substance 2,5-dimethoxyphenethylamine (2,5-DMPEA). These substances have a molecular weight of 181, and major fragment ions in their electron ionization mass spectra at m/z 151/152. The trifluoroacetyl, pentafluoropropionyl, and heptafluorobutryl derivatives of these primary amines were prepared and evaluated by gas chromatography with mass spectrometry detection (GC-MS). The mass spectra for these derivatives do not show unique fragment ions to allow the specific identification of a particular isomer. Thus, GC-MS does not provide for the confirmation of identity of any one of the six isomers to the exclusion of the other five compounds. However, GC-MS does divide the compounds into two groups depending on the mass of the base peak. GC with infrared detection provides direct confirmatory data for the identification of 2,5-DMPEA from the other regioisomers involved in the study. Perfluoroacylated derivatives of the six regioisomeric dimethoxyphenethylamines were successfully resolved via capillary GC on a non-polar stationary phase consisting of 50% phenyl and 50% methyl polysiloxane (Rxi-50).     

DNA bending by asymmetrically tethered cations: influence of tether flexibility

BACKGROUND: We have been studying the proposal that laterally asymmetric charge neutralization along the DNA double helix can induce collapse toward the neutralized surface. Results of previous experiments implied that such a phenomenon can occur, suggesting a role for local interphosphate repulsive forces in DNA shape and rigidity. RESULTS: We now show that, whereas six ammonium ions tethered to one DNA face on flexible propyl chains can induce detectable DNA curvature, tethering of ammonium ions on rigid propynyl tethers does not induce DNA curvature. Molecular modeling indicates differing propensities for phosphate salt bridge formation between propyl- and propynyl-tethered ammonium ions. CONCLUSIONS: Ammonium ion localization is suggested as a key factor in induced bending. Rigidification of the double helix by stacking of propyne groups cannot be excluded.     

Spectrophotometric Determination of Cobalt with Di-2-Pyridyl Ketone Benzoylhydrazone

Abstract

A method for the spectrophotometric determination of cobalt (II) by complexation with di-2-pyridyl ketone benzoylhydrazone (DPKBH) in 50% (v/v) ethanolic solution is described. Cobalt (II) forms a 1:2 complex with DPKBH. The complex has maximum absorbance at 370 nm. Beer's law is obeyed over the range 0.1 – 2.8 μg.ml^?1. The effect of pH, effect of excess reagent, stability of the complex and the tolerance limit of many metal ions have been reported. The method is applied to the determination of cobalt in different alloys containing other metals ions.     

Environmental magnetism and climate change

A major and pressing problem is to understand how, and how fast, the Earth's climate has changed in the past, with and without human influences on the global carbon cycle. Magnetic, remanence-acquiring, minerals, mostly iron oxides and sulphides, occur ubiquitously in sediments. They can act as sensitive recorders of past climates, because as climate has varied (from glacial to interglacial, for example), the mineralogy, magnetic domain state, composition and source of these minerals has varied. Here, the magnetic properties of windblown dust and interbedded soil layers of the Chinese Loess Plateau are used to calculate rainfall for the last million years, identifying the waxing and waning of the Southeast Asian summer monsoon. Comparison of our magnetic rainfall record on land with environmental records from the deep-sea shows that summer monsoon intensity is linked with growth and decay of continental-sized ice sheets, in turn reflecting changes in the Earth's orbit around the Sun.     

Comment to: Perturbation estimates for the nonlinear matrix equation X−A ∗ X q A=Q (0<q<1) by G. Jia and D. Gao

We show that the perturbation estimate for the matrix equation X?A ^? X ^q A=Q (0<q<1), due to G. Jia and D. Cao, published in this journal, is wrong.