Anisotropic and branched gold nanoparticles have great potential in optical, chemical and biomedical applications. However their syntheses involve multi-step protocols and the use of cytotoxic agents. Here, we report a novel one-step method for the preparation of gold nanostructures using only Hantzsch 1,4-dihydropyridines as mild reducing agents.
View Article and Find Full Text PDFPhotochem Photobiol
January 2014
The electronic nature of substituents attached to the 4-aryl moiety of 1,4-dihydropyridines strongly affects the photophysical and photochemical behavior of these family of compounds. The presence of an electron donor substituent on the 4-aryl moiety (or the absence of electron-withdrawing ones) modifies the luminescence lifetimes (τ < 100 ps) and diminishes the photodecomposition quantum yields. For electron-withdrawing substituents, the photodegradation quantum yield is affected by the media, changing more than two orders of magnitude as the polarity is increased.
View Article and Find Full Text PDFNitroimidazole PA-824 is part of an exciting new class of compounds currently undergoing clinical evaluation as novel TB therapeutics. The recently elucidated mechanism of action of PA-824 involves reduction of the nitroimidazole ring and subsequent nitric oxide release. The importance of this compound and its unique activity prompted us to explore how substitution of the nitroimidazole ring would affect electrochemical reduction and antitubercular activity.
View Article and Find Full Text PDFThis work reports the electrochemical oxidation of three newly synthesized C4-hydroxyphenyl-substituted 1,4-dihydropyridine derivatives in dimethylsulfoxide. The reactivity of the compounds with ABAP-derived alkylperoxyl radicals in aqueous buffer pH 7.4, was also studied.
View Article and Find Full Text PDFEI mass spectra of products of the dihydropyridine Hantzsch synthesis using hydroxy and methoxy aldehydes as starting materials are reported. The reaction products (C-4 hydroxy- and methoxyphenyl-1,4-dihydropyridines and chromeno[3,4,c]-pyridines) were derivatized with N-methyl-N-(trimethylsilyl)-trifluoracetamide to be analyzed by gas chromatographic techniques. Fragmentation pathways for 1,4-dihydropyridines and chromeno-pyridines are proposed.
View Article and Find Full Text PDFIn this work, a liquid chromatography stability-indicating method was developed and applied to study the hydrolytic behavior of simvastatin in different pH values and temperatures. The selected chromatographic conditions were a C18 column; acetonitrile-28 mM phosphate buffer solution, pH 4 (65 + 35) as the mobile phase; 251 degrees C column temperature; and flow rate 1 mL/min. The developed method exhibited an adequate repeatability and reproducibility (coefficient of variation 0.
View Article and Find Full Text PDFIn this work both the electrochemical behavior and the analysis of the hypnotic pyrazolopyrimidine derivative zaleplon were studied. Zaleplon in ethanol-0.1M Britton Robinson buffer solution (30-70) showed 2 irreversible, well-defined cathodic responses in the pH range of 2-12 using differential pulse polarography (DPP), tast polarography, and cyclic voltammetry.
View Article and Find Full Text PDFPurpose: To study the reactivity of C4-substituted 1,4-dihydropyridines (1,4-DHP), with either secondary or tertiary nitrogen in the dihydropyridine ring, toward SIN-1-derived peroxynitrite in aqueous media at pH 7.4.
Methods: Reactivity was followed by changes in the absorptivity of the UV-Vis bands corresponding to 1,4-DHP.
This work reports the electrochemical oxidation of a series of three synthesized 4-substituted-1,4-dihydropyridine derivatives in different electrolytic media. Also, an EPR characterization of intermediates and the reactivity of derivatives towards ABAP-derived alkyl radicals are reported. Dynamic, differential pulse and cyclic voltammetry studies on a glassy carbon electrode showed an irreversible single-peak due to the oxidation of the 1,4-dihydropyridine (1,4-DHP) ring via 2-electrons to the corresponding pyridine derivative.
View Article and Find Full Text PDFPurpose: To evaluate the reaction of a large series of pharmacologically significant 1,4-dihydropyridine (1,4-DHP) compounds with superoxide (O2.-) in dimethylsulfoxide using differential pulse voltammetry and controlled potential electrolysis.
Methods: Differential pulse voltammetry was used to track the consumption of O2.
A gas chromatography/mass spectrometry (GC/MS) method for the qualitative and quantitative determination of the calcium-channel antagonists C-4-substituted 1,4-dihydropyridines, and their corresponding N-ethyl derivatives, is presented. Also, the electrochemical oxidation and the reactivity of the compounds with alkyl radicals derived from 2,2'-azobis-(2-amidinopropane) were monitored by GC/MS. Mass spectral fragmentation patterns for the C-4-substituted 1,4-dihydropy-ridine parent drugs were significantly different from those of their oxidation products, generated either by electrochemical oxidation or by reaction with alkyl radicals.
View Article and Find Full Text PDFLercanidipine in ethanol-0.04M Britton-Robinson buffer (20 + 80) gives an irreversible anodic response on a glassy carbon electrode in a broad pH range (2-12) that depends on pH. This signal can be attributed to oxidation of the 1,4-dihydropyridine ring to give the corresponding pyridine derivative.
View Article and Find Full Text PDFThe effects of some imine and amine derivatives of vanillin on the respiration rate of mouse mammary adenocarcinoma TA3 line, its multiresistant variant TA3-MTX-R line and mouse hepatocytes, together with their respective mitochondrial fractions, are described. These derivatives inhibit respiration in both tumour cell lines more effectively than vanillin in the absence or presence of the uncoupler CCCP. Since both types of derivatives block the electron flow, mainly through the NADH-CoQ span, they behave as oxidative phosphorylation inhibitors.
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