Photodegradation of nimodipine and felodipine in microheterogeneous systems

Indexación: Web of Science; ScieloThe photochemical behavior of nimodipine (NIMO) and felodipine (FELO), photolabile drugs widely used as antihypertensive calcium channel blockers, is studied in constrained media. Specifically, we are interested in the kinetic analysis of 4-aryl-1,4-dihydropyridine photodegradation processes when they are incorporated in biological-mimicking systems like micelles or liposomes. In order to establish if the nature of the head of surfactant (ionic or nonionic) could be important modulating the photo-reactivity of these drugs, we studied the photodegradation of NIMO and FELO incorporated in micelles formed with sodium dodecyl sulfate (SDS, anionic), dodecyl-pyridinium chloride (DPC, cationic) and mono lauryl sucrose ester (MLS, nonionic) as surfactants. Additionally, the results of the photodegradation of these compounds in liposomes were also included. The results clearly indicate that both dihydropyridines studied, NIMO and FELO, are located near to the interface, but the surface charge of micelles does not affect neither, the photodegradation rate constant nor the photodegradation products profile. The absence of singlet oxygen generation in micellar media is consistent with the proposition of these 4-aryl-1,4-dihidropyridines located near to the interface of the micelle, where a polar environment is sensed. In addition, the ethanol preferential location on membranes and dihydropyridine enhanced photodegradation by alcohol presence are interesting results to consider in future research.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072012000300025&nrm=is

Capitulo 2. Ciencias Naturales y Ciencias Básicas, Ingeniería y Tecnología

La diseminación de la Levitación Magnética, a pesar de lo antiguo de su tecnología, ha sido limitada. Debido a sus inconvenientes prácticos de implementación, su uso es bastante restringido, comparado con otras tecnologías (SCMaglev japonés, Transrapid alemán, o productos comerciales para ocio y entretenimiento). Con el boom de las tecnologías limpias y amigables con el medio ambiente y en concordancia con los objetivos del milenio, es pertinente plantearse el objetivo de optimizar el proceso de Levitación Magnética para generar un aprovechamiento de las ventajas de esta tecnología a nivel mecánico, eléctrico, y ambiental.  Actualmente la UNAD adelanta un proyecto de investigación cuyo objetivo es generar un modelo físico matemático de levitación magnética para aplicaciones en ingeniería. De este proyecto se ha derivado una primera revisión sistemática de los principios físicos y los modelos vigentes en Levitación Magnética

Multiple Scenario Generation of Subsurface Models:Consistent Integration of Information from Geophysical and Geological Data throuh Combination of Probabilistic Inverse Problem Theory and Geostatistics

Neutrinos with energies above 1017 eV are detectable with the Surface Detector Array of the Pierre Auger Observatory. The identification is efficiently performed for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for Earth-skimming \u3c4 neutrinos with nearly tangential trajectories relative to the Earth. No neutrino candidates were found in 3c 14.7 years of data taken up to 31 August 2018. This leads to restrictive upper bounds on their flux. The 90% C.L. single-flavor limit to the diffuse flux of ultra-high-energy neutrinos with an E\u3bd-2 spectrum in the energy range 1.0 7 1017 eV -2.5 7 1019 eV is E2 dN\u3bd/dE\u3bd < 4.4 7 10-9 GeV cm-2 s-1 sr-1, placing strong constraints on several models of neutrino production at EeV energies and on the properties of the sources of ultra-high-energy cosmic rays

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Polarography of an acidic degradation product from cephalexin

2-Hydroxy-3-phenyl-6-methylpyrazine is identified as the product obtained by acidic degradation of cephalexin in the presence of formaldehyde. In 5M hydrochloric acid this product gives a well-defined reduction wave with a half-wave potential of -0.45 V vs. SCE. The wave is irreversible and diffusion-controlled. The diffusion current shows a linear relation with the cephalexin concentration and can be used for determination of cephalexin in plasma. © 1982

Electrochemical reduction of nicergoline and its analytical determination in dosage forms

Electrochemical reduction of nicergoline was studied at different pH and concentrations using differential pulse polarography and linear sweep voltammetry. Both techniques reveal that the reduction process occurs with strong adsorption of the product. Nicergoline is an excellent model for the previously developed theory related to the effects of strong adsorption of electroactive species in voltammetry. At concentrations below 0.1 mM, the adsorption prepeak is linearly dependent on nicergoline concentration. This peak was used to develop a new differential pulse polarographic method for the determination of the drug in pharmaceutical dosage forms. The method is simple and not time-consuming because nitrogen purging of samples and previous separation of the excipients were not needed. A comparative UV spectrophotometric assay was applied. Recovery data and composite and uniformity content studies for both methods are reported. © 1992

Electrochemical generation and reactivity of free radical redox intermediates from ortho-and meta-nitro substituted 1,4-dihydropyridines

This paper reports a comprehensive study by cyclic voltammetry on the electrochemical characteristics and the reactivity of the one-electron reduction product from a series of nitro aryl 1,4-dihydropyridines in mixed and aprotic media. In addition, the effects of 1,4-DHP on the oxygen consumption of T. cruzi epimastigotes are reported. One-electron reduction products from 1,4-DHP derivatives significantly reacted with both thiol compounds and the nuclei acid bases, adenine and uracil. This reactivity was significantly higher than the natural decay of the radicals in mixed media. Based on these results the following tentative order of reactivity towards the xeno/endobiotics is as follows: cysteamine > glutathione > adenineuracil. Both the stability and the reactivity of the nitro radical anions electrochemically generated from 1,4-DHP showed a linear dependence with pH. The sensitivity to pi-I of the radicals derived from o-nitro substituted derivatives was significantly higher than m-

Cyclic voltammetric study of the nitro radical anion from nitrendipine generated electrochemically

Electrochemical studies on nitrendipine using mixed aqueous/dimethylformamide (DMF) solvent have allowed us to generate the one-electron reduction product, the nitro radical anion, RNO.-2. The voltammetric technique has been employed to study the tendency of RNO.-2 to undergo further chemical reactions. The electrochemical process corresponds to a dimerization reaction that is initiated electrochemically. The cyclic voltammetric technique has allowed the rate constant and the half-life time to be determined for the decay of RNO.-2 in aqueous DMF mixed media and by extrapolation in aqueous media. © 1992

In vitro binding between glutathione and cloxacillin by a.c. polarography

The interaction of glutathione with cloxacillin was investigated by a new a.c. polarographic procedure. The theoretical treatment used to describe the interaction is strongly consistent with the experimental results. The stability constant, K, and coordination number, p, were calculated from the a.c. polarographic data. Under physiological conditions, we obtained a K value of 3.74×1014 and a p value of 3.12 suggesting 1:3 interaction for the glutathione-cloxacillin species. The coordination number is pH-dependent with a maximum value being obtained under physiological conditions. © 1983 Elsevier Sequoia S.A