Nitrofurazone and its nitroheterocyclic analogues: a study of the electrochemical behavior in aqueous medium

The biological action of drugs with potential antichagasic activities can be better understood by knowing their reduction mechanism. For this proposal, the electrochemical reduction of nitrofurazone (NF) and its analogues, nitrofurfurilidene thiosemicarbazone (NFS), nitrothiophene semicarbazone (NT), nitrothiophene thiosemicarbazone (NTS), was studied by differential pulse and cyclic voltammetries and chronoamperometry in aqueous medium by using a glassy carbon electrode. Those three synthetic analogues have oxygen and sulfur atoms arranged between the nitroheterocyclic ring (furan and thiophene, respectively) and the carbonyl group (semicarbazone and thiosemicarbazone, respectively). The respective hydroxylamine derivatives are the main products formed in acidic medium, being its formation linearly pH dependent. Although chronoamperometric data show that this reduction involves 4 electrons, its corresponding reduction voltammetric wave, in alkaline medium, is unfolded and a reversible reduction peak at a more positive potential appears. This peak is characterized as a nitro anion radical formation, whose decay is caused by a disproportionation reaction. Its kinetic stability was studied by the current ratio values of the R - NO2/R - NO2•- redox couple and the second-order constant (k2) was determined, being NTS the analogue that registered the highest stability.A compreensão do mecanismo de redução de compostos com potencial atividade antichagásica pode contribuir para o melhor entendimento de sua ação biológica. Com este objetivo, a redução eletroquímica de nitrofural (nitrofurazona, NF) e seus análogos, nitrofurfurilideno tiossemicarbazona (NFS), nitrotiofeno semicarbazona (NT), nitrotiofeno tiossemicarbazona (NTS), foi estudada pelas voltametrias de pulso diferencial, cíclica e cronoamperometria em meio aquoso, utilizando eletrodo de carbono vítreo. Esses três análogos sintéticos apresentam átomos de oxigênio e de enxofre distribuídos no anel heterocíclico (furano e tiofeno, respectivamente) e no grupo carbonila (semicarbazona e tiossemicarbazona, respectivamente). A hidroxilamina é o principal produto formado em meio ácido, sendo sua formação linearmente dependente do pH. A cronoamperometria mostrou que esta redução envolve 4 elétrons. Entretanto, em meio alcalino, esta onda de redução é desdobrada e um pico reversível a potencial mais positivo foi registrado, correspondendo à formação nitro ânion radical. O nitro ânion radical sofre desproporcionamento e sua estabilidade cinética foi avaliada aplicando a razão de corrente correspondente ao par reversível R - NO2/R - NO2•- e as constantes de segunda ordem (k2) foram determinadas. A partir dos valores de k2 observou-se que o análogo NTS registrou a maior estabilidade.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade de São Paulo Faculdade de Ciências Farmacêuticas Departmento de FarmáciaUniversidade Federal de São Paulo (UNIFESP) Departmento de Ciências Exatas e da TerraUNIFESP, Departmento de Ciências Exatas e da TerraProc. 2011/11499-0SciEL

Comparison of the voltammetric behavior of metronidazole at a DNA-modified glassy carbon electrode, a mercury thin film electrode and a glassy carbon electrode

The electroanalytical performance at three electrodes: DNA-modified galssy carbon electrode, mercury thin film electrode and glassy carbon electrode, for the study of the electrochemical reduction of metronidazole is compared. All three electrodes showed a similar trend in the reduction mechanism for metronidazole, depenent on pH in the acid and neutral region and independent in alkaline media, although there was a shift in the peak potentials to more negative values when a bare glassy carbon electrode was used compared to the other two. Besides the advantage of using a solid electrode for the reduction of metronidazole, the DNA-modified galssy carbon electrode enables a lower detection limit of 1.0 muM owing to the preconecentration of the drug on the electrode surface, which is not the case for the mercury thin film or bare glassy carbon electrodes

Electrochemical study of simple coumarin and its determination in aqueous infusion of Mikania glomerata

The present study aims the development and application of an electrochemical method for simple coumarin determination in aqueous media by using a boron-doped diamond electrode (BDDE). The studies were carried out at pH 8.0 by cyclic voltammetry (CV) and registered an irreversible reduction process controlled by diffusion with the peak potential recorded around -1.6 V. The square wave voltammetry analysis (SWV) showed the reversible behavior of the electrochemical reduction of coumarin at the same pH. Additionally, the reversibility of the process was improved by increasing the solution pH. The chronoamperometry study showed that the coumarin reduction process involves two electrons. From the optimized SWV parameters, the analytical curve was constructed in a linear range between 0.5 × 10-5 and 10.0 × 10-5 mol L-1. The limits of detection and quantification were 1.5 × 10-6 mol L-1 and 4.5 × 10-6 mol L-1, respectively. The coumarin was determined in an aqueous infusion of Mikania glomerata, showing recovery values between 92 and 104%.O presente estudo teve por objetivos o desenvolvimento e a aplicação de um método eletroquímico para a determinação da cumarina simples em meio aquoso utilizando o eletrodo de diamante dopado com boro (BDDE). Os estudos foram realizados em pH 8,0 utilizando a voltametria cíclica (CV) e observou-se um processo de redução irreversível controlado por difusão com um pico de redução em torno de -1,6 V. Entretanto, foi possível observar por voltametria de onda quadrada (SWV) que no mesmo pH a redução da cumarina possui um caráter reversível. Além disso, esta reversibilidade se tornou mais evidente com o aumento do pH da solução. Um estudo cronoamperométrico mostrou que o processo de redução da cumarina envolve dois elétrons. A partir dos parâmetros otimizados da SWV uma curva analítica foi construída no intervalo linear de 0,5 × 10-5 a 10,0 × 10-5 mol L-1. Os limites de detecção e de quantificação foram 1,5 × 10-6 mol L-1 e 4,5 × 10-6 mol L-1, respectivamente. A cumarina foi determinada em amostras de Mikania glomerata (infusão aquosa) com valores de recuperação entre 92 e 104%.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Federal de São Paulo (UNIFESP) Instituto de Ciências Ambientais, Químicas e Farmacêuticas Departamento de Ciências Exatas e da TerraUniversidade Federal do ABC Centro de Ciências Naturais e HumanasUNIFESP, Instituto de Ciências Ambientais, Químicas e Farmacêuticas Depto. de Ciências Exatas e da Terra2008/50588-6SciEL

Análisis Crítico de la Representación Discursiva de la Mujer Migrante Venezolana en los Medios de Comunicación Digitales del Perú.

The present research aimed to critically analyze the discursive representation of Venezuelan migrant women in Peru's digital media. The theoretical and methodological foundations adopted were the attitude system of Martin and White's (2005) Appraisal Theory and van Dijk's (2016) Critical Discourse Analysis. An analytical methodology was employed, with a qualitative and documentary design. A corpus composed of fifteen (15) news articles from three Peruvian digital media outlets (La República, Trome, and Perú 21) was analyzed. These articles referenced Venezuelan migrant women and were published between 2019 and 2023, a period during which the country experienced the highest influx of Venezuelan migrants (Inter-Agency Coordination Platform for Refugees and Migrants from Venezuela, 2023). Taking into account the different perspectives and ideologies of each newspaper, three major semantic nodes were identified. In the case of La República, the most common discursive representation constructed was that of the woman as a vulnerable victim. Trome, on the other hand, portrayed them as sensual and forbidden beings. Meanwhile, Perú 21 constructed a representation of them as aggressive and dangerous victimizes. Based on these findings, it was concluded that Peru's digital media discursively represent Venezuelan migrant women in a negative light, focusing on judging, discrediting, and dehumanizing them. La presente investigación tuvo como objetivo analizar críticamente la representación discursiva de la mujer migrante venezolana en los medios de comunicación digitales del Perú. Los fundamentos teóricos y metodológicos adoptados fueron el sistema de actitud de la Teoría de Valoración de Martin y White (2005) y el Análisis Crítico del Discurso de van Dijk (2016). Se empleó una metodología de índole analítica, con un diseño cualitativo y documental. Se analizó un corpus compuesto por quince (15) artículos de prensa provenientes de tres medios de comunicación digitales del Perú (La República, Trome y Perú 21) con referencias a las mujeres migrantes venezolanas y publicados entre 2019 y 2023, puesto que, durante este tiempo, el país experimentó el mayor flujo migratorio de venezolanos (Plataforma de Coordinación Interagencial para Refugiados y Migrantes de Venezuela, 2023). Tomando en cuenta las diferentes valoraciones e ideologías de cada diario, se logró construir tres grandes nódulos semánticos. En cuanto al diario La República, se encontró que la representación discursiva más común que construyó fue aquella que reduce a la mujer a una víctima vulnerable. En el caso del diario Trome, este las retrata como un ser sensual y prohibido. En cambio, la representaciónque construyó el diario Perú 21 se limita al de una victimaria agresiva y peligrosa. A partir de estos hallazgos, se concluyó que los medios de comunicación digitales del Perú representan discursivamente a la mujer migrante venezolana de manera negativa y se enfoca en juzgarlas, desprestigiarlas y deshumanizarlas

Electrochemical and Theoretical Studies on the Artesunate Reduction

Malaria is the most devastating tropical disease in the world and this scenario is worsened by the absence of effective treatment. However, the plasmodium resistance to artemisinin does not show clinical relevance. The drug mechanism of action is associated to the endoperoxide moiety breakage. Artesunate is a semi-synthetic derivative of artemisinin and its absorption is facilitated due to its higher solubility in water. As a sesquiterpene lactone, artesunate can be electrochemically reduced in aqueous media on the glassy carbon electrode, having been studied by cyclic voltammetry, square wave voltammetry and chronoamperometry. The artesunate voltammetric reduction is diffusion-controlled and significantly irreversible. Its reduction is pH-independent, but from pH = 6.0 the cathodic current values increase in alkaline media, indicating that the proton-equilibrium occurs after the electron transfer step. The an values calculated vary from 0.30 to 0.37, leading to the 0.0975 s-1 value for ks. From the chronoamperometric data, two electrons (1.9 ± 0.4) are involved in the reduction process, being confirmed by the exact number of electrons obtained for artemisinin (1.9 ± 0.2). According to these results and computational findings, both drugs have the same reduction mechanism with the breakage of the endoperoxide bridge and consequent diol-derivative formation followed by the deoxy analog stabilization through the existence of a set of reactions involving protonation and charge transfer steps on the electrode surface. DOI: http://dx.doi.org/10.17807/orbital.v12i3.143

Opportunities for autonomous UAV in harsh environments

AbstractThis paper describes the challenges raised from the use of Unmanned Aerial Vehicles (UAVs) on the exploration of inhospitable places that present limitations and risks to humans; for instance, we describe the case of cave exploration. UAVs have emerged as an attractive alternative for performing this task in a safety and reliable manner. However, challenges regarding control management, accurate positioning and navigation, and reliable wireless connectivity need to be addressed in order to achieve effective solutions. Herein, we address those challenges and present possible solutions for enabling the use of UAVs in harsh environments.Abstract This paper describes the challenges raised from the use of Unmanned Aerial Vehicles (UAVs) on the exploration of inhospitable places that present limitations and risks to humans; for instance, we describe the case of cave exploration. UAVs have emerged as an attractive alternative for performing this task in a safety and reliable manner. However, challenges regarding control management, accurate positioning and navigation, and reliable wireless connectivity need to be addressed in order to achieve effective solutions. Herein, we address those challenges and present possible solutions for enabling the use of UAVs in harsh environments

Ensino remoto em tempos de pandemia: considerações sobre o ensino não presencial emergencial na Universidade Federal de São Carlos (UFSCAR): Remote education in pandemic times: considerations about the emergency Off-site teaching at the Universidade Federal de São Carlos (UFSCAR)

Por conta da pandemia da Covid-19, o ambiente universitário precisou adaptar suas atividades e o processo de ensino e aprendizagem. Na Universidade Federal de São Carlos (UFSCar), a experiência contraditória do ENPE trouxe diversas complicações e agravantes. Por meio da realização de entrevistas, questionários e do levantamento documental, bem como da participação observante em espaços de decisão institucionais e da experiência em oferecer, monitorar e participar de aulas realizadas de forma remota, buscamos apontar as características do ensino remoto, em geral, e das particularidades do ensino não-presencial emergencial, em específico, além de apontar algumas alternativas e possibilidades.&nbsp

International recommendations for glucose control in adult non diabetic critically ill patients

The purpose of this research is to provide recommendations for the management of glycemic control in critically ill patients.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishedPour la Société Française d'Anesthésie-Réanimation (SFAR); Société de Réanimation de langue Française (SRLF) and the Experts grou