Author
Juan A. Squella
Other affiliations: Electrochemical Society
Bio: Juan A. Squella is an academic researcher from University of Chile. The author has contributed to research in topics: Cyclic voltammetry & Nitro. The author has an hindex of 29, co-authored 210 publications receiving 3173 citations. Previous affiliations of Juan A. Squella include Electrochemical Society.
Topics: Cyclic voltammetry, Nitro, Nitro compound, Radical, Polarography
Papers published on a yearly basis
Papers
More filters
••
TL;DR: The results indicate that nifurtimox and related compounds act as redox cyclers, whereas the most active in the series, the 5-nitroimidazole megazol essentially acts as thiol scavenger particularly for trypanothione, the cofactor for try panothione reductase, an essential enzyme in the detoxification process.
155 citations
••
TL;DR: From the pH-dependence of the peak current it is possible to affirm that pH 2 is the better condition for the oxidative activity of gallate radicals showing that the antioxidant behaviour of these compounds are important in the stomach acid.
118 citations
••
TL;DR: The formation of the nitro radical anion as the product of the one electron reduction of nitro compounds generates a series of important consequences passing from chemical to biological aspects as discussed by the authors.
Abstract: The redox chemistry of different nitro compounds of biological significance is focused to understand how the reduction of the nitro group can play an active role in several aspects as: electroanalytical determinations, free radical generation and stability and free radical reactivity. We have focused our studies to a lot of pharmaceuticals belonging mainly to the following families: calcium antagonists as nitrobenzene substituted 1,4-dihydropyridines, antibacterial and anti protozoan agents as nitroimidazoles and nitrofurans. The formation of the nitro radical anion as the product of the one electron reduction of nitro compounds generates a series of important consequences passing from chemical to biological aspects. We have used electrochemical techniques to study the formation, stability and reactivity of this nitro radical anion in different media. From cyclic voltammetric experiments it is possible qualitatively to visualize the formation of the nitro radical anion through the one-electron reversible couple due to the redox system nitro / nitro radical anion . Furthermore also is possible the quantitative determination of the kinetic rate constant of the nitro radical anion decay and the interaction constants with other molecules. Although substituents may affect the redox potential and consequently the stability or reactivity of the nitro radical anions, other factors are important in regulation of these properties. Among these factors, it is possible to mention the nature of the reaction media making possible the occurrence of intermolecular reactions of the father-son type between the nitro radical anion and an acidic hydrogen present in the molecules.
91 citations
••
TL;DR: In this paper, a glassy carbon electrode (GCE) with multi-walled carbon nanotubes (MWCNTs) using 1,3-dioxolane as a dispersant agent, resulting in a stable and reproducible electrochemical sensor was applied to study the food dyes tartrazine, sunset yellow and carmoisine.
Abstract: Food colorants are chemicals added to foods and soft drinks during manufacturing or processing. However, some of these chemicals represent potential risks to human health, especially if they are consumed in excess. Here, we modified a glassy carbon electrode (GCE) with multi-walled carbon nanotubes (MWCNTs) using 1,3-dioxolane as a dispersant agent, resulting in a stable and reproducible electrochemical sensor. The resulting sensor was applied to study the food dyes tartrazine, sunset yellow and carmoisine, showing high sensitivity and reproducibility. The influences of the scan rate, pH, amount of MWCNTs and accumulation time were studied. Moreover, the developed method was successfully applied in the determination of colorants in commercial soft drinks and compared with a chromatographic method. The resulting concentrations were compared based on the maximum amount of soft drink that a child and an adult can consume before reaching the admissible daily intake (ADI) of each colorant.
73 citations
••
TL;DR: In this paper, the antioxidant capacity of hydroxylated coumarins and hydroxybenzoic acids was evaluated against reactive oxygen species (ROS) using oxygen radical absorbance capacity-fluorescein (ORAC-FL), electron spin resonance (ESR) spin trapping, quenching of superoxide anion, cellular antioxidant activity (CAA), and a ferric reducing ability of plasma (FRAP assay).
57 citations
Cited by
More filters
••
[...]
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These
9,929 citations
••
TL;DR: This paper presents a new state-of-the-art implementation of the iChEM (Collaborative Innovation Center of Chemistry for Energy Materials) Key Laborotary of Catalysis, which automates the very labor-intensive and therefore expensive and therefore time-heavy and expensive process ofalysis.
Abstract: and Fuels Changzhi Li,† Xiaochen Zhao,† Aiqin Wang,† George W. Huber,†,‡ and Tao Zhang*,† †State Key Laborotary of Catalysis, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China ‡Department of Chemical and Biological Engineering, University of WisconsinMadison, Madison, Wisconsin 53706, United States
1,977 citations
••
TL;DR: This Review focuses on pharmacological strategies to attenuate the toxic effects of peroxynitrite, which include its catalytic reduction to nitrite and its isomerization to nitrate by metalloporphyrins, which have led to potential candidates for drug development for cardiovascular, inflammatory and neurodegenerative diseases.
Abstract: Peroxynitrite--the product of the diffusion-controlled reaction of nitric oxide with superoxide radical--is a short-lived oxidant species that is a potent inducer of cell death Conditions in which the reaction products of peroxynitrite have been detected and in which pharmacological inhibition of its formation or its decomposition have been shown to be of benefit include vascular diseases, ischaemia-reperfusion injury, circulatory shock, inflammation, pain and neurodegeneration In this Review, we first discuss the biochemistry and pathophysiology of peroxynitrite and then focus on pharmacological strategies to attenuate the toxic effects of peroxynitrite These include its catalytic reduction to nitrite and its isomerization to nitrate by metalloporphyrins, which have led to potential candidates for drug development for cardiovascular, inflammatory and neurodegenerative diseases
1,804 citations
••
TL;DR: This review is intended to give a general background to the use of cyclodextrin as solubilizers as well as highlight kinetic and thermodynamic tools and parameters useful in the study of drug Solubilization bycyclodextrins.
1,674 citations
••
TL;DR: This review comprises the main characteristics of O2(•-) followed by generation methods, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted.
Abstract: Superoxide ion (O2•–) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O2•– is rather scarce. In addition, numerous studies on O2•– were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O2•– reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O2•– so as to enable researchers to venture into future research. It comprises the main characteristics of O2•– followed by generation methods. The reaction types of O2•– are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O2•– environmental chemistry is also discussed. The detection methods of O2•– are categorized and elaborated. Special attention is given to the f...
1,356 citations