Probing of the pH-Dependent Redox Mechanism of a Biologically Active Compound, 5,8-Dihydroxynaphthalene-1,4-dione

Munir, Shamsa; Rana, C Usman Ali; Shah, Syed Mujtaba

doi:10.1071/ch13373

Cited by 5 publications

(2 citation statements)

References 24 publications

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“…A regular shift in the location of cathodic peak with change in pH of the medium indicated the involvement of proton during electron transfer reaction. [22][23][24][25] The dislocation of peak stopped at pH close to10 indicating the reduction of HAC to occur only by the involvement of electrons in highly alkaline conditions. 26 Intersection of the linear segments of peak potential versus pH plot (Fig.…”

Section: Resultsmentioning

confidence: 99%

pH Dependent Electrochemistry of Anthracenediones at a Glassy Carbon Electrode

Ullah

Rauf

Rana

et al. 2015

J. Electrochem. Soc.

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The voltammetric response of 1-hydroxy-2(hydroxymethyl)anthracene-9,10-dione (HAC) and 1,8-dihydroxy-4,5-dinitro anthracenedione (DHDN) was investigated at a glassy carbon electrode in acidic, neutral and basic media by cyclic, square wave and differential pulse voltammetry. The oxidation of DHDN was evidenced by the appearance of one irreversible and two reversible peaks in the square wave voltammograms. The shift of peak potentials with change in pH demonstrated proton coupled electron transfer reactions. DHDN exhibited two steps pH dependent reduction while HAC reduced in a single step involving two electrons and two protons. The square wave voltammetric response showed the quasi-reversible nature of the reduction process of HAC. However, its oxidation followed irreversible behavior. The results of sensitive voltammetric techniques helped in proposing the electrode reaction mechanism of HAC and DHDN. Moreover, physical parameters such as diffusion coefficient, pKa and electron transfer rate constant were determined from scan rate, pH and concentration effects. Aromatic compounds with reducible electrophores play significantly important role in electron transport chains and photosynthesis.1,2 The primary metabolites of such compounds have been reported to act as potent antioxidants 3,4 Some of their metabolites function in the Mitchellian redox loops of mitochondrial and chloroplast electron transport chains. Their secondary metabolites are structurally diverse compounds that play defensive roles in many organisms. Tricyclic electro-reducible compounds find extensive applications in pharmacology and industry.5 Most of the biological activities and inhibitory effects of such compounds are related to their redox behavior and hydrogen bonding characteristics.6-8 Moreover, their redox properties are greatly dependent on the nature, number and position of different substituents. The synthesis, selection and application of new bicyclic and tricyclic electroactive compounds with more selective biological activity require the understanding of factors that could tune their redox characteristics. 9 Keeping this in mind, we investigated the electrochemical fate of tricyclic compounds, 1,8-dihydroxy-4,5-dinitro anthracenedione (DHDN) and 1-hydroxy-2(hydroxymethyl)anthracene-9,10-dione (HAC) having both electron donating and withdrawing groups attached to the aromatic rings. The hydroxyl groups of DHDN are expected to result in intramolecular hydrogen bonding. The nitro and OH groups present on the basic framework of the molecule have electron withdrawing and donating mesomeric effects. The nitro groups being electron acceptor will facilitate the ionization of OH groups and thus cause to lower the pK a value of the molecule. In addition, the intramolecular hydrogen bonding of OH with keto group is expected to influence the electrochemical characteristics of the molecule. These possibilities prompted us to examine the electron transfer reactions of DHDN by electrochemical techniques.A plethora of anthracenediones have been ...

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Section: Resultsmentioning

confidence: 99%

pH Dependent Electrochemistry of Anthracenediones at a Glassy Carbon Electrode

Ullah

Rauf

Rana

et al. 2015

J. Electrochem. Soc.

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“…Recent publications have discussed carbon paste composites to detect heavy metals via cyclic voltammetry (CV) and square wave anodic stripping voltammetry (SWASV). SWASV has been recognized to be a cost-effective, precise and sensitive electrochemistry tool for determining trace metals at parts per billion (ppb) level simultaneously (11)(12)(13)(14). In this experiment, In (III) is pre-concentrated on the carbon paste ZrO 2 /TiO 2 (working electrode) (14) via electrochemical reduction for a specified length of time, then the electrochemical stripping from the working electrode surface results in the faradaic signal, which correlates to the analyte's concentration.…”

Section: Introductionmentioning

confidence: 99%

A Carbon Paste Composite Electrode with Mixture of Zirconium Dioxide and Titanium Dioxide to Detect Heavy Metals Studied by SEM and XPS

et al. 2014

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The purpose of this study is to show that an alternative and novel modified electrode such as the zirconium dioxide with titanium dioxide (ZrO 2 /TiO 2 ) carbon paste electrode could be utilized in the area of highly toxic metal detection such as the highly toxic metal indium. The challenges of the development of an electrochemical sensor over the last two decades which possess the following qualities such as user friendly, robust, selective, low detection limits and allowing for fast analyses in toxic metal detection are the reasons for this investigation.

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