Solvation of 1-Amino-4-Hydroxy-9,10-Anthraquinone Governs Its Electrochemical Behavior in Non-Aqueous and Aqueous Media: A Cyclic Voltammetry Study

Abstract

The electrochemical behavior of 1-amino-4-hydroxy-9,10-anthraquinone (1-AHAQ) was studied in acetonitrile, dimethyl formamide and dimethyl sulfoxide. In such solvents 1-AHAQ undergoes successive two one-electron reduction forming semiquinone and quinone dianion respectively in which the first step is completely reversible and the second step is quasi-reversible. The reduction and oxidation potentials are dependent on the polarity of the media. The electrochemical parameters are evaluated and correlated with the polarity index of the media. During such reductions a comproportionation reaction operates between the quinone (1-AHAQ) and its dianion (1-AHAQ2–) to form a semiquinone radical (1-AHAQ• –). The apparent comproportionation constants are calculated to find a comparative account on the stability of the radical intermediate in such solvents. In the presence of benzoic acid the electrochemical behavior of 1-AHAQ is altered significantly which is determined in this study. Role of the polarity of the solvents, intra or intermolecular hydrogen bonding and acidic additives on the stability of the radical species is evaluated. In aqueous buffer the reduction of 1-AHAQ follows a one step two-electron process where a kinetic study was carried out to determine the apparent charge transfer rate constants at various scan rates. The results show that electrochemical behavior of 1-AHAQ in non-aqueous and aqueous media mimics the action of anthracycline anticancer drugs which may find a similarity in their biological activities at the cellular level.

1-Amino-4-hydroxy-9,10-anthraquinone – An analogue of anthracycline anticancer drugs, interacts with DNA and induces apoptosis in human MDA-MB-231 breast adinocarcinoma cells: Evaluation of structure–activity relationship using computational, spectroscopic and biochemical studies

“…The electrochemical aspect of the molecule at physiological pH (7.4) is an important step for a molecule in determining its biological action. However, in earlier studies [32] , [33] the electrochemical reduction of 1-AHAQ was not studied in aqueous buffer at physiological pH (7.4) and that is the reason why in the present study we report the redox behavior of 1-AHAQ in aqueous solution at pH 7.4. This shows a quasireversible two-electron reduction at –665 mV corresponding to the reduction of quinone to quinone dianion [ Fig.…”

“…In our very recent studies [32] , [33] we observed that 1-AHAQ undergoes single step quasi-reversible reduction by two electrons in aqueous media at neutral pH (7.0). The electrochemical aspect of the molecule at physiological pH (7.4) is an important step for a molecule in determining its biological action.…”

“…1-AHAQ ( Scheme 1 ) (96%), purchased from Alfa Aesar, Germany, was purified and characterized by methods described in our recent reports [32] , [33] . The pH and ionic strengths of aqueous solutions were maintained by using Hepes buffer and NaCl, respectively (both were of AR Grade, Spectrochem, India).…”

“…Very recently we reported in detail the electrochemical property of 1-AHAQ [32] , [33] and its copper complex and showed that the molecule mimics the anthracycline drugs that are already in practice. This was a pointer to us that 1-AHAQ might exhibit a potential antitumor activity as anthracyclines owing to the similarity in electrochemical behavior, an important parameter to determine therapeutic efficiency.…”

Influence of Nonionic Surfactant on Hydrolysis of Vinyl Sulfone Reactive Dye

“…While in an organic hydrophobic environment like DMSO, hydrogen of the secondary amine (-NH-) and one hydrogen of amino group (-NH 2 ) would prefer to form intramolecular hydrogen bonding. Another hydrogen of the amino group could form intermolecular hydrogen with negatively charged oxygen of the DMSO molecule [23]. Some possible structures of KN-R in aqueous solution and organic solvent are shown in Fig.…”