Interaction of Quinone-Related Electron Acceptors with Hydropersulfide Na₂S₂: Evidence for One-Electron Reduction Reaction

Abstract

We previously reported that 9,10-phenanthraquinone (9,10-PQ), an atmospheric electron acceptor, undergoes redox cycling with dithiols as electron donors, resulting in the formation of semiquinone radicals and monothiyl radicals; however, monothiols have little reactivity. Because persulfide and polysulfide species are highly reducing, we speculate that 9,10-PQ might undergo one-electron reduction with these reactive sulfides. In the present study, we explored the redox cycling capability of a variety of quinone-related electron acceptors, including 9,10-PQ, during interactions with the hydropersulfide Na 2 S 2 and its related polysulfides. No reaction occurred when 9,10-PQ was incubated with Na 2 S; however, when 5 μM 9,10-PQ was incubated with either 250 μM Na 2 S 2 or Na 2 S 4 , we detected extensive consumption of dissolved oxygen (84 μM). Under these conditions, both the semiquinone radicals of 9,10-PQ and their thiyl radical species were also detected using ESR, suggesting that a redox cycle reaction occurred utilizing one-electron reduction processes. Notably, the perthiyl radicals remained stable even under aerobic conditions. Similar phenomenon has also been observed with other electron acceptors, such as pyrroloquinoline quinone, vitamin K 3 , and coenzyme Q10. Our experiments with Nmethoxycarbonyl penicillamine persulfide (MCPSSH), a precursor for endogenous cysteine persulfide, suggested the possibility of a redox coupling reaction with 9,10-PQ inside cells. Our study indicates that hydropersulfide and its related polysulfides are efficient electron donors that interact with quinones. Redox coupling reactions between quinoid electron acceptors and such highly reactive thiols might occur in biological systems.

Naphthoquinones Oxidize H2S to Polysulfides and Thiosulfate, Implications for Therapeutic Applications

“…Persulfide radicals may also be produced by reactions of polysulfides with the quinones [ 34 ] (Equation (12)), H 2 S 2 + NQ → HS 2 ·− + NQ ·− + H + two of which could then form a tetrasulfide or one plus a thiyl radical would form a trisulfide.…”

“…Persulfide radicals may also be produced by reactions of polysulfides with the quinones [34] (Equation ( 12)),…”

Bi2Te3–Au Nanocomposite Schottky Junction with Peroxidase Activity for Glucose Sensing

“…To detect the electron-mediated mechanism of POD, we have used the BQ probe which is one of the well-known electron acceptors that transforms into hydroquinone (HQ) in the presence of electrons and protons and can easily be analyzed by UV–vis spectroscopy. − In our work, we started the reaction by combining BQ (0.02 mM) with Bi 2 Te 3 –Au 0.5 (0.1 mg/mL) in acetate buffer solution (0.1 M, pH 5.5). The solution was incubated for 12 h in the dark at room temperature.…”

Reaction Mechanisms of H2S Oxidation by Naphthoquinones

“…Conversely, Abiko et al [14] reported that 9,10-phenanthraquinone (9,10-PQ) undergoes one-electron reduction reactions with inorganic polysulfides (Na 2 S 2 and Na 2 S 4 ) but not with Na 2 S (which forms H 2 S when dissolved). Furthermore, we failed to observe reactions between anthraquinone and H 2 S. These factors raise the question of whether there are fundamental differences between anthraquinones and naphthoquinones in their ability to redox cycle with small thiols.…”