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Reaction Mechanisms of H 2 S Oxidation by Naphthoquinones.
- Source :
- Antioxidants; May2024, Vol. 13 Issue 5, p619, 22p
- Publication Year :
- 2024
-
Abstract
- 1,4-naphthoquinones (NQs) catalytically oxidize H<subscript>2</subscript>S to per- and polysufides and sulfoxides, reduce oxygen to superoxide and hydrogen peroxide, and can form NQ-SH adducts through Michael addition. Here, we measured oxygen consumption and used sulfur-specific fluorophores, liquid chromatography tandem mass spectrometry (LC-MS/MS), and UV-Vis spectrometry to examine H<subscript>2</subscript>S oxidation by NQs with various substituent groups. In general, the order of H<subscript>2</subscript>S oxidization was DCNQ ~ juglone > 1,4-NQ > plumbagin >DMNQ ~ 2-MNQ > menadione, although this order varied somewhat depending on the experimental conditions. DMNQ does not form adducts with GSH or cysteine (Cys), yet it readily oxidizes H<subscript>2</subscript>S to polysulfides and sulfoxides. This suggests that H<subscript>2</subscript>S oxidation occurs at the carbonyl moiety and not at the quinoid 2 or 3 carbons, although the latter cannot be ruled out. We found little evidence from oxygen consumption studies or LC-MS/MS that NQs directly oxidize H<subscript>2</subscript>S<subscript>2–4</subscript>, and we propose that apparent reactions of NQs with inorganic polysulfides are due to H<subscript>2</subscript>S impurities in the polysulfides or an equilibrium between H<subscript>2</subscript>S and H<subscript>2</subscript>S<subscript>n</subscript>. Collectively, NQ oxidation of H<subscript>2</subscript>S forms a variety of products that include hydropersulfides, hydropolysulfides, sulfenylpolysulfides, sulfite, and thiosulfate, and some of these reactions may proceed until an insoluble S<subscript>8</subscript> colloid is formed. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 20763921
- Volume :
- 13
- Issue :
- 5
- Database :
- Complementary Index
- Journal :
- Antioxidants
- Publication Type :
- Academic Journal
- Accession number :
- 177460854
- Full Text :
- https://doi.org/10.3390/antiox13050619