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Reduction of nitric oxide to HNO by sodium dithionite: kinetics and mechanism.

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Title: Reduction of nitric oxide to HNO by sodium dithionite: kinetics and mechanism.
Authors: Vargas, Paola1 (AUTHOR), Venâncio, Mateus F.2 (AUTHOR), Rocha, Willian R.3 (AUTHOR), Suarez, Sebastián A.4 (AUTHOR) sebastian.suarez@uam.es, Doctorovich, Fabio A.1 (AUTHOR) doctorovich@qi.fcen.uba.ar
Source: Dalton Transactions: An International Journal of Inorganic Chemistry. 6/23/2026, Vol. 55 Issue 24, p9223-9233. 11p.
Subjects: Sodium dithionite, Nitroxyl, Nitric oxide, Chemical kinetics, Oxidation-reduction reaction, Metalloproteins, Electron donors
Abstract: Sodium dithionite is a widely used reductant in biochemical and industrial applications, yet its intrinsic instability and complex redox chemistry continue to pose challenges for mechanistic interpretation. One relatively underexplored aspect is its reactivity with nitric oxide (NO˙), a small redox-active signalling molecule. While dithionite is commonly employed to reduce metal centres in enzymes, its potential interaction with NO˙ may influence experimental outcomes in aqueous redox systems. Here, we show that under anaerobic, near-neutral aqueous conditions, dithionite reacts with NO˙ leading to the formation of azanone (HNO, nitroxyl), the one-electron-reduced and protonated congener of nitric oxide. Formation of HNO is supported by direct trapping experiments using Mn(III) porphyrins and by indirect detection of N2O, a characteristic product of HNO dimerization. These findings reveal a previously overlooked route for HNO generation in dithionite-containing systems and highlight potential artefacts in biochemical experiments involving NO˙ and strong reductants, particularly in studies probing thiol reactivity or metalloprotein function. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Sodium dithionite is a widely used reductant in biochemical and industrial applications, yet its intrinsic instability and complex redox chemistry continue to pose challenges for mechanistic interpretation. One relatively underexplored aspect is its reactivity with nitric oxide (NO˙), a small redox-active signalling molecule. While dithionite is commonly employed to reduce metal centres in enzymes, its potential interaction with NO˙ may influence experimental outcomes in aqueous redox systems. Here, we show that under anaerobic, near-neutral aqueous conditions, dithionite reacts with NO˙ leading to the formation of azanone (HNO, nitroxyl), the one-electron-reduced and protonated congener of nitric oxide. Formation of HNO is supported by direct trapping experiments using Mn(III) porphyrins and by indirect detection of N2O, a characteristic product of HNO dimerization. These findings reveal a previously overlooked route for HNO generation in dithionite-containing systems and highlight potential artefacts in biochemical experiments involving NO˙ and strong reductants, particularly in studies probing thiol reactivity or metalloprotein function. [ABSTRACT FROM AUTHOR]
ISSN:14779226
DOI:10.1039/d6dt00559d