Mechanistic studies of oxidative decomposition of Angeli's salt and PAPA NONOate

Nitric oxide, (·)NO, and product of its one-electron reduction, nitroxyl NO(-), are important molecules in the biochemistry of living organisms. At physiological conditions nitroxyl exists in its protonated form, HNO. Angeli's salt, AS, and diazeniumdiolates, NONOates, are widely used donors of HNO and (·)NO, correspondingly. In this work we observed oxidative decomposition of AS and PAPA NONOate in the presence of mild oxidizing agents, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, cPTIO, and 2,2'-azinobis(3-ethylbenzolthiazoline-6-sulfonate) radical, ABTS(·-). The observed unexpected fast oxidative decomposition of AS with release of NO instead of HNO suggests the need for a reevaluation of some of the biological effects of AS assigned to action of HNO. While oxidative decomposition of NONOate did not result in release of alternative NOx specimen but only (·)NO, it significantly affects the rates and stoichiometry of (·)NO release. In summary, possible contribution of oxidative decomposition of AS and NONOates should be taken into account upon interpretation of their actions in chemical and biological systems.