Angeli’s salt is regarded as a classical nitroxyl (NO-) donor, but under certain conditions evolution of NO is also observed.¹ It spontaneously dissociates in a pH-dependent, first-order process with a half-life of 2.3 minutes at 37°C (pH 7.4) to liberate 0.54 moles of NO per mole of parent compound.^1,2

1 Maragos, C.M., Morley, D., Wink, D.A., et al. Complexes of ·NO with nucleophiles as agents for the controlled biological release of nitric oxide. Vasorelaxant effects. J Med Chem 34 3242-3247 (1991).

2 Keefer, L.K., Nims, R.W., Davies, K.M., et al. “NONOates” (1-substituted diazen-1-ium-1,2-diolates) as nitric oxide donors: Convenient nitric oxide dosage forms. Methods Enzymol 268 281-293 (1996).

Maragos, C.M., Morley, D., Wink, D.A., et al. Complexes of ·NO with nucleophiles as agents for the controlled biological release of nitric oxide. Vasorelaxant effects. J Med Chem 34 3242-3247 (1991).

Keefer, L.K., Nims, R.W., Davies, K.M., et al. “NONOates” (1-substituted diazen-1-ium-1,2-diolates) as nitric oxide donors: Convenient nitric oxide dosage forms. Methods Enzymol 268 281-293 (1996).

Fukuto, J.M., Hobbs, A.J., and Ignarro, L.J. Conversion of nitroxyl (HNO) to nitric oxide in biological systems: The role of physiological oxidants and relevance to the biological activity of HNO. Biochem Biophys Res Commun 196 707-713 (1993).