Table 1.

The most commonly used NO donors.

NO Donor	Released Molecules	Conditions of NO Release	References
Sodium nitroprusside (SNP, sodium nitroferricyanide(III) dihydrate)	NO+, CN−, a mixture of ferrocyanide and ferricyanide products	Photolysis after irradiation with UV-Vis light (except red light). Reaction with reducing agents (e.g., thiols, haemoproteins, and ascorbate) in darkness.	[23,24,25]
RSNO compounds, e.g., S-nitroso-N-acetyl-D-penicillamine (SNAP) S-nitrosoglutathione (GSNO)	•NO, NO+, NO−, disulphide	Disruption by heat; UV light; and some metal ions, superoxides, and seleno compounds. Metal ions (Cu+, Fe2+, Hg2+, and Ag+) serve as important catalysts for the decomposition of the compounds.	[26,27]
3-Morpholinosydnonimine (SIN-1)	•NO, O2•−, ONOO−, SIN-1C	Decomposition occurs under alkaline pH and is facilitated by oxygen and Vis light irradiation. In vivo, oxidizing agents stimulate •NO production from SIN-1 at low oxygen concentrations. Under such conditions, SIN-1 is likely to behave more like an •NO donor than an ONOO− donor.	[23,26,28]
Diazeniumdiolates (NONOates), e.g., Diethylenetriamine NONOate (DETA-NONOate, alternative name NOC-18),	•NO, NO+, NO−, NO2−, nucleophile residue	Decomposition is spontaneous and pH- and temperature-dependent. Dissociation to NO is acid-catalysed, and the rate decreases as the pH increases.	[29,30]
Angeli’ salt (sodium α-oxyhyponitrite, belongs to the NONOate compounds)	NO−, •OH, HNO	Spontaneous dissociation in a pH-dependent manner.	[26]
Acidified nitrite	2NO2− + 2H+⇌ N2O3 + H2O N2O3⇌ NO2 + NO	The reaction requires a high NO2− concentration and low pH or the presence of the reductants. e.g., ascorbate. Under less acidic pH, the reduction of NO2− to NO is catalysed by metalloproteins (e.g., haemoglobin).	[31,32]
Roussin’s black salt ((KFe4S3(NO)7), the tetra-iron–sulfur-nitrosyl cluster)	NO * and ferric precipitates	Photolysis at λ increases from 313 to 546 nm.	[33]

* The form of NO was not specified.