Although many recent studies have established that nitric oxide (NO) is an important bioregulatory agent of the smallest size in a range of physiological processes from vasodilation and platelet aggregation to neurotransimission and immune system, possible indirect contribution of endogenous and induced NO carriers, i.e., NO donors, is recently highlighted. Generally the physiological concentration of free NO is very low. In order to understand uncovered Janus-faced actions of NO, and reorganize complicated contribution of the isoforms of nitric oxide synthases (NOS), structural design and synthesis of novel NO donors, which can realize controlled release of NO or NO equivalents in terms of the rate and place (i.e., targeting), are desired. Herein we review briefly the recent studies about the chemical natures of potential NO donors, particularly of S-nitrosothiols and
N-nitrosamines. The latter compounds can be considered as potential NO/NO
+ donors. However, the relation of the structures of
N-nitrosamines, in particular of aliphatic
N-nitrosamines, to the characteristics of release of NO or NO
+ remains unclear. A new category of NO donors based on the
N-nitrosoamines of 7-azabicyclo [2.2.1] heptanes was described. These compounds can undergo heterolytic
N-NO bond cleavage. The postulate that
N-NO bond cleavage of
N-nitrosamines is enhanced by a reduction of the resonance in the
N-NO group arising from the structural features is proposed.
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