30] Synthesis, chemistry, and applications of nitroxyl ion releasers sodium trioxodinitrate or Angeli's salt and piloty's acid

Abstract

Unlike nitric oxide (NO+), which at pH 7 exists formally as a constituent of metal nitrosyl compounds and S-nitrosothiols, NO- can exist in solution. NO- is formed transiently during reaction of NO with various reductants such as hydroxylamine and is an essential intermediate in some of the reactions attributed to NO. This chapter describes the chemistry of NO- , its formation and stability, and the use of two releasers of NO-, sodium trioxodinitrate (Angeli's salt) and N-hydroxybenzenesulfonamide (Piloty's acid). The chapter also discusses the complications in the application of Piloty's acid. When introducing NO- releasers into biological systems, it must be borne in mind that they are reducing agents and will rapidly react with biological oxidizing agents. NO+, by contrast, is an oxidizing species and is particularly reactive toward thiols. The electronic state in which NO- is formed is critical; the triplet state rapidly reacts with O2 to produce peroxynitrite. This reaction may be significant in view of the relatively high concentration of O2 in comparison with O2