Peroxynitrite a strong biological oxidant

As demonstrated in recent years, one of the major factors of oxidative stress, generated in the circulatory system, in both acute and chronic pathological conditions, is peroxynitrite (ONOO –) [4]. Peroxynitrite is a strong biological oxidant and nitrating compound, generated in vivo from a rapid reaction of two relatively less reactive, but commonly found, of free radicals: nitrogen monoxide (NO ) and superoxide (O2–) [8]. This reaction occurs spontaneously and is not catalyzed by any enzyme. A fundamental reaction of ONOO – in biological systems is its fast reaction with carbon dioxide (k = 5,7 ź 104 M–1 s–1) and yields a short-lived intermediate, nitrosoperoxycarbonate (ONOOCO 2 –), which homolyzes leads to the formation of carbonate (CO 3–) and nitrogen dioxide (NO 2) radicals (yield ~35%) [29, 30] (Fig. 1), which are one-electron oxidants. ONOO – is responsible for oxidative modifications in a wide variety of biomolecules and is capable to induce of nitrative changes in sulfur and aromatic amino acids, especially 3-nitrotyrosine and dityrosine formation [17] (Fig. 2). This article describes the formation, reactivity and biological action of peroxynitrite