Protection against peroxynitrite‐dependent tyrosine nitration and <i>α</i>₁‐antiproteinase inactivation by oxidized and reduced lipoic acid

Peroxynitrite, formed by combination of superoxide radical with nitric oxide, is a reactive tissue‐damaging species apparently involved in the pathology of several human diseases. Peroxynitrite nitrates tyrosine residues and inactivates α 1 ‐antiprotinase. We show that both lipoic acid and dihydrolipoic acid efficiently protect against damage by peroxynitrite. By contrast, other disulphides tested did not. The biological antioxidant effects of lipoate/dihydrolipoate may involve scavenging of reactive nitrogen species as well as reactive oxygen species.