MnTBAP chloride is a cell permeable superoxide dismutase (SOD) mimetic and peroxynitrite scavenger.A potent inhibitor of peroxynitrite-induced oxidative reactions (peroxynitrite scavenger), but not a scavenger of nitric oxide (NO). In addition, it protects endothelial cells in a dose-dependent manner (EC50 ~40 μM) against paraquat (2 mM) and inhibits the oxidation of Dihydrorhodamine 123 by peroxynitrite.