The present invention relates to Pyridyl-Substituted Porphyrin Compounds, compositions comprising an effective amount of a Pyridyl-Substituted Porphyrin Compound and methods for treating or preventing injury due to exposure to a reactive species, erectile dysfunction due to surgery, lung disease, hyperoxia, neurodegenerative disease, liver disease, myocardial damage during cardioplegia, an inflammatory condition, a reperfusion injury, an ischemic condition, a cardiovascular disease, diabetes, a diabetic complication, cancer, a side effect of cancer chemotherapy, or a radiation-induced injury, or to prolong the half-life of an oxidation-prone compound, comprising administering to a subject in need thereof an effective amount of a Pyridyl-Substituted Porphyrin Compound.