Design of manganese porphyrin modified with mitochondrial signal peptide for a new antioxidant.

A new design of antioxidant, consisting of manganese (Mn) porphyrin and signal peptide for mitochondrial targeting, is reported. The resulting Mn-porphyrin-oligopeptide conjugate exhibited significant superoxide dismutase (SOD) activity and decomposed peroxynitrite (ONOO-). The new antioxidant caused the swelling of isolated mitochondria. By using the pH-sensitive drug carrier for intracellular delivery, furthermore, the new conjugate recovered the viability of lipopolysaccharide (LPS)-stimulated macrophage RAW 264.7 cells. These results suggest that the Mn-porphyrin modified with signal peptide for mitochondrial targeting is promising for a new class of antioxidants.