Synthesis of Cationic Manganese Porphyrin Bearing Alkylsulfonio Groups and Evaluation of Their Antioxidant Activities

Abstract

A water-soluble cationic 5, 10, 15, 20-tetrakis(2-dimethylsulfoniophenyl)-porphinatomanganese(III) ion (MnT2M₂SuP) and a 5, 10, 15, 20-tetrakis(4-dimethylsulfoniophenyl)porphinatomanganese(III) ion (MnT4M₂SuP) were synthesized as superoxide dismutase (SOD) mimics which were introduced into PEG-liposome composed of dimyristoylphosphatidylcholine (DMPC) and Pluronic F-68 to examine the effect of the liposome on the capacity for use as drug delivery system (DDS) to maintain and perpetuate blood circulation. Fluorescence spectra in pseudo blood circulation experiments indicated that MnT4M₂SuP continued to be bundled in PEG-liposome, while fluorescence from cross-section of cell observed by confocal laser scanning microscope indicated that PEG-liposome was ingested into a cell. SOD activity was determined by stopped-flow analysis, which allowed the determination of k_cat values for the reaction of the metalloporphyrins with superoxide anion radical (·O₂^-). Solution of PEG-liposome loaded with MnT2M₂SuP or MnT4M₂SuP were the most effective catalyst as a SOD mimic to decompose ·O₂^- at second-order rate constants of 3.5-4.5×10⁷ M^-1s^-1.