New class of potent catalysts of O2˙− dismutation. Mn(III)ortho-methoxyethylpyridyl- and di-ortho-methoxyethylimidazolylporphyrins

摘要: Three new Mn(III) porphyrin catalysts of O2˙− dismutation (superoxide dismutase mimics), bearing ether oxygen atoms within their side chains, were synthesized and characterized: 5,10,15,20-tetrakis[N-(2-methoxyethyl)pyridinium-2-yl]porphyrin (MnTMOE-2-PyP5+), Mn(III)5,10,15,20-tetrakis[N-methyl-N′-(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTM,MOE-2-ImP5+) 5,10,15,20-tetrakis[N,N′-di(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTDMOE-2-ImP5+). Their catalytic rate constants for dismutation( disproportionation) the related metal-centered redox potentials vs. NHE are: log kcat = 8.04 (E1/2 = +251 mV) MnTMOE-2-PyP5+, 7.98 (E1/2 = +356 MnTM,MOE-2-ImP5+ 7.59 (E1/2 = +365 MnTDMOE-2-ImP5+. The porphyrins compared to previously described SOD mimics 5,10,15,20-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP5+), 5,10,15,20-tetrakis(N-n-butylpyridinium-2-yl)porphyrin (MnTnBu-2-PyP5+) 5,10,15,20-tetrakis(N,N′-diethylimidazolium-2-yl)porphyrin (MnTDE-2-ImP5+). MnTMOE-2-PyP5+ has chains same length E1/2, as MnTnBu-2-PyP5+ (kcat = 7.25, E1/2 = + 254 mV), yet it is 6-fold more potent a catalyst dismutation, presumably due presence oxygen. kcatvs. E1/2 relationship all Mn porphyrin-based thus far studied discussed. None compounds toxic Escherichia coli in concentration range (up 30 μM), protected SOD-deficient E. concentration-dependent manner. At 3 μM levels, MnTDMOE-2-ImP5+, an atom each eight was most effective offered much higher protection than MnTE-2-PyP5+, while MnTDE-2-ImP5+ very low efficacy.