engleski

Acid-Base Properties of Manganese N-alkylpyridylporphyrins in Aqueous Media

Oxidative stress has been implicated in numerous diseases. Reactive oxygen and nitrogen species, such as superoxide and peroxynitrite, play a major role in oxidative stress, as well as in the signal transduction pathways under physiological and patological conditions. As their removal is redox-based, there is a growing interest in developing redox-active metal complexes as prospective drugs. Among the most widely studied are Mn(II) cyclic polyamines, Mn(III) salen derivatives, and Mn(III) porphyrins. Based on structure-activity relationship (SAR) it was found that Mn porphyrins are among the most efficient SOD mimics with potency approching that of SOD enzymes. The most potent ones Mn(III)N-alkylpyridylporphyrins bear positive charges in a close proximity to the metal site, affording thermodynamic and kinetic facilitation for the reaction with negativly charged superoxide. In aqueous solution, manganese N-alkylpyridylporphyrins are coordinated with axial water molecules, and they can undergo up to two ionization steps in the alkaline pH range. Published data concerning these ionization reactions are diverse, both in the methods and in the results. Due to the recognized biological relevance of MnIIIP/MnIIP redox couple in the catalyzed dismutation of superoxide radical ion, we have performed detailed spectrophotometric and potentiometric investigations of acid-base properties of the selected manganese N-alkylpyridylporphyrine derivatives in these two oxidation states.

manganese; porphyrins; SOD

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