Water exchange of the water soluble porphyrin Mn(III)TTEG-2-PyP5+ and its reaction with N-hydroxyurea

The properties of Mn(III)TTEG-2-PyP5+, an efficient in vivo SOD mimic and potential drug to treat oxidative stress related diseases, and its reaction with Nhydroxyurea (HU) were studied in a basic aqueous medium. The pK values were determined by spectrophotometric titrations, the water exchange, along with that of other two analogous manganese(III) prophyrins, was studied based on temperature dependent 17O NMR measurements. The stoichiometry and the kinetics of the reaction with N-hydroxyurea was studied by a variety of methods including ion chromatography, electrospray mass spectrometry and UV-Vis spectroscopy. It was shown that photochemical side reactions occur even under the low light intensities used in stopped flow experiments.