Determination of residual manganese in Mn porphyrin-based superoxide dismutase (SOD) and peroxynitrite reductase mimics.
The awareness of the beneficial effects of Mn porphyrin-based superoxide dismutase (SOD) mimics and peroxynitrite scavengers on decreasing oxidative stress injuries has increased the use of these compounds as mechanistic probes and potential therapeutics. Simple Mn2+ salts, however, have SOD-like activity in their own right both in vitro and in vivo. Thus, quantification/removal of residual Mn2+ species in Mn-based therapeutics is critical to an unambiguous interpretation of biological data. Herein we report a simple, sensitive, and specific method to determine residual Mn2+ in Mn porphyrin preparations that combines a hydrometallurgical approach for separation/speciation of metal compounds with a spectrophotometric strategy for Mn determination. The method requires only common chemicals and a spectrophotometer and is based on the extraction of residual Mn2+ by bis(2-ethylhexyl)hydrogenphosphate (D2EHPA) into kerosene, re-extraction into acid, and neutralization followed by UV-vis determination of the Mn2+ levels via a Cd2+-catalyzed metallation of the H2TCPP4- porphyrin indicator. The overall procedure is simple, sensitive, specific, and amenable to adaptation. This quantification method has been routinely used by us for a large variety of water-soluble porphyrins.
Rebouças
Júlio S
JS
Department of Radiation Oncology, Duke University Medical School, Durham, NC 27710, USA.
Kos
Ivan
I
Vujasković
Zeljko
Z
Batinić-Haberle
Ines
I
D002138:Calibration; D002623:Chemistry Techniques, Analytical; D002626:Chemistry, Pharmaceutical / Q000379:methods; D004340:Drug Contamination; D008345:Manganese / Q000737:chemistry*; D008670:Metals / Q000737:chemistry; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism*; D011166:Porphyrins / Q000737:chemistry*; D015203:Reproducibility of Results; D012995:Solubility; D013053:Spectrophotometry / Q000379:methods; D013482:Superoxide Dismutase / Q000378:metabolism*; D013678:Technology, Pharmaceutical / Q000379:methods; D014867:Water / Q000737:chemistry
D008670:Metals; D011166:Porphyrins; D014867:Water; D008345:Manganese; D010088:Oxidoreductases; D013482:Superoxide Dismutase; C109110:peroxynitrite reductase