Spin trapping of ibuprofen radicals: evidence that ibuprofen is a hydroxyl radical scavenger.

The purpose of this study was to use electron paramagnetic resonance (EPR) spectroscopy to determine if ibuprofen, [2-(4-isobutylphenyl) propanoic acid], a potent nonsterodial anti-inflammatory agent, could modify hydroxyl radicals generation in vitro. Ibuprofen (IBU; 0.1-50 mM) in water or water alone was added to EPR tubes containing ferrous sulfate (0.5-2.0 mM), and either 5,5-dimethyl-1-pyrroline-N-oxide (DMPO; 40 mM) or alpha-phenyl N-tert-butyl nitrone (PBN; 48 mM). Hydrogen peroxide (1 mM) was added to inititate the Fenton reaction, and the systems were then analyzed by EPR spectroscopy to determine the type and relative quantity of free radical(s) produced. IBU caused a dose-dependent decrease of signal intensity of the hydroxyl radical adduct of DMPO (DMPO-OH) which is an indication that IBU either scavenges the hydroxyl radical and/or chelates iron. In addition, other radicals (presumably IBU radicals) produced in these systems were trapped by both DMPO (aN = 16.1 G, aH beta = 24.0 G) and PBN (aN = 15.7 G, aH beta = 4.4 G and aN = 17.0 G, aH beta = 2.1 G). The signal height of these IBU radicals increased in systems containing ferrous sulfate (1 mM), hydrogen peroxide (1 mM), PBN (48 mM), and increasing IBU concentrations. Therefore, we conclude that IBU scavenges the hydroxyl radical. If IBU chelated iron, then less hyroxyl radicals would be generated, less IBU radical formed and the signal height of IBU radicals trapped by PBN would have decreased.(ABSTRACT TRUNCATED AT 250 WORDS)