J. Biol. Chem., Vol. 261, Issue 17, 7811-7815, 06, 1986
Nitrobenzyl radical metabolites from microsomal reduction of nitrobenzyl chlorides
SN Moreno, J Schreiber and RP Mason
The o-, m-, and p-nitrobenzyl chlorides are reduced aerobically and
anaerobically by NADPH and rat hepatic microsomes. Under aerobic
conditions, these nitro anion radicals reduce oxygen to superoxide as
demonstrated by oxygen consumption and spin trapping of superoxide with
5,5-dimethyl-1-pyrroline N-oxide. At low oxygen concentration, the p- and
o-nitro anion radicals undergo intramolecular electron transfer and
decompose to carbon-centered nitrobenzyl radicals, which can be spin-
trapped with t-nitrosobutane. The p-nitrobenzyl (o-nitrobenzyl) radical
adduct was characterized by a nitrogen hyperfine splitting of 16.5 G (17.1
G) and two equivalent beta-hydrogen hyperfine splittings of 10.6 G (14.4
G). The spin trap 5,5-dimethyl-1-pyrroline N-oxide also yields adducts
characteristic of carbon-centered free radicals. This unimolecular
decomposition is much faster than the disproportionation decay, which is
characteristic of most nitro anion radicals, and the primary o- and
p-nitrobenzyl chloride anion radicals never achieve detectable
concentrations. The nitrobenzyl radical trapping is not inhibited by
metyrapone or CO. In contrast, the m-nitrobenzyl anion radical does achieve
a detectable steady-state concentration, which is increased 20% by either
metyrapone or a CO atmosphere.