Oxidation and radical intermediates associated with the glutathione conjugation of mucochloric acid.

The inactivation of the drinking water mutagen mucochloric acid (MCA) by reduced glutathione (GSH) was linked to the formation of an MCA-GSH conjugate, a nonmutagen in the Salmonella typhimurium (TA100) plate incorporation assay. Anaerobic formation of MCA-GSH is found now to be associated with oxidized glutathione (GSSG) and unconverted MCA. The anaerobic reaction of GSH with MCA in the presence of the radical trap 2-methyl-2-nitrosopropane (tNB; "tert-nitrosobutane") gives rise to an electron paramagnetic resonance (EPR) resulting from the overlapping spectra of two radical adducts. The first species exhibited hyperfine coupling constants of aN = 13.65 G and aH beta = 0.73 G. The second radical adduct exhibited a three-line signal of aN = 12.8 G. The first species is assigned to an adduct of the MCA radical because deuteration of MCA (5-deuterio-MCA) caused the beta-hydrogen hyperfine coupling to collapse. The second radical adduct is unaffected by the deuteration of MCA. Thus, the involvement of both GSSG and a carbon-centered MCA radical in the action of MCA on GSH is indicated.