Inhibition of cumene hydroperoxide-induced lipid peroxidation by a novel pyridoindole antioxidant in rat liver microsomes.

The ability of stobadine, a novel pyridoindole antioxidant, to inhibit lipid peroxidation induced by cumene hydroperoxide was investigated in rat liver microsomes. In the micromolar range stobadine effectively inhibited lipid peroxidation as measured by the formation of thiobarbituric acid reactive products. The peroxidation-related degradation of microsomal cytochrome P-450 was prevented by stobadine in the same pattern. Another line of evidence in support of the antioxidant action of stobadine was given by its inhibition of cumene hydroperoxide-induced oxygen consumption in microsomal incubations. Inhibition of lipid peroxidation was not a function of decreased bioactivation of cumene hydroperoxide, as stobadine did not affect the rate of cytochrome P-450 dependent cleavage of cumene hydroperoxide. Neither had stobadine any effect on cytochrome P-450 peroxidase function characterized by the rate of cumene hydroperoxide-dependent oxidation of TMPD, and no direct spectral interaction with microsomal cytochrome P-450 was observed in the micromolar region. We suggest that it is the ability of stobadine to scavenge alkoxyl and peroxyl radicals that is predominantly responsible for the observed antioxidant effect.