When cannabidiol (CBD) was incubated with hepatic microsomes of mice in the presence of an NADPH-generating system, a significant decrease of cytochrome P-450 content was observed by measuring its carbon monoxide difference spectra. The decrease of cytochrome P-450 by CBD required NADPH and molecular oxygen. The effect was partially inhibited by SKF 525-A but not by various scavengers of active oxygen species, superoxide anion, hydroxyl radical and singlet oxygen. The incubation of CBD with hepatic microsomes did not affect total heme but decreased significantly free sulfhydryl contents in the microsomes. The derivatives of CBD modified in the resorcinol moiety, CBD-monomethyl- and dimethylethers, almost lost the effect on cytochrome P-450, whereas those modified in the terpene moiety, 8,9-dihydro- and 1,2,8,9-tetrahydro-CBDs exhibited some potency to inactivate cytochrome P-450. The inactivation of cytochrome P-450 by CBD and related compounds led to the inhibition of hepatic microsomal P-nitroanisole O-demethylase and aniline hydroxylase activities. These results suggest that the resorcinol moiety of CBD plays some role in the inactivation of cytochrome P-450 by the cannabinoid.
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