Effect of seneciphylline and senecionine on hepatic drug metabolizing enzymes in rats.

The effect of oral administration of the pyrrolizidine alkaloids, seneciphylline and senecionine, from Senecio vulgaris (Compositae) on activities of hepatic epoxide hydrase, glutathione-S-transferase, aminopyrine-N-demethylase and arylhydrocarbon hydroxylase (AHH) was investigated in microsomes of young male albino rats. Seneciphylline significantly increased the activities of epoxide hydrase and glutathione-S-transferase but caused reduction of cytochrome P-450 and related monooxygenase activities. Senecionine failed to stimulate epoxide hydrase while it diminished the activities of glutathione-S-transferase, aminopyrine demethylase and AHH. Seneciphylline and senecionine could not produce any prominent in vitro effect on the hepatic drug metabolizing enzymes under study, except slight stimulation of epoxide hydrase activity by both the alkaloids and slight reduction of aminopyrine demethylase activity by senecionine.