Toxic alkaloids and their interaction with microsomal cytochrome P-450 in vitro

Studies on the binding spectra of certain alkaloids with rat liver microsomes revealed that brucine, scopolamine and strychnine are type I compounds, whereas boldine, emetine, nicotine, reserpine and sanguinarine show type II binding. In contrast, colchicine and solanine failed to produce any measurable binding spectra. In vitro incubation of colchicine, nicotine or scopolamine with microsomal suspensions and NADPH resulted in demethylation of these alkaloids, while the incubation of boldine, brucine, emetine, reserpine, sanguinarine or solanine showed little or no dealkylation reaction. Furthermore, the effect of these alkaloids on the in vitro microsomal metabolism of a drug, benzphetamine, has also been studied.