Microsomal metabolism of pyrrolizidine alkaloids from Senecio jacobaea. Isolation and quantification of 6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine and N-oxides by high performance liquid chromatography.

The metabolism in vitro of four pyrrolizidine alkaloids from the poisonous plant Senecio jacobaea was studied. The pyrrolizidine alkaloids jacobine, jacoline, senecionine, and seneciphylline, all macrocyclic diesters of retronecine, were incubated with rat liver microsomes. Analysis of incubation extracts by HPLC with a PRP-1 reverse phase styrene-divinylbenzene resin column revealed the presence of two major metabolites, 6,7-dihydro-7-hydroxy-l-hydroxymethyl-5H-pyrrolizine and an N-oxide derivative. Mass spectrometry was used to confirm the structure of metabolites isolated by preparative HPLC using the PRP-1 column and a C-8 reverse phase column. Quantitative HPLC analysis using the PRP-1 column allowed the comparison of the rates of formation of the dihydropyrrolizine derivative and N-oxides from the four alkaloids.