Metabolism of pyrrolizidine alkaloids by Peptostreptococcus heliotrinreducens and a mixed culture derived from ovine ruminal fluid.

A mixed culture of ovine ruminal microbes metabolizes the macrocyclic pyrrolizidine alkaloids present in the plant Senecio jacobaea, including jacobine and seneciphylline. Previous attempts to identify metabolites of these alkaloids have not been successful. The objective of this study was to compare the metabolism of pyrrolizidine alkaloids by a mixed culture of ovine ruminal microbes to the metabolism of pyrrolizidine alkaloids by the known organism Peptostreptococcus heliotrinreducens. P. heliotrinreducens metabolizes the pyrrolizidine alkaloids heliotrine and lasiocarpine to 7alpha-hydroxy-1-methylene-8alpha-pyrrolizidine and 7alpha-angelyl-1-methylene-8alpha-pyrrolizidine, respectively. This organism does not metabolize the pyrrolizidine alkaloids jacobine or seneciphylline. A mixed culture of ovine ruminal microbes also metabolized heliotrine and lasiocarpine to identical methylene compounds. This mixed culture also metabolized jacobine and seneciphylline, with the production of very low levels of the corresponding 1-methylene compounds. Samples were analyzed by TLC and GC/MS. Copyright 2002 Elsevier Science B.V.