Configuration of necine pyrroles--toxic metabolites of pyrrolizidine alkaloids.

The commonly accepted belief regarding the configuration of the major pyrrole metabolite of pyrrolizidine alkaloids has been revised. This paper provides evidence that a racemic mixture of (+/-) 6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine is the product of the microsomal transformation of esters of heliotridine and retronecine instead of pure(+) or (-) enantiomers, commonly referred to as dehydroheliotridine and dehydroretronecine. The toxicological significance of these results is under investigation.