Pyrrolic Metabolites from Non-toxic Pyrrolizidine Alkaloids

THERE is evidence that some or all of the cytotoxic effects of unsaturated pyrrolizidine alkaloids are, in some animals, caused by pyrrolic metabolites formed by enzymatic dehydro-genation of the alkaloids in the liver^1,2. These metabolites are dihydropyrrolizine alcohols like I in Fig. 1 or their esters II; one such alcohol has been identified³. Compared with the parent alkaloids these metabolites are highly reactive alkylating agents, capable of reacting chemically with tissue constituents^1,2,4.