Chemical and toxicological studies on bracken fern, Pteridium aquilinum var. latiusculum. VII. The inability of bracken extracts containing pterosins to cause cattle bracken poisoning.

Methanol extracts of bracken frond and rhizomes prepared using a metallic extraction vessel, were proved incapable of producing bracken poisoning in calves. Nevertheless, they contained appreciable quantities of pterosins and pterosides. Thus the poisonous principle(s) in bracken responsible for the toxicological effects are not associated with these major sesquiterpenoids of the plant.