Carcinogenic principles isolated from bracken fern.

The carcinogenicity of bracken fern, Pteridium aquilinum, was demonstrated most clearly by the experiment of Evans and Mason in 1965. We have performed fractionation of the aqueous extract by means of the assay based on carcinogenicity and isolated an unstable norsesquiterpene glucoside of illudane type named ptaquiloside (PT). It was proved that PT is the carcinogenic principle present in bracken fern, inducing mammary cancer and multiple ileal tumors in high incidences when given orally to female Sprague-Dawley rats. The present review article deals with the explanation of carcinogenicity of bracken fern, progress in separation of carcinogenic fraction, isolation of PT, and its carcinogenic activity in rats.