Carcinogenicity in rats of ptaquiloside isolated from bracken.

The nature of the carcinogen present in bracken fern has not yet been elucidated. Very recently, we succeeded in isolating ptaquiloside, a novel norsesquiterpene glucoside of the illudane type, from bracken. Ptaquiloside was shown to be a carcinogenic principle of bracken fern. It induces mammary cancer and multiple ileal tumors in high incidences when given orally to female Sprague-Dawley rats.