Comparative study of carcinogenic activity in each part of bracken.

Abstract

The carcinogenic activity of the curled tops and stalks of the young bracken fronds and also of the fronds and rhizomes was compared in inbred strain ACI rats. Rats received the pellets containing the curled tops or the stalks of bracken fronds for 2 months. In another experiment, rats were fed the pellets containing the bracken fronds or rhizomes for 4 months. A control group was fed a normal diet. Carcinogenic activity was observed in each part of the bracken, and tumors were most frequently induced in the ileum. In rats given the curled tops, the incidence and multiplicity of the intestinal tumors were higher than in those receiving the stalks. Furthermore, in rats fed the pellets containing the bracken rhizomes, the latent period of the tumor was shorter and the multiplicity was much higher than in those given the fronds. However, the starch from the bracken rhizomes was not carcinogenic. Conceivably the bracken carcinogen was water soluble and washed away in the preparation process. These results showed that the carcinogenic activity of the curled tops of the young bracken fronds was stronger than that of the stalks and that the carcinogenic activity of the bracken rhizomes was stronger than that of the young frond.