Carcinogenic activity of coltsfoot, Tussilago farfara l

The carcinogenicity of young, pre-blooming flowers of coltsfoot, Tussilago farfara L., which is a herb of the tribe Senecioneae, family Compositae, and widely used as a herbal remedy, was studied in inbred strain ACI rats. Rats were divided into 4 groups: Group I received 32% coltsfoot diet for 4 days, and subsequently 16% diet until the termination of experiment. Groups II and III respectively received 8% and 4% coltsfoot diet for 600 days. Group IV was fed a normal diet as a control group. The experiments were terminated 600 days after the start of administration of coltsfoot diet. All the rats in Group I survived beyond 380 days after the start of feeding and 8 out of 12 rats developed hemangioendothelial sarcoma in the liver, whereas only one out of 10 rats developed the tumor in Group II, and no tumors were observed in Group III. Chemical studies on the dried, young flowers used in this experiment suggested that the carcinogenicity of coltsfoot is most probably due to senkirkine, a hepatotoxic pyrrolizidine alkaloid.