(A lot of plants in the Boraginaceae contain hepatotoxic pyrrolizidine alkaloids. Comfreys are among them. More info here: Livertoxic PAs --Henriette.)
The root of Symphytum officinale, Linné (Nat. Ord. Boraginaceae). Europe; naturalized in the United States.
Common Name: Comfrey.
Principal Constituents.—Mucilage in quantity, tannin and asparagine.
Preparation.—Tinctura Symphyti, Tincture of Symphytum (recent root, 8 ounces; Alcohol, 16 fluidounces). Dose, 1 to 10 drops.
Action and Therapy.—This drug is chiefly mucilaginous and used, therefore, as a demulcent in pulmonary, gastric, and renal irritation and inflammations. With many it is a favorite for irritative cough, with bloody expectoration; and in mucous disorders with a tendency to hemorrhage. In ancient days it was lauded as a vulnerary, even to promoting the quick healing of fractured bones, a myth that was more recently revived in England because of the discovery of a principle (allantoin) found in the plant.
The Eclectic Materia Medica, Pharmacology and Therapeutics, 1922, was written by Harvey Wickes Felter, M.D.