Common comfrey
General poisoning notes:
Common comfrey (Symphytum officinale) is an introduced and naturalized herb found on damp roadsides and waste places in many parts of Canada. This plant contains several pyrrolizidine alkaloids, which cause veno-occlusive symptoms, liver cirrhosis, and death. Humans have been affected after ingesting herbal teas and medicines. Rats have developed hepatocellular tumors after ingesting the alkaloid symphytine, found in common comfrey. Canadian health officials have sought to ban sale of some comfrey products. Animals normally do not ingest the plant because of the bristly hairs. Topical herbal preparations are not considered toxic because the alkaloids do not reach the liver (Steuart 1987, Huxtable 1989, Ridker and McDermott 1989). Russian comfrey (Symphytum X uplandicumNym. [synonymy: Symphytum peregrinum Ledeb.]) has been grown in Canada in Lethbridge, Alta., and Vancouver Island, as a trial forage crop for livestock, but it was not found to be suitable. This plant may be available from some nursery seed suppliers. Russian comfrey also contains pyrrolizidine alkaloids and should not be taken internally as a herb remedy.
Nomenclature:
Scientific Name: Symphytum officinale L.
Vernacular name(s): common comfrey
Scientific family name: Boraginaceae
Vernacular family name: borage
Symphytum officinale L.
Geographic Information
Alberta, British Columbia, New Brunswick, Newfoundland, Ontario, Quebec
Notes on Poisonous plant parts:
The roots have greater concentrations of pyrrolizidine alkaloids than the leaves. Animals do not commonly ingest the plants because of the bristly leaves (Cooper and Johnson 1984, Huxtable 1989).
Toxic parts:
All parts, leaves, roots
Notes on Toxic plant chemicals:
Common comfrey contains several pyrrolizidine alkaloids, including echimidine, heliosupine, lycopsamine, and symphytine. Alkaloids were found in the plant totalling 0.07% dry weight in roots and 0.062% in dry leaves, and 0.006% in fresh leaves. Two alkaloids found in common comfrey were shown to cause liver and bladder tumors in rats; the roots have more toxins the than leaves. Some commercial products of roots and leaves sold as herbal teas and medicinal preparations have a total alkaloidal concentration of 270 mg/kg (leaves) and 2900 mg/kg (roots). Ingesting a cup of tea made from the roots may contain 8.5 mg of alkaloid, which is 26 mg per cup if the gelatinous residue is consumed. [Huxtable 1989].
Toxic plant chemicals:
Echimidine, heliosupine, lycopsamine
Echimidine
Animals/Human Poisoning:
Note: When an animal is listed without additional information, the literature (as of 1993) contained no detailed explanation.
Humans
General symptoms of poisoning:
Ascites, liver, cirrhosis of
Notes on poisoning:
Ingesting pyrrolizidine alkaloids for several months leads to veno-occlusive problems and severe portal hypertension, which can lead to cirrhosis of the liver and death. Symptoms include ascites, edema, and reduced urinary output. Children are more susceptible than adults. In two cases, one women was estimated to consume at least 85 mg of pyrrolizidine alkaloids from a herbal leaf preparation over 6 months; another woman consumed 512 mg over 6 months (comfrey-pepsin preparation) (Huxtable 1990). Ridker and McDermott (1989) note that pulmonary endothelial hyperplasia can also occur from direct exposure to these alkaloids. Rats have developed hepatocellular tumors because of the alkaloid symphytine.
