This inspired us to investigate the mutagenicity of comfrey in rat liver, a target tissue for its carcinogenesis, by using a transgenic rat mutational model ( Dycaico et al, 1994). Although induction of hepatic tumours has been associated with the pyrrolizidine alkaloids (PAs) that are present in comfrey, and PAs are genotoxic and carcinogenic by binding to liver DNA in humans and animals ( Prakash et al, 1999 Fu et al, 2004), a comprehensive study of comfrey mutagenesis has not been conducted. There is little known about the mechanism of tumour induction by comfrey. There are presently, however, no restrictions on the use of comfrey in many parts of the world. This concern led the US Food and Drug Administration to request voluntary removal of products containing comfrey from the market in 2001 ( FDA, 2001).

Although there are no epidemiological data regarding the carcinogenicity of comfrey, these adverse effects have raised questions of its potential carcinogenicity in humans. It induced hepatic veno-occlusive disease in humans ( Ridker et al, 1985 Weston et al, 1987 Bach et al, 1989 Ridker and McDermott, 1989 Yeong et al, 1990) and hepatocellular adenomas and haemangioendothelial sarcomas in rat liver ( Hirono et al, 1978). Comfrey, however, is hepatotoxic in livestock and humans and carcinogenic in experimental animals. It has been used as an herbal medicine for more than 2000 years to treat broken bones, tendon damage, ulcerations in the gastrointestinal tract, lung congestion, and joint inflammation, and to promote wound healing ( Rode, 2002). Comfrey is consumed by humans as a vegetable and a tea. Common name of comfrey reportedly comes from con firma (Latin meaning with strength) in reference to its reputation for healing wounds and broken bones (leaves and roots contain allantoin).Comfrey ( Symphytum officinale) is a tall perennial plant with large hairy leaves and small purple flowers ( Winship, 1991 Betz et al, 1994). Specific epithet means sold in shops and was often applied to plants with supposed medicinal properties. Genus name comes from the Greek words symphyo meaning to grow together and phyton for plant as the plant was believed to help heal wounds. Although some controversy still exists regarding internal use, plants are now generally considered by most experts to be unsafe and dangerous for ingestion. Leaves were also once used for herbal teas. Young leaves and stems were once cooked as a vegetable (like spinach). Internally, comfrey has been used to treat a number of other medical problems including ulcers and colitis. Leaves and roots have been used for many years in poultices for treating a variety of external inflammations, rashes, swellings, cuts, bruises, sprains or broken bones. Over time, comfrey has naturalized along roadsides and in waste areas throughout much of the U.S.

Immigrants first brought the plant to America in the 1600s for medicinal use. Comfrey (also commonly called knitbone or boneset) has been cultivated since 400 B. Tubular, bluebell-like, white to pink to purple flowers appear in drooping clusters (scorpiod cymes) in mid-spring to early summer. Upper leaves are decurrent and much smaller than the basal ones. Large, pointed, hairy, ovate-lanceolate, dark green basal leaves grow to 8” long. Symphytum officinale, commonly called comfrey, is a large, coarse, tuberous-rooted, clumping perennial (to 3’ tall and 2.5’ wide) that is primarily grown today as an ornamental for its attractive foliage and spring flowers.

Use of symphytum officinale