Family • Boraginaceae - Symphytum officinale - COMPREY / KNITBONE

Scientific names

Symphytum officinale

Other names

Comprey (Engl.) Black root (Engl.)
Komprey (Tag.) Symphytum radix (Engl.)
Slippery root (Engl.)

General info
· An ancient herb known since 400 B.C., used by the Greeks to treat bronchial problems, wound healing and mending of broken bones. The name “Comfrey” is a corruption of con firma, the uniting of bones.
· The healing constituent is allantoin. Ingredients may be steeped or dissolved in hot water; boiling should be avoided as this may cause the breakdown of allantoin.


Additional Sources and Suggested Readings

(1) Mutagenic effects of aqueous extracts of Symphytum officinale L. and of its alkaloidal fractions / Mirosawa Fumanowa et al / Journal of Applied Toxicology • Volume 3 Issue 3, Pages 127 – 130 / DOI 10.1002/jat.2550030304


(3) Comfrey (Symphytum Officinale. L.) and Experimental Hepatic Carcinogenesis: A Short-term Carcinogenesis Model Study / Maria Fernanda Pereira Lavieri Gomes et al / eCAM 2010 7(2):197-202 / doi:10.1093/ecam/nem172

(4) Notes on poisoning: Symphytum officinale / Canadian Biodiversity Information Facility

(5) Action of some proteic and carbohydrate components of Symphytum officinale upon normal and neoplastic cells / Olinescu A et al / Arch Microbiol Immunol. 1993 Apr-Jun;52(2):73-80.

(6) Absence of mutagenic effects of a particular Symphytum officinale L. liquid extract in the bacterial reverse mutation assay./ Benedek B et al / Phytother Res. 2009 Oct 13

(7) Safety assessment of food and herbal products containing hepatotoxic pyrrolizidine alkaloids: interlaboratory consistency and the importance of N-oxide determination / Cao Y et al / Phytochem Anal. 2008 Nov;19(6):526-33.

Hardy, leafy perennial. Thick rhizomes, black outside and white inside, containing a mucilaginous juice. Leaves are entire, lanceolate to ovate-lanceolate, up to 10 inches long, deep green and hairy. Flowers are variable in color, blue, yellow or white, borne on short curved racemes, with five-lobed calyx and five stamens. Fruits are nutlets.

Introduced in the Philippines in the late 60s; cultivated; propagated by seed.

Toxicity ! 
• Hepatotoxicity: Since the late 70’s, subject of persisting concerns and debate on certain alkaloid contents that may cause liver damage, veno-occlusive liver disease, ascites and hepatic fibrosis.
• Advice is given against use of comfrey as salad green or tea.
• In July 2001, the US FDA took steps to stop the marketing of comfrey as a dietary supplement. (Source)


Parts utilized 
Leaves , flowers and roots.

Chemical constituents and properties
· Considered antitussive, expectorant, haemostatic, vulnerary, homepathy.
• Contains allantoin, between 0.6 to 0.8 % to which is attributed its wound-healing properties.
• Phenolic acids: rosmarinic, chloogenic, caffeic and lithospermic acids.
• Contains potentially hepatotoxic compounds: pyrrolizidine alkaloids, including heliosupine, echimidine, heliosuipine, lycopsamine, symphytine and cynoglossine. The alkaloid concentration is highest in small, young leaves. Roots also contain high levels of these compounds.


Confirmed source of vitamin B12, although in negligible amounts that would require consumption of 4 pounds of comfrey daily for minimum daily requirement.
· Decoction of leaves used for a variety of illnesses: Asthma, cough, ulcers, constipation, hypertension.
· Poultice of fresh leaves used for sprains and fractures, inflammatory swelling, external wounds, sores, athlete’s foot, burns, insect bites, and abscesses.
· Used for excessive menstrual flow, cancer, angina, gums disease
· Juice of leaves used for a variety of skin ailments and wounds healing; apply three times daily.
· Decoction of tea as a sleep-aid.
· Roots and leaves used for broken bones and wounds.
· In Ayurveda, used for peptic ulcer.
· In Polish pharmacopoeia, as Radix symphyti, recommended as expectorant, especially for children.


Study Findings
• Antiproliferative: Study of effects of chronic oral treatment of rats with 10% comfrey ethanolic extract was evaluated in a RHM (resistant hepatocyte model) showed the treatment reduced cell proliferation.
· Mutagenic Effects: Mutagenic effects of aqueous extracts of Symphytum officinale L. and of its alkaloidal fractions – Aqueous solutions of three alkaloid fractions were studied for antimitotic and mutagenic activity. Results showed mutagenic activity to be induced by lasiocarpine, by alkaloidal fraction 1 and by diluted infusions from Radix symphyti. Fraction III had only antimitotic effect.
• Herbal Tea Concerns / Pyrrolizidine Alkaloids / Hepatotoxicity: Analysis of herbal teas made from the leaves of comfrey (Symphytum officinale): reduction of N-oxides results in order of magnitude increases in the measurable concentration of pyrrolizidine alkaloids: The concentration of symphytine and echimidine varied considerably in different tea leaves preparation. Since alklaoids are known to be hepatotoxic, and because the concentration of pyrrolizidine alkaloids may be underestimated, consumption of comfrey herbal teas, in native or packaged forms, is not advised.
• Roots reported to increase incidence of liver tumors in rats; other studies suggest it is carcinogenic.
• Proliferative / Antimitotic: Results indicate crude extract and its proteic fraction stimulate invivo proliferation of studied neoplastic cells and and antimitotic effect on human T lymphocytes in vitro stimulated with PHA.
• Non-mutagenic: Study of the comfrey root fluid extract contained in Kytta-Salbe (R) f and Kutta Plasma (R) f was not mutagenic in bacterial reverse mutation assay.
• Safety Assessment : Study highlighted significant differences in the reported identification of pyrrolizidine alkaloids from the same plant species, and demonstrates the inadequacy of some procedures to include N-oxides in the assessment of pyrrolizidine alkaloid-related safety of food and herbal products.

Safety studies
· Probably safe when used topically on unbroken skin. Use should be limited to 4 to 6 weeks per year at less than 100 mcg of unsaturated pyrrolizidine alkaloids. However, with toxicity concerns, it is advisable to seek alternatives.
· Avoid oral use. Probably not safe when taken orally. Potential for liver toxicity.
· Contraindicated in pregnancy and lactation.

Ointments, root and leaf extracts in the cybermarket.