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Symphytum officinale L.

Protologue
Sp. pl. 1: 136 (1753).
Family
Boraginaceae
Chromosome number
2n = 24, 40, 48, 56
Vernacular names
Common comfrey, consound, knitbone (En). Grande consoude, oreille de vache (Fr). Consolda maior, grande consolda, orelhas de asno (Po).
Origin and geographic distribution
Symphytum officinale originates from Europe, where it is widespread, and has been introduced in North America and Asia. It is cultivated in several Mediterranean, African and Asian countries. In Africa it is cultivated on a small scale only, mainly in Madagascar and South Africa.
Uses
All parts of Symphytum officinale are medicinally used in its area of natural distribution, and the flowers, leaves and rootstocks are official in several European pharmacopoeias. Fresh leaves are widely used as a poultice on wounds, burns, bruises, sprains, insect bites, sore joints, pulled tendons, broken bones and irritated skin. Leaf decoctions or infusions have been used to treat colds, gum problems, rheumatism, arthritis, gout, scrofula, pleuritis, leucorrhoea, gastro-intestinal ulcers and as an anti-inflammatory, but internal use is now discouraged. Fresh rootstocks are commonly used for healing wounds and ulcers (including gastric ulcers), and flower infusions to treat cough and diarrhoea. Medicinal applications in Africa are very limited, but the plant is used in Madagascar as a pain-killing poultice. In Europe and also in Madagascar Symphytum officinale is planted together with crops such as tomato and potato against bacterial diseases (mainly bacterial wilt caused by Ralstonia solanacearum) and insect pests, and as a green manure and mulch. The leaves are occasionally eaten as a cooked vegetable and fed to livestock, but these uses should be discouraged because of the presence of toxic pyrrolizidine alkaloids. The plant is a well-known ornamental, and also occasionally used for this purpose in Africa.
Production and international trade
Most Symphytum officinale is cultivated in Europe and the United States, but amounts are not known.
Properties
All parts of Symphytum officinale contain allantoin (0.5–1.7%), mucilage (29%), triterpene saponins, choline, asparagine, tannins (8–9% in the aerial parts, 4–6% in the rhizomes), silicic acid (4%), and pyrrolizidine alkaloids (0.003–0.2% in the leaves, especially the young ones, 0.2–0.6% in the rhizomes). The major pyrrolizidine alkaloids are intermedine, lycopsamine, 7-acetyllycopsamine and 7-acetylintermedine. Many pyrrolizidine alkaloids are toxic and several have been shown to be hepatotoxic, pneumotoxic, carcinogenic and mutagenic. For this reason it is forbidden by law to use Symphytum officinale as an internal herbal remedy in many European countries. The external application of Symphytum officinale preparations for use in case of contusions, strains and spraining is considered safe because absorption of pyrrolizidine alkaloids through the skin is negligible.
All parts of Symphytum officinale contain allantoin, but the rootstock is richest (up to 1.7%). Allantoin is known for its healing, soothing and anti-irritating properties, and is used in anti-acne products, sun care products and clarifying lotions.
In a study using patients suffering from acute ankle sprains, the percutaneous efficacy of an ointment of Symphytum officinale rootstock extract was confirmed decisively, reducing pain as well as oedema. A crude extract of full-grown leaves only showed a slight analgesic activity in rats, and did not show anti-inflammatory activity.
Many pyrrolizidine alkaloids are not palatable and livestock avoid eating them if other forages are available. There are large differences in susceptibility to pyrrolizidine alkaloids in different animals; pigs are most susceptible, followed by horses and cattle, goats, and finally sheep.
Botany
Perennial, roughly hairy herb up to 120 cm tall, with fleshy rootstock; stem stout, winged, hollow, often branched. Leaves in a rosette and alternate on the stems, simple and entire; stipules absent; petiole up to 10 cm long, stem leaves sessile; blade ovate-lanceolate to ovate, up to 25 cm × 15 cm, decurrent at base into petiole or stem, apex acuminate, pinnately veined. Inflorescence a terminal scorpioid cyme without bracts, many-flowered. Flowers bisexual, regular, 5-merous, pendulous; pedicel 2–6 mm long; calyx with lanceolate lobes; corolla with cylindrical tube 12–18 mm long and small lobes, white to pink or purple-violet, with scales at throat; stamens inserted at the middle of the corolla tube, filaments short; ovary superior, 4-celled, style slender and exserted, stigma head-shaped, small. Fruit consisting of 4 ovoid nutlets 5–6 mm long, glossy dark brown or black, enclosed by the calyx. Seedling with epigeal germination; hypocotyl 7–15 mm long, epicotyl absent; cotyledons elliptical-oblong, 1–2.5 cm long, leafy, shortly stalked.
Symphytum comprises about 35 species and is native to Europe and western Asia. There are no indigenous species in tropical Africa.
Symphytum officinale plants are long lived. The flowers are self-incompatible and are mainly pollinated by bumble bees. The nutlets have a fleshy appendix and are dispersed by ants.
Ecology
Symphytum officinale occurs in its natural distribution area in damp grassland and on river banks. It tolerates most soils except the most sandy and dry ones, and grows well on heavy clay soils.
Management
Symphytum officinale can be propagated by seed, division or through in-vitro propagation from root explants. Optimal planting distance is 70 cm × 70 cm. It should preferably be planted in open localities or with partial shade in a deep, rich soil. Comfrey rust (Melampsorella symphyti) is the biggest problem in cultivation. The infection can be reduced by removing the infested leaves. Symphytum officinale is a host for the nematode Meloidogyne incognita. The rootstocks should be harvested at the beginning or end of the growing season, when the allantoin levels are highest. Yields of dry rootstocks are 5–12 t/ha, depending on soil type. Harvested plant parts are used fresh or dried in the shade for future use. The rootstocks can also be split down the middle and dried in an oven at 40–60°C.
Genetic resources and breeding
Symphytum officinale is widespread and common throughout its natural distribution area. Several cultivars and hybrids with other Symphytum spp. are commercially traded in Europe as garden ornamentals.
Prospects
The use of Symphytum officinale in phytotherapy should be restricted to external applications due to the presence of toxic pyrrolizidine alkaloids. The efficacy in the treatment of sprains, small wounds and skin irritation without adverse effects has been confirmed by clinical tests, and for these purposes Symphytum officinale deserves wider application. The use as a vegetable should be discouraged, but the interplanting with crops to reduce diseases and pests, as practised locally in Madagascar, is interesting and warrants more attention from research.
Major references
• B.I.M.T.T., 2000. Les avantages de la culture de la consoude. Tantely 4: 6.
• Rahetlah, V.B., 2002. Etudes des effets des exudates rauviaires de Symphytum officinale uplandicum (grande consoude) contre le flétrissement bactérien de Lycopersicum esculentum Mill. dû à Ralstonia solanacearum E.F. Smith. Mémoire DEA de Biochimie: Option biochimie, biotechnologies, microbiologie, Faculté des sciences, Université d’Antananarivo, Antananarivo, Madagascar. 67 pp.
• Schmelzer, G.H. & Horsten, S.F.A.J., 2001. Symphytum officinale L. In: van Valkenburg, J.L.C.H. & Bunyapraphatsara, N. (Editors). Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. Backhuys Publishers, Leiden, Netherlands. pp. 524–528.
• van Wyk, B.E. & Gericke, N., 2000. People’s plants: a guide to useful plants of southern Africa. Briza Publications, Pretoria, South Africa. 351 pp.
Other references
• Evreux, C., 1989. La grande consoude, Symphytum officinale L., Borraginacées. Thèse de Doctorat en Pharmacie, Université Grenoble I, Grenoble, France. 74 pp.
• Koll, R., Buhr, M., Dieter, R., Pabst, H., Predel, H.G., Petrowicz, O., Giannetti, B., Klingenburg, S. & Staiger, C., 2004. Efficacy and tolerance of a comfrey root extract (Extr. Rad. Symphyti) in the treatment of ankle distorsions: results of a multicenter, randomized, placebo-controlled, double-blind study. Phytomedicine 11(6): 470–477.
• Mei, N., Guo, L., Fu, P.P., Heflich, R.H. & Chen, T., 2005. Mutagenicity of comfrey (Symphytum officinale) in rat liver. British Journal of Cancer 92(5): 873–875.
• Rajaobelimahefa, L., 1990. La consoude est aussi un insecticide qui élimine les insectes nuisibles aux cultures. Matoy 3: 20.
• Stickel, F. & Seitz, H.K., 2000. The efficacy and safety of comfrey. Public Health Nutrition 3(4A): 501–508.
Sources of illustration
• Schmelzer, G.H. & Horsten, S.F.A.J., 2001. Symphytum officinale L. In: van Valkenburg, J.L.C.H. & Bunyapraphatsara, N. (Editors). Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. Backhuys Publishers, Leiden, Netherlands. pp. 524–528.
Author(s)
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Based on PROSEA 12(2): ‘Medicinal and poisonous plants 2’.

Editors
G.H. Schmelzer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
A. Gurib-Fakim
Faculty of Science, University of Mauritius, Réduit, Mauritius
Associate editors
C.H. Bosch
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
M.S.J. Simmonds
Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, United Kingdom
R. Arroo
Leicester School of Pharmacy, Natural Products Research, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Photo editor
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Lemmens, R.H.M.J., 2006. Symphytum officinale L. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). Prota 11(1): Medicinal plants/Plantes médicinales 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, flowering stem; 2, part of opened corolla; 3, fruit enclosed by calyx; 4, nutlet.
Source: PROSEA



flowering branch
obtained from J. De Laet



inflorescence
obtained from J. De Laet



calyx with style and corolla
obtained from J. De Laet



part of infructescence
obtained from J. De Laet