Arnica species (Arnica)

A. cordifolia Hook
A. fulgens Pursh
A. sororia Greene

The European Arnica montana L. is the most widely used source of arnica preparations, but the three North American species named above also supply material used in drug products and are officially listed as sources of arnica in the American Pharmaceutical Association's "National Formulary." All of these species are reported to have similar properties. Medicinally, the three North American species are generally not distinguished from each other or from the European species. Arnica angustifolia Vahl both from North America and Eurasia has also been reported to be medicinal; however, the extent to which the North American A. chamissonis Less. is a drug source is unclear. In the following, all of the drug species are referred to collectively as "arnica."

English Common Names

Arnica, wolf's-bane.

The European plant is called arnica, European arnica, mountain daisy, mountain tobacco, mountain snuff, leopard's bane (leopard's-bane), sneezewort, and fall-kraut. The Mexican antimicrobial herb, Heterotheca inuloides Cass., is sometimes also referred to as "Arnica." "Arnica" from Brazil might be Solidago microglossa DC., which has been recommended as a substitute for A. montana.

French Common Names

Arnica.

Arnica cordifolia

Morphology

Arnicas are erect, perennial herbs 10-70 cm tall. The leaves are opposite, with smooth or toothed margins. Both simple and glandular (i.e., gland-tipped) hairs are often present. The basal leaves, 4-20 cm long, are the longest, while the uppermost leaves are short and stalkless. The leaves are particularly useful in distinguishing the three North American drug species. Arnica cordifolia has long-stalked basal leaves that are broadly ovate and more or less heart-shaped, whereas A. fulgens and A. sororia have lanceolate leaves that are tapered at the base and have relatively short stalks. Arnica fulgens has dense tufts of brown hair in axils of old leaves whereas A. sororia has at most a few whitish hairs in the axils. The one to seven yellow flower heads of the drug species are 1.5-3 cm across and are produced in July and August. The seeds, actually achenes (one-seeded dry fruits), are 3-10 mm long with a whitish or brownish pappus. (The pappus refers to the hairs or bristles at the top of the achene, a feature possessed by many members of the daisy family, which serves for dispersal, for example by wind or attachment to animals.) The rhizomes are short and thick in the grassland species (A. fulgens and A. sororia), but long and creeping in A. cordifolia.

Arnica sororia

Classification and Geography

The genus Arnica includes about 28 species of the north temperate region, most occurring in the montane region of western North America. All three North American species that supply drugs occur in the western cordillera. Arnica fulgens and A. sororia are found largely on the high plains and interior valleys. They were once thought to be best treated as varieties of a single species, but recent studies have shown that they are quite distinct, although more closely related to each other than to other species of the genus.

The wide ranging A. cordifolia is found in the western American mountains, with isolated populations in Manitoba and the Lake Superior region. The northern populations differ from southern populations in flavonoid composition. Studies suggest that A. cordifolia gave rise to a number of narrowly distributed species of Oregon and California. Within A. cordifolia the alpine or subalpine var. pumila (Rydb.)

Maguire is distinguished by its relatively small size, narrower leaves and more glandular achenes. Arnica cordifolia has five races differing in chromosome number, with the ancestral types (the diploids, with the lowest chromosome number) restricted to the unglaciated territory in northeastern Oregon and southern Yukon. Isolated eastern occurrences of A. cordifolia in the Lake Superior region were first discovered on the Kewenaw Peninsula and the plants were described as the new species, A. whitneyi Fernald, but subsequent study suggested that they were better combined with the western A. cordifolia.

The species was recently discovered in Sibley Park on the shore of Lake Superior. There are about 50 other arctic-alpine vascular plant species that were left as isolated disjuncts on or near to the cold Lake Superior shore following the glacial retreat 10,000 years ago.

Distribution Map

Description of this image follows.
Description of the above image

Arnica fulgens occurs from southeastern British Columbia and central Alberta east to southwestern Manitoba and south to northwestern Colorado and west to northeastern California. Arnica sororia occurs from southcentral British Columbia east to southwestern Saskatchewan and south to northeastern Colorado and northern Utah and west to northeastern California. The wide ranging A. cordifolia is found in the western American mountains, with isolated populations in Manitoba and the Lake Superior region. Its main range extends from southern Yukon and southwestern Northwest Territories south to the northern portions of New Mexico, Arizona, Nevada and California.

Ecology

Arnica cordifolia occurs in woodlands and along woodland edges. Cutting and thinning of forests have resulted in population increase. Prairies are the primary habitats of A. fulgens and A. sororia. The latter two species reproduce sexually and are self-incompatible. Many different insects including bees, flies and butterflies visit the flowers and serve as pollinators. In contrast, A. cordifolia produces seeds without fertilization, but like many other such apomicts, it can presumably also take advantage of occasional fertilization following pollination by insects. A study in The Netherlands suggested that the European A. montana is largely self-incompatible and has an outcrossing mating system.

Low levels of grazing have been found to be necessary to maintain Arnica montana in some European grasslands where it is otherwise outcompeted by grasses. Acidification of nutrient-poor soils in The Netherlands due to air pollution has been related to a decline in populations of A. montana.

Medicinal Uses

Arnica fulgens

Arnica montana, the European species, was used in folk medicine in Europe for a variety of purposes, just as North American Indians employed indigenous American species medicinally. This old remedy was used particularly as a counterirritant, an agent applied locally to produce superficial inflammation in order to reduce pain in deeper adjacent areas. Bactericidal and fungicidal properties also led to use in treatment of abrasions and gunshot wounds in Europe. Arnica was also used to treat tumours. Most of these treatments are outmoded.

Arnica is still primarily used as a counterirritant, usually as a hydroalcoholic extract, to reduce the inflammation and pain of bruises, sprains, and aches. Its use declined with the development of effective synthetic painkillers. It is more popular in Europe, where it is available in creams, than in North America. Application to damaged skin seems unwise considering the high irritation capability and, as noted below, it is sufficiently toxic that internal use is unwarranted.

Toxicity

Arnica should not be taken internally as it is sufficiently toxic that it can cause fatal poisoning. Unidentified substances that it contains can produce stress on the nervous system, the digestive system and the circulatory system, resulting in muscular weakness, collapse and even death. Experiments with small animals have confirmed that arnica causes cardiac toxicity and large increases in blood pressure. This herb was listed in a Health Canada document, Herbs used as non-medicinal ingredients in non-prescription drugs for human use, as unacceptable as a non-prescription drug product for oral use.

Arnica is a popular homeopathic remedy, i.e., it is orally consumed in very diluted doses that are said to be too weak to cause harm (see Homeopathic in Glossary for reference to an information source with the viewpoint that homeopathy is without scientific merit). External use may cause contact dermatitis due to the allergenic helanin, a sesquiterpene lactone (which has medicinal properties), and other constituents. Arnica should not be applied to broken or damaged skin. Given the potential for allergenic reactions, it seems unwise to use this herb except under qualified medical supervision.

Chemistry

In some cases entire plants or the roots are utilized, but most often drugs are obtained from the dried flower heads which yield a yellowish-brown powder containing arnicin, volatile oil, resin and tannin. Numerous chemical constituents have been reported, but it was only recently discovered that certain sesquiterpenoid lactones were responsible for some of the beneficial effects, particularly the anti-inflammatory action. Helenalin, dihydrohelenalin, and their esters are among the most active principles. Isomeric alcohols such as arnidiol and foradiol have been reported to contribute to counterirritant action. Much of what is known of the medicinal properties and their chemical basis has been published in Europe.

Arnica montana and A. chamissonis ssp. foliosa have been adulterated by blending with Heterotheca inuloides, but a chromatographic method has been developed to rapidly detect this in Arnica drugs. A number of other species of the aster family have also been used to adulterate arnica preparations.

Non-medicinal Uses

Arnica montana yields an oil which has been used in perfumery. Arnica montana, A. cordifolia, and A. fulgens are all grown as garden ornamentals.

Arnixa Montana (European arnica)

Agricultural and Commercial Aspects

Germany markets as many as 300 drug preparations containing arnica extract, while Canada has about 20 such products. Arnica is obtained from both wild and cultivated sources. The US is apparently a more important supplier than Canada, with material collected in the wild from Montana, Wyoming and the Dakotas. Decline of the wild sources and the likely capability of both the North American and European plants to grow throughout much of Canada, as well as demonstrated ease of cultivation, make arnica a potentially interesting diversification crop for Canada.

Arnica montana has become particularly scarce in some parts of Europe, making the cultivated crop more significant. This species is now cultivated as a drug source in parts of Europe and in northern India. Highly productive clones have been produced in Bavaria, with over a hundred flower heads and more than 1% of both flavonoids and sesquiterpene lactones in the harvested drug preparations. Optimal cultivation conditions, including substrates, fertilization and climate, for productivity of A. montana in Germany and Russia have been determined. Studies in the Venetian Alps have suggested that Tephritis arnicae, a troublesome, widespread fly pest that feeds on the ovaries in the flower heads of A. montana, might be controlled effectively with natural parasites. Related species of Arnica, such as A. foliosa and A. chamissonis, have been found to be useful as alternative drug sources.

Some characteristics of the North American species of Arnica adapt them to cultivation. These include:

  • rapid maturation (i.e., flowering) in the second year after growth from seed;
  • rapid multiplication by rhizomes;
  • upper parts harvest readily, leaving the rhizomes for subsequent growth;
  • self-seeding by some species, so replanting is not necessary.

Myths, Legends, Tales, Folklore, and Interesting Facts

  • One of the stranger old-time medicinal preparations is "toad ointment," used to treat sprains, strains, lame back, rheumatism, caked breast, caked udders, etc. A recipe is: put four good-sized toads into boiling water and cook until very soft; remove them and boil the water down to 1/2 pint; add 1 pound of fresh churned, unsalted butter and simmer; add 2 ounces of tincture of arnica.
  • Although not safe for internal consumption by humans, Arnica cordifolia has been identified as an important constituent of the diet of elk and mule deer.
  • Applied to the bald scalp, arnica is said to make hair grow (although skin irritation is the more likely result).
  • Large quantities of arnica were used to treat soldiers during World War II.
  • Arnica, from the European Arnica montana, is said to be one of the most frequently used homeopathic remedies for sports injuries, including "Tennis Elbow." Swiss mountain climbers have sought out the herb and chewed it to relieve sore, tired muscles (a dangerous practice in view of its poisonous and allergenic properties).
  • Arnica montana was attractively pictured (along with crowberry) on a 1995 Swedish postal stamp.

Selected References

  • Baillargeon, L., Drouin, J., Desjardins, L., Leroux, D., and Audet, D. 1993. The effects of Arnica montana on blood coagulation. Randomized controlled trial. Can. Fam. Physician 39: 2362-2367. [In French.]

  • Bomme, U., and Daniel, G. 1994. First results on selection breeding of Arnica montana L. Gartenbauwissenschaft 59(2): 67-71

  • Bomme, U., Rinder, R., and Voit, K. 1991. Influence of substrates and fertilization on raising transplants of Arnica montana L. Gartenbauwissenschaft 56(3): 106-113.

  • Cayouette, J. 1999. Kohlmeister et Kmoch, deux moraves en Ungava, en 1811. Flora Quebeca 3(3): 7-8. [Mentions medicinal use of Arnica angustifolia.]

  • Conchou, O., Nichterlein, K., and Voemel, A. 1992. Shoot tip culture of Arnica montana for micropropagation. Planta Med. 58: 73-76.

  • Downie, S.R. 1988. Morphological, cytological, and flavonoid variability of the Arnica angustifolia aggregate (Asteraceae). Can. J. Bot. 66: 24-39.

  • Downie, S.R., and Denford, K.E. 1986. The taxonomy of Arnica frigida and Arnica louiseana (Asteraceae). Can. J. Bot. 64: 1355-1372.

  • Downie, S.R., and Denford, K.E. 1986. The flavonoids of Arnica frigida and Arnica louiseana (Asteraceae). Can. J. Bot. 64: 2748-2752.

  • Downie, S.R., and Denford, K.E. 1987. The biosystematics of Arnica fulgens and Arnica sororia (Asteraceae). Can. J. Bot. 65: 559-570.

  • Downie, S.R., and Denford, K.E. 1988. Taxonomy of Arnica (Asteraceae) subgenus Arctica. Rhodora 90: 245-276.

  • Downie, S.R., and Denford, K.E. 1988. Flavonoid variation in Arnica subgenus Arctica. Biochem. Syst. Ecol. 16: 133-138.

  • Ediger, R.I., and Barkley, T.M. 1978. Arnica. In North American Flora. Series II, Part 10. Edited by C.T. Rogerson. New York Botanical Garden, New York, NY.

  • Fennema, F. 1992. Sulphur dioxide and ammonia deposition as possible causes for the extinction of Arnica montana. Water Air Soil Pollut. 62: 325-336.

  • Fernald, M.L. 1935. Critical plants of the upper Great Lakes region of Ontario and Michigan. Rhodora 37: 324-341.

  • Gervais, C., Grandtner, M.M., Doyon, D., and Guay, L. 1990. Nouvelles stations d'Arnica lanceolata Nutt. et d'A. chamissonis Less. au Québec: notes cytologiques et écologiques. Naturaliste can. 117: 127-131.

  • Given, D.R., and Soper, J.H. 1981. The arctic-alpine element of the vascular flora of Lake Superior. Natl. Mus. Nat. Sci. Publ. Bot. 10: 70 pp.

  • Gruezo, W.S., and Denford, K.E. 1994. Taxonomy of Arnica L. subgenus Chamissonis Maguire (Asteraceae). Asia Life Sci. 3: 89-212.

  • Gruezo, W.S., and Denford, K.E. 1995. A cytogeographic investigation of Arnica L. subgenus Chamissonis Maguire (Asteraceae) in western North America. Asia Life Sci. 4: 95-124.

  • Gruezo, W.S., and Denford, K.E. 1995. Foliar flavonoid variation in Arnica L. subgenus Chamissonis Maguire (Asteraceae) in western North America. Asia Life Sci. 4: 151-170.

  • Hausen, B.M. 1978. Identification of the allergens of Arnica montana L. Contact Dermatitis 4: 308.

  • Hausen, B.M. 1980. Arnica allergy. Hautarzt 31(1): 10-17. [In German.]

  • Herrmann, H.D., Willuhn, G., and Hausen, B.M. 1978. Helenalinmethacrylate, a new pseudoguaianolide from the flowers of Arnica montana L., and the sensitizing capacity of their sesquiterpene lactones. Planta Med. 34: 299-304.

  • Hocking, G.M. 1945. American arnica in medicine. Chem. Dig. 4: 10-12.

  • Jenelten, U., and Feller, U. 1992. Mineral nutrition of Arnica montana L., and Arnica chamissionis ssp. foliosa Maguire: differences in the cation acquisition. J. Plant Nutr. 15: 2351-2361.

  • Kalemba, D., Gora, J., Kurowska, A., and Zadernowski, R. 1986. Comparisons of the chemical composition of inflorescences of Arnica spp. Herba Pol. 32(1): 9-18.

  • Kating, H., and Seidel, F. 1967. Cultivation experiments with Arnica species. Ii. Vegetative propagation of Arnica montana L. Planta Med. 15: 420-429. [In German.]

  • Kating, H., Rinn W., and Willuhn, G. 1970. Studies on the substance of species of Arnica. 3. Fatty acids in etheric oils of the flowers of various species of Arnica. Planta Med. 18: 130-146. [In German.]

  • Kaziro, G.S. 1990. Metronidazole (Flagyl) and Arnica montana in the prevention of post-surgical complications, a comparative placebo controlled clinical trial. Br. J. Clin. Pract. 44: 619-621.

  • Labadie, R.P. 1968. Arnica montana L. Pharm. Weekbl. 103: 769-781. [In Dutch.]

  • Levin, W., and Willuhn, G. 1987. Sesquiterpene lactones from Arnica chamissonis Less. Vi. Identification and quantitative determination by high performance liquid and gas chromatography. J. Chromatogr. 41: 329-342.

  • Luijten, S.H., Gerard, J., Oostereijer, B., van Leeuwen, N.C., and den Nijs, H.C.M. 1996. Reproductive success and clonal genetic structure of the rare Arnica montana (Compositae) in the Netherlands. Plant Syst. Evol. 201: 15-30.

  • Maguire, B. 1943. A monograph of the genus Arnica. Brittonia 4: 386-510.

  • Marquis, R.J., and Voss, E.G. 1981. Distributions of some western North American plants in the Great Lakes region. Mich. Bot. 20: 53-82.

  • Merfort, I. 1988. Acetylated and other flavonoid glycosides from Arnica chamissonis. Phytochemistry 27: 3281-3284.

  • Merfort, I. 1992. Caffeoylquinic acids from flowers of Arnica montana and Arnica chamissonis. Phytochemistry 31: 2111-2113.

  • Merfort, I., and Wendisch, D. 1992. New flavonoid glycosides from Arnicae flos DAB 9. Planta Med. 58: 355-357.

  • Merfort, I., and Wendisch, D. 1993. Sesquiterpene lactones of Arnica cordifolia, subgenus Austromontana. Phytochemistry 34: 1436-1437.

  • Merfort, I., Marcinek, C., and Eggert, A. 1986. Flavonoid distribution in Arnica subgenus Chamissonis. Phytochemistry 25: 2901-2903.

  • Passreiter, C.M., Willuhn, G., and Roeder, E. 1992. Tussilagine and isotussilagine: two pyrrolizidine alkaloids in the genus Arnica. Planta Med. 58: 556-557.

  • Pietta, P.G., Mauri, P.L., Bruno, A., and Merfort, I. 1994. MEKC as an improved method to detect falsifications in the flowers of Arnica montana and A. chamissonis. Planta Med. 60: 369-372.

  • Rinn, W. 1970. Isobutyric acid thymylester -- main constituent of etheric oil of rhizomes and roots of Arnica chamissonis. Planta Med. 18: 147-149. [In German.]

  • Rudzki, E., and Grzywa, Z. 1977. Dermatitis from Arnica montana. Contact Dermatitis 3: 281-282.

  • Scaltriti, G.P. 1985. The insects of medicinal plants: Arnica montana L., and two of its phytophagous insects. Redia 68: 355-364.

  • Schroeder, H., Loesche, W., Strobach, H., Leven, W., Willuhn, G., T ill, U., and Schroer, K. 1990. Helenalin and 11-alpha, 13-dihydrohelrnalin, two constituents from Arnica montana L., inhibit human platelet function via thiol-independent pathways. Thromb. Res. 57: 839-846.

  • Schulte, K.E., Rucker, G., and Reithmayr, K. 1969. Certain constituents of Arnica chamissonis and other Arnica species. Lloydia 32: 360-368. [In German.]

  • Schwabe, A. 1990. Syndynamic processes in Nardo callunetea communities: changes in fallow land after renewed cattle grazing and life history of Arnica montana L. Carolinea 48: 45-68.

  • Speight, P. 1980. Arnica, the wonder herb; the remedy that should be in every home. C. W. Daniel Company Limited, Saffron Walden, Essex, England. 45 pp.

  • Torres, L.M.B., Akisue, M.K., and Roque, N.F. 1987. Quercitrin from Solidago microglossa DC., the Arnica of Brazil. Rev. Farm. Bioquim. univ. Sao Paulo 23(1): 33-40.

  • Vanhaelen, M. 1973. Identification of carotenoids in Arnica montana. Planta Med. 23: 308-311. [In German.]

  • Willuhn, G. 1972. Studies on components of Arnica species. V. Content and content differences of volatile oil in various organs of Arnica species. Planta Med. 21: 221-245. [In German.]

  • Willuhn, G. 1972. Studies on the components of Arnica species. Vi. Characterization and preparative separation of volatile oils from roots, rhizoma, leaves and flowerheads of various Arnica species. Planta Med. 21: 329-342. [In German.]

  • Willuhn, G. 1972. Studies on the components of Arnica species. Vii. Composition of the volatile oil from subterranian organs and flower heads of various Arnica species. Planta Med. 22: 1-3. [In German.]

  • Willuhn, G 1972. Fatty acids of the essential oil from leaves of Arnica montana and Arnica longifolia. Z. Naturforsch. B. 27: 728. [In German.]

  • Willuhn, G., Kresken, J., and Leven, W. 1990. Further helenanolides from the flowers of Arnica chamissonis ssp. foliosa. Planta Med. 56: 111-114. [In German.]

  • Woerdenbag, H.J., Merfort, I., Passreiter, C.M., Schmidt, T.J., Willuhn, G., Van-Uden, W., Pras, N., Kampinga, H.H., and Konings, A.W.T. 1994. Cytotoxicity of flavonoids and sesquiterpene lactones from Arnica species against the GLC-4 and the COLO 320 cell lines. Planta Med. 60: 434-437.

  • Wolf, S.J. 1980. Cytogeographical studies in the genus Arnica (Compositae: Senecioneae). I. Am. J. Bot. 67: 300-308.

  • Wolf, S.J. 1987. Cytotaxonomic studies in the genus Arnica (Compositae: Senecioneae). Rhodora 89: 391-400.

  • Wolf, S.J., and Denford, K.E. 1983. Flavonoid variation in Arnica cordifolia: an apomictic polyploid complex. Biochem. Syst. Ecol. 11: 111-114.

  • Wolf, S.J., and Denford, K.E. 1984. Taxonomy of Arnica (Compositae) subgenus Austromontana. Rhodora 86: 239-309.

  • Wolf, S.J., and Denford, K.E. 1984. Flavonoid diversity and endemism in Arnica subgenus Austromontana. Biochem. Syst. Ecol. 12: 183-188.

  • Wolf, S.J., and Whitkus, R. 1987. A numerical analysis of flavonoid variation in Arnica subgenus Austromontana. Am. J. Bot. 74: 1577-1584.

  • Ziegler, B., Michler, B., and Arnold, C.G. 1992. Arnica montana L.: a protected plant as a source of a pharmacopoeia drug. Pharm. Zeit. Wissen. 137: 198-201.