Arnika

Arnica montana, also known as leopard's bane, mountain tobacco and mountain arnica, is a European flowering plant in the daisy family Asteraceae. It is an aromatic herbaceous perennial about 18-60 cm tall. Each flower head has orange-yellow disc florets in the centre, bordered by 10 to 15 yellow ray florets. The plant has been used as a herbal medicine, but there is insufficient clinical evidence for its therapeutic use. Ointments made from the plant are used to treat bruises, sprains, rheumatism, varicose veins and diverse skin infections.

Origin and Production

Arnica montana is widespread across most of Europe. It is absent from the Celtic Isles and the Italian and Balkan peninsulas. It mostly grows on alpine meadows, up to nearly 3,000 m. It does not grow on lime soil. The plant is becoming rarer, particularly in the north of its distribution, largely due to increasingly intensive agriculture and commercial wildcrafting. Arnica is among the European medicinal plants whose populations are considered to be declining. It is cultivated on a large scale in Estonia. France and Romania produce it for the international market. The flowers are harvested when fully developed and dried without bract or receptacles.

Chemistry

The main constituents of Arnica montana are essential oils, fatty acids, thymol, pseudoguaianolide sesquiterpene lactones and flavanone glycosides. Pseudoguaianolide sesquiterpenes make up 0.2-0.8% of the flower head. They are the toxin helenalin and its fatty esters. Helenalin, a toxic sesquiterpene lactone, has the formula C₁₅H₁₈O₄. Two chemotypes of Arnica montana are known: the helenalin type is native to Central Europe, and the dihydrohelenalin type, which contains only traces of helenalin, is native to Spain. 2,5-Dimethoxy-p-cymene and thymol methyl ether are the primary components of the essential oils from the plant's roots and rhizomes. The standardised CO2 extract contains 0.2-0.4% essential oil, and it also contains esters of the triterpenediols arnidiol, faradiol, maniladiol and calenduladiol.

Safety

The US Food and Drug Administration has classified Arnica montana as an unsafe herb because of its toxicity. It should not be taken orally or applied to broken skin where absorption can occur. Arnica may produce contact dermatitis when applied to skin.

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