Arnica (Ár-ni-ca) is a genus with about 30 perennial, herbaceous species, belonging to the sunflower family (Asteraceae). The genus name Arnica may be derived from the Latin arna, "lamb", in reference to the soft, hairy leaves.
This circumboreal and montane genus occurs mostly in the temperate regions of western North America, while two are native to Eurasia (A. angustifolia and A. montana).
Arnica used to be included in the tribe Senecioneae, because it has a pappus of fine bristles. This was soon questioned and Nordenstam (1977) placed it tentatively in tribe Heliantheae s.l. This arrangement also became uncertain because of the sesquiterpene lactone chemistry in certain species. Lately Arnica was placed in an unresolved clade together with Madiinae, Eupatorieae, Heliantheae s.s. and Pectidinae.
Several species, such as Arnica montana and Arnica chamissonis contain helenalin, a sesquiterpene lactone that is a major ingredient in anti-inflammatory preparations (mostly against bruises).
Arnica species are used as food plants by the larvae of some Lepidoptera species including Bucculatrix arnicella.
In herbal medicine, Arnica usually refers to Arnica montana, a mountain plant used for relief of bruises, stiffness, and muscle soreness. Arnica is widely used as a salve for bruises and sprains , and sometimes as a tincture , for the same anti-inflammatory, pain-relieving purposes. Tablets are also available. In homeopathy it has a wider use. It is available in natural/health food stores, most commonly in gel form, to be applied to the affected area approximately three times daily.
They have a deep-rooted, erect stem, that is usually unbranched. Their downy, opposite leaves are borne towards the apex of the stem. The ovoid, leathery, basal leaves are arranged in a rosette.
They show large yellow or orange flowers, 6-8 cm wide with 10-15 long ray florets and numerous disc florets. The phyllaries (a bract under the flowerhead) has long spreading hairs Each phyllary is associated with a ray floret. Species of Arnica, with an involucre (a circle of bracts arranged surrounding the flower head) arranged in two rows, have only their outer phyllaries associated with ray florets. The flowers have a slight aromatic smell.
The seed-like fruit has a pappus of plumose, white or pale tan bristles.
Arnica acaulis (Walt.) B.S.P. -- Common Leopardbane
Maguire, B. (1943). "A monograph of the genus Arnica (Senecioneae, Compositae)". Brittonia4: 386–510.
Wolf, S.J. & K.E. Denford (1984). "Taxonomy of Arnica (Compositae) subgenus Austromontana". Rhodora Journal of the New England Botanical Club86 (847): 239 - 309.
Nordenstam, B. 1977 Senecioneae and Liabeae—systematic review. In V. H. Heywood, J. B. Harborne, and B. L. Turner [eds.], The biology and chemistry of the Compositae, vol. II, 799–830. Academic Press, London, UK
Baldwin, B. G. (1999). "New combinations in Californian Arnica and Monolopia". Novon9: 460–461.
Lyss, G., T. J. Schmidt, H. L. Pahl, and I. Merfort (1999). "Anti-inflammatory activity of Arnica tincture (DAB 1998) using the transcription factor NF-kappaB as molecular target". Pharmaceutical and Pharmacological Letters9: 5–8.
Wolf, S. J., and K. E. Denford (1984). "Taxonomy of Arnica (Compositae) subgenus Austromontana". Rhodora86: 239–309.