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, which is 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.
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 9 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. The entire plant has a strong and distinct pine-sage odor when the leaves of mature plants are rubbed or bruised.
Uses and toxicity
Arnica montana has long been used medicinally, It contains the toxin helenalin, which can be poisonous if large amounts of the plant are eaten, and contact with the plant can also cause skin irritation. The roots contain derivatives of thymol, which are used as fungicides and preservatives and may have some anti-inflammatory effect.
Arnica is currently used in liniment and ointment preparations used for strains, sprains, and bruises. Commercial arnica preparations are frequently used by professional athletes. The thymol derivatives concentrated in the plants roots have been clinically shown to be effective vasodilators of subcutaneous blood capillaries. Arnica preparations used topically have been demonstrated to act as an anti-inflammatory and assist normal healing processes by facilitating transport of blood and fluid accumulations through a dilating action of subcutaneous blood capillaries. If ingested, the toxin helenalin produces severe gastroenteritis, and internal bleeding of the digestive tract if enough material is ingested.
- Arnica acaulis (Walt.) B.S.P. -- Common Leopardbane
- Arnica alpina (L.) Olin -- Alpine Arnica (synonym of Arnica angustifolia subsp. alpina)
- Arnica amplexicaulis Nutt. -- Clasping Arnica, Streambank Arnica (synonym of Arnica lanceolata subsp. amplexicaulis)
- Arnica angustifolia Vahl -- Narrowleaf Arnica
- Arnica angustifolia subsp. alpina (L.) I. K. Ferguson
- Arnica angustifolia subsp. tomentosa Downie & Denford
- Arnica cernua T.J. Howell -- Serpentine Arnica
- Arnica chamissonis Less. -- Chamisso Arnica
- Arnica chamissonis subsp. foliosa (Nutt.) Maguire
- Arnica cordifolia Hook. -- Heart-leaf Leopardbane, Heartleaf Arnica
- Arnica dealbata Baldwin (formerly Whitneya dealbata)
- Arnica discoidea Benth. -- Rayless Arnica
- Arnica X diversifolia Greene (pro sp.) -- Curtis Churchmouse Threeawn, Rayless Arnica, Sticky Arnica
- Arnica frigida C.A. Mey. ex Iljin -- Snow Arnica (synonym of Arnica griscomii subsp. frigida)
- Arnica fulgens Pursh -- Foothill Arnica, Orange Arnica, Shining Leopardbane
- Arnica x gracilis Rydb. -- Smallhead Arnica (a natural hybrid between A. latifolia and A. cordifolia)
- Arnica griscomii Fernald
- Arnica griscomii subsp. frigida (C. A. Mey. ex Iljin) S. J. Wolf
- Arnica griscomii subsp. griscomii Downie & Denford
- Arnica lanceolata Nutt. -- Arnica, Lanceleaf Arnica
- Arnica lanceolata subsp. amplexicaulis (Nutt.) Gruezo & Denford
- Arnica lanceolata subsp. lanceolata Gruezo & Denford
- Arnica latifolia Bong. -- Broadleaf Arnica
- Arnica lessingii (Torr. & Gray) Greene -- Nodding Arnica
- Arnica lessingii subsp. lessengii
- Arnica lessingii subsp. norbergii Hult. & Maguire
- Arnica lonchophylla Greene -- Longleaf Arnica
- Arnica lonchophylla subsp. arnoglossa (Greene) Maguire
- Arnica lonchophylla subsp. lonchophylla
- Arnica longifolia D.C. Eat. -- Longleaf Arnica, Spearleaf Arnica
- Arnica louiseana Farr -- Lake Louise Arnica
- Arnica mallotopus (formerly Mallotopus japonicus)
- Arnica mollis Hook. -- hairy arnica, wooly arnica
- Arnica montana L. -- Mountain Arnica
- Arnica nevadensis Gray -- Nevada Arnica
- Arnica ovata Greene
- Arnica parryi Gray -- Nodding Arnica, Parry's Arnica
- Arnica rydbergii Greene -- Rydberg Arnica, Rydberg's Arnica, Subalpine Arnica
- Arnica sachalinensis (Regel) A. Gray
- Arnica sororia Greene -- Twin Arnica
- Arnica spathulata Greene -- Klamath Arnica
- Arnica unalaschcensis Less. -- Alaska Arnica
- Arnica venosa Hall -- Shasta County Arnica
- Arnica viscosa Gray -- Mt. Shasta Arnica
- Maguire, B. (1943). "A monograph of the genus Arnica (Senecioneae, Compositae)". Brittonia 4 386–510.
- Wolf, S.J. & K.E. Denford (1984). "Taxonomy of Arnica (Compositae) subgenus Austromontana". Rhodora Journal of the New England Botanical Club 86 (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". Novon 9 460–461.
- 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 Letters 9 5–8.
- Wolf, S. J., and K. E. Denford (1984). "Taxonomy of Arnica (Compositae) subgenus Austromontana". Rhodora 86 239–309.