Arnica
montana L.
Standardized Common
Name: Arnica
Other Common Names: Leopard’s Bane,
Wolf’s Bane, Mountain Tobacco
Family: Asteraceae
(Compositae)
Taxonomy: Arnica
includes about 32 species of perennial herbs, which are native to cooler parts
of the Northern Hemisphere, with a center of diversity in western North
America. Arnica montana is one of two species native to Europe.
Description: Rhizomatous
perennial herb. Stem usually unbranched, 15–60 cm high, pubescent. Basal leaves
petiolate, oblanceolate, obtuse, to 17 cm long; cauline leaves opposite, 3(2–4)
pairs, ovate to obovate, lanceolate or oblanceolate, 4–18 cm long, 2–5 cm
broad; base usually sheathing; apex obtuse; margins entire or barely toothed;
upper surface pubescent and glandular. Peduncle 10–30 cm high; heads 3(1–7),
with terminal head much larger than lateral heads. Heads hemispheric to
top-shaped; terminal heads 15–22 mm high. Involucre of 16–22(–26) bracts
(phyllaries) in two main whorls, with ring of smaller bracts at the base;
phyllaries lanceolate, (10–)12–17 mm long, acute, pubescent. Ray florets
usually 11–15; disk florets numerous. Ray
florets pistillate, ligulate, in terminal heads 18–25(–30) mm long and
(4–)5–8 mm broad, yellow to yellow-orange, 3-toothed. Disk florets perfect; corolla 8.4–11.3 mm long in terminal
heads, narrowly to broadly goblet-shaped, with 5 triangular-lanceolate lobes;
tube and base of limb pubescent especially at juncture of tube and limb
(collar); filaments attached at collar; anthers yellow; pappus of bristles
about as long as corolla, usually straw-colored (sometimes darker), bearing
small setae. Disk achenes 6–10 mm long, tapering at base, pubescent with short
stiff double hairs and glandular hairs; ray achenes smaller than those of disk,
with shorter pappus.
Parts
in Commerce:
Florets
Identification: Fragments of the
subtending bracts and receptacle may be found in the material. Where loose
florets are measured, the larger florets should always be selected to ensure
that they belong to the terminal heads from which measurements in the
literature were taken. The lateral heads are smaller, so the presence of
florets that are qualitatively similar but smaller therefore does not
demonstrate contamination. The type and quantity of pubescence present on each
structure is also important for purposes of identification.
- Phyllaries in
two main whorls with smaller phyllaries at base, lanceolate, (10–)12–17 mm
long, 2–4 mm broad, light olive to reddish brown
- Phyllaries
ciliate and pubescent at apices with hairs with a string-of-beads shape
and often with long-stalked glandular hairs having stalks two cells thick
(never with stalks one cell thick)
- Ray florets
usually 11–15; disk florets numerous
- Ray florets
female, ligulate, yellow-orange, the largest 18–25(–30) mm long and
(4–)5–8 mm broad
- Ray floret
apices with 3 (rarely 2) teeth, 1–3 mm long
- Ray florets with
7 or more veins, sparsely pubescent with straight hairs
- Disk floret corollas
narrowly goblet-shaped (tubular below, with limb portion widening above
attachment of anthers), with 5 triangular lobes
- Larger disk
corollas 8.4–11.3 mm long, with tube 3–4.8 mm long and limb 5–6.6 mm long
- Lower portion of
disk corolla pubescent with long, coarse septate hairs, especially at
juncture of tube and limb (collar), and sometimes with small,
short-stalked glandular hairs
- Disk florets
have a pappus of 1 whorl of bristles, about as long as corolla (not with a
second short outer whorl)
- Pappus bristles
straw-colored or darker, not pure white, bearing setae along their length;
setae very short (0.1–0.15, rarely to 0.2 mm), not fluffy-looking
- Anthers
yellowish; filaments attached at collar
Adulterants: A variety of
yellow-flowered composites, including Doronicum
spp., Heterotheca inuloides Cass., Calendula officinalis L., and Inula britannica L. and other Inula spp., have been reported to be
adulterants of Arnica. These and a
number of other composite genera with superficially similar flowering heads are
distinguishable by the presence of fewer main veins in the ligules or by the
absence of the pappus or differences in its basic structure.
Other
species of Arnica have been sold as
substitutes (and, indeed, evidence for the pharmacological superiority of A. montana over these others is
lacking). These can be difficult to tell apart, as there is no single floral
feature that distinguishes A. montana
from all other species. However, most material in commerce comes from Europe,
where only two species exist, so the potential for substitution is minimized.
The second European species, A. angustifolia Vahl, has a white pappus
and the teeth of the ray florets are often >3 mm long. If A. montana
must be distinguished from other species, glandular hairs with stalks two cells
wide are perhaps the most obvious positive character, as they are found only in
A. montana and the American Arnica acaulis (Walt.) B.S.P.; however,
they are not always present.
Arnica
chamissonis Less. subsp. foliosa (Nutt.) Maguire: A. montana is commonly collected in Europe from wild populations,
and the root is sometimes collected as well as the flowers. As a result, the
species is threatened by overharvesting. Other species of Arnica were screened for chemical resemblance to A. montana, and A. chamissonis subsp. foliosa
was determined to be the most similar. In the interest of conservation, its use
as a substitute for A. montana is
promoted in Europe, and is increasingly considered acceptable by European
pharmacopoeias.
A. chamissonis subsp. foliosa is widely distributed in western
North America and is variable enough that well over a dozen species-level
synonyms have been published for it. Its flowers differ from those of A. montana in several characters:
- Ligules
usually 12–18 mm long, shallowly toothed, pale yellow
- Involucral
bracts pubescent with slender, multicellular hairs that do not resemble a
string of beads; hairs two cells wide never present
- Disk
corollas tubular, not widening above limb, usually 7.5–8.7 mm long
- Disk
corollas with soft hairs; collar not much more pubescent than remainder of
corolla
- Bristles
of disk pappus occasionally longer than 0.2 mm
References:
Ferguson
IK. Arnica. In: Tutin TG, Heywood VH, Burges NA, et al., eds. Flora
Europaea. Vol. 4. Cambridge: Cambridge University Press; 1976:189–190.
Maguire
B. A monograph of the genus Arnica
(Senecioneae, Compositae). Brittonia. 1943;4:386–510.
Wichtl M, ed. Herbal Drugs and Phytopharmaceuticals, 3rd English ed. Stuttgart:
medpharm Scientific Publishers and Boca Raton, FL: CRC Press; 2004:54–59.
Youngken HW. Text-Book of Pharmacognosy, 5th ed. Philadelphia, PA: The
Blakiston Company; 1943:875–878.
Figure
8:
a–b, Arnica montana head and disk floret; c–d, A. chamissonis
head and sectioned head.