Flos Arnicae, Herbal Medicine Plant

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Definition
Flos Arnicae consists of the dried fl ower heads (capitula) of Arnica montana
L. (Asteraceae) (1–3).

Synonyms
Doronicum arnica Desf., D. montanum Lam. (4). Asteraceae are also
known as Compositae.

Selected vernacular names
Arnica, arnika, arnique, betoine des montagnes, betouana, Bergwohlverleih,
celtic bane, dokhanolfouh, Echtes Wolferlei, estourniga, estrunica,
Fallkraut, Kraftwurz, leopard’s bane, mountain arnica, mountain tobacco,
St Luzianskraut, Stichwurzel, strunica, Verfangkraut, Wohlverleih,
wolf’s bane, Wundkraut (4–9).

Geographical distribution
Indigenous to central Europe. Widely cultivated around the world (1, 4, 7).

Description
A perennial herb, 20–50 cm high. Aerial portion consists of a basal
rosette of entire oblanceolate leaves up to 17 cm long, five to seven
veins, from the centre of which projects an erect, simple, glandular
hairy stem up to 0.6 m high. Stem bears two to four pairs of cauline
leaves, ovate, elliptic-oblong, lanceolate or oblanceolate, with rounded
or rounded-toothed apex and clothed with numerous nonglandular
and glandular hairs, up to 16 cm long and 5 cm wide. Peduncles, one
to three, bearing alternate bracteoles, extending from the uppermost
pair of cauline leaves; glandular–puberulent, each terminating in a
hemispherical or turbinate capitulum bearing orange-yellow flowers,
which are tubular. Fruits, black to brown, five-ribbed, with a bristle
tuft of hairs (5, 8).
78

Plant material of interest: dried fl ower heads
General appearance

Capitulum about 20 mm in diameter and 15 mm deep, with a peduncle
2–3 cm long. Involucre with 18–24 elongated lanceolate bracts, 8–10 mm
long with acute apices, arranged in one or two rows, green with yellowishgreen
external hairs visible under a lens. Receptacle, about 6 mm in diameter,
convex, alveolate and covered with hairs; periphery bears about 20
ligulate fl orets 20–30 mm long; disc bears a greater number of tubular
fl orets about 15 mm long. Ovary, 4–8 mm long, crowned by a pappus of
whitish bristles 4–8 mm long. Some brown achenes, crowned or not by a
pappus, may be present (3).

Organoleptic properties
Odour: characteristic aromatic (1, 3, 5); taste: bitter and acrid (1, 5).

Microscopic characteristics

Epidermis of corolla papillose, containing yellow-orange globular masses,
some cells also containing dark brown–black patches of phytomelan;
base of corolla tube of ligulate fl orets with uniseriate covering trichomes
of four to six cells, up to 1 mm in length; bristles of pappus four to six
cells in diameter and barbed by exertion of the pointed cell apices. Cells
of ovary or fruit walls contain abundant black patches of phytomelan.
Corolla and ovary wall with numerous composite glandular trichomes;
ovary wall with numerous appressed twin hairs each composed of two
narrow parallel cells diverging at the tips. Pollen grains spiky, spherical
35–52 μm in diameter, with fi nely granular exine, spines up to 8 μm long,
three pores and furrows (1).

Powdered plant material

Light yellowish-brown to light olive-brown. Epidermis of the involucre
bracts with stomata and trichomes, which are more abundant on the outer
surface. Trichomes include: uniseriate multicellular covering trichomes,
50–500 μm long, particularly abundant on the margins; secretory trichomes
about 300.0 μm long with uni- or biseriate multicellular stalks
and with multicellullar, globular heads, abundant on the outer surface;
similar trichomes, 80.0 μm long, abundant on the inner surface of the
bract. Epidermis of the ligulate corolla consists of lobed or elongated
cells, a few stomata and trichomes of different types: covering trichomes,
with very sharp ends, whose length may exceed 500 μm; secondary trichomes
with multicellular stalks and multicellular globular heads. Ligule
ends in rounded papillose cells. Epidermis of the ovary covered with trichomes:
secondary trichomes with short stalks and multicellular globular
79
heads; twinned covering trichomes usually consisting of two longitudinally
united cells, with common punctuated walls, their ends sharp and
sometimes bifi d. Epidermis of the calyx consists of elongated cells bearing
short, unicellular, covering trichomes pointing towards the upper end of
the bristle. Pollen grains, about 30 μm in diameter, rounded, with spiny
exine, and three germinal pores (3).

General identity tests

Macroscopic and microscopic examinations (1, 3–5), and thin-layer chromatography
for phenolic compounds (3).


Purity tests
Microbiological

Tests for specifi c microorganisms and microbial contamination limits are
as described in the WHO guidelines on quality control methods for medicinal
plants (10).

Foreign organic matter

Not more than 5.0% (3).

Total ash

Not more than 10% (3).

Acid-insoluble ash
Not more than 1.2% (11).

Sulfated ash
Not more than 13% (2).

Water-soluble extractive
Not less than 17% (2).

Alcohol-soluble extractive
Not less than 15% using 45% ethanol (1).

Loss on drying
Not more than 10% (3).

Pesticide residues
The recommended maximum limit of aldrin and dieldrin is not more than
0.05 mg/kg (12). For other pesticides, see the European Pharmacopoeia
Flos Arnicae
80
 (12) and the WHO guidelines on quality control methods for medicinal
plants (10) and pesticide residues (13).

Heavy metals
For maximum limits and analysis of heavy metals, consult the WHO
guidelines on quality control methods for medicinal plants (10).

Radioactive residues
Where applicable, consult the WHO guidelines on quality control
methods for medicinal plants (10) for the analysis of radioactive isotopes.

Other purity tests
Chemical tests to be established in accordance with national requirements.

Chemical assays
Contains not less than 0.40% of total sesquiterpene lactones calculated as helenalin
tiglate, determined by high-performance liquid chromatography (3).

Major chemical constituents
The major constituents include the essential oil (0.5%), fatty acids (content
not specifi ed), thymol (content not specifi ed), pseudoguaianolide
sesquiterpene lactones (0.2–0.8%) and fl avonoid glycosides (0.2–0.6%)
(4, 9, 14). The primary sesquiterpene lactones are helenalin, 11α,13-dihydrohelenalin
and their fatty acid esters. Flavonoids include glycosides
and/or glucuronides of spinacetin, hispidulin, patuletin and isorhamnetin,
among others (4, 7, 9, 14–16). The structures of helenalin and 11α,13-
dihydrohelenalin are presented below.

Medicinal uses
Uses supported by clinical data
None.


Pharmacology
Experimental pharmacology
Analgesic and anti-infl ammatory activity

In vitro, helenalin, 5.0 μmol/l, signifi cantly (P < 0.01) suppressed the activity
of prostaglandin synthetase in mouse and rat homogenates, and human
polymorphonuclear neutrophils, indicating an anti-infl ammatory
effect (18). Human polymorphonuclear neutrophil chemotaxis was
inhibited by helenalin, 5.0 μmol/l, in vitro. It was concluded that the
α-methylene-γ-lactone moiety played a role in the anti-infl ammatory
activity of this compound (18). Helenalin, 4.0 μmol/l, selectively inhibited
the transcription factor nuclear factor (NF)-κβ (19).
Intragastric administration of 100.0 mg/kg body weight (bw) of an
80% ethanol extract of Flos Arnicae reduced carrageenan-induced hind
paw oedema by up to 29% in rats (20). Intraperitoneal administration of
2.5–5.0 mg/kg bw of helenalin signifi cantly (P < 0.001) inhibited carrageenan-
induced hind paw oedema in rats by 77% after 72 hours (21). Intraperitoneal
administration of 20.0 mg/kg bw of helenalin strongly inhibited
acetic acid-induced writhing by 93% in mice but did not have
analgesic effects in mice in the hot-plate test. Intraperitoneal administration
of 2.5 mg/kg bw of helenalin to rats inhibited arthritis induced by
Mycobacterium butyricum by 87% (21).

Antioxidant activity
The effect of a tincture of Flos Arnicae on lipid peroxidation and glutathione
metabolism in rat liver was assessed following induction of hepatitis
by the administration of carbon tetrachloride. Intragastric administration
of 0.2 ml/g bw of the tincture to rats decreased the rate of lipid oxidation
and increased the activities of the enzymes involved in glutathione metabolism
(22). Intragastric administration of 0.2 ml/g bw of the tincture
per day for 14 days to rats with hepatitis induced by carbon tetrachloride
led to a normalization of the hydrolytic enzymes (23).

Antitumour activity
Helenalin is cytotoxic to a wide variety of cancer cell lines in vitro, with a
median effective dose (ED50) range of 0.03–1.0 μg/ml (24–27). Intraperi-
Flos Arnicae
82
WHO monographs on selected medicinal plants
toneal administration of 1.5–33.3 mg/kg bw of helenalin to mice and rats
had antitumour activity against a variety of chemically induced tumours
(28–30).

Cardiovascular effects
Flos Arnicae and extracts of the fl ower heads have cardiotonic and hypotensive
effects in various animal models. Intravenous administration of a
single dose of 1.0 ml of a tincture of the fl ower heads to rabbits had negative
chronotropic effects and reduced blood pressure (31). Intravenous administration
of 1.0 ml of an aqueous or 95% ethanol extract of the fl ower
heads had cardiotonic effects in frogs, and a tincture demonstrated hypotensive
activity in rabbits after intravenous administration of 1.0 ml (32,
33). A 30% ethanol extract of the fl ower heads, 0.1–0.3% in the bath medium,
had positive inotropic effects in isolated guinea-pig hearts (33).
Intravenous administration of 5.0 g/kg bw of a fl uid extract or tincture of
the fl ower heads increased the blood pressure of cats and guinea-pigs (34).
Helenalin, 50.0 μg/ml, decreased intracellular calcium levels in cultured
fi broblasts, and potentiated the responses induced by vasopressin
and bradykinin (35). Intravenous administration of helenalin had cardiotoxic
effects in mice (25.0 mg/kg bw) and dogs (90.0 mg/kg bw) (36).

Choleretic activity

Intravenous administration of 1.0 ml of a 95% ethanol extract of the fl ower
heads to dogs increased bile secretion by 25–120% (37). Intragastric administration
of a hot aqueous extract of the fl ower heads had choleretic effects
in rats (dose not specifi ed) (38) and dogs (50.0 ml/animal) (39).

Toxicology
The oral median lethal dose (LD50) of a 30% ethanol extract of the fl ower
heads was 37.0 ml/kg in mice (33). The intragastric LD50 for helenalin has
been established for numerous species: mice 150.0 mg/kg bw, rats
125.0 mg/kg bw, rabbits 90.0 mg/kg bw, hamsters 85.0 mg/kg bw and
ewes 125.0 mg/kg bw (40).

Uterine stimulant effects
Intragastric administration of a tincture of the fl ower heads (dose not
specifi ed) had uterine stimulant effects in guinea-pigs (41). Intragastric
administration of a hot aqueous extract of the fl ower heads (dose not
specifi ed) stimulated uterine contractions in rats (38).

Clinical pharmacology
No information available. Clinical trials of homeopathic preparations
were not assessed.
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Adverse reactions
Numerous cases of dermatitis of toxic or allergic origin have been reported
(42), usually following prolonged, external application of a tincture
of Flos Arnicae. The compounds responsible for the hypersensitivity
reaction are the sesquiterpene lactones helenalin and helenalin acetate
(43). Cross-reactivity to other Asteraceae fl owers has been reported (44–47).
The fl ower heads are irritant to the mucous membranes and ingestion
may result in gastroenteritis, muscle paralysis (voluntary and cardiac), an
increase or decrease in pulse rate, heart palpitations, shortness of breath
and death. A fatal case of poisoning following the ingestion of 70.0 g of a
tincture of the fl ower heads has been reported (48).
A case of severe mucosal injuries following the misuse of an undiluted
mouth rinse with a 70% alcohol content, which also contained oil of peppermint
and Flos Arnicae, has been reported (49).

Contraindications
Flos Arnicae is used in traditional systems of medicine as an emmenagogue
(9), and its safety during pregnancy and nursing has not been established.
Therefore, in accordance with standard medical practice, the fl ower
heads should not be administered to pregnant or nursing women. Flos
Arnicae is also contraindicated in cases of known allergy to Arnica or
other members of the Asteraceae (Compositae) (37, 42, 50, 51).

Warnings
A fatal case of poisoning following the ingestion of 70.0 g of a tincture of
Flos Arnicae has been reported (48). Internal use of Flos Arnicae or extracts
of the fl ower heads is not recommended. For external use only. Do
not apply to open or broken skin. Keep out of the reach of children (17).



Precautions
General
Avoid excessive use. Chronic, frequent external applications may induce
allergy-related skin rashes with itching, blister formation, ulcers and superfi
cial necrosis. Prolonged treatment of damaged or injured skin or indolent
leg ulcers may induce the formation of oedematous dermatitis with
the formation of pustules (17).

Carcinogenesis, mutagenesis, impairment of fertility
Helenalin has cytotoxic effects in vitro (see Experimental pharmacology).
However, in the Salmonella/microsome assay, helenalin was not muta-
Flos Arnicae
genic in S. typhimurium strains TA102, TA98 or TA100 at concentrations
of up to 30 μg/ml (52, 53).

Pregnancy: teratogenic effects
Intraperitoneal administration of 6.0–20.0 mg/kg bw of helenalin was not
teratogenic in mice (21).

Pregnancy: non-teratogenic effects
See Contraindications.

Nursing mothers
See Contraindications
.
Paediatric use
See Warnings. For external use only. Do not apply to abraded or broken
skin.

Other precautions
No information available on precautions concerning drug interactions; or
drug and laboratory test interactions.

Dosage forms
Dried fl ower heads and other galenical preparations. Store protected from
light and moisture (7).

Posology
(Unless otherwise indicated)
For external applications only, apply undiluted externally on the affected
area two or three times daily: infusion for compresses, 2 g of Flos Arnicae
per 100 ml water; tincture for compresses, one part Flos Arnicae to 10
parts 70% ethanol; mouth rinse, 10-fold dilution of tincture, do not swallow;
ointment, 20–25% tincture of Flos Arnicae or not more than 15%
essential oil (vehicle not specifi ed) (17).

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