St. John's-wort
General poisoning notes:
St. John''s-wort (Hypericum
perforatum) is a naturalized herb found in eastern Canada and British
Columbia. The plant contains hypericin, which is a primary photosensitizing
chemical. Ingestion has caused skin problems in cattle, horses, rabbits, sheep,
and swine. The skin problems occur on white or light-colored skin; dark skin is
not affected. Severe symptoms such as convulsions, staggering, and coma have
occurred in some animals. Loss of wool quality occurs in sheep, and the meat of
affected animals is of poor quality. This plant is widespread in Canada. The
reaction is more severe if fresh plants are eaten, but dried plants can also
cause photosensitization, even though 80% of the hypericin is lost (Araya and
Ford 1981, Cooper and Johnson 1984, Crompton et al. 1988).
Description
Perennial herb.
Stems 10-110 cm long, erect, or sometimes rooting at the base, 2-lined, smooth,
with branches ascending. Leaves sessile or subsessile, 5-35 mm long, 2-14 mm
broad, narrowly ovate to elliptic-oblong or linear or sometimes oblanceolate,
apex obtuse or mucronate to rounded, base cuneate to rounded, entire with
intramarginal and often a few laminar black glands. Inflorescence a
(1-)5-many-flowered, subcorymbose or broadly pyramidal cyme with ultimately
monochasial branches; flowers 1.5-2.5 cm in diameter. Sepals 3-6 mm long,
lanceolate to oblong or elliptic, acute to acuminate or shortly aristate, free,
entire.. Petals + narrowly oblanceolate, 8-15 mm long, with marginal black dots
and sometimes (not in Pakistan) laminar black lines. Stamens in `3' fascicles
(2+2+1). Ovary 3-locular, 2-3.5 mm long; styles c. 2 x longer than the ovary,
free, divergent, incurved near apex. Capsule (4-)5-9 mm long, ovoid to
pyramidal, each valve with dorsal vittae and lateral vescicles, Seeds 1.0-1.2
mm long, shortly apiculate, not carinate; testa reti¬culate-pitted.
Nomenclature:
Scientific Name: Hypericum perforatum L.
Vernacular
name(s): St. John's-wort
Scientific family
name: Guttiferae
Vernacular family
name: St. John's-wort
Geographic Information
Europe and N.
Africa to W. China and N.W., India (Kumaun). Introduced into E. Asia, America.
Australasia and S. Africa.
Canada: British
Columbia, New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward
Island, Quebec.
Toxic parts:
Flowers, leaves.
Notes on Toxic plant chemicals:
Hypericin, a
fluorescent pigment, is regarded as a derivative of naphthodianthrone. The
pigment is contained in small black dots that are just visible to the naked eye
on leaves and petals. The chemical is a primary photosensitizer because the
photodynamic action occurs in the skin (Araya and Ford 1981).
Toxic plant chemicals:
Hypericin.
Animals/Human Poisoning:
Note: When an
animal is listed without additional information, the literature (as of 1993)
contained no detailed explanation.
Cattle
General symptoms of poisoning:
Muzzle, dry, restlessness, skin,
dry.
Horses
General symptoms of poisoning:
Appetite, loss of, coma, gait,
staggering, skin, peeling of.
Rabbits
General symptoms of poisoning:
Death, liver, cirrhosis of, skin,
peeling of.
Sheep
General symptoms of poisoning:
Convulsions, erythema, skin,
peeling of.
Swine
General symptoms of poisoning:
Skin,
flushed, skin, peeling of.
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