St. John's wort

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St. John's Wort



Hypericum perforatum is the most medicinally important species of the Hypericum genus, commonly known as St. John's wort. There are as many as 400 species in the genus, which is part of the Guttiferae family. Native to Europe, St. John's wort is found throughout the world. It thrives in sunny fields, open woods, and gravelly roadsides. Early colonists brought this valuable medicinal to North America, and the plant has become naturalized in the eastern United States and California, as well as in Australia, New Zealand, eastern Asia, and South America.
The entire plant, particularly the round, black seed, exudes a slight, turpentine-like odor. The woody, branched root spreads from the base with runners that produce numerous stalks. The simple, dark green leaves are veined and grow in opposite, oblong-obvate pairs on round, branching stalks that reach 3 ft (91.4 cm) high. Tiny holes, visible when the leaf is held to the light, are actually transparent oil glands containing the chemical photo sensitizer known as hypericin. These characteristic holes inspired the species name, perforatum, Latin for perforated. The bright yellow, star-shaped flowers, often clustered in a trio, have five petals. Each blossom has many showy stamens. Black dots along the margins of the blossom contain more of the red-pigmented chemical hypericin. The herb is also useful as a dye. The flowers bloom in branching, flat-topped clusters atop the stalks in mid-summer, around the time of the summer solstice. St. John's wort, sometimes called devil's flight or grace of God, was believed to have magical properties to ward off evil spirits. It's generic name hypericum is derived from a Greek word meaning "over an apparition." The herb was traditionally gathered on mid-summer's eve, June 23. This date was later christianized as the eve of the feast day of St. John the Baptist. This folk custom gave the plant its popular name. The Anglo-Saxon word wort means medicinal herb.


St. John's wort has been known for its numerous medicinal properties as far back as Roman times. It was a valued remedy on the Roman battlefields where it was used to promote healing from trauma and inflammation. The herb is vulnerary and can speed the healing of wounds, bruises, ulcers, and burns. It is popularly used as a nervine for its calming effect, easing tension and anxiety, relieving mild depression, and soothing emotions during menopause. The bittersweet herb is licensed in Germany for use in cases of mild depression, anxiety, and sleeplessness. It is useful in circumstances of nerve injury and trauma, and has been used to speed healing after brain surgery. Its antispasmodic properties can ease uterine cramping and menstrual difficulties. St. John's wort acts medicinally as an astringent, and may also be used as an expectorant. The hypericin in St. John's wort possesses anti-viral properties that may be active in combating certain cancers, including many brain cancers. An infusion of the plant, taken as a tea, has been helpful in treating night-time incontinence in children. The oil, taken internally, has been used to treat colic, intestinal worms, and abdominal pain. The medicinal parts of St. John's wort are the fresh leaves and flowers. This valuable remedy has been extensively tested in West Germany, and is dispensed throughout Germany as a popular medicine called, Johnniskraut. Commercially prepared extracts are commonly standardized to 0.3% hypericin.

Clinical studies

A 1988 study at New York University found the antiviral properties in hypericin, a chemical component of Hypericum, to be useful in combating the virus that causes AIDS. Additional studies are under way through the Federal Drug Administration (FDA) to determine the effectiveness of the herb as a treatment for AIDS. Hypericin extract has also been reported to inhibit a form of leukemia that sometimes occurs after radiation therapy. Numerous clinical studies have found hypericum preparations to have an antidepressive effect when used in standardized extracts for treatment of mild depression. Clinical trials continue with this important herbal anti-depressant, particularly in view of its relative lack of undesirable side effects in humans.


An oil extract can be purchased commercially or prepared by combining fresh flowers and leaves of St. John's wort in a glass jar and sunflower or olive oil. Seal the container with an airtight lid and leave on a sunny windowsill for four to six weeks, shaking daily. The oil will absorb the red pigment. Strain through muslin or cheesecloth, and store in a dark container. The medicinal oil will maintain its potency for two years or more. The oil of St. John's wort has been known in folk culture as "Oil of Jesus." This oil makes a good rub for painful joints, varicose veins, muscle strain, arthritis, and rheumatism. Used in a compress it can help to heal wounds and inflammation, and relieve the pain of deep bruising.
An infusion is made by pouring one pint of boiling water over 1 oz (28 g) of dried herb, or 2 oz (57 g) of fresh, minced flower and leaf. Steep in a glass or enamel pot for five to 10 minutes. Strain and cover. Drink the tea warm. A general dose is one cupful, up to three times daily.
Capsule: Dry the leaves and flowers and grind with mortar and pestle into a fine powder. Place in gelatin capsules. The potency of the herb varies with the soil, climate and harvesting conditions of the plant. A standardized extract of 0.3% hypericin extract, commercially prepared from a reputable source, is more likely to yield reliable results. Standard dosage is up to three 300 mg capsules of 0.3% standardized extract daily.
A tincture is prepared by combining one part fresh herb to three parts alcohol (50% alcohol/water solution) in glass container. Set aside in dark place, shaking the mixture daily for two weeks. Strain through muslin or cheesecloth, and store in dark bottle. The tincture should maintain potency for two years. Standard dosage, unless otherwise prescribed, is 0.24-1 tsp added to 8 oz (237 ml) of water, up to three times daily.
A salve is made by warming 2 oz (59 ml)of prepared oil extract in double boiler. Once warmed, 1 oz (28 g) of grated beeswax is added and mixed until melted. Pour into a glass jar and cool. The salve can be stored for up to one year. The remedy keeps best if refrigerated after preparation. The salve is useful in treating burns, wounds, and soothing painful muscles. It is also a good skin softener. St. John's wort salve may be prepared in combination with calendula extract (Calendula officinalis) for application on bruises.


Consult a physician prior to use. Pregnant or lactating women should not use the herb. Individuals taking prescribed psychotropic medications classified as selective serotonin reuptake inhibitors, or SSRI, such as Prozac, should not simultaneously use St. John's wort. Many herbalists also discourage use of St. John's wort by individuals taking any other anti-depressant medication.
Cattlemen dislike the shrub because there have been some reports of toxicity to livestock that overgraze in fields abundant with the wild herb. Toxic effects in livestock include reports of edema of the ears, eyelids, and the face due to photosensitization after ingestion of the herb. Exposure to sunlight activates the hypercin in the plant. Adverse effects have been reported in horses, sheep, and swine and include staggering, and blistering and peeling of the skin. Toxicity is greater in smaller mammals, such as rabbits.

Side effects

When used either internally or externally, the herb may cause photo-dermatitis in humans with fair or sensitive skin when exposed to sun light or other ultraviolet light source. There have been some reports of changes in lactation in some nursing women taking the hypericum extract. Changes in the nutritional quality and flavor of the milk, and reduction or cessation of lactation have also been reported. It can also cause headaches, stiff neck, nausea and vomiting, and high blood pressure.


St. John's wort can interact with amphetamines, asthma inhalants, decongestants, diet pills, narcotics, and amino acid tryptophan and tyrosine, as well as certain foods. Reactions range from nausea to increased high blood pressure. Consult a practitioner prior to using St. John's wort.



American Botanical Council. PO Box 201660, Austin, TX 78720-1660.


Herb Research Foundation.

Key terms

Antispasmodic — Relieves mild cramping or muscle spasm.
Expectorant — Promotes the discharge of mucus from respiratory system.
Nervine — Soothes and calms the nervous system.
Vulnerary — Heals wounds, bruises, sprains, and ulcers.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

St. John's wort

a shrubby perennial (Hypericum perforatum) with numerous orange-yellow flowers with petals that may be speckled black along their margins. Although widely used as an antidepressant, this herb has not been shown, in clinical trials, to be superior to placebo in the treatment of major depression.
Farlex Partner Medical Dictionary © Farlex 2012

St. John's wort

(sānt jonz wōrt)
Any of various herbs or shrubs of the genus Hypericum, used as a treatment for mild depression in alternative medicine.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

St. John's wort

(sānt jonz wōrt)
Shrubby perennial herb (Hypericum perforatum). Although widely used as an antidepressant, has not been shown, in clinical trials, to be superior to placebo in treatment of major depression.
Medical Dictionary for the Dental Professions © Farlex 2012
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Most clinical trials have used St. John's wort extract standardized to 0.3 % hypericin content, with the most common dose being 300 mg three times daily for up to six weeks.
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