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St. Johns Wort

St. Johns Wort

Botanical Description & Habitat

Hypericum perforatum


Common names

John's wartKlamath weed
MillpertuisRosin rose
Tiptoe weed

Found in dry soil and in sunny places. It is a common herb distributed all over the world.

A shrubby, aromatic perennial herb, the leaves are oblong to linear, and covered with transparent oil glands. St. Johns wort bears a turpentine-like odor. The plant reaches a height of 90 cm and bears heads of bright yellow flowers with five petals each and numerous stamens.

Medicinal parts
Leaves and stems, dried, gathered during flowering.

It must be dried immediately to avoid loss of potency.

Historical Properties & Uses

St. Johnswort is often used to calm the nerves, especially in cases of anxiety and depression. Its natural tranquilizing effect is due to the presence of hypericin, a dianthrone pigment. St. Johnswort is also used in the treatment of insomnia and bed-wetting. It possesses a cholagogue action: its oil extract, as well as encapsulated powders, is effective for digestive and gastrointestinal problems. Certain extracts have been used topically to treat burns, wounds and inflammations with proven benefit. It contains up to 10% tannin, which imparts a strong astringent property.

One of the strongest properties of St. Johnswort is its antibiotic action; it is effective against several strains of bacteria and viruses. It is occasionally included in anti-cancer preparations, an application which has received experimental support. It demonstrates antispasmodic and expectorant properties as well.

St. Johnswort is classified as unsafe by the FDA, but probably poses no threat to humans at normal dosage levels.

This herb has approval status by the German Commission E for intenral and external uses.

Internally it is used for psychovegetative disturbances, depressive moods, anxiety etc. Oily preparations are useful for dyspepsia.

Externally, oil of hypericum may be applied for bruises, burns and myalgia.


Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.

Method of Action

St. Johnswort Is Tranquilizing
The primary active constituent of St. Johnswort is hypericin. To the presence of this chemical are ascribed the tranquilizing and photosensitizing properties. At least one study on humans has shown even very small doses of hypericin can produce tranquilizing effects.

The method of action may be through an ability to increase blood flow to stressed tissues. It is also capable of reducing capillary fragility which would contribute to its hypotensive action. Paradoxically, St. Johnswort has been found to enhance uterine tonus.

St. Johnswort Has Antibacterial, Antiviral Activity
Incubated at 37 degrees C. for seven days with the H37Rv strain of Mycobacterium tuberculosis, St. Johnswort extract produced inhibition at concentrations 1:80 and even higher. This makes it one of the better plants with such activity.

Hyperforin, recently isolated from St. Johnswort, is reported to be inhibitory toward a number of gram positive organisms. The plant has given negative antibiotic tests, but positive results have been obtained also. Among the organisms inhibited are Micrococcus pyogens var. aureus, Bacillus dysenteriae, Micrococcus aureus and Bacillus subtilis.

The "prenylierten phloroglucine" in St. Johnswort also has antibacterial activity. Extracts from St. Johnswort were found to cause a strong inhibition of influenza virus A/PR8 multiplication in the chick embryo. The tannic acid complex was shown to significantly inhibit influenza virus.

St. Johnswort Is An Antihelminthic
Liquid extract of this herb is effective against dipilidiasis, hymenolepidiasis, and somewhat less effective against ascaridiasis in dogs, without toxicity to the host except at very high doses which have a mild hypotensive effect. Smaller doses stimulate the cardiovascular system. Intravenous dosage does not affect the depth or frequency of respiration. Clinical tests have been favorable.

St. Johnswort Has Cholagogue Properties
Cholagogue activity of St. Johnswort is thought to be due to alkaloids, including nicotinic acid and nicotinamide and other hetereocyclic, nitrogen containing principles.

St. Johnswort Has Some Anticancer Action
Hyperoside (or hyperforat), from St. Johnswort, has been found to have some anti-cancer properties. It appeared to act by normalizing glucose metabolism in brain tumor slices, thus inhibiting tumorous growth. Psorospermin from St. Johnswort has antileukemic property.

A Tincture Of St. Johnswort Is Effective Topically
The "red" tincture has been found effective in treating burns and other skin lesions in dogs. Researchers used an extract containing hypericin, free quercitin and chlorogenic acid, but found that hypericin was the active component. They treated six cases of eczema, one case of cutaneous distemper, one torn wound, and one case of necrosis. All therapeutic results were favorable and there were no harmful side effects. The authors hypothesized the action was due to the ability of hypericin to increase cellular respiration and enhance metabolism in treated areas.

Drug Interactions & Precautions

Possible Interactions
St. Johnswort should be used with caution in conjunction with CNS depressants or stimulants. St. John's Wort inhibits MAOI's.

Certain antipsychotic drugs, (e.g., the phenothiazines), as well as other psychoactive agents which are poorly absorbed in the gastrointestinal tract, may be even more poorly absorbed if St. Johnswort is being used.

The antituberculous activity of St. Johnswort may potentiate the adverse effects of other antituberculous drugs, especially ethionamide.

Topical application of this astringent herb, in conjunction with the acne product tretinoin (retinoic acid, vitamin A acid), may adversely affect the skin.

To minimize central nervous system depression and possible synergism, it would be wise to avoid using St. Johnswort with procarbazine antineoplastic drugs.

Furthermore, the antibiotic property of St. Johnswort may interact in an undetermined manner with other antibiotic preparations.

In the absence of other hard data, it may still be assumed observable interactions may occur between the many central nervous system drugs and the psychoactive principles in St. Johnswort.

Safety Factors & Toxicity

St. Johnswort is regarded as unsafe by the FDA and is included as such in their Policy Compliance Guides. The inclusion of St. Johnswort in these guides is most curious. The herb is not listed in the 1976 edition of the Registry of Toxic Effects of Chemical Substances, which is the official government publication for all known toxic chemicals, together with references to those articles which were used to establish that toxicity. The absence of hypericin on the list indicates no studies have ever been done to show the substance is toxic to man. Hypericin is also missing from all volumes of the federally published TOXICOLOGY.

Hypericin, isolated from the plant, has been shown to be a photosensitizer. The Merck Index mentions H. perforatum produces photosensitivity upon ingestion, but it doesn't specify humans. The reference given (BIOCHEMICAL JOURNAL, 34, 790, 1940) is not even addressed to St. Johnswort; however, it does mention the plant in an anecdotal sort of way as causing "a characteristic photosensitization" in animals grazing upon it.

Perhaps the best reference for the effects of H. perforatum in animals is E. Hurst, THE POISON PLANTS OF NEW SOUTH WALES, 1942. Hurst lists as symptoms, dermatitis, digestive upsets, loss of production, and even death in horses, cattle, and sheep. W.C. Muenscher, in his POISONOUS PLANTS OF THE UNITED STATES explains further that animals with pigmented skin or those not exposed to bright sunlight do not show any symptoms from eating the plants. Muensher further states animals do not eat enough of it, except under starvation conditions, to cause pronounced symptoms.

In virtually all discussions of H. perforatum toxicity, no mention is made of human toxicity. There is no documentation of even one case of human toxicity. Which is not to say human toxicity never occurs; naked humans grazing in the field on a sunlit day may have serious problems.

St. John's Wort has approval status by the German Commission E as an antidepressant and anti-inflammatory.


Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.

Preparation & Administration

Three times a day

Dried herb
2-4 grams

made from 1 tsp of dried herb

Fluid extract
1:1 in 25% alcohol, 2-4 ml

1:10 in 45% alcohol, 2-4 ml

This herb has approval status by the German Commission E.

Recommended daily dosages in Germany are as follows:

2 - 4 g of the herb.
0.2 1 mg hypericin.


Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.

Note: This Herbal Preparation information is a summary of data from books and articles by various authors. It is not intended to replace the advice or attention of health care professionals.



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Hypericum perforatum

St. John's Wort 2.

? Southwest School of Botanical Medicine