St John's thumbnail (at least it isn't his hangnail...) St John's Wort - Hypericum perforatum:


The plant is a low-growing (1-3 inches) perennial with small yellow flowers which tend to bloom in early summer. The fuzzy appearance of the flower is due to the many stamens of the flower.

The oil or alcohol extract of St. John's Wort is reddish purple in color. It is not water soluble, but it is light-sensitive.

Growing Info:

The plant grows readily in meadow conditions. A native of central Europe which has naturalized itself to New England (if not other regions) in North America. (There are around 25 species of this plant, most research has been conducted on H. perferatum, with some on H. brasiliense.)

Culinary Uses:

There do not appear to be any culinary uses for St. John's Wort. Using the extract is recommended over using the plant as-is.

Medicinal Uses in Folklore:

Ointments would be used to treat wounds. Its antidepressant properties were utilized.

Scanning the Scientific Literature:

The antiviral and anti-oxidase active ingredients of St. John's Wort appear to be hypericin and the structurally-related pseudohypericin. Each seems to have its own pharmacodynamics, with hypericin the most highly studied, and presumably the most active ingredient.

Hypericin is a naturally occurring photosensitizer that exhibits potent antiviral activity in the presence of light. While maintaining a good level of light is a potential problem in the body, there is at least one clinical study underway investigating the effect of hypericin on HIV in people with the AIDS virus. Hypericin may also have beneficial effects against other viral agents, such as FLV, cytomegalovirus (HCMV), parainfluenza virus, and certain types of herpes simplex viruses. There is speculation that by using chemoluminescence in the bloodstream, hypericin could be triggered to act photodynamically against viruses. Such chemoluminescence could be triggered by the luciferin-luciferase reaction (which is how fireflies get their flash). Perhaps exposure to proper wavelengths of light may also help. Hypericin may also have a lipophilic ("fat-loving") mode of action, potentially binding the lipid in viral membranes.

Hypericum extract is more than just hypericin/pseudohypericin, and has been used clinically to treat depression. In Germany, it is marketed as an anti-depressant. In one study it yielded results far superior to that of a placebo. There was no negative effect on cognitive function, nor on concentration or attention abilities of the subjects. The antidepressive effect of hypericum extract might be explained in part in terms of a mild monoamine oxidase (MAO) inhibition, although the constituent hypericin itself does not act in this fashion. It is still uncertain which component(s) of the plant produces the anti-depressive effect, so the mode of action is still uncertain. The anti-depressive effect initiates over a period of one to two months.

Hypericum extracts also apparently have some antimutagenic, anti-inflammatory, and anti-staphylococcal activities.

Another ingredient of the oil extract, hyperforin, may have some efficacy in wound healing.

Excessive consumption of these extracts can cause rashes if the individual is exposed to strong light. Varro Tyler rates it a plus on probable safety.

Other Info:

On St. John's Eve, June 24th, these plants would be gathered and hung in windows and by doors to ward off lightening and evil spirits.


Photo from Henriette's Herbal Homepage

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This information is not intended to replace medical advice or treatment. If conditions worsen, or persist, consult your healthcare practitioner.

Last Updated: March 7, 1999.

Last Updated: April 16, 1998.