St. John's wort, botanically named Hypericum perforatum L., is a widely available herbal medicine. Linnaeus knew about this plant because it is a native of Europe, but this herbaceous perennial has become naturalized in temperate pasture lands and meadows around the world. Normally it is half to three-quarters of a meter in height, but in the Pacific Northwest plants of H. perforatum can be substantially taller. Hence in northern California it acquired the common name Klamathweed.
I grew up with H. perforatum in northern Ohio, where, frankly, in my youth I never had the curiosity to study this knee-high plant very carefully, so when I visited family this summer in Michigan, St. John's wort was on my "must-see" list of activities. (You can imagine how exciting I can be on vacation, if botanical items are a major source of entertainment for me!).
The plant's early association with Christianity is revealed in its common name, referring to St. John the Baptist, or in its less well known Irish and Welsh names that refer to the Virgin Mary. Had I known in early years how St. John's wort, like a fairy, supposedly protects against evil beings, chases demons, and can silence poltergeists (see A. R. Vickery, "Traditional uses and folklore of Hypericum in the British Isles," Economic Botany 35:289-295, 1981), I might have found many of my own uses for this plant.
Seriously, this species is discussed extensively in the major reference books on poisonous plants (e.g., John M. Kingbury, Poisonous Plants of the United States and Canada, 1964), because H. perforatum has been a significant cause of livestock poisoning around the world. It is interesting to speculate that the tiny brown seeds of this species probably dispersed from Europe with the livestock. Typically livestock have the sense to avoid ingesting St. John's wort, but if, for example, they eat shoots that are included in weedy hay, animals develop severe skin lesions and necrosis when their skin becomes hypersensitive to sunlight. In the older textbooks, this is referred to as photosensitization, because a pigment in the plant, not unexpectedly called hypericin, causes skin problems only when exposed to sunlight. Newer accounts have termed this phototoxicity. Skin that is protected from radiation by dense fur or dark melanin pigmentation is generally unaffected.
Hypericin is produced by St. John's wort in special spherical glands. When a leaf is held up to sunlight, scores of these scattered glands appear like tiny translucent (yellowish) windows, which Linnaeus recognized as being like perforations (perforatum). In Europe, this plant character was treated by practitioners of the Doctrine of Signatures as a sign from God that the plant was to be used as a cure for punctures or cuts in the skin. Herbal medicine still recommends hypericin oil for cuts. When the yellow petal is crushed, the hypericin turns red, as if the plant is bleeding--another indication in folk medicine for using this plant to treat wounds.
The photodynamic hypericin is a fluorescent pigment that, when purified, is red in acid and green in a base. It is also stable when dried or heated, so it remains active when consumed as dry tablets, dry or liquid capsules, or even in hot drinks. Hypericin, which has been studied in laboratories for 150 years, is a napthodianthrone derivative that readily enters the bloodstream and is not broken down in the liver. This compound absorbs sun energy, and when it is fully oxidized turns black in plant tissues. Old leaves, but particularly flower petals and even the apex of each anther, possess the blackened form of these glands.
St. John's wort and hypericin have been used for treating a very long list of human maladies, too extensive even to list here. Need a sedative, a mild pain-killer, a treatment for diarrhea, something to soothe hemorrhoids or settle your stomach? Over the years, H. perforatum has been prescribed by herbalists for all of these. More recently, St. John's wort has been heavily promoted as an antidepressant and an anxiety treatment, and its reputation for controlling mild depression has been bolstered by a number scientific studies. Advice and many cautions for this type of treatment can be found on the internet.
Even more exciting and controversial has been the use of this plant against HIV. The antibacterial property of chemicals in St. John's wort has been known for some time, and interest especially intensified when microbiologists discovered that hypericin inhibits the replication of certain viruses in test tubes. In July 1988, a research group reported in Proceedings of the National Academy of Sciences (85:5230-5234) that hypericin and pseudohypericin, both found in Hypericum, prevented rapid viral replication in mice infected with a retrovirus similar to HIV.
The antiviral activity of Hypericum has been observed in laboratory and animal studies on hepatitis B, herpes, and a few other viruses, probably because hypericin is a strong oxidizer. But in human studies, the antiviral effects have not been easily observed. To match titers used in test tube and animal studies, huge doses would be required for humans, and high levels of hypericin typically cause skin problems, painful itching, and extreme sensitivity to light, as foreseen with animal poisoning literature. Some research also indicates that hypericin may interfere with the beneficial activities of other anti-HIV drugs, such as AZT, and of drugs used to treat microbiological infections often contracted by AIDS patients. Yet, a world desperate for solutions is reluctant to give up hope that St. John's wort may indeed be a way to protect against evil beings.
ARTHUR C. GIBSON, MEMBG Director