Introduction
Among the many medicinal herbs used throughout the long history of Occidental
culture, St. John's wort, Hypericum perforatum L., has always been
and still is of great interest. From the time of the ancient Greeks down
through the Middle Ages, the plant was considered to be imbued with magical
powers and was used to ward off evil and protect against disease. As a practical
folk-remedy, it has been used widely to heal wounds, remedy kidney troubles,
and alleviate nervous disorders, even insanity.
In the last thirty years Hypericum perforatum has undergone extensive
clinical and laboratory testing. The present article reviews the plant's
botany, history of use, chemistry, pharmacology, pharmacodynamics, medical
uses, and preparations.
Botany
Taxonomy and Description
St. John's wort is a member of the genus Hypericum, of which there are 400 species worldwide.
There is some disagreement as to the plant's family, some placing Hypericum in the segregate family Hypericaceae, while others place it in the family Guttiferae. However, most researchers now think that the
morphological and chemical differences of the two families are insufficient to justify separating them (1,2).
The plants are described as glabrous perennials, erect and usually woody at the base. The ovate to linear
leaves are sessile, opposite, and well-supplied with translucent glandular dots. The regular flowers have five
short, subequal, entire, imbricate, basally connate sepals, and five persistent-withering yellow petals. The
ovary is superior, capsicular, and three-styled. Stamens are many, arranged in bundles of threes, and the
flowers are profuse, arranged in branched cymes which bloom from June until September. In the absence of
insect pollination, apomixis commonly occurs.
St. John's wort should not be confused with rose of sharon (H. calycinum), a common
ornamental ground-cover in the United States. Rose of sharon flowers and leaves are much larger than those
of St. John's wort (though interestingly, anti-biotic substances have been extracted from H.
calycinum that are similar in activity to substances in H. perforatum (3).
Range and Habitat
St. John's wort is native to Europe, West Asia, North Africa, Madeira and the Azores, and is naturalized in
many parts of the world, notably North America and Australia (4,5). The plant spreads rapidly by means of
runners or from the prodigous seed production and can invade pastures, disturbed sites, dirt roads, the sides
of roads and highways, and sparse woods.
In the western United States, St. John's wort is especially prevalent in northern California and southern
Oregon, hence one of its common names, "Klamath Weed". Because of the known photosensitizing
properties of the plant, which can be toxic to cows and sheep, it has been considered a pest in some places.
Prior to 1949, it was estimated to inhabit 2.34 million acres of rangeland in northern California. For years
an attempt was made to control the plant with herbicides6, but with little success.
The solution to the problem with St. John's wort in northern California finally proved to be with biological
methods of control, not pesticides. In 1946, the leaf-beetles Chrysolina quadrigemina Rossi, and to
a lesser extent C. hyperici Forst, were introduced from Australia, where it had been observed that
they had a voracious appetite for Hypericum. Their appetite proved to be so voracious, in fact, that
by 1957 northern California's stands of St. John's wort were reduced to only 1% of their original number (5).