Nature's Pharmacopeia: A World of Medicinal Plants


Hypericum perforatum

St. John’s wort is an herbaceous perennial native to Europe that now grows both in cultivation and in the wild throughout the world’s temperate zones.133 The plant grows close to the ground, with stems rarely reaching 1 meter in height. Leaves are small, green, and oval, approximately 1 to 3 centimeters in length, with numerous translucent dots (that give the impression of perforations) and occasional glandular black spots.134 Flowers are bright yellow, with petals also bearing black spots. The flowers and aerial parts of the plant have been used in European medicine for at least 2000 years (figure 14.16).


FIGURE 14.16   St. John’s wort.

Recognized in the works of the Greek and Roman writers, St. John’s wort was listed by Dioscorides as “good for hip ailments” and able to draw out “much bilious matter and excrement.” He also suggested it as a treatment for burns when applied to the injured skin.135 The influential Greek physician Galen (129–ca. 216) considered the herb hot and dry, according to the humoral medical framework that he advanced.136To herbalists of the medieval period, the plant was associated with mystical powers in folk medicine, able to offer protection to those who used it, not by ingesting or applying it but simply by holding a sprig (figure 14.17).137 In 1546, the German physician Hieronymus Bock (1498–1554) conveyed the popular wisdom in writing: “Many people carry these plants with them against evil spirits and thunderstorms.”138

The controversial alchemist Paracelsus (1493–1541), who rejected classical humoral theory in favor of a folk and mystical medical practice, saw divine signs in St. John’s wort’s physical properties, according with his belief in the Doctrine of Signatures. The pores in the leaves and the red juice expressed when its flower petals are crushed demonstrated to him that the plant was placed on earth as a heavenly gift to heal the injuries of mortals.139 “I declare to you that the holes that make the leaves so porous indicate that this plant is a help for all inward and outward openings in the skin—whatever should be driven out through the pores,” Paracelsus explained, “and the putrefaction of its flowers into the form of blood, that is a sign that it is good for wounds.” He also recommended St. John’s wort stems and flowers, carried near the body or applied to the skin, to drive “phantasms out of people.”140


FIGURE 14.17   The use of St. John’s wort to ward off demons, as shown in an illustration in an Italian herbal, ca. 1475–ca. 1525. (TR F Herbal, Special Collections, University of Vermont Library, fol. 27r; lower half: Erba ypericon)

While generations of physicians had considered St. John’s wort valuable for ailments as diverse as broken bones and kidney stones, by the seventeenth century medical authorities also began to recommend the herb for “mental aberrations” such as “false imaginings, melancholy, fears, and corruption of the intellect.”141 The perception of St. John’s wort’s therapeutic value declined over time, as a popular British herbal from 1812 listed the herb only to treat urinary symptoms, wounds, and bruises; a French medical book of 1822 remarked at the lost status of an herb that had once been lauded for its “imaginary virtues” but by then had fallen into near oblivion.142 Still, the author suggested that it might have some utility for chest congestion and menstrual irregularity.143

Revived interest in St. John’s wort in the medical community during the twentieth century prompted its testing for effects on depression, ability to heal wounds, and as a possible antiviral agent. St. John’s wort foliage and flowers contain an array of potentially bioactive chemicals, including the pigments hypericin and related compounds, which accumulate to 0.05 to 0.3 percent and are responsible for the red color of the sap that exudes from crushed fresh herb, and the chemical hyperforin, which reaches 4 percent in the aerial portion of the plant (figure 14.18).144 There are also polyphenolic chemicals that might be responsible for some physiological effects. Extracts are usually made in alcohol (either ethanol or methanol) and water and administered orally or topically.145


FIGURE 14.18   Bioactive chemicals in St. John’s wort: hypericin; hyperforin.

Laboratory tests suggest that hypericin and hyperforin have a wide range of interactions with components of various neurotransmitter signaling systems in the brain, although experiments demonstrating specific activities have not been uniformly replicated.146 The collective evidence seems to indicate that the combination of constituents in St. John’s wort extract has effects on the mood-related serotonin system, inhibiting reuptake of the neurotransmitter at the synapse and possibly increasing the abundance of its receptor. St. John’s wort extract may also interact with the dopamine system, the acetylcholine system, the GABA system, and others, a clear impetus to further investigation of the many possible ways that St. John’s wort might influence the mind.147

In the clinic, various St. John’s wort extracts have been tested for their possible effect on depression versus placebo or synthetic antidepressant drugs. Statistical analysis of a body of literature demonstrated that patients taking the herb experienced a reduction of depressive symptoms superior to those taking a placebo preparation and on par with those taking the antidepressants. Furthermore, St. John’s wort induced fewer side effects than the synthetic pharmaceutical treatment.148

Extracts of St. John’s wort have also been investigated for their ability to aid in wound healing, and small-scale studies have indicated that a lotion made of the herb might be useful for this function. Antibacterial and antiviral activity has also been demonstrated in the laboratory.149

Appreciated by the ancients for its diverse roles in humoral, folk, and magical medicine, St. John’s wort’s use against depression is supported by a growing body of evidence. While medieval commentators noted the red juice issuing from crushed flowers and perceived it as a sign to use the plant to treat bloody sores, modern laboratory tests indicate its possible usefulness to improve wound healing and block infection, properties that can now be tested in the clinic. With further attention, examination of this plant’s rich lore and complex assortment of chemical products might advance as-yet untested applications to human health.