St. John’s wort (SJW), known botanically as Hypericum perforatum, is a sprawling, leafy herb that grows in open, disturbed areas throughout much of the world’s temperate regions. The use of this species as an herbal remedy to treat a variety of internal and external ailments dates back to the time of the ancient Greeks. Since then, it has remained a popular treatment for anxiety, depression, cuts, and burns. Recent research suggests the effectiveness of this herb in treating other ailments, including cancer, inflammation-related disorders, and bacterial and viral diseases, and as an antioxidant and neuroprotective agent. Pharmaceutical companies, particularly in Europe, prepare standard formulations of this herb that are taken by millions of people. Worldwide annual sales of products made from SJW presently exceed several billion dollars. Further, SJW produces dozens of biologically active substances, although two—hypericin (a naphthodianthrone) and hyperforin (a lipophilic phloroglucinol)—have the greatest medical activity. Other compounds, including the flavonoids rutin, quercetin, and kaempferol, also appear to have medical activity. H. perforatum has been intensively studied on isolated tissue samples, using animal models and through human clinical trials. The effectiveness of SJW as an antidepression agent is particularly well studied, and the underlying mechanisms are well understood. SJW preparations have relatively few adverse effects when taken alone at the recommended dosages. However, numerous interactions with other drugs have been reported. Recent research shows these interactions result from the ability of SJW constituents to induce intestinal or hepatic enzymes that either remove drugs from the body or metabolize them to inactive forms. This chapter examines the constituents, modes of action, and adverse interactions of SJW, providing an up-to-date synthesis of a large body of literature that has developed over the past 30 years regarding this widely taken herbal remedy. Some recommendations regarding future research needs are also presented.
Copyright © 2011 by Taylor and Francis Group, LLC.