Circulation 60,475 • Volume 14, No. 2 • Summer 1999

St. John’s Wort Charge Refuted by Herbalist

Robert S. McCaleb

To the Editor

We were quite concerned to read a Letter to the Editor published in your Winter 1997-98 Newsletter (page 29) which contains rather serious misinformation about the herb St. John’s wort (“Beware ‘St. John’s Wort,’ Potential Herbal Danger”).

In this letter, Dr. Rick Cirodia states, “Upon investigation, we have discovered the active ingredient [of St. John’s wort] is hypericum, a strong inhibitor of MAO, types A and B.”

Current research shows that St. John’s wort (Hypericum perforatum) is not a strong MAO inhibitor.1 The antidepressant activity of the herb was initially hypothesized to be due to MAO inhibition,2 but further research has shown that neither St. John’s wort extracts nor their key chemical compounds are significant MAOIs. The feeble MAOI activity is no longer believed to make a substantial contribution to the therapeutic effect of St. John’s wort.3 I am sending by mail the three articles on the subject which are cited here.

The ingredient cited by Dr. Cirodia as hypericum is actually called hypericin, and is one of several plant compounds under investigation as “active ingredients” of St. John’s wort. St. John’s wort is widely marketed and used in Europe as a government-approved antidepressant drug. In the United States, it is marketed as a dietary supplement. Numerous controlled clinical studies have demonstrated that St. John’s wort extract is effective in relieving symptoms of mild-to-moderate depression and that the herb is generally safe and well tolerated.

We realize that letters to the editor are not typically peer-reviewed or subjected to rigorous fact-checking. We invite you and your readers to contact us at the Herb Research Foundation if you have questions or concerns about the safety or efficacy of botanicals. Our fee-based services include custom botanical literature searching, herb information brochures and packets, and an herb hotline.

Robert S. McCaleb, President Herb Research Foundation Boulder, CO 303-449-2265


  1. Thiede, HM and Walper, A. Inhibition of MAO and COMT by Hypericum Extracts and Hypericin. Jnl. Geriatric Psychiatry and Neurology, v.7, supp. 1, S54-56; 1994.
  2. Suzuki, O, Katsumata, Y, Oya, M, Blady, S and Wagner, H. Inhibition of Monoamine Oxidase by Hypericin, Planta Medica, 272-274; 1984.
  3. Perovic, S and Muller, WEG. Pharmacological Profile of Hypericum Extract: Effect on serotonin uptake by postsynaptic receptors, Arzneim.-Forsch./Drug Res. 45(11), Nr. 11; 1995.