St. John's wort

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Editor, – I enjoyed reading Professor Mitchell's article on Hypericum perforatum, 'St. John's wort - quack medicine or novel antidepressant treatment?' (Aust Prescr 1999;23:112-3). It is nice to see some openness about herbal medicine in the medical profession. I would like to comment on hyperforin, one of the active ingredients in hypericum. It is true that studies have confirmed the antidepressant activity of hyperforin, however, this compound is very unstable, especially during the drying process of the herb, hence it is unlikely that the extracts which have been shown to be effective in many different clinical trials contained any hyperforin. Yet they worked. The hypericums may not have antidepressant activity in their isolated form, however one study has shown that oligomeric procyanidins (OPCs) are necessary for the bioavailability of hypericum. Hypericum extracts are now being marketed which are standardized to both hypericum and hyperforin, however these are only marker compounds for quality control. When the whole herb extract is used, St. John's wort is a safe and effective medicine for depression, anxiety and tension.

Michael Thomsen
Medical Herbalist
South Hobart, Tas.