St. John’s Wort: Quality Issues and Active Compounds

St. John’s wort (Hypericum perforatum L.) (SJW) contains numerous compounds with documented biological activity. Constituents that have stimulated the most interest include the naphthodianthrones, hypericin and pseudohypericin; a broad range of fl avonoids, including rutin, quercetin, quercitrin, miquelianin, amentofl avone, and hyperoside; and the phloroglucinols hyperforin and adhyperforin. Although there are some contradictions, most data suggest that several groups of active compounds are responsible for the antidepressant effi cacy of the plant extract. Thus, according to the current state of scientifi c knowledge, the total extract has to be considered as the active substance. Data on effi cacy and quality of SJW extracts have to be taken into consideration. Owing to the fastgrowing SJW market in the United States, more and more SJW products (herb and extracts) are sold at varying levels of quality. Considerable differences exist in the composition of biologically active constituents among various commercially available preparations of SJW. Furthermore, the documented characterization of SJW preparations in published randomized controlled trials has been less than adequate. Future scientifi c and clinical publications about the effi cacy of SJW would benefi t from a full pharmaceutical and phytochemical description of the extract. SJW is used for the treatment of mild to moderate depression. The antidepressant effi cacy of SJW extracts has been confi rmed in numerous clinical studies and was assessed in metaanalyses (1, 2). The pharmacological actions of SJW have likewise been extensively reviewed (3– 6). Reports about the mechanism of antidepressant action of SJW extracts and their constituents both in vivo and in vitro have also been published. Antidepressant activity was reported for the phloroglucinol derivative hyperforin (for a review, see [7]), for the naphthodianthrones hypericin and pseudohypericin (8– 10), and for several fl avonoids (11– 14). The role and the mechanisms of these different compounds are still a matter of debate. However, based on recent results, it appears that the prevailing simplistic view of one plant → one active compound → one mechanism of action is incorrect. It is more likely that the multiple bioactive compounds contribute to the antidepressant activity of the crude plant extract in a complex manner. This review focuses on the present knowledge about the active constituents of SJW and their contribution to antidepressant activity.