Abstract
Over the last few years, St. John's Wort products have enjoyed a tremendous surge in interest and sales for the therapy of mild to moderate depression. Although the complete spectrum of active substances in this herbal extract has not yet been elucidated, it is certain that hyperforin is an important component. Further, it appears that the hypericins may also contribute to the antidepressive activity. In this study, the content uniformity of eleven St. John's Wort products sold exclusively in pharmacies was determined. The main objective was to determine the batch-to-batch reproducibility of the various products. The hyperforin was analysed according to a previously published HPLC method, while the total hypericin content was determined by an electrochemical method. The results indicate that some, but not all, products show very reproducible batch-to-batch properties. Also, individual products have different hypericin and hyperforin levels, and are therefore not switchable--even when products are manufactured under similar extraction and processing conditions, have the same raw material:extract ratios (on a dry basis) and contain the same amount of extract per unit dosage form.