Enrichment of hyperforin from St. John's wort (Hypericum perforatum) by pilot-scale supercritical carbon dioxide extraction.

St. John's Wort (Hypericum perforatum L.) was extracted with supercritical carbon dioxide using a pilot batch extraction plant. The effects of pressure, temperature, flow rate and extraction time were examined with respect to extraction yield and hyperforin content. Supercritical carbon dioxide showed a high selectivity for phloroglucinols. Extracts were analyzed using an isocratic HPLC method with a mixture of hyperforin/adhyperforin as an external standard. Within the studied range of extraction pressure (90-150 bar) and extraction time (1-5 h), extraction at 90 bar for 3 h and 120 bar for 1 h provided higher hyperforin content (up to 35%) in the resulting extracts. An increase in extraction temperature showed a negative effect, leading to increased degradation of hyperforin into orthoforin. When the total mass of carbon dioxide passing the extraction vessel was kept constant, changes in mass flow rate did not affect the extraction result.