Optimization of supercritical fluid extraction for the separation of hyperforin and adhyperforin in St. John’s wort (Hypericum perforatum L.)
Supercritical fluid extraction (SFE) with neat CO2 was optimized for selective removal of hyperforin and adhyperforin from St. John’s wort. High extraction efficiencies were achieved when the fluid density was 0.60 g ml−1 or above. The maximum extraction efficiency of hyperforin and adhyperforin could be achieved with a very mild condition such as 30 °C and 80 atm (density = 0.64 g ml−1). Under these conditions, the amount of hyperforin extracted was comparable to the results of conventional solvent-based extractions (ultrasonic or boiling). The maximum quantity of hyperforin extracted from the St. John’s wort was around 12 mg/g dry plant and the reproducibility of the SFE method was comparatively good (RSD = 10%). Hyperforin and adhyperforin were isolated from the crude SFE extract (using HPLC) with purities of 98.7 and 93.3%, respectively. The identity of the isolated hyperforins was confirmed by NMR and MS methods.