Optimization of High Hydrostatic Pressure Process for the Extraction of Kirenol from Siegesbeckia orientalis L. Using Response Surface Methodology

High hydrostatic pressure (HHP) extraction method was optimized to maximize the extraction yield of kirenol from Siegesbeckia orientalis. Operating parameters such as extraction pressure (100-600 MPa), pressure holding time (3-20 min), feed-to-solvent ratio (1:10-1:90 (w/v)), and solvent (ethanol) concentration (0-100%) were investigated individually by mono-factor experiments. Then, the optimal extraction conditions were determined using response surface methodology. Box-Behnken design was applied to evaluate the effects of three independent variables (extraction pressure, solvent concentration, and feed-to-solvent ratio) on the extraction yield of kirenol from S. orientalis. Extraction pressure, solvent concentration, and feed-to-solvent ratio affected the extraction yields significantly, whereas the pressure holding time had no significant effect. The optimal processing conditions, which gave a maximum extraction yield of 85.9% kirenol from the raw material, were as follows: extracting pressure 320 MPa, pressure holding time 5 min, ethanol concentration 18%, and feed-to-solvent ratio 1:76 (w/v).