Experimental design on supercritical extraction of essential oil from valerian roots and study of optimal conditions

Supercritical CO2 extraction from valerian (Valeriana officinalis L.) roots was studied. The objective of this study was to optimize the independent process parameters (temperature, pressure, dynamic time and modifier volume) in order to attain the highest yield of the essential oil and valerenic acids as the desired compounds. The process optimization was based on a simplex centroid design (mixture design), coupled with the statistical and graphical analysis of the results. Due to the features of mixture method and to the proper ratios of four independent variables, the optimal points were in the range of temperature (37 °C), pressure (24.3–25.0 MPa), dynamic time (19–24 min) and modifier volume (100–200 μl).