Optimization of the supercritical extraction of rosmarinic acid from clary sage residue and the antioxidant activity of the extracts

This study focuses on the extraction of bioactive compounds from clary sage (Salvia sclarea L.) distillation residue with carbon dioxide under supercritical conditions. The target component is rosmarinic acid, a naturally occurring phenolic compound with strong antioxidant properties. Response surface methodology was applied to optimize the operating temperature, pressure and the co-solvent composition in the range of 40-100 degrees C, 100-600 bar, and 0-100 % ethanol in water (v/v), respectively. The quantification of rosmarinic acid was performed using HPLC and the antioxidant activity of extracts was measured using DPPH assay. Results showed that the yield of extraction of rosmarinic acid and the antioxidant activity of the extracts varied significantly at each extraction condition. Based on the optimization study, the optimum pressure, temperature and the composition of the co-solvent were 100 bar, 65 degrees C and 35 % ethanol, respectively, with more than 8 mg/g of rosmarinic acid concentration obtained.