Selective extraction of carnosic acid, carnosol, and rosmarinic acid from Rosmarinus officinalis L. using supercritical fluid and their antioxidant activity

Rosmarinus officinalis L. is one of the most widely exploited medicinal plants for its bioactive compounds, including rosmarinic acid (RA), carnosic acid (CA) and carnosol (CAR). This study aims to selectively extract these compounds, using supercritical fluids extraction with carbon dioxide and ethanol as co-solvents, based on the Hansen solubility parameters approach. This approach predicted that CA and CAR are highly soluble in the supercritical fluid. However, a weak interaction was predicted between RA and this fluid. The experimental findings indicated the highest amounts of RA and CA were observed at 150 bar and 80°C, resulting in yields of 3.43 mg/g dry weight (DW), and 18.9 mg/g DW, respectively. Favourable extraction conditions for CAR were recorded at 250 bar and 40°C, with a content of 19.1 mg/g DW. Evaluation of antioxidant activity using DPPH tests revealed that extracts obtained at 250 bar at 40 and 80°C rich in CAR have a stronger antioxidant power.