Extraction of Carnosic Acid and Carnosol from Sage (Salvia officinalis L.) Leaves by Supercritical Fluid Extraction and Their Antioxidant and Antibacterial Activity

Sage (Salvia officinalis L.) is a good source of antioxidant compounds, carnosic acid and carnosol being the prominent ones. Both are soluble in CO2, and our goal was to investigate the application of supercritical CO2 extraction to obtain sage extracts rich in these compounds. The effect of pressure, temperature, and CO2 flow rate on the carnosic acid and carnosol yield was studied. These variables were optimized by response surface methodology (RSM). The pressure significantly affected carnosol extraction, while the extraction of carnosic acid was affected by the pressure, temperature, and CO2 flow rate. Carnosic acid content varied from 0.29–120.0 µg mg−1, and carnosol content from 0.46–65.5 µg mg−1. The optimal conditions according to RSM were a pressure of 29.5 MPa, a temperature of 49.1°C, and a CO2 flow rate of 3 kg h−1, and the sage extract yield was calculated to be 6.54%, carnosic acid content 105 µg mg−1, and carnosol content 56.3 µg mg−1. The antioxidant activities of the sage extracts were evaluated by the scavenging activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH). Sage extract obtained at 30 MPa and 40°C with 2 kg h−1 CO2 flow rate with a carnosic acid content of 72 µg mg−1 and carnosol content of 55 µg mg−1 exhibited the highest antioxidant activity (80.0 ± 0.68%) amongst the investigated supercritical fluid extracts at 25 µg mL−1 concentration. The antimicrobial properties of extracts were tested on four bacterial strains: Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus. The extract with a carnosic acid content of 116 µg mg−1 and a carnosol content of 60.6 µg mg−1 was found to be the most potent agent against B. subtilis.