SUPERCRITICAL-FLUID EXTRACTION OF NATURAL ANTIOXIDANTS FROM ROSEMARY - COMPARISON WITH LIQUID SOLVENT SONICATION

Supercritical fluid extraction (SFE) and liquid solvent sonication, in combination with two different sample treatments, were compared for t he extraction of natural antioxidants from rosemary leaves. Dried, gro und, and sieved rosemary leaves (20 mg) were subjected to SFE with CO2 at 355 bar at 100 degrees C (CO2 density 0.72 g/mL) for 20 min at a l iquid now rate of 4 mL/min. The analytes were concentrated on an ODS t rap and subsequently eluted with acetone, Antioxidants in the SF and l iquid solvent extract were analyzed by HPLC, Compounds of known antiox idant activity such as carnosol, carnosic acid, and methyl carnosate w ere identified by mass spectrometry of the HPLC fractions collected, F reezing and grinding the samples in Liquid nitrogen resulted in decrea sed carnosic acid recoveries, Supercritical CO2 extraction provided th e highest recovery of carnosic acid from rosemary leaves (35.7 mg/g), the lowest relative standard deviation (4.4%), and the cleanest extrac t-no cleanup prior to HPLC was required. Among the liquid solvents stu dies, only acetone provided comparable results (73% recovery relative to SC-CO2 extraction); however, it required decoloration with active c arbon prior to HPLC analysis.