Supercritical fluid extraction from rosemary ( Rosmarinus officinalis): Kinetic data, extract's global yield, composition, and antioxidant activity

Abstract

In the present work the global yields isotherms and the overall extraction curves for the system rosemary ( Rosmarinus officinalis) + CO 2, the chemical composition and antioxidant activity of the extracts were determined. The experiments were performed in two supercritical extraction units. The following bed height to bed diameter ratios were used: 0.67, 1.34, 2.8, 5.6, and 8.4. The global yields were determined for the isotherms of 30 and 40 °C for pressures of 100–300 bar. The overall extraction curves were determined at 40 °C and 300 bar. Rosemary extracts were also obtained by hydrodistillation (volatile oil) and extraction with solvent, ethanol and hexane were used. The chemical compositions of the extracts were determined by gas chromatography; the contents of phenolic diterpenes (carnosoic and rosmarinic acids) were determined by UV spectrophotometry. The antioxidant activity was measured by the coupled reaction of beta-carotene and linolenic acid. The largest global yield (5% dry basis) was obtained at 40 °C and 300 bar. The major compounds detected in the extracts were camphor and 1,8-cineol. The long term antioxidant activity varied from 80% for the extract obtained at 150 bar and 30 °C to 95% for the extract obtained at 300 bar and 40 °C. The content of carnosoic acid was nine times larger for the extract obtained at 300 bar and 40 °C as compared to the volatile oil. The models of Crank, Esquível et al., Goto et al., Martínez et al., Sovová, and Tan and Liou quantitatively fitted the overall extraction curves. Nonetheless, the mean square deviations for the models of Martínez et al., Crank, and Tan and Liou were approximately five times larger than that for the models of Goto et al., Sovová, and Esquível et al.