Supercritical CO2 extraction of Rosmarinus eriocalyx growing in Algeria: chemical composition and antioxidant activity of extracts and their solid plant materials

Supercritical fluid extraction using carbon dioxide (SFE-CO2) is an eco-friendly, safe and effective extraction technique used on an industrial level to obtain flavour and fragrances as well as bioactive compounds from aromatic plants. In the present work, we investigated the SFE-CO2 extracts obtained from leaves and flowers of Rosmarinus eriocalyx, an aromatic shrub growing in Algeria and used similarly to R. officinalis. The SFE-CO2 extracts were obtained from R. eriocalyx using the following parameters: extraction time 180 min (including 30 min of static extraction), pressure 45 MPa; temperature 70°C. The chemical profiles of SFE-CO2 extracts were determined by gas chromatography-mass spectrometry (GC–MS). β-Amyrin and camphor were major compounds in the leaf extract, whereas tetradecenoic and linolenic acids were abundant in the flower extract. The amounts of tocopherols in the SFE-CO2 extracts were determined by high performance liquid chromatography (HPLC) analysis. Here, α-tocopherol attained noteworthy concentrations (8839 μg/g dw). The antioxidant activity of SFE-CO2 extract, plant powder and residue after SFE-CO2 extraction was assessed using three different methods, namely ABTS, FRAP and DPPH assays. The overall activity was as follows: plant powder > residue after SFE-CO2 extraction > SFE-CO2 extracts. Findings showed that R. eriocalyx is a rich source of antioxidant compounds, especially the plant material, and that considerable part of polar bioactive components still remain in the solid residue after SFE-CO2 extraction. Consequently, both lipophilic SFE-CO2 extract and antioxidant-rich extraction residues may be of interest for various industrial applications.