2.2. Extraction of artemisinin by pressurized liquid extraction (PLE)
Undistilled control samples (1.0 g) and PRD of A. annua biomass were mixed with 3.5 g of diatomaceous earth and ground using a mortar and pestle. These ground samples were then funneled into one of the pressurized liquid extraction (PLE) stainless steel cells (ASE 350, Dionex Corp.) for pressurized extraction. The solvents used were petroleum ether (similar properties to hexane, used for industrial extraction of artemisinin) and water (to test if high pressure could improve water extraction). Both extracts were submitted to HPLC analysis. An aqueous acetone: water: acetic acid (70:29.5:0.5) extractant was used for the ORAC assay. The ASE 350 was set for static: 5 min; flush: 100%; purge: 60 s; cycle: 3; temperature: 70 °C; and 1500 psi, and allowed to run overnight. The next day, the samples were prepared for HPLC and ORAC analyses.