Potential Methods to Improve the Efficiency of Artemisinin Extraction from Artemisia annua

Recently, there has been a move to improve the extraction of artemisinin in terms of energy, solvent and purification costs and so, as a result, many innovative processes, such as supercritical fluid extraction (SFE), pressurised solvent extraction (PSE), microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE), are currently being explored. The most basic industrial-scale method for extracting artemisinin involves high volumes of heated organic solvents, such as petroleum ether and hexane, coupled with extended extraction time periods in order to achieve reasonable quantities of extract. Solvent considerations are not only underpinned by the solubility of artemisinin but also that of other phytological compounds which can complicate the purification stages. This has lead to some of the obvious alternative solvent choices, such as ethanol, being considered as unviable. Therefore, some of the more modern technologies have largely maintained the use of the traditional solvents but altered the parameters with which they are used, such as increasing pressures and temperatures of reactants in order to speed up extraction. This chapter will include an evaluation of the aforementioned alternate extraction techniques (SFE, PSE, MAE and UAE), including consideration of artemisinin yield, extract purity and industrial feasibility, in addition to examining the advantages and disadvantages of a range of solvent polarities.