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),
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Potential Methods to Improve the Efficiency of Artemisinin Extraction from Artemisia annua Rhianna Briars and Larysa Paniwnyk
Abstract 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.
8.1 Conventional Industrial Extraction The most implemented technique to extract artemisinin is conducted simply through multiple soakings of dried and crushed Artemisia annua leaves in boiling organic solvents, for between 10 and 48 h each time. The solvents most often employed for R. Briars (&) L. Paniwnyk Coventry University, Faculty of Health and Life Sciences, Priory Street, Coventry CV1 5FB, UK e-mail: [email protected]
T. Aftab et al. (eds.), Artemisia annua - Pharmacology and Biotechnology, DOI: 10.1007/978-3-642-41027-7_8, Springer-Verlag Berlin Heidelberg 2014
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this extraction are hexane or petroleum ether (Elsohly et al. 1990; Christen and Veuthey 2001; Cutler et al. 2006; Lapkin et al. 2006; Kuhn and Wang 2007; Liu et al. 2011). Soxhlet extractors are the easiest way to achieve this as the leaf material can have a constant infusion of boiling solvent (Ormeño et al. 2011) (Fig. 8.1). The time frame for extraction can be reduced by using flow or percolated systems; these methods still require a series of solvent steeps but each one lasts only 120 min (Cutler et al. 2006; Sticher 2008) (Fig. 8.2). This technology is simple and the investment cost is low but due to the protracted and arduous extraction times of 6 h, minimum, there is a great consumption of energy; and yet the yields are still quite low with only around 60–70 % overall extraction efficiency and recovery (in regard to artemisinin
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