Comparative Assessment of Technologies for Extraction of Artemisinin

Abstract

This paper describes results of a multiobjective comparative assessment of several established and emerging technologies for extraction of a natural antimalarial substance, artemisinin. Extractions by hexane, supercritical carbon dioxide, hydrofluorocarbon HFC-134a, ionic liquids, and ethanol were considered. Hexane extraction is an established technology and appears to be the most cost-effective. However, it is characterized by lower rates and efficiency of extraction than all other considered techniques and is also worse in terms of safety and environmental impact. Similarly, EtOH extraction was found to be worse than hexane in all assessment parameters. The new technologies (scCO2, HFC, and ILs) are based on nonflammable solvents and are characterized by faster extraction cycles and more complete extraction of the useful substances and enable continuous extraction processes with reduced solvent inventory. Ionic liquid and HFC-134a technologies show considerable promise and should be able to compete with hexane extraction in terms of cost-effectiveness following due process optimization. New technologies are also considerably safer (no risk of explosions, low toxicity) and greener (having a lower environmental impact in use, potential for biodegradability after use). The methodology of comparative assessment of established and emerging technologies is discussed.

Recent developments in the rapid analysis of plants and tracking their bioactive constituents

“…They are expensive but on the other hand can be recycled and have special dissolving properties. An example of their application in phytochemistry is the extraction of the antimalarial drug artemisinin (Lapkin et al 2006). Another powerful development is the large scale introduction of high-resolution MS (HRMS).…”

The impact of impurities in various crude A. annua extracts on the analysis of artemisinin by liquid chromatographic methods

“…Malaria remains one of the world's most prevalent diseases, with an estimated 500 million cases worldwide each year that result in over one million deaths [1]. Eighty percent of all deaths attributed to malaria occur in Sub-Saharan Africa, particularly in children under the age of five [2].…”

“…Traditional solvents used for extraction include hexane, ethanol, petroleum ether, chloroform and toluene. More advanced extractions involve the use of supercritical CO 2 [5][6][7], ionic liquids [1], HFC-134a [1] and microwave assisted extraction (MAE) [8], which have all reported high efficiencies when compared to conventional extraction techniques. However, many of these technologies remain beyond the technical and capital reach of most producers in developing countries.…”

“…For smaller producers, the choice between traditional extraction solvents is complicated by the large number of conflicting reports in the literature [1]. Many experiments that compare extraction solvents use techniques such as soxhlet extraction that are not representative of those utilised in industry and which may lead to misleading conclusions.…”

“…This conclusion was supported by a chromatogram of an ethyl acetate extract but the chromatograms for the hexane, acetonitrile or chloroform extracts were not presented. As no reference to pure ethyl acetate extractions can be identified in the literature and acetonitrile would be unacceptably hazardous to use on a large scale [1], these findings do not necessarily invalidate HPLC-UV analysis of industrial extracts. The modified WHO Monograph method developed by Lapkin et al [11], hereon referred to as "Modified HPLC Protocol", was not applied to ethanol extracts and although a method does exist for their analysis it involves the prior derivatisation of artemisinin [9].…”