Effect of ultrasound on the extraction of artemisinin from Artemisia annua

Artemisinin, found in the leaves of Artemisia annua, is used in the production of ‘Artemisinin Combination Therapies’ for the treatment of malaria. The cost of these drugs is high due to protracted traditional extraction methods, using solvents at high temperatures, and the extensive purification needed due to the presence of impurities within crude extracts. Ultrasound, as an alternative method, has the potential to reduce the energy costs of extracting artemisinin, due to low temperature rupturing of glands on the leaf surface. The co-extraction of impurities may also be reduced through the use of these lower temperatures. The level of artemisinin extracted under various extraction parameters was evaluated either through conventional steeping or with the addition of 40 kHz of ultrasound (n = 3). Each extract was analysed using high performance liquid chromatography (HPLC) and the concentration of artemisinin present was calculated. A basic technique of accessing the purity of crude extracts was also implemented by using the peaks observed on the HPLC trace. Higher artemisinin concentration and purity are observed in ultrasonic extractions performed at low temperatures, with ultrasonic extractions performed at 25 °C emulating conventional steeping at 35 °C, suggesting that heating costs could be reduced through the application of ultrasound. These observations show that ultrasound at low temperatures increases the yield of artemisinin extracted from A. annua by around 58% and the extracts appear purer when compared to conventional steeping; therefore the use of ultrasound during extraction has the potential for producing lower cost artemisinin-based treatments.

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► Comparison of conventional steeping and ultrasonic extraction of artemisinin from Artemisia annua.
► Yields shown to be higher in ultrasonic extractions at all 3 temperatures (25 °C, 35 °C and 45 °C).
► The proportion of artemisinin (to co-extracted impurities) is higher in ultrasonic extractions at the lowest temperature of 25 °C.
► Performing extractions at this low temperature with the presence of ultrasound could prove to have smaller energy costs.