Ultrasonic Assisted Extraction of Artemisinin from Artemisia annua L. Using Poly(Ethylene Glycol): Toward a Greener Process

Poly(ethylene glycol) (PEG), a kind of “green” medium, was used to extract artemisinin from the Chinese herb Artemisia annua L. to replace the traditional volatile and explosive solvents like petroleum ether, diethyl ether, etc. PEGs, with different molecular weights, show excellent ability for artemisinin extraction, and the extraction efficiency decreased with the increase of molecular weight. It was also demonstrated that ultrasonic irradiation could further enhance extraction efficiency compared with conventional water bath heating. Results indicate that the extraction amount of artemisinin from one gram of the leaves could reach 15.8 mg/g under the optimal conditions with ultrasonic power of 100 W, the temperature of 50 °C, time of 1 h in PEG-200, which were optimized by response surface method. Compared with Soxhlet extraction using petroleum ether (PE), the method developed here shows higher extraction efficiency (15.8 mg/g for PEG vs. 14.9 mg/g for PE process) and shorter extraction time (1 h vs. ca. 12 h). Additionally, artemisinin in the PEG solution can be recovered using resin adsorber. The results show that the recovery of artemisinin could reach almost 100% by D101 or H103 porous resin, and then the drug could be desorbed from the resin by ethanol or ethyl acetate. Moreover, the kinetic and mechanism studies of the extraction process revealed that ultrasonic irradiation could enhance mass transfer and the hydrogen bonding interactions between artemisinin and PEG further facilitate the separation of artemisinin from the leaves. This work provides an alternative process for efficient artemisinin extraction by using an environmentally benign medium with outfield intensification, which could be potentially extended to the production of other natural drugs.