71. Analysis and Isolation of Potential Artemisinin Precursors from Waste Streams of Artemisia Annua Extraction
Rodger W. Stringham, Gary L. Moore, David S. Teager, and Tai-Yuen Yue, ACS Omega, (2018) DOI: 10.1021/acsomega.8b00974
High-performance liquid chromatography, liquid chromatography–mass spectrometry, and gas chromatography–mass spectrometry methods were developed to analyze the process waste streams of Artemisia Annua extraction. 13C NMR spectra were obtained at the field strength of 15 MHz using a Magritek Spinsolve 60 NMR spectrometer. Results from these methods suggested that the final waste from the extraction process could serve as a source of dihydroartemisinic acid (DHAA) that could be converted to additional artemisinin. Two additional impurities were isolated and identified in the waste material as well as in A. annua leaf samples. That these impurities also appear as side-products in chemical transformations of DHAA to artemisinin supports the conclusion that the in vivo transformation proceeds as nonspecific oxidations. These impurities do not appear in isolated artemisinin. A simple, high-yielding procedure for recovery of DHAA from the primary waste stream was developed.