Literally Green Chemical Synthesis of Artemisinin from Plant Extracts

Abstract

Active pharmaceutical ingredients are either extracted from biological sources-where they are synthesized in complex, dynamic environments-or prepared in stepwise chemical syntheses by reacting pure reagents and catalysts under controlled conditions. A combination of these two approaches, where plant extracts containing reagents and catalysts are utilized in intensified chemical syntheses, creates expedient and sustainable processes. We illustrate this principle by reacting crude plant extract, oxygen, acid, and light to produce artemisinin, a key active pharmaceutical ingredient of the most powerful antimalarial drugs. The traditionally discarded extract of Artemisia annua plants contains dihydroartemisinic acid-the final biosynthetic precursor-as well as chlorophyll, which acts as a photosensitizer. Efficient irradiation with visible light in a continuous-flow setup produces artemisinin in high yield, and the artificial biosynthetic process outperforms syntheses with pure reagents.

Keywords: artemisinin; chlorophyll; extraction; natural product synthesis; photooxidation.