Quantification of artemisinin in Artemisia annua extracts by 1 H‐NMR

Artemisinin is a polycyclic sesquiterpene lactone that is highly effective against multidrug‐resistant strains of Plasmodium falciparum , the etiological agent of the most severe form of malaria. Determination of artemisinin in the source plant, Artemisia annua , is a challenging problem since the compound is present in very low concentrations, is thermolabile and unstable, and lacks chromophoric or fluorophoric groups. The ain of this study was to develop a simple protocol for the quantification of artemisinin in a plant extract using an 1 H‐NMR method. Samples were prepared by extraction of leaf material with acetone, treatment with activated charcoal to remove chlorophylls and removal of solvent. 1 H‐NMR spectra were measured on samples dissolved in deuterochloroform with tert ‐butanol as internal standard. Quantification was carried out using the $\d{$\delta$}$ 5.864 signal of artemisinin and the δ 1.276 signal of tert ‐butanol. The method was optimised and fully validated against a reference standard of artemisinin. The results were compared with those obtained from the same samples quantified using an HPLC‐refractive index (RI) method. The 1 H‐NMR method gave a linear response for artemisinin within the range 9.85–97.99 m m ( r 2 = 0.9968). Using the described method, yields of artemisinin in the range 0.77–1.06% were obtained from leaves of the A. annua hybrid CPQBA × POP, and these values were in agreement with those obtained using an HPLC‐RI. Copyright © 2008 John Wiley & Sons, Ltd.