Medicinal Plant Artemisia Annua Research Articles

The mechanism of the spontaneous autoxidation of dihydroartemisinic acid

Dihydroartemisinic acid undergoes slow spontaneous autoxidation to artemisinin and other natural products, which have been reported from the medicinal plant Artemisia annua. The mechanism of this complex transformation is shown to involve four steps: (i) initial reaction of the Δ 4,5-double bond of dihydroartemisinic acid with molecular oxygen, (ii) Hock cleavage of the resulting tertiary allylic hydroperoxide; (iii) oxygenation of the enol product from Hock cleavage; and (iv) cyclization of the resulting vicinal hydroperoxyl-aldehyde to the 1,2,4-trioxane system of artemisinin.

Extraction of artemisinin and artemisinic acid from Artemisia annua L. using supercritical carbon dioxide

Artemisinin (an antimalaric compound) and its major precursor artemisinic acid, isolated as the active principles of the medicinal plant Artemisia annua L., were extracted by supercritical fluid extraction (SFE) and analyzed by supercritical fluid chromatography (SFC) using a capillary column, coupled with a flame ionization detector (FID). With optimized operating conditions, artemisinin and artemisinic acid were quantitatively extracted at a flow-rate of 2 ml min −1 in less than 20 min. The supercritical fluid was composed of carbon dioxide and 3% methanol with temperature and pressure fixed at 50°C and 15 MPa, respectively. From the kinetic curves, it appears that the extraction of artemisinin is not limited by the diffusion of the analyte from the plant into the extraction fluid but rather by the elution process. These conditions avoided degradation of the analyte and gave clean extracts ready to be analyzed by SFC. The SFE-SFC-FID method was successfully applied to six samples of A. annua containing various concentrations of artemisinin and artemisinic acid. Results were compared with two conventional liquid solvent extraction processes.