Artemisinic acid

Artemisia annua accumulates substantial quantities of unique and highly useful antimalarial sesquiternoid artemisinin and related phytomolecules as well as its characteristic essential oil in its glandular trichomes. The phytomolecules are mainly produced in its leaves and inflorescences. Artemisia annua plants were grown under NaCl salinity (50, 100 and 200 mM) stress conditions imposed throughout the entire life cycle of the plant. Results revealed that specialized metabolites like artemisinin, arteannuin-B, artemisinic acid + dihydroartemisinic acid and essential oil accumulation were positively modulated by NaCl salinity stress. Interestingly, total content of monoterpenoids and sesquiterpenoids of essential oil was induced by NaCl salinity treatment, contrary to previous observations. Production of camphor, the major essential oil constituent was induced under the influence of treatment. The metabolic acclimation and manifestations specific to terpenoid pathway are analysed vis-a-vis vegetative to reproductive periods and control of the modulation. WRKY and CYP71AV1 play a key role in mediating the responses through metabolism in glandular trichomes. The distinctness of the salinity induced responses is discussed in light of differential mechanism of adaptation to abiotic stresses and their impact on terpenoid-specific metabolic adjustments in A.

Artemisinin, in the form of artemisinin-based combination therapies (ACTs), is currently the most important compound in the treatment of malaria. The current commercial source of artemisinin is Artemisia annua, but this represents a relatively expensive source for supplying the developing world. In this study, the possibility of producing artemisinin in genetically modified plants is investigated, using tobacco as a model. Heterologous expression of A. annua amorphadiene synthase and CYP71AV1 in tobacco led to the accumulation of amorphadiene and artemisinic alcohol, but not artemisinic acid. Additional expression of artemisinic aldehyde Δ11(13) double-bond reductase (DBR2) with or without aldehyde dehydrogenase 1 (ALDH1) led to the additional accumulation dihydroartemisinic alcohol. The above-mentioned results and in vivo metabolic experiments suggest that amorphane sesquiterpenoid aldehydes are formed, but conditions in the transgenic tobacco cells favour reduction to alcohols rather than oxidation to acids. The biochemical and biotechnological significance of these results are discussed.

A rapid and simple RP-TLC method for simultaneous quantification of pharmacologically important sesquiterpene artemisinin (AM) together with its precursors arteannuin-B (AB) and artemisinic acid (AA) in the inflorescence part of Artemisia annua plant has been developed. The RP-TLC of sesquiterpenes was performed on RP-18 F254 S thin-layer chromatographic plates by developing in mobile phase, containing 0.2% TFA in water/ACN (35:65, v/v). The densitometric determination of AM, AB and AA was carried out after derivatization with anisaldehyde reagent at 426 nm in absorption-reflectance mode.