Artemisinin biosynthesis in growing plants of Artemisia annua. A 13CO2 study

Biosynthesis of artemisinin – revisited

“…The fractions obtained from EtOAcÁhexane (55:50 and 60:40) afforded white crystals of 21 which were again recrystallized from hot MeOH. The structure of 21 was confirmed by 1 H and 13 C-NMR spectra and its comparison with the spectroscopy data available in the literature (Rimada et al 2009;Schramek et al 2010).…”

“…These findings could be explained through the schematic representation shown in Figures 1Á3. The IPP (6) and DMAPP (7) units combine to form GPP (8) which combines with another molecule of IPP to form (E,E)-FPP (9) (Schramek et al 2010). Because of the possible stereochemical requirements for cyclization to cadinane skeleton before the formation of amorphadiene (13) the (E,E)-FPP (9) may be converted to NPP (10), the (E,Z)-isomer of FPP (Picaud et al 2005) (Figure 1), although this step has not been claimed by many scientists but appears to be logical as mentioned above (Picaud et al 2005).…”

“…In order to achieve higher targets through in vivo and in vitro systems, the knowledge of biosynthetic pathway from the earliest precursors to artemisinin is essential. A lot of publications have come up over the last 25 years giving information on the biosynthesis of artemisinin (21) (Akhila et al 1987;Schramek et al 2010) artemisinic acid (14) (Akhila et al 1990;Covello et al 2007), and amorphadiene (Bouwmeester et al 1999) by using 14 C and 13 C-labeled precursors. The complete pathway to artemisinin can be divided into three steps: (1) biosynthesis of farnesyl pyrophosphate (FPP, 9) from CO 2 , acetate, glucose, and isopentenylpyrophosphate (IPP, 6)/dimethylallylpyrophosphate (DMAPP, 7) (C 5 units) through the mevalonic acid (MVA) or non-MVA pathways; (2) cyclization of FPP (9) to amorphadiene (13); and (3) biosynthesis of artemisinic acid (14), dihydroartemisinic acid (15), and artemisinin (21) from amorphadiene (13).…”

“…The isotopologue data confirm the previously proposed mechanism for the cyclization of (E,E)-FPP to amorphadiene (13) and its oxidative conversion to artemisinin (21). The experiments were performed on live plants by using an atmosphere of 13 CO 2 (Schramek et al 2010). It has been amicably demonstrated now in bacteria and phototrophic eukaryotes that in addition to MVA pathway the DXP path also exists during the formation of IPP (6) and DMAPP (7) which are the building blocks of all the terpene compounds (Rohmer et al 1993(Rohmer et al , 1996Eisenreich et al 1997Eisenreich et al , 1998Eisenreich et al , 2001Lichtenthaler 1999;Rohmer 1999;Hoeffler et al 2002).…”

“…There are also reports that both the pathways exist in higher plants, and a 'crosstalk' between the two pathways can be explained by the exchange of metabolic intermediates between the cytoplasm and the plastids (Arigoni et al 1997;Hemmerlin et al 2003;Schuhr et al 2003;Towler and Weathers 2007). In a recent report (Schramek et al 2010) geranyl pyrophosphate (GPP) (8) was shown to cross over the plastidial wall into cytosol and become part of FPP (9) which was finally converted to artemisinin (21).…”