Seasonal variations of artemisinin and its biosynthetic precursors in tetraploid Artemisia annua plants compared with the diploid wild-type

Using colchicine we induced tetraploidy in Artemisia annua L. plants. During a vegetation period we monitored the time course of the levels of artemisinin, its direct precursors, the biosynthetically related sesquiterpenes and the essential oil content in the diploid (wild-type) and tetraploid A. annua plants. The averaged artemisinin level in tetraploids was 38% higher than that of the wild-type as measured over the whole vegetation period. In contrast, the averaged essential oil content of the tetraploids over this period was 32% lower. This might suggest a reciprocal correlation between artemisinin (sesquiterpenes) and the essential oil content (monoterpenes). The averaged biomass of the leaves of the tetraploid plants was lower compared to the wild-type plants. Therefore, the artemisinin yield per m(2) tetraploids was decreased by 25%. Although the tetraploid plants were smaller than the wild-type plants, certain individual organs like the leaves were considerably larger, and seeds obtained by cross pollination between tetraploid A. annua plants had a spectacular size. In principle, tetraploid A. annua can be a useful starting material for a breeding program in order to obtain larger and faster growing plants, which produce higher levels of artemisinin

Isolation and identification of dihydroartemisinic acid from Artemisia annua and its possible role in the biosynthesis of artemisinin

Dihydroartemisinic acid (2) was isolated as a natural product from Artemisia annua in a 66% yield, and its structure was confirmed by H-1 and C-13 NMR spectroscopy. Compound 2 could be chemically converted to artemisinin (4) under conditions that may also be present in the living plant. The results suggest that the conversion of 2 into 4 in the living plant might be a nonenzymatic conversion