Biosynthesis of artemisinin in gamma-irradiated Artemisia annua plantlet proceeds via a mixed origin of isoprene units

Abstract

Artemisia annua is a traditional herb that used for antimalarial drug in China. The well-known antimalarial agent, artemisinin, is a sesquiterpene lactone bearing an endoperoxide and theoretically biosynthesized from the terpenoid pathway. The present study, the wild type A. annua shoots were irradiated with gamma ray 650 of cobalt-60, obtaining A. annua TBB strain [1]. The A. annua TBB plantlets were then induced and propagated in Murashige and Skoog medium (MS) supplemented with 3% (w/v) sucrose and 0.8% (w/v) agar, under 16h of photo-period (2000 lux). Plantlets containing high-yield artemisinin were selected from A. annua TBB and used as plant materials for isotopic glucose feeding experiment. Plantlet cultures of irradiated A. annua TBB (10-day old) from MS agar medium were transferred into 250-ml erlenmeyer flasks and grown for 30 days on shelf culture, in distilled water supplemented with 3% (w/v) glucose solution, a mixture of [1 – 13C]glucose (99% 13C enrichment) and unlabeled D-glucose (1:1 ratio). Artemisinin was isolated and their 13C-labeling patterns examined using quantitative NMR spectroscopy. Analysis of the patterns of 13C-enrichment revealed that all the isoprene units in the skeleton of artemisinin were supplied from both the DXP and the MVA pathways.