Seasonal and Post-harvest Accumulation of Artemisinin, Artemisinic Acid, and Dihydroartemisinic Acid in Three Accessions of Artemisia annua Cultivated in West Virginia, USA

Artemisia annua from Brazil, China, and Switzerland were cultivated in Beckley, WV, for three growing seasons (June to October, 2005 to 2007). Plants were sampled periodically from 30 days after field transplanting until flowering, and analyzed for artemisinin (Art) artemisinic acid (AA), and dihydroartemisinic acid (DHAA) seasonal accumulation by HPLC. In a separate experiment, harvested plants were freeze-, sun, and shade dried (for three weeks), and oven dried (45°C, 24h). All cultivars, early flowering or not, reached peak artemisinin between August 28 and September 1^st, coinciding with day lengths shorter than 13.2h, reported as flowering-inducing photoperiod for A. annua [1], and average temperatures of 21°C. AA was mostly unchanged throughout the season, while DHAA followed the same trend as Art accumulation, except for the Brazilian clone in which DHAA decrease as Art increased. While Art and DHAA were similarly concentrated (g/100 g) in freeze-dried samples, DHAA and AA significantly decreased while artemisinin generally increased during drying, indicating that some DHAA and AA converted into Art during drying. Art increased from freeze-dried<oven dried<sun-dried ≈ shade-dried plants. The post-harvest data for artemisinin accumulation is consistent with two previous reports from Indiana, USA [2] and Tasmania, Australia [3]. Data on both concentration and seasonal accumulation of artemisinin precursors have not been previously reported. Overall, artemisinin accumulates at the end of the vegetative stage/pre-flowering stage, independent of the cultivar, and is not degraded by Oven, Sun or Shade drying. Artemisinin tends to increase with the latter two methods, which have practical application for its commercial production. Acknowledgements: Thanks are due to Robert Arnold and Barry Harter, USDA-ARS, for their valuable help on data collection and analysis of these experiments. References: [1] Ferreira JFS, et al. (1995) Planta Medica 61: 167–170. [2] Ferreira J, Charles D, Simon J, Janick J (1992) HortScience Vol. 27, p. 650. [3] Laughlin JC (2002) Acta Horticulturae Vol. 576, p. 315–320.