Distribution and ecological impact of artemisinin derived from Artemisia annua L. in an agricultural ecosystem

The sesquiterpene lactone artemisinin is currently the most promising agent in reducing dispersion of the malaria parasite in infected patients. Artemisinin is a secondary metabolite produced by Artemisia annua L. The plant is cultivated worldwide at large scale to meet the global demand. Artemisinin is known to pose herbicidal and antimicrobial effects, implying environmental risks. In this study, content of artemisinin in plants was related to the concentrations and distribution in the soil during a growth season. The long term effect of artemisinin on activity of the soil bacteria was studied from analysis of the protein synthesis (incorporation rate of leucine) in slurries from plots with and without A. annua. Further, short-term effects of artemisinin were examined by counting bacterial colony forming units from suspensions of these two soils growing on artemisinin-spiked and non-spiked agar. The concentration of artemisinin in the upper 10 cm soil varied from below the limit of detection (10.6 μg kg−1 soil) to 440 μg kg−1 soil and was highest at the stage of flowering. The distribution of artemisinin was diffuse and artemisinin was detected up to 15 m from the plants, indicating that wind was a key factor in horizontal dispersal of artemisinin. Adsorption potential of artemisinin to soil particles was found to decline with depth. Artemisinin leached from topsoil to subsoil layers measured after an intense rain event, giving maximum concentrations at 70–90 cm depths and no detectable artemisinin in the topsoil. Cultivation on agar media showed that addition of artemisinin had a negative impact on growth of soil bacteria that had not previously being exposed to artemisinin, while bacteria from the A. annua soils were unaffected by the artemisinin spiking. Cultivation of A. annua also appeared to impact the proportion of culturable bacteria and composition of the bacterial populations. Our study demonstrates that artemisinin is a mobile compound in soil environments and that the cultivation of A. annua impacts bacterial activity and composition in soils in situ. ► Dispersal of artemisinin from Artemisia annua L. cultivation was studied in soil. ► The distribution of artemisinin in soil was diffuse and was influenced by wind. ► Artemisinin leached to subsurface layers despite strong adsorption to the topsoil. ► Cultivation of A. annua impacted the microbial activity and composition.