Historical and experimental evidence for enhanced concentration of artemesinin, a global anti-malarial treatment, with recent and projected increases in atmospheric carbon dioxide

Although the role of rising atmospheric carbon dioxide concentration [CO₂] on plant growth and fecundity is widely acknowledged as important within the scientific community; less research is available regarding the impact of [CO₂] on secondary plant compounds, even though such compounds can play a significant role in human health. At present, Artemisia annua, an annual plant species native to China, is widely recognized as the primary source of artemesinin used in artemesinin combination therapies or ACTs. ACTs, in turn, are used globally for the treatment of simple Plasmodium falciparum malaria, the predominant form of malaria in Africa. In this study, artemesinin concentration was quantified for multiple A. annua populations in China using a free-air CO₂ enrichment (FACE) system as a function of [CO₂]-induced changes both in situ and as a function of the foliar ratio of carbon to nitrogen (C:N). The high correlation between artemesinin concentration and C:N allowed an historical examination of A. annua leaves collected at 236 locations throughout China from 1905 through 2009. Both the historical and experimental data indicate that increases in artemesinin foliar concentration are likely to continue in parallel with the ongoing increase in atmospheric [CO₂]. The basis for the [CO₂]-induced increase in artemesinin is unclear, but could be related to the carbon: nutrient hypothesis of Bryant et al. (1983). Overall, these data provide the first evidence that historic and projected increases in atmospheric [CO₂] may be associated with global changes in artemesinin chemistry, potentially allowing a greater quantity of drug available for the same area of cultivation.