Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2006
Publication Date: 2/13/2007
Citation: Ferreira, J.F. 2007. Nutrient Deficiency in the Production of Artemisinin, Dihydroartemisinic Acid, and Artemisinic Acid in "Artemisia annua" L. Journal of Agricultural and Food Chemistry. 55:1686-1694.
Interpretive Summary: Artemisia annua is the only source of artemisinin, the only effective chloroquine-resistant anti-malarial. Currently, there is no published practical approach on how to increase artemisinin production by the plant, which could eventually bring down the price of artemisinin-based antimalarial drugs. In this work, we have grown A. annua in a poor and acidic soil from West Virginia and measured the accumulation of leaf biomass and artemisinin concentration (g/100g) and total yield (g/plant) under greenhouse conditions. The treatments consisted of soil amended with N, P, K, and lime (complete) or lacking one of these amendments. Artemisia annua can grow in a poor soil if the appropriate pH level (5.0 to 6.0) is achieved. Nitrogen was the most required macronutrient for growth, and potassium was the least required for plant growth and leaf biomass accumulation. Artemisinin concentration (g/100g) in plants submitted to potassium-deficient treatments increased 75% over the concentration in plants grown in soils with the ‘complete’ treatment. Although leaf biomass accumulation under potassium deficiency was 29% lower than in plants grown with the ‘complete’ treatment, the total artemisinin yield (in g/plant) was 21% higher than in plants grown with the ‘complete’. There was no treatment effect on the concentration or yield of the artemisinin precursors artemisinic acid and dihydroartemisinic acid. This work shows that a A. annua farmer can succeed in growing the crop in an poor soil once an minimal pH of 5 is achieved, but higher biomass accumulation can be achieved with pH=6.0, based on field data connected to this experiment. It also shows that cultivation in soils mildly deficiency in potassium can provide both an increase in artemisinin concentration (g/100g) of over 70% and in artemisinin yield (g/plant) of over 20%, besides saving on potassium fertilization. Agronomic gains can be achieved despite poor soils and with the cultivars already available on the market.
Technical Abstract: Artemisia annua became a valuable agricultural crop after the WHO recommended artemisinin as a component of ACT (artemisinin-combination based therapies) for malaria in 2001. A cloned, greenhouse-grown, Artemisia annua (Artemis) subjected to an acidic soil and macronutrient deficit was evaluated for artemisinin production. Lack of lime (L) and macronutrients (N, P, K) reduced leaf biomass accumulation. When L was provided (pH=5.1), the highest average leaf biomass was achieved with the 'complete' (+N, +P, +K, +L) treatment (70.3g/plant), and the least with the untreated (-N,-P,-K, and –L) treatment (6.18 g/plant). The nutrient least required for biomass accumulation per plant (g) was K (49.0g), followed by P (36.5g), and N (14.3g). Artemisinin concentration (g/100g) was significantly higher (75.5%) in '–K' plants when compared to plants under the 'complete' treatment (1.62% vs. 0.93%). Although artemisinin total yield (g/plant) was 21% higher in '-K' plants, it was not significantly different from plants under the 'complete' treatment (0.80 vs. 0.66 g/plant). There were no marked treatment effects for concentration (g/100g) or yield (g/plant) of both dihydroartemisinic acid and artemisinic acid, although higher levels were achieved in plants under the 'complete' or '-K' treatments. There was a positive and significant correlation between artemisinin and both artemisinic acid and dihydroartemisin acid, in g/100g and g/plant. This is the first report where potassium deficiency significantly increases the concentration (g/100g) of artemisinin. Thus, under a mild potassium deficiency, Artemisia annua farmers could achieve similar gains in artemisinin/ha, while saving on potassium fertilization, increasing the profitability of artemisinin production.