Foliar treatment with MSB (menadione sodium bisulphite) to increase artemisinin content in Artemisia annua plants

Abstract

Artemisinin is a sesquiterpene lactone endoperoxide, recognized for its application as a treatment for malaria. Besides, it has activity against several types of cancers, as well as anti-viral and anti-inflammatory properties. The chemical synthesis of artemisinin is quite complex and economically unfeasible. Hence, artemisinin is typically obtained from Artemisia annua plants in low quantities in relation to the biomass. A strategy to increase the biosynthesis of secondary metabolites would be the application of elicitors. In this work, the effect of treating A. annua plants with menadione sodium bisulphite (MSB) is studied. An initial dose-optimization was conducted by treating the plants with different MBS concentrations (0, 0.2, 0.8, 1, 2, 3 and 4 mM) and artemisinin was quantified 48 h after treatment. The highest artemisinin content (3.71 mg artemisinin g−1 DW) was obtained with 1 mM of MSB. Then, harvesting time was optimised (24, 48 and 72 h after treatment application) with 1 mM of MSB. The largest increase in artemisinin content was observed at 48 h with an increment of 62.37 % over the control. The treatment increased H2O2 content, as well as the activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX). Besides, MSB up-regulated HMGR (the gene for 3-hydroxy-3-methylglutaryl-CoA reductase) and DXS (the gene for 1-deoxy-D-xylulose-5-phosphate synthase) 24 h after treatment. Both genes are involved in the MVA (mevalonate) and MEP (2C-methylerythritol 4-phosphate) pathways, respectively. These pathways represent the initiation of artemisinin biosynthesis. Thus, MSB application and the consequent up-regulation of early biosynthetic pathway genes along with the triggered oxidative stress may have been contributed to the observed increase in artemisinin production.