Closed polybag foliar methyl-jasmonate treatment: New technology for rapid enhancement of bioactive withanolide biosynthesis in field-grown plants of Withania somnifera

Abstract

Withania somnifera (L.) Dunal, is an important medicinal plant with tremendous use in the herbal drug industry. Withanolides are the major bioactive metabolites present in the leaves of W. somnifera. However, due to the low abundance of withanolides, it is difficult to fulfil the market demand. The rationale of this study was to develop a simple technology for enhanced withanolide biosynthesis in field-grown plants of W. somnifera. Exogenous elicitor-treatment to the field-grown plants is an effective strategy to increase the production of many plant secondary metabolites. In this study, a high-performance liquid chromatography method was developed for the rapid separation of withanolides from the leaves along with phenolic acid and flavonoids. Field-grown plants of W. somnifera were directly used for methyl jasmonate elicitor treatment using a novel closed polybag approach. In this approach, branches were covered with a polybag and then MeJa was injected using a specially designed vial. Methyl-jasmonate (20μM) treatment for 4 h resulted in 2.2-fold, 1.9-fold, 2.0-fold, and 2.2-fold increase in withaferin A, withanolide A, withanolide D, and withanone production, respectively, over the control treatment. Methyl-jasmonate -treatment increased the transcript levels of four key withanolide biosynthetic genes, namely 3-hydroxy-3-methylglutaryl coenzyme A reductase, squalene synthase, squalene epoxidase, and cycloartenol synthase. Methyl-jasmonate -treated leaf extracts and isolated pure withanolides also showed a significant cytotoxic effect against selected human breast cancer cell line. These results suggest that MeJa-treatment using a closed polybag system is an effective and easy-to-perform elicitation strategy for the enhanced production of bioactive withanolides using field-grown plants of W. somnifera. Farmers and industry can easily adapt this technology to meet the growing demand for bioactive withanolides.