Drought stress increases iridoid glycosides biosynthesis in the roots of Scrophularia ningpoensis seedlings

In China, Scrophularia ningpoensis Hemsl (Scrophulariaceae) has been cultivated for many years; however, the effects of drought on the content of secondary metabolites in Radix Scrophulariaceae are still unknown. The study investigated the medicinal components of S. ningpoensis including harpagoside, aucubin, catalpol, harpagide, and cinnamic acid in relation to drought stress. Three ecotypes of S. ningpoensis at seedling stage were subjected to progressively three levels of osmotic stress for 10 days and then the superoxide anion content of leaves at different stages was determined, as well as the content of the components in the roots of S. ningpoensis detected by High-Performance Liquid Chromatography (HPLC). The contents of four iridoids glycosides in the roots along with the superoxide anion content in leaves under osmotic stress were higher than those with no osmotic stress in every ecotype, whereas cinnamic acid decreased. Drought stress could increase the iridoid glycosides and decrease the cinnamic acid content of roots in S. ningpoensis seedlings.