The Influence of Methyl Jasmonate and Salicylic Acid on Secondary Metabolite Production in Rehmannia Glutinosa Libosch. Hairy Root Culture

Rehmannia glutinosa hairy roots were used to evaluate the effect of methyl jasmonate (MeJa) and salicylic acid (SA) on increase of root biomass and production of iridoids (catalpol, harpagide) and phenylethanoids (verbascoside and isoverbascoside). The elicitors were added to 23-day-old culture separately at concentrations between 50 and 200 μM or in combinations at concentrations of 50 and 100 μM. Roots were harvested 72 h and 120 h after elicitation. The type of elicitor, its concentration and exposure time were found to strongly affect the content of each analyzed compound. A 72-hour treatment with 200 μM MeJa was the most effective in increase of verbascoside content (60.07 mg·DW−1 equivalent to 845.45 mg·L−1) and isoverbascoside (1.77 mg·DW−1 equivalent to 24.94 mg·L−1): these respective amounts were roughly 10- and 6.4-fold higher than the control values (unelicited roots). Exposure to 150 μM MeJa provided optimal harpagide content after 72 hours (0.136 mg·DW−1; 7.5-fold increase compared to the control), and catalpol content after 120 hours (up to 2.145 mg·DW−1). The combination of MeJa and SA also resulted in higher levels of secondary metabolites compared to the control culture, although these levels were lower than those observed for MeJa alone at the optimal concentration and exposure time. SA alone was less efficient in enhancing metabolite production than MeJa.