Methyl jasmonate elicits enhancement of bioactive compound synthesis in adventitious root co-culture of Echinacea purpurea and Echinacea pallida

Co-culture of adventitious roots (ARs) of Echinacea purpurea (L.) Moench and E. pallida is a novel method for the production of Echinacea bioactive compounds. In the co-culture system, implementation of an elicitation strategy can likely promote bioactive compound accumulation in ARs. Therefore, in this work, methyl jasmonate (MeJA) was tested as an elicitor to treat 30-d-old bioreactor cultured ARs and the effect of MeJA concentrations on metabolite accumulation to select an optimal concentration of this elicitor. Furthermore, the antioxidant enzyme activities of ARs were also determined for understanding the mechanism of MeJA elicitation. Results showed that the 25 μM MeJA treatment increased metabolite accumulation in ARs with maximum production of phenolics (728.2 mg L−1), flavonoids (622.2 mg L−1), and caffeic acid derivatives (255.3 mg L−1 cichoric acid and 143.9 mg L−1 echinacoside); however, the highest polysaccharide production (approximately 440 mg L−1) was determined at 50 to 200 μM MeJA. The activities of antioxidant enzymes (superoxide dismutase, peroxidase, ascorbate peroxidase, and catalase) reached maximum levels with 25 μM MeJA, demonstrating a close relationship between antioxidant enzymes and secondary metabolite synthesis of co-cultured Echinacea ARs. In addition, the bioactive compound content in MeJA-treated ARs was compared with that in natural plant roots. The result indicated that the contents of phenolics, flavonoids, and caffeic acid derivatives (cichoric acid and echinocoside) were higher in the co-cultured ARs than in plant roots of E. purpurea and E. palida.