Elicitation of secondary metabolism in Hypericum perforatum by rhizosphere bacteria and derived elicitors in seedlings and shoot cultures

Context: Hypericum perforatum L. (Guttiferae) appears as an alternative treatment to mild and moderate depression and been traditionally used as a health enhancer based on the phytochemicals hyperforin and hypericin. However, field grown medicinal plants show variable levels of phytopharmaceuticals depending on environmental conditions. Elicitation is a good strategy to trigger secondary metabolism. Objective: This study explored the ability of 6 rhizobacterial strains to trigger secondary metabolism in H. perforatum seedlings and molecular elicitors from the most effective strain N5.18 were tested in shoot cultures. Materials and methods: Hypericin and pseudohypericin were determined on seedlings and shoot cultures by HPLC. Three putative elicitors from bacterial culture media were assayed in three different concentrations. Results: Strain N5.18 significantly increased hypericin up to 1.2 ppm and pseudohypericin up to 3.4 ppm, over controls (0.3 and 2.5 ppm, respectively) when delivered to seedlings. In shoot cultures, only pseudohypericin was detected (168.9 ppm) and significant increases were observed under the different elicitors, reaching values of 3164.8 ppm with small elicitors in the middle concentration. Discussion and conclusion: Secondary metabolism in plants is highly inducible due to its role in plant communication and defense. Our findings demonstrate that some beneficial bacterial strains are able to trigger secondary metabolism in H. perforatum plants when delivered through the roots and bacterial determinants released to culture media are able to reproduce the effect in shoot cultures. Therefore, these elicitors have great potential to enhance phytopharmaceutical production.