Effects of sucrose and polyethylene glycol on hypericins content in Hypericum adenotrichum

Background: Hypericum adenotrichum contain many biologically active compounds, some of which, especially hypericins (hypericin and pseudohypericin), have antidepressant, antimicrobial, antiviral, and antitumor properties. In this paper, we report the effects of osmotic stress on the production of hypericins in H. adenotrichum under in vitro conditions. Osmotic stress is an abiotic elicitor that can alter the physiological and biochemical properties of plants, as well as decrease or increase the concentrations of secondary metabolites in plant tissues. Material and Methods: Sucrose and polyethylene glycol (PEG) were used to cause osmotic stress. Seedlings of H. adenotrichum were grown on a modified MS medium containing sucrose (15, 30, 45, and 60 g/L) or PEG (2.5, 10, and 15 g/L) for 15 and 30 days. Then, H. adenotrichum seedlings were extracted with methanol. These extracts were analysed by HPLC to investigate the changes in hypericins levels. Results: Under osmotic stress conditions, the concentrations of hypericins changed in seedlings of H. adenotrichum. Treatment with 10 g/L PEG for 15 days increased production of hypericin (2.1-fold) and pseudohypericin (2.3-fold), but PEG treatment for 30 days affected less hypericins levels when compared to PEG treatment for 15 days. The amount that the hypericins increased was minimal and proportional with the amount of sucrose up to treatment with 45 g/L sucrose, and then the hypericins decreased at 60 g/L of sucrose treatment for 15 days. In sucrose treatment, the highest hypericins levels were observed in the control seedlings at 30 days treatment period of sucrose. Conclusions: These results can be evaluated in experimental botany and in the technology of Hypericum species cultivation for pharmaceutical applications.