Effects of yeast extract on antioxidant activity and tropane alkaloids production in hairy roots cultures of Hyoscyamus reticulatus L.

Hyoscyamus species such as Hyoscyamus reticulatus L. are rich sources of tropane alkaloids, mainly hyoscyamine and scopolamine, which are used for their mydriatic, antispasmodic, anticholinergic, analgesic and sedative properties. Due to complex chemical structures, these alkaloids are obtained from natural sources, mainly Solanaceae plants. Elicitation of secondary metabolites biosynthetic pathways by different kind of elicitors is an effective strategy to increase secondary metabolites productivity. In the present study, in order to increase production of tropane alkaloids, cotyledon-derived hairy root cultures transformed with Agrobacterium rhizogenes strain A7, were elicited with yeast extract (YE) as biotic elicitor. Effect of different concentrations (0, 125, 250, 500 and 1000mg/l) of YE elicitor at different exposure times (24, 48 and 72 h) were investigated. According to the results, YE at the concentration of 500 and 250 mg/l after 48 h treatment, significantly increased hyoscyamine (2-fold) and scopolamine (2.5-fold) production in comparison with control, respectively. The results showed that treatment with different concentrations of YE and also increasing the exposure time led to significant decrease in growth of hairy roots in comparison with control. The activity of antioxidant enzymes including catalase, guaiacol peroxidase, and ascorbate peroxidase was also elevated in treated hairy roots rather than of the control. Based on the results, it can be concluded that elicitation with YE leads to induce an oxidative stress. These results suggest that YE could be used as an effective elicitor in plant biotechnology for the production of plant secondary metabolites such as tropane alkaloids.