Ag enhanced silymarin production in hairy root cultures of Silybum marianum (L.) Gaertn

Seeds of Silybum marianum which have been used to treat liver diseases have an active component called silymarin. Hairy root cultures of S. marianum could be able to produce silymarin. There is evidence that the use of elicitors has been an important strategy for improving the production of secondary metabolites. Elicitation is an interesting topic to investigate cell signaling pathway in secondary metabolite biosynthesis. Lipoxiganase is an important enzyme in octadecanoid pathway related to the biosynthesis of jasmonic acid. The relationship between elicitors and jasmonic acid signaling pathways has been shown in previous researches. In the present study, we examined silymarin accumulation, linoleic acid content and lopoxigenas activity in hairy roots of S. marianum induced through the use of an abiotic elicitor, Ag. Hairy root cultures of S. marianum were fed by different concentration of Ag (0.2, 0.4, 0.8, 1 and 2 mM) and harvested 72h after elicitation. Detection and identification of flavonolignans was carried out by high performance liquid chromatograph method. The highest content of silymarin was 0.56 mg g -1 DW that was obtained with 2 mM of Ag which was 2 times of non-treated hairy roots. In the next stage, hairy roots were treated with 2 mM Ag for different times (0, 24, 48, 72, 96 and 120h). The highest silymarin production reached to 1.2 mg g -1 DW, 96h after elicitation. The content of silybin, isosilybin, taxifolin, silycristin and silydianin were 0.069, 0.031, 0.688, 0.388 and 0.024 mg g -1 DW, respectively. The maximum lipoxigenase activity was obtained 72h after elicitation that was 4.33 times of non-treated hairy roots. Linoleic acid content was 19.9 mg g -1 DW, 96h after elicitation. Dry weight of treated hairy roots decreased, as compared to non-treated hairy roots. It is feasible that elicitation with Ag changes lipoxigenase activity which mediates signal transduction pathway for production of silymarin.