Influence of Plant Growth Regulators on Callus Induction, Silymarin Production and Antioxidant Activity in Milk Thistle (Silybum marianum L. Gaertn.) under Tissue Culture Medium

The Silybum marianum (L.) Gaertn. is the dicotyledonous herbs of the Asteraceae family that is important in medical industry. The biological active compound of S. marianum is a mixture of several flavonolignals generally known as silymarin. The purpose of this study was to optimize S. marianum tissue culture for callus induction, silymarin production and comparison of some biochemical traits between explants and its derived callus. In this experimental study, the seeds were surface sterilized and transferred to MS medium to achieve sterile seedlings. Then, the effects of different concentrations of 2,4-D either alone or in combination with Kin were investigated on callus induction and silymarin production of root and leaf explants from sterile seedlings. The experiment was performed in complete randomized design with three replicates. The results revealed that the highest percentage of callus induction and silymarin accumulation (14.4%) were observed with 0.5 and 1 mg/L 2,4-D and Kin in root explant after one month. The quantitative and qualitative data from HPLC method revealed that the major flavonolignans in the root and its derived callus was isosilybin B (ISBNB). But the main component in leaf explant and its derived callus was silydianin (SDN). The results showed that silymarin level in root and leaf explants was lower than their derived callus. Meanwhile lignin amount in the root and leaf explants was much higher than corresponding callus. In addition, peroxidase activity was significantly higher in callus derived from root explant, compared to leaf explant and its derived callus. The current data demonstrated that callus derived from root explants can be an efficient source for silymarin production