Enhancement of Silymarin Accumulation Using Precursor Feeding in 'Silybum marianum' Hairy Root Cultures

This study focused on the effect of different concentrations of L- phenylalanine (0, 1, 10 and 100 μM) as the precursor, on the phenylalanine ammonia-lyase activity, naringenin content, root biomass and silymarin production in Silybum marianum hairy roots. Precursor was added to the medium of adventitious roots on the 30th day of culture and the roots were harvested on 0, 24, 48, 72, 96 and 120h after feeding. Detection and identification of flavonolignans was carried out by high performance liquid chromatography method. Cultures supplemented with phenylalanine 10 μM increased the root biomass (0.43 g) 1.89 fold compared to control (0.23 g) 72h after feeding. Phenylalanine 100 μM after 72h was found optimal feeding condition for production of silymarin (1.84 fold higher than that of the control). However, the stimulatory effect of 100 μM phenylalanine could be attributed to the taxifoline (0.143 mg g-1 DW), silydianin (0.117 mg g-1 DW) and silybin (0.031 mg g-1 DW) contents were greatly rose up to 4.16, 2.44 and 1.58 fold greater than that of untreated cultures (0.03, 0.05 and 0.02 mg g-1 DW) after 72h, respectively. Furthermore, the content of naringenin, precursor of flavonolignans indicated the similar pattern at 100 μM concentration 72h after treatment which was 4.64 fold greater than untreated cultures (0.005 mg g-1 DW). All three concentrations of added phenylalanine stimulated phenylalanine ammonia-lyase activity suggest utilization of phenylalanine for the initial step of phenyl-propanoid metabolism. This is the first report on PHE feeding as the precursor for silymarin accumulation in S. marianum adventitious root cultures.