Influence of exogenous salicylic acid on flavonolignans and lipoxygenase activity in the hairy root cultures of Silybum marianum

Silymarin is one of the most potent antioxidant so far developed from plant sources used as hepatoprotectants. Influence of different concentrations (0, 1, 2, 4, 6 and 8 mg/50 ml culture) and exposure time (24, 48, 72, 96 and 120 h) of salicylic acid on lipoxygenase activity, linoleic acid content, growth and production of silymarin in hairy root cultures of S. marianum were investigated. Detection and identification of flavonolignans was carried out by high performance liquid chromatograph method. Salicylic acid enhanced silymarin production (1.89 mg g⁻¹ DW). The optimal feeding condition was the addition of salicylic acid (6 mg/50 ml culture) after 24 h in which the silymarin content was 2.42 times higher than the control (0.78 mg g⁻¹ DW). The content of silybin, isosilybin, silychristin, silydianin and taxifolin were 0.703, 0.017, 0.289, 0.02 and 0.863 mg g⁻¹ DW respectively in these samples, while in non-treated hairy roots were 0.027, 0.046, 0.23, 0.022 and 0.453 respectively. Lipoxygenase activity also affected by elicitation. lipoxygenase activity increased 24 h after treatment by ∼1.57- fold (0.21 Δ OD₂₃₄/mg protein min⁻¹). Upon elicitation with salicylic acid, linoleic acid content of hairy roots (38.26 mg g⁻¹ DW) were also elevated after 24 h, in which the linoleic acid content was 2.37 times higher than the control (16.1 mg g⁻¹ DW). It is feasible that elicitation with salicylic acid regulates the jasmonate pathway, which in turn mediates the elicitor-induced accumulation of silymarin.