Silybum marianum L. extracts are being used as antihepatotoxic therapy for liver diseases. Silymarin is a polyphenolic flavonoid mixture isolated from milk thistle which is believed to be responsible for the plant's hepatoprotective action. Regeneration of Silybum marianum plants from shoot tip explants and assessment of their morphogenic potential, silymarin total concentration and its major constituents upon exposure to medium composition alteration and different elicitors' application was targeted. Different concentrations of NaCl, quercetin, gamma irradiation and dried fungal extracts were used to elicit silymarin production in the cultures. The chemical composition of silymarin and its total concentration was investigated through HPLC at all the experiment stages. Multiple shoots were recorded after 3 weeks of culture on MS medium containing various concentrations of BA and/or NAA. IAA was more effective than NAA and IBA in inducing robust roots in shoot cultures. The flowering plants recorded 20 % and 40 % of the total plants number in the multiplication and rooting stages respectively. The highest total silymarin concentration reached its peak with (10 Gy) gamma-irradiation to be 6.598 % dry weight in the in vitro regenerated shoot tip explants. The in vitro grown flowers showed 1.7 times more sylimarin productivity as compared to that of the wild grown congruent.
Keywords: Gamma irradiation; HPLC; Milk thistle; Shoot tip cultures; Silymarin.