Abstract
Background: A useful technique for growing large amounts of plant material is in vitro propagation of important medicinal plants. The present investigation deals with the enhancement of secondary metabolite production via elici-tation using gamma (gamma)-radiation and phenylalanine (Phe) precursor feeding in callus cultures of Silybum marianum L.Results: Seeds were exposed to two doses of gamma-radiation (25 and 50 Gy) and the calli derived from stem explants obtained from seedlings of these radiated seeds were treated with different concentrations of Phe. The biosynthe-sis of phenols and flavonoids was evaluated. It was found that callus cultures derived from explants of the seeds exposed to 25 Gy gamma-radiation and treated with 4 mg/l Phe accumulated the maximum phenolic content (34.27 +/- 0.02 mg/g d.wt.), while the highest flavonoid content (9.56 +/- 0.12 mg/g d.wt.) was found in callus cultures derived from explants of seeds radiated with 25 Gy gamma-radiation and subjected to 1 mg/l Phe. Similarly, HPLC quantification revealed that the production of flavonoids was highly accumulated (1343.06 mu g/mg d.wt.) in callus cultures from explants of seeds exposed to 25 Gy gamma-radiation and grown at 1 mg/l Phe compared to the other treatments. In addition, a total of 11 important flavonoids have been determined in all callus cultures, except for acacetin-7-O-rutinoside, which was not found in the callus culture of the control. Conclusions: These findings suggest that gamma-radiation combined with Phe can improve the metabolism of S. mari-anum L. and could be used to produce such valuable metabolites on a commercial scale.