Effects of light regimes on in vitro seed germination and silymarin content in Silybum marianum

Silybum marianum is an economically important crop worldwide. It is renowned for production of biologically important silymarin. Average sale of silymarin is about US$ 8 billion/annum and its demand varies from 18 to 20 tons/year. Despite of its demand, there is lack of research efforts on cultivation and improvement of this plant. We hereby established feasible seed germination protocol for production of healthier and chemically consistent plantlets. Combination of benzyladenine (BA, 0.5 mg l−1) + gibberellic acid (GA3, 1.5 mg l−1) + thidiazuron (TDZ, 1.0 mg l−1) produced optimum germination frequency in seeds kept in 2 weeks dark and subsequently transferred to 2 weeks light (16 h photoperiod) conditions. Correlation among mean shoot length, mean root length, set of antioxidative enzyme activities was also observed in current report. Silymarin was determined by high performance liquid chromatography (HPLC). Considerable amount of silymarin (5.48 mg g−1 DW) was detected in our study, which was comparative to other reports available. Antioxidant activity (1,1-diphenyl-2-picrylhydrazyl; FRSA) and phenylalanine ammonia lyase (PAL) activity was also determined. Silymarin content had shown direct relationship with these activities. It showed that silymarin was a major antioxidant in current report. This study provides basis for expedited production of S. marianum plantlets with feasible content of silymarin.

► An efficient protocol for in vitro seed germination of Silybum marianum was developed.
► Combination of plant growth regulators with light and dark conditions enhanced germination.
► A correlation between growth parameters and antioxidative enzyme activities was observed.
► 5.48 m g−1 DW silymarin was detected by HPLC.
► This study provides an efficient process for commercial production of liver protecting drug.