Effects of iron and cupper ions on sulforaphane content and peroxidase activity in Lepidium draba seedlings

Sulforaphane (SFN) is an isothiocyanate which is produced through glucoraphanin hydrolysis via myrosinase activity. In the present study, SFN content and peroxidase activity has been assessed in treated Lepidium draba seedlings with different concentrations of iron and copper during 8 and 16 hours treatment. The results showed that the SFN content drastically elevated at treatment with 1 mg/L Fe2+ after 8 hours treatment which was around two-fold compared to the control. But its content decreased in treated seedlings with higher Fe2+ concentrations as well as treatment with all concentrations of Cu2+. Furthermore, promotion of peroxidase activity was seen in the treated seedlings with the both elicitors. The data revealed that not only the inhibitory effect of Cu2+ on SFN production was stronger than Fe2+, but its stimulatory effect on peroxidase activity was also remarkable especially after 16 hours treatment. It seems that the metals induce triggering of reactive oxygen species (ROS) which at low Fe2+ concentration leads to induce glucoraphanin biosynthesis pathway. While at higher Fe2+ concentrations as well as treatment seedlings with Cu2+, ROS lead to induce antioxidant enzyme system.