Effects of Iron Ions on Rosmarinic Acid Production and Antioxidant System in Melissa officinalis L. Seedlings

Aims: In this study, effects of various Fe2+ concentrations on the physico-chemical parameters including contents of rosmarinic acid, flavonoid and anthocyanin as well as antioxidant enzymes activity in Melissa officinalis seedlings were analyzed. Furthermore, some morphological parameters and contents of chlorophyll and carotenoid were investigated in 45-day-old M. officinalis seedlings in presence of various Fe2+ concentrations.
Study Design: completely random designs.
Place and Duration of Study: Department of Biotechnology, Institute of Science and High technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran.
Methodology: 45-day-old seedlings were treated with different Fe2+ concentrations and then physico-chemical parameters of them were evaluated after 8 and 16 hours incubation periods. Rosmarinic acid content was measured using HPLC and the flavonoid and anthocyanin contents were determined using a spectrophotometer. Morphological properties including seed germination, root and shoot elongation and dry biomass of the 45-day-old Fe2+-treated seedlings were analyzed.
Results: The results showed that the contents of rosmarinic acid, flavonoid and anthocyanin drastically decreased in all treatments compared to the control. In this condition, the activity of superoxide dismutase and peroxidase were increased more significantly after 8 hours treatment rather than 16 hours. The results revealed that changes in rate of germination, shoot elongation and dray biomass were not statically significant. Although, the root growth was decreased in presence of Fe2+ compared to control, that was significant at the level of 5% at the highest Fe2+ concentration.
Conclusion: Accumulation of free radicals under treatment conditions may lead to suppression of protein synthesis or degradation of them as indirectly confirmed by reduced protein content. Therefore, it may be concluded that the decrease in contents of rosmarinic acid, flavonoid and anthocyanin results from a reduction of enzyme levels in their biosynthesis pathways. The decrease in root growth can be due to exposition of the organ to the excess of Fe2+, more increased uptake of the ion and triggering of free radicals. Furthermore, low rate in Fe2+ transportation to the shoots and elevated levels of chlorophyll and carotenoid contents may have roles in preventing damages to this organ.