Effects of 1-octyl-3-methylimidazolium bromide on the antioxidant system of Lemna minor

Ionic liquids have gained more attention due to their excellent properties in many different scientific fields. However, previous researches indicated that ionic liquids have adverse effects on organisms. The objective of this study was to evaluate the effects of 1-octyl-3-methylimidazolium bromide ([C(8)mim]Br) on the aquatic plant duckweed (Lemna minor) by exposure of the plant to 0.25 to 2 mg L-1 of [C(8)mim]Br for 28 days. Exposure to [C(8)mim]Br significantly decreased the photosynthetic pigment contents at 21 and 28 days. The activities of superoxide dismutase and catalase and the total antioxidant capacity level increased at 7 days of exposure and decreased at the termination of exposure. In contrast, the H2O2 content and peroxidase activity in all treatments increased during the period of exposure. Furthermore, marked increase of malondialdehyde content occurred in duckweed after 21 to 28 days of exposure. In addition, reactive oxygen species (ROS) scavenger dimethyl thiourea prevents duckweed from oxidative damage caused by [C(8)mim]Br. These results suggest that ROS might be involved in the mechanism of ionic liquid-induced toxicity in L. minor.