The antioxidant response of Lemna paucicostata upon phenol exposure

Phenol exposure caused a significant reduction in the growth rate of Lemna paucicostata with an IC50 of 234.5±5.8 mg/L. Additionally, phenol caused a dose-dependent increase in the formation of reactive oxygen species (ROS). However, lipid peroxidation was not significantly affected, implying that the membrane lipids are protected by antioxidants under phenol-induced oxidative stress. The ascorbate content decreased in a phenol dose-dependent manner in accordance with the increase in ROS formation, and ascorbate peroxidase activity increased at a low phenol concentration. In contrast, phenol caused remarkable increases in both the total glutathione content and the activities of enzymes involved in glutathione redox- cycling, i.e., glutathione peroxidase and glutathione reductase. Catalase and guaiacol peroxidase activities were also increased, while superoxide dismutase activity decreased. Our results suggest that the phenol-induced increases in glutathione, glutathione redox-cycling enzymes, and H2O2-scavenging enzymes are important components of the adaptive response to phenol exposure. Thus, these increases can be used as indicators of the oxidative stress caused by phenol.