GSH Protects the Cells from High Concentrations of Thymoquinone.

The aim of the present study was to evaluate the potential protective effect of glutathione (GSH) on cells grown in a high concentration of thymoquinone (TQ). This quinone, as the main active compound of seed oil, exhibits a wide range of biological activities. At low concentrations, it acts as an antioxidant, and at high concentrations, an antimicrobial agent. Therefore, any interactions between thymoquinone and glutathione are crucial for cellular defense against oxidative stress. In this study, we found that GSH can conjugate with thymoquinone and its derivatives in vitro, and only fivefold excess of GSH was sufficient to completely deplete TQ and its derivatives. We also carried out studies on cultures of GSH-deficient strains grown on a minimal medium in the presence of different concentrations of TQ. The strains harboring mutations in gene and were about two- and fourfold more sensitive (256 and 128 µg/mL, respectively) than the wild type. It was also revealed that TQ concentration has an influence on reactive oxygen species (ROS) production in strains-at the same thymoquinone concentration, the level of ROS was higher in GSH-deficient strains than in wild type.