An organo-selenium compound that displays potent antioxidant properties. Acts as a glutathione peroxidase (GPX) mimic as well as being an excellent scavenger of peroxynitrite. The glutathione peroxidase-like activity of ebselen inhibits cyclooxygenase (COX) and lipoxygenases at micromolar concentrations. Also acts as a histone-lysine demethylase (HKDM) inhibitor. Inhibits JARID1B protein with an IC₅₀ of 5.17 µM.