Ebselen acts as a glutathione peroxidase mimic and is an excellent scavenger of peroxynitrite with a rate constant of 2 x 106 M−1s−1. The glutathione peroxidase-like activity of ebselen inhibits cyclooxygenase and lipoxygenases at micromolar concentrations.

A diselenide-bridged amino acid that has both anti- and pro-oxidant actions; can be reduced by low molecular thiols and disulfide reductases to selenocysteine; has cytostatic effects in a range of cancer cell types.

The predominant form of selenium found in Brazil nuts, grains, soy beans, and legumes; promotes cell cycle progression and has antioxidant and anticancer activity.