**Abstract**

The present chapter describe a series of synthetic organoselenium compounds such as ebselen analogues, diaryl selenides, spirodioxyselenurane, spirodiazaselenuranes and its Glutathione peroxidise (GPx) catalytic activity. These ebselen related compounds either by modifying the basic structure of ebselen or incorporating some structural features of the native enzyme, a number of small-molecules of selenium compounds as functional mimics of GPx are discussed. In addition to this, spirodioxyselenuranes and spirodiazaselenuranes are important class of hypervalent selenium compounds, whose stability highly depends on the nature of the substituents attached to the nitrogen atom. The glutathione peroxidase (GPx) mimetic activity of all the selenium compounds showed significantly by facilitating the oxidation of the selenium centre. In contrast to this, ebselen analogue shows significant antioxidant activity compared with spirodiazaselenuranes and its derivatives.

**Keywords:** spirodiazaselenuranes, antioxidant activity, selenoenzymes, ebselene
