Ebselen, a useful tool for understanding cellular redox biology and a promising drug candidate for use in human diseases.

Ebselen is an organoselenium compound with glutathione peroxidase (GPx)-like hydroperoxide reducing activity. Moreover, ebselen has its own unique reactivity, with functions that GPx does not have, since it reacts with many kinds of thiols other than glutathione. Ebselen may affect the thioredoxin systems, through which it may contribute to regulation of cell function. With high reactivity toward thiols, hydroperoxides, and peroxynitrite, ebselen has been used as a useful tool in research on cellular redox mechanisms. Unlike α-tocopherol, ebselen does not scavenge lipid peroxyl radicals, which is another advantage of ebselen for use as a research tool in comparison with radical scavenging antioxidants. Selenium is not released from the ebselen molecule, which explains the low toxicity of ebselen. To further understand the mechanism of cellular redox biology, it should be interesting to compare the effects of ebselen with that of selenoprotein P, which supplies selenium to GPx. New medical applications of ebselen as a drug candidate for human diseases such as cancer and diabetes mellitus as well as brain stroke and ischemia will be expected.