α-Tocopherol is the active form of vitamin E. It functions as an hydroperoxyl radical scavenger and protects the organism from oxidative damage. α-Tocopherol plays a crucial role in cell signalling and regulating immune responses. α-Tocopherol deficiency is associated with abetalipoproteinemia, cystic fibrosis and celiac disease. It has antiproliferative effects. It inhibits arsenite-induced damage of human fibroblasts.

α-Tocopherol has been used:

• as a standard to determine its concentration by reverse-phase high-performance liquid chromatography
• to study its rescue effects on chlorine dioxide (ClO₂) cytotoxicity
• to assess its protective effects on acetaminophen (APAP)-mediated liver damage

Tocopherols (TCP) (vitamin E) are a series (α, β, γ and δ) of chiral organic molecules that vary in their degree of methylation of the phenol moiety of the chromanol ring. Tocopherols are lipid soluble anti-oxidants that protect cell membranes from oxidative damage. α-Tocopherol is the form of tocopherol preferentially absorbed by homo sapiens. Various isofroms and analogues of tocopherol have opposing and differentiated regulatory activities in vivo.