AKA: Vitamin E
Tocopheryl Acetate is an esterified form of vitamin E (or Tocopherol).
Tocopherol is a fantastic antioxidant in its primary form and serves an important function as the main oil-soluble antioxidant for skin cells. It works closely with vitamin C to protect the skin from oxidative stress. You can read more about vitamin E here: Tocopherol. Tocopheryl Acetate is a yellow, oily liquid that has been chemically modified to be more stable in skincare formulations than regular Tocopherol. Many beneficial antioxidants are prone to oxidation when exposed to air or light, and so manufacturers often prefer the stabilized versions.
Studies on mice, rats, and human skin samples have shown that Tocopheryl Acetate gets readily absorbed into the skin, where it very slowly gets converted to regular vitamin E. We can thus safely assume that it will give us the same (although slightly slowed down) antioxidant benefits as Tocopherol.
In other studies, Tocopheryl Acetate displayed protective properties against UV-induced skin wrinkling and was able to repair UV-induced DNA and lipid damage.