ABSTRACT
Vitamin E, a known antioxidant and commonly used dietary supplement, occurs naturally in eight different forms: α, β, γ and δ tocopherols and α, β, γ and δ tocotrienols. These differ in the saturation of their side chains and the number and position of methyl groups around the chromanol head structure. Both tocopherols and tocotrienols share this chromanol ring, but tocopherols have a completely saturated phytol tail side chain whereas tocotrienols have double bonds at the 3’, 7’ and 11’ positions of the tail (Figure 24.1) (Kamat et al. 1997; Saito et al. 2003). The Greek letter designates the position at which methyl groups are located on the ring. The most biologically active form of vitamin E is considered to be α-tocopherol, due to its relatively slow metabolism and consequent high bioavailability (Brigelius-Flohe and Traber, 1999). α-tocopherol also has the highest level of antioxidant activity among the vitamins E (Brigelius-Flohe and Traber, 1999).
