Eight different isomeric forms of vitamin E (4 tocopherols and 4 tocotrienols) have been found in nature. Tocotrienols (α, β, γ and δ) are identical in structure to tocopherols except for the degree of saturation in their side chain. However, α-tocopherol is considered to be the most active form of vitamin E in humans. It has been found that the concentrations of vitamin E isomers in human feces are higher than in plasma – possibly due to its limited absorption from the diet, suggesting that it could play a protective role against RONS produced in the GI tract (Halliwell.
