Stability and reactivity of tocopherols: Theoretical study

Introduction:

Reports indicate that there are conflicting results in clinical studies on the regulation of vitamin E (the α isoform) of allergic inflammation. They also strongly recommend considering the dietary intake of tocopherols because the γ isoform is more abundant in Western diets. On the other hand, the reverse phase HPLC technique does not distinguish between the two isomers β and γ but it has been widely used; as if the majority of vegetable oils were devoid of β-tocopherol.

Computational details:

Structures and stabilities are obtained with DFT and PM3. The natural orbitals of the bonds (NBO) calculations were carried out using the program NBO.

Results and discussion:

Comparison of results in the two media (gaseous and aqueous) permitted the following conclusions:

• The two iso-forms β and γ remain almost the same stability.
• The transfer of electrons takes place in the direction: α < β < γ < δ in the gaseous and aqueous medium.
• A difference in electronegativity for β and γ isoformsis clearly visible.

Our results may contribute to understand the behavior of tocopherols in reaction media, in particular their toxicities.