Vitamin E: CHEMISTRY

Vitamin E is a family of homologues

R₁=CH₃, R₂= CH₃ α
R₁=CH₃, R₂= H β
R₁=H, R₂= CH₃ γ
R₁=H, R₂= CH₃ δ

All the 8 forms of vitamin E exist i vegetable food.
In food production, the form α-tocopherolacetate or other ester-compounds is preferred.

Measurement of activity of vitamin E
Rat fetal resorption

Diet without vitamin E

Amount of fetus indicates vitamin E activity.

Stereoisomers
Natural alpha-tocopherol is the RRR-alpha (or ddd-alpha) form. The synthetic dl,dl,dl-alpha ("dl-alpha") form is not as active as the natural ddd-alpha ("d-alpha") tocopherol form. This is mainly due to reduced vitamin activity of the 4 possible stereoisomers which are represented by the l or S enantiomer at the first stereocenter (an S or l configuration between the chromanol ring and the
tail, i.e., the SRR, SRS, SSR, and SSS stereoisomers). The 3 unnatural "2R" stereoisomers with natural R configuration at this 2' stereocenter, but S at one of the other centers in the tail (i.e., RSR, RRS, RSS).

Biological activity of stereoisomers, where RRR is set to 100 %
Fetal rat resorption:
RRR: 100 %
RRS: 90 %
RSS: 73 %
SSS: 60 %
RSR: 57 %
SRS: 37 %
SRR: 31 %
SSR: 21 %