Vitamin E consists of two families of compounds, the tocopherols and tocotrienols,
characterised by a 6-chromanol ring and an isoprenoid side chain. The members of each
family are designated alpha((
α)-, beta(β)-, gamma(γ)-, or delta(δ)- according to the
position of methyl groups attached to the chroman nucleus. Therefore, 8 stereoisomers
of the large vitamin E family are possible but only the RRR-form occurs naturally.
Tocopherols and tocotrienols are differentiated by their phenyl “tails” as these are
saturated in the tocopherols but unsaturated in the tocotrienols (Combs, 1992).