This article is a review of the fundamental chemistry of the tocophero
ls and tocotrienols relevant to their antioxidant action. Despite the
general agreement that a-tocopherol is the most efficient antioxidant
and vitamin E homologue in vivo, there was always a considerable discr
epancy in its ''absolute'' and ''relative'' antioxidant effectiveness
in vitro, especially when compared to gamma-tocopherol. Many chemical,
physical, biochemical, physicochemical, and other factors seem respon
sible for the observed discrepancy between the relative antioxidant po
tencies of the tocopherols in vivo and in vitro. This paper aims at hi
ghlighting some possible reasons for the observed differences between
the tocopherols (alpha-, beta-, gamma-, and delta) in relation to thei
r interactions with the important chemical species involved in lipid p
eroxidation, specifically trace metal ions, singlet oxygen, nitrogen o
xides, and antioxidant synergists. Although literature reports related
to the chemistry of the tocotrienols are quite meager, they also were
included in the discussion in virtue of their structural and function
al resemblance to the tocopherols.