The synthesis of Vitamin E and other tocochromanols in plants

The synthesis of tocochromanols by plants is of major importance in human nutrition as the biosynthesis is responsible for vitamin E. There are two major classes of tocochromanols each of which have four different forms:

1. Tocopherols - a, b, g, d
2. Tocotrienols - a, b, g, d

Of these it is a-tocopherol that has the most vitamin E activity; a-tocotrienol, b-tocopherol also have vitamin E activity, but at about 25 to 50% of that of a-tocopherols. g-tocopherol has even less (~15%) vitamin E activity. The others have 3% or less activity.

Structure of Tocochromanol

All tocochromanols are amphipathic in nature. The creation of the polar head of the molecule can be traced back to the metabolism of amino acids, whereas the tail of the tocochromonals cis created from phytyl-diphosphate (tocopherols) or geranylgeranyl diphosphate (tocotrienols). The four main types of each tocochromanol are a result of differing quantities or positions of methyl groups on the aromatic ring.

The use of vitamin E in the body

Although all tocochromanols have biological activity, from a nutritional point of view it is the a-tocopherol that are of the greatest importance as the body is able to make more efficient use of this form of vitamin E. Once in the body vitamin E can act as an antioxidant and therefore has a role to play in the reduction of free radicals; this helps to protect against damage to DNA, and in turn helps to protect against the risk of getting many cancers.

The use of vitamin E in plants

In plants the elimination of vitamin E (tocochromanols) is not lethal. It has been shown to play a role in the protection of seed storage lipids.

The next section on the Synthesis of vitamins in plants takes a look at the tocochromanol pathway.