Posted by Larry Hoover on November 10, 2004, at 17:23:02
In reply to different forms of VitE? d dl » Larry Hoover, posted by tealady on November 10, 2004, at 16:09:00
> Hi,
> Just wondering what type of VitE is best to take?
>
> I used to buy d-alpha Tocopherol (500IU), but have noticed a cheaper type in the shops lately dl-alpha Tocopherol?
> Would both types be natural in our body?
> ...and then you said there was 8 isomers :)
> are they all natural in our body?I'm glad for the questions, as you have caught me being sloppy with the science.
There are four tocopherols, alpha-, beta-, gamma-, and delta-. Their names are arbitrary (not related to structure). The alpha is 5,7,8-trimethyltocopherol (also tocol, rather than tocopherol). The other ones have fewer methyl groups. I don't know just how significant those differences are, but there seems to be some fairly substantial evidence that the beta,gamma,delta forms do different things than the alpha does. The strongest evidence is for the gamma, 7-,8-dimethyl form, as an essential antioxidant in its own right.
All these molecules are d-isomers, in the natural form. I think that I got the idea that each of these form also came in l-isomers, but strictly speaking, that's not correct.
The very same naming rules apply to a closely related form of vitamin E called a tocotrienol. There is alpha-, beta- etc. too. So, there are four tocopherols and four tocotrienols.
But it gets real messy when you start talking about the d-,l-alpha tocopherol supplements. There are three chiral centres in the molecule, and there are thus 3² = 8 diasteriomers in synthetic alpha-tocopherol. There are two enantiomers in natural d-,l-alpha tocopherol.
Confused? Try making sense of this: http://www.chem.qmul.ac.uk/iupac/misc/toc.html
Steer clear of synthetic vitamin E. Go for "mixed tocopherols", or check for some gamma-tocopherol on the label, along with the alpha-. I've also seen "mixed tocopherols with tocotrienols", which I suppose would be best.
Phew.
Lar
poster:Larry Hoover
thread:412398
URL: http://www.dr-bob.org/babble/alter/20041108/msgs/414349.html