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α-Tocopherol[1]
Tocopherol, alpha-.svg
IUPAC name
Identifiers
CAS number 59-02-9 Yes check.svgY
PubChem 14985
EC number 200-412-2
SMILES
InChI
InChI key GVJHHUAWPYXKBD-IEOSBIPEBS
ChemSpider ID 14265
Properties
Molecular formula C29H50O2
Molar mass 430.71 g/mol
Density 0.950 g/cm³
Melting point

2.5-3.5 °C

Boiling point

200-220 °C at 0.1 mmHg

 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

α-Tocopherol is a type of tocopherol with formula C29H50O2. It has E number "E307".

α-Tocopherol is a form of vitamin E that is preferentially absorbed and accumulated in humans.[2] The measurement of "vitamin E" activity in international units (IU) was based on fertility enhancement by the prevention of spontaneous abortions in pregnant rats relative to alpha-tocopherol.

There are three stereocenters in alpha-tocopherol, so this is a chiral molecule.[3] The eight stereoisomers of alpha-tocopherol differ in the arrangement of groups around these stereocenters. In the image of RRR-alpha-tocopherol below, all three stereocenters are in the R form. However, if the middle of the three stereocenters were changed (so the hydrogen was now pointing down and the methyl group pointing up), this would become the structure of RSR-alpha-tocopherol. RSR-alpha-tocopherol and RRR-alpha-tocopherol are diastereomers of each other. These stereoisomers can also be named in an alternative older nomenclature, where the stereocenters are either in the d or l form.[4]

1 IU of tocopherol is defined as ⅔ milligrams of RRR-alpha-tocopherol (formerly named d-alpha-tocopherol or sometimes ddd-alpha-tocopherol). 1 IU is also defined as 1 milligram of an equal mix of the eight stereoisomers, which is a racemic mixture called all-rac-alpha-tocopheryl acetate. This mix of stereoisomers is often called dl-alpha-tocopheryl acetate, even though it is more precisely dl,dl,dl-alpha-tocopheryl acetate). However, 1 IU of this racemic mixture is not now considered equivalent to 1 IU of natural (RRR) α-tocopherol, and the Institute of Medicine and the USDA now convert IU's of the racemic mixture to milligrams of equivalent RRR using 1 IU racemic mixture = 0.45 "milligrams α-tocopherol".[5]

References

  1. ^ Merck Index, 11th Edition, 9931.
  2. ^ Rigotti A (2007). "Absorption, transport, and tissue delivery of vitamin E". Mol. Aspects Med. 28 (5-6): 423–36. doi:10.1016/j.mam.2007.01.002. PMID 17320165.  
  3. ^ Jensen SK, Lauridsen C (2007). "Alpha-tocopherol stereoisomers". Vitam. Horm. 76: 281–308. doi:10.1016/S0083-6729(07)76010-7. PMID 17628178.  
  4. ^ Brigelius-Flohé R, Traber MG (1 July 1999). "Vitamin E: function and metabolism". Faseb J. 13 (10): 1145–55. PMID 10385606. http://www.fasebj.org/cgi/pmidlookup?view=long&pmid=10385606.  
  5. ^ Composition of Foods Raw, Processed, Prepared USDA National Nutrient Database for Standard Reference, Release 20 USDA, February 2008
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