alpha-Tocopherol

α-Tocopherol is a type of vitamin E. It has E number "E307". Vitamin E exists in eight different forms, four tocopherols and four tocotrienols. All feature a chromane ring, with a hydroxyl group that can donate a hydrogen atom to reduce free radicals and a hydrophobic side chain which allows for penetration into biological membranes. Compared to the others, α-tocopherol is preferentially absorbed and accumulated in humans.

α-Tocopherol[1]
Names
IUPAC name
(2R)-2,5,7,8-Tetramethyl-2-[(4R,8R)-(4,8,12-trimethyltridecyl)]chroman-6-ol
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.375
EC Number
  • 200-412-2
E number E307a (antioxidants, ...)
UNII
Properties
C29H50O2
Molar mass 430.71 g/mol
Appearance yellow-brown viscous liquid
Density 0.950 g/cm3
Melting point 2.5 to 3.5 °C (36.5 to 38.3 °F; 275.6 to 276.6 K)
Boiling point 200 to 220 °C (392 to 428 °F; 473 to 493 K) at 0.1 mmHg
Pharmacology
A11HA03 (WHO)
Hazards
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
1
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

Vitamin E is found in a variety of tissues, being lipid-soluble, and taken up by the body in a wide variety of ways. The most prevalent form, α-tocopherol, is involved in molecular, cellular, biochemical processes closely related to overall lipoprotein and lipid homeostasis. Ongoing research is believed to be "critical for manipulation of vitamin E homeostasis in a variety of oxidative stress-related disease conditions in humans."[2] One of these disease conditions is the α-tocopherol role in the use by malaria parasites to protect themselves from the highly oxidative environment in erythrocytes.[3]

Stereoisomers

α-Tocopherol has three stereocenters, so it is a chiral molecule.[4] The eight stereoisomers of α-tocopherol differ in the configuration of these stereocenters. RRR-α-tocopherol is the natural one.[5] The older name of RRR-α-tocopherol is d-α-tocopherol, but this d/l naming should be no longer used, because whether l-α-tocopherol should mean SSS enantiomer or the SRR diastereomer is not clear, from historical reasons. The SRR may be named 2-epi-α-tocopherol, the diastereomeric mixture of RRR-α-tocopherol and 2-epi-α-tocopherol may be called 2-ambo-α-tocopherol (formerly named dl-α-tocopherol). The mixture of all eight diastereomers is called all-rac-α-tocopherol[6]

One IU of tocopherol is defined as ⅔ milligram of RRR-α-tocopherol (formerly named d-α-tocopherol). 1 IU is also defined as 0.9 mg of an equal mix of the eight stereoisomers, which is a racemic mixture, all-rac-α-tocopheryl acetate. This mix of stereoisomers is often called dl-α-tocopheryl acetate.[7] Starting with May 2016, the IU unit is made obsolete, such that 1 mg of "Vitamin E" is 1 mg of d-alpha-tocopherol or 2 mg of dl-alpha-tocopherol.[8]


References
  1. Merck Index, 11th Edition, 9931.
  2. Rigotti A (2007). "Absorption, transport, and tissue delivery of vitamin E". Molecular Aspects of Medicine. 28 (5–6): 423–36. doi:10.1016/j.mam.2007.01.002. PMID 17320165.
  3. Shichiri M, Ishida N, Hagihara Y, Yoshida Y, Kume A, Suzuki H (2019). "Probucol induces the generation of lipid peroxidation products in erythrocytes and plasma of male cynomolgus macaques". Journal of Clinical Biochemistry and Nutrition. 64 (2): 129–142. doi:10.3164/jcbn.18-7. PMC 6436040. PMID 30936625.
  4. Jensen SK, Lauridsen C (2007). "Alpha-tocopherol stereoisomers". Vitamins and Hormones. 76: 281–308. doi:10.1016/S0083-6729(07)76010-7. PMID 17628178.
  5. Brigelius-Flohé R, Traber MG (July 1999). "Vitamin E: function and metabolism". FASEB Journal. 13 (10): 1145–55. doi:10.1096/fasebj.13.10.1145. PMID 10385606.
  6. IUPAC Nomenclature of Tocopherols and Related Compounds
  7. "Composition of Foods Raw, Processed, Prepared USDA National Nutrient Database for Standard Reference, Release 20" (PDF). USDA. February 2008. Archived from the original (PDF) on 2012-02-19.
  8. "Unit Conversions". National Institutes of Health. Retrieved 2018-11-21.
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