Α-Tocopherol

α-Tocopherol (alpha-tocopherol) is a type of vitamin E. Its E number is "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, along with an aromatic ring is situated near the carbonyls in the fatty acyl chains of the phospholipid bilayer, allows for penetration into biological membranes.^[2] It is found most in the membrane's non-raft domains, associated with omega-3 and 6 fatty acids, to partially prevent oxidation.^[3] The most prevalent form, α-tocopherol, is involved in molecular, cellular, biochemical processes closely related to overall lipoprotein and lipid homeostasis. Compared to the others, α-tocopherol is preferentially absorbed and accumulated in humans.

α-Tocopherol^[1]

Names
Preferred IUPAC name (2R)-2,5,7,8-Tetramethyl-2-[(4R,8R)-4,8,12-trimethyltridecyl]-3,4-dihydro-2H-1-benzopyran-6-ol
Identifiers
CAS Number	59-02-9 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:18145 Y
ChEMBL	ChEMBL47 Y
ChemSpider	14265 Y
DrugBank	DB00163 Y
ECHA InfoCard	100.000.375
EC Number	200-412-2
E number	E307a (antioxidants, ...)
PubChem CID	14985
UNII	N9PR3490H9 Y
CompTox Dashboard (EPA)	DTXSID0026339
InChI InChI=1S/C29H50O2/c1-20(2)12-9-13-21(3)14-10-15-22(4)16-11-18-29(8)19-17-26-25(7)27(30)23(5)24(6)28(26)31-29/h20-22,30H,9-19H2,1-8H3/t21-,22-,29-/m1/s1 Y Key: GVJHHUAWPYXKBD-IEOSBIPESA-N Y InChI=1/C29H50O2/c1-20(2)12-9-13-21(3)14-10-15-22(4)16-11-18-29(8)19-17-26-25(7)27(30)23(5)24(6)28(26)31-29/h20-22,30H,9-19H2,1-8H3/t21-,22-,29-/m1/s1 Key: GVJHHUAWPYXKBD-IEOSBIPEBS
SMILES Cc1c(O)c(C)c(CC[C@](CCC[C@@H](CCC[C@@H](CCCC(C)C)C)C)(C)O2)c2c1C
Properties
Chemical formula	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
Solubility in water	insoluble
Solubility	soluble in alcohol, ether, acetone, oils
Pharmacology
ATC code	A11HA03 (WHO)
Hazards
NFPA 704 (fire diamond)	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. Ongoing research is believed to be "critical for manipulation of vitamin E homeostasis in a variety of oxidative stress-related disease conditions in humans."^[4] 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.^[5] A second of these disease conditions is the α-tocopherol antioxidant properties' role cardiovascular heart disease. In preventing LDL (low-density lipoprotein) oxidation, it is able to decrease chances of atherosclerosis and arterial build-up.^[6]

Synthesis

To synthesize the ⍺-diastereomer selectively, tocol acetate is transformed to the naturally occurring, kinetically favored α-tocopherol after being catalyzed by the lipase enzyme. This reaction occurs under biological conditions, commonly in the digestive system.^[7]

Stereoisomers

α-Tocopherol has three stereocenters, so it is a chiral molecule.^[8] The eight stereoisomers of α-tocopherol differ in the configuration of these stereocenters. RRR-α-tocopherol is the natural one.^[9] The older name of RRR-α-tocopherol is d-α-tocopherol, but this d/l naming should no longer be 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.^[10] The α-Tocopherol is the most active diastereomer biologically, while being maintained at a high level in plasma and tissues of many different animal species.^[11]

One IU of tocopherol is defined as 2⁄3 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.^[12] 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.^[13]