Editing Tocopherol (section)

==Supplements==
Commercial vitamin E supplements may be classified into several distinct categories:
* Fully synthetic vitamin E, "dl-α-tocopherol", the most inexpensive, most commonly sold supplement form usually as the acetate ester
* Semi-synthetic "natural source" vitamin E esters, the "natural source" forms used in tablets and multiple vitamins; these are highly fractionated d-α-tocopherol or its esters, often made by synthetic methylation of gamma and beta {{chem name|d,d,d tocopherol}} vitamers extracted from plant oils.
* Less fractionated "natural mixed tocopherols" and high d-γ-tocopherol fraction supplements

===Synthetic all-racemic===
Synthetic vitamin E derived from petroleum products is manufactured as all-[[racemic]] α-tocopheryl acetate with a mixture of eight stereoisomers. In this mixture, one α-tocopherol molecule in eight molecules are in the form of ''RRR''-α-tocopherol (12.5% of the total).<ref>{{cite journal | vauthors = Weiser H, Riss G, Kormann AW | title = Biodiscrimination of the eight α-tocopherol stereoisomers results in preferential accumulation of the four 2R forms in tissues and plasma of rats | journal = The Journal of Nutrition | volume = 126 | issue = 10 | pages = 2539–49 | date = October 1996 | pmid = 8857515 | doi = 10.1093/jn/126.10.2539 | doi-access = free }}</ref>

The 8-isomer ''all-rac'' vitamin E is always marked on labels simply as '''dl-tocopherol''' or '''dl-tocopheryl acetate''', even though it is (if fully written out) {{chem name|dl,dl,dl-tocopherol}}. The present largest manufacturers of this type are [[DSM (company)|DSM]] and [[BASF]].

Natural α-tocopherol is the RRR-α (or ddd-α) form. The synthetic {{chem name|dl,dl,dl-α}} ("dl-α") form is not so active as the natural ddd-α ("d-α") tocopherol form. This is mainly due to reduced vitamin activity of the four possible stereoisomers that are represented by the ''l'' or ''S'' enantiomer at the first stereocenter (an S or l configuration between the chromanol ring and the tail, i.e., the SRR, SRS, SSR, and SSS stereoisomers).<ref name=Jensen>{{cite book |last1=Jensen |first1=S |last2=Lauridsen |first2=C |title=α-Tocopherol Stereoisomers |journal=Vitamins & Hormones |volume=76 |pages=281–308 |year=2007 |doi=10.1016/S0083-6729(07)76010-7 |pmid=17628178|isbn=9780123735928 }}</ref> The three unnatural "2R" stereoisomers with natural R configuration at this 2' stereocenter, but S at one of the other centers in the tail (i.e., RSR, RRS, RSS), appear to retain substantial RRR vitamin activity, because they are recognized by the [[alpha-tocopherol transfer protein]], and thus maintained in the plasma, where the other four stereoisomers (SRR, SRS, SSR, and SSS) are not. Thus, the synthetic all-rac-α-tocopherol, in theory, would have approximately half the vitamin activity of RRR-α-tocopherol in humans. Experimentally, the ratio of activities of the 8 stereoisomer racemic mixture to the natural vitamin, is 1 to 1.36 in the rat pregnancy model (suggesting a measured activity ratio of 1/1.36 = 74% of natural, for the 8-isomer racemic mix).<ref>"Taken together, these data indicate that of the eight stereoisomers (RRR, RSR, RRS, RSS, SRR, SSR, SRS, SSS) in all-rac-α-tocopherol, only the four 2R-forms (RRR, RSR, RSS, RRS) are recognized by α-TTP and maintained in the plasma. Indeed, the Food and Nutrition Board (Food and Nutrition Board and Institute of Medicine, 2000) has defined that only α-tocopherol, specifically the 2R-forms of α-tocopherol, can fulfill the human requirement for vitamin E. Thus, all-rac-α-tocopherol has only half the activity of RRR-α-tocopherol." Taken from the discussion in {{cite journal | vauthors = Lauridsen C, Engel H, Craig AM, Traber MG | title = Relative bioactivity of dietary RRR- and all-rac-α-tocopheryl acetates in swine assessed with deuterium-labeled vitamin E | journal = Journal of Animal Science | volume = 80 | issue = 3 | pages = 702–7 | date = March 2002 | pmid = 11890405 | doi = 10.2527/2002.803702x | url = http://jas.fass.org/cgi/reprint/80/3/702.pdf | access-date = 2008-03-12 | archive-url = https://web.archive.org/web/20081217124036/http://jas.fass.org/cgi/reprint/80/3/702.pdf | url-status = dead | archive-date = 2008-12-17 }}</ref>

Although it is clear that mixtures of stereoisomers are not so active as the natural ''RRR''-α-tocopherol form, in the ratios discussed above, specific information on any side effects of the seven synthetic vitamin E stereoisomers is not readily available.

===Esters===
[[File:Tocopherylacetat.svg|thumb|200px|class=skin-invert-image|α-tocopheryl acetate, an [[acetate]] [[ester]] of α-tocopherol ]]

Manufacturers also commonly convert the phenol form of the vitamins (with a free [[hydroxyl]] group) to [[ester]]s, using acetic or succinic acid. These tocopheryl esters are more stable and are easy to use in vitamin supplements. α-Tocopheryl esters are de-esterified in the gut and then absorbed as the free tocopherol.<ref name=Mathias>{{cite journal | vauthors = Mathias PM, Harries JT, Peters TJ, Muller DP | title = Studies on the in vivo absorption of micellar solutions of tocopherol and tocopheryl acetate in the rat: demonstration and partial characterization of a mucosal esterase localized to the endoplasmic reticulum of the enterocyte | journal = Journal of Lipid Research | volume = 22 | issue = 5 | pages = 829–37 | date = July 1981 | doi = 10.1016/S0022-2275(20)37355-7 | pmid = 7288289 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Ajandouz EH, Castan S, Jakob S, Puigserver A | title = A fast, sensitive HPLC method for the determination of esterase activity on α-tocopheryl acetate | journal = Journal of Chromatographic Science | volume = 44 | issue = 10 | pages = 631–3 | year = 2006 | pmid = 17254374 | doi = 10.1093/chromsci/44.10.631 |doi-access=free}}</ref> [[Tocopheryl nicotinate]], [[tocopheryl linolate]], and [[tocopheryl palmitate]] esters are also used in cosmetics and some pharmaceuticals.

===Mixed tocopherols===
"Mixed tocopherols" in the USA contain at least 20% w/w other natural R, R,R- tocopherols, i.e. R, R,R-α-tocopherol content plus at least 25% R, R,R-β-, R, R,R-γ-, R, R,R-δ-tocopherols.{{Citation needed|date=October 2012}}

Some brands may contain 20.0% w/w or more of the other tocopherols and measurable tocotrienols. Some mixed tocopherols with higher γ-tocopherol content are marketed as "High Gamma-Tocopherol". The label should report each component in milligrams, except R, R,R-α-tocopherol may still be reported in IU. Mixed tocopherols also may be found in other nutritional supplements.{{Citation needed|date=October 2012}}