Tocopheryl acetate

α-Tocopheryl acetate, also known as vitamin E acetate, is a synthetic form of vitamin E. It is the ester of acetic acid and α-tocopherol.[2] The U.S. Centers for Disease Control and Prevention says that vitamin E acetate is a very strong culprit of concern in the 2019 outbreak of vaping-associated pulmonary injury (VAPI),[3] but there is not yet sufficient evidence to rule out contributions from other chemicals.[4][5]

RRR-α-Tocopheryl acetate
Names
IUPAC name
[(2R)-2,5,7,8-Tetramethyl-2-[(4R,8R)-4,8,12-trimethyltridecyl]chroman-6-yl] acetate
Other names
α-Tocopherol acetate
Vitamin E acetate
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.000.369
UNII
Properties
C31H52O3
Molar mass 472.743 g/mol
Appearance pale yellow, viscous liquid[1]
Melting point –27.5 °C [1]
Boiling point 240 °C decays without boiling[2]
insoluble[1]
Solubility soluble in acetone, chloroform, diethyl ether; poorly soluble in ethanol[1]
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).
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Infobox references

Use in cosmetics

α-Tocopheryl acetate is often used in dermatological products such as skin creams. It is not oxidized and can penetrate through the skin to the living cells, where about 5% is converted to free tocopherol. Claims are made for beneficial antioxidant effects.[6] α-Tocopheryl acetate is used as an alternative to tocopherol itself because the phenolic hydroxyl group is blocked, providing a less acidic product with a longer shelf life. It is believed that the acetate is slowly hydrolyzed after it is absorbed into the skin, regenerating tocopherol and providing protection against the sun's ultraviolet rays.[7] Tocopheryl acetate was first synthesized in 1963 by workers at Hoffmann-La Roche.[8]

Although there is widespread use of tocopheryl acetate as a topical medication, with claims for improved wound healing and reduced scar tissue,[9] reviews have repeatedly concluded that there is insufficient evidence to support these claims.[10][11] There are reports of vitamin E-induced allergic contact dermatitis from use of vitamin E derivatives such as tocopheryl linoleate and tocopherol acetate in skin care products. Incidence is low despite widespread use.[12]

Misuse

Ingredient in vape liquids
See also: 2019–20 vaping lung illness outbreak, Vaping-associated pulmonary injury, and Lacing (drugs) § Cannabis

On September 5, 2019, the United States Food and Drug Administration (US FDA) announced that 10 out of 18, or 56% of the samples of vape liquids sent in by states, linked to recent vaping related lung disease outbreak in the United States, tested positive for vitamin E acetate[13] which had been used as a thickening agent by illicit THC vape cartridge manufacturers.[14] On November 8, 2019, the Centers for Disease Control and Prevention (CDC) identified vitamin E acetate as a very strong culprit of concern in the vaping-related illnesses, but has not ruled out other chemicals or toxicants as possible causes.[3] The CDC's findings were based on fluid samples from the lungs of 29 patients with vaping-associated pulmonary injury, which provided direct evidence of vitamin E acetate at the primary site of injury in all the 29 lung fluid samples tested.[3] Research suggests when vitamin E acetate is inhaled, it may interfere with normal lung functioning.[5] A 2020 study found that vaporizing vitamin E acetate produced carcinogenic alkenes and benzene, but also exceptionally toxic ketene gas, which may be a contributing factor to the pulmonary injuries.[15]

Chemistry

At room temperature, α-tocopheryl acetate is a fat-soluble liquid. It has 3 chiral centers and thus 8 stereoisomers. It is made by esterifying α-tocopherol with acetic acid. 2R,4R,8R-isomer, also known as RRR-α-tocopheryl acetate, is the most common isomer used for various purposes. This is because α-tocopherol occurs in the nature primarily as RRR-α-tocopherol.[2]

α-Tocopherol acetate does not boil at atmospheric pressure and begins to degrade at 240 °C.[2] It can be vacuum distilled: it boils at 184 °C at 0.01 mmHg, at 194 °C (0.025 mmHg) and at 224 °C (0.3 mmHg). In practice, it is not degraded notably by air, visible light or UV-radiation. It has a refractive index of 1.4950–1.4972 at 20 °C.[1]

α-Tocopherol acetate is hydrolyzed to α-tocopherol and acetic acid under suitable conditions or when ingested by people.[2]

References
  1. The Merck index (12th ed.). Merck. 1996. p. 1580. ISBN 9780911910124.
  2. "Safety assessment of the substance α-tocopherol acetate for use in food contact materials". EFSA Journal. 14 (3): 4412. 2016. doi:10.2903/j.efsa.2016.4412.
  3. "Transcript of CDC Telebriefing: Update on Lung Injury Associated with E-cigarette Use, or Vaping". Centers for Disease Control and Prevention. 8 November 2019. This article incorporates text from this source, which is in the public domain.
  4. Feldman, Ryan; Meiman, Jonathan; Stanton, Matthew; Gummin, David D. (June 2020). "Culprit or correlate? An application of the Bradford Hill criteria to Vitamin E acetate". Archives of Toxicology. 94 (6): 2249–2254. doi:10.1007/s00204-020-02770-x. ISSN 1432-0738. PMID 32451600.
  5. "Outbreak of Lung Injury Associated with E-Cigarette Use, or Vaping". Centers for Disease Control and Prevention. 8 November 2019. This article incorporates text from this source, which is in the public domain.
  6. Linus Pauling Institute Research Report: All About E at the Wayback Machine (archived February 23, 2015)
  7. Beijersbergen van Henegouwen G, Junginger H, de Vries H (1995). "Hydrolysis of RRR-alpha-tocopheryl acetate (vitamin E acetate) in the skin and its UV protecting activity (an in vivo study with the rat)". J Photochem Photobiol B. 29 (1): 45–51. doi:10.1016/1011-1344(95)90251-1. PMID 7472802.
  8. Mayer, H.; Schudel, P.; Rüegg, R.; Isler, O. (1963). "Über die Chemie des Vitamins E. 3. Mitteilung. Die Totalsynthese von (2R, 4′R, 8′R)- und (2S, 4′R, 8′R)-α-Tocopherol". Helvetica Chimica Acta. 46 (2): 650–671. doi:10.1002/hlca.19630460225. ISSN 0018-019X.
  9. Panin G, Strumia R, Ursini F (2004). "Topical alpha-tocopherol acetate in the bulk phase: eight years of experience in skin treatment". Ann. N. Y. Acad. Sci. 1031: 443–447. Bibcode:2004NYASA1031..443P. doi:10.1196/annals.1331.069. PMID 15753192.
  10. Sidgwick GP, McGeorge D, Bayat A (2015). "A comprehensive evidence-based review on the role of topicals and dressings in the management of skin scarring". Arch. Dermatol. Res. 307 (6): 461–477. doi:10.1007/s00403-015-1572-0. PMC 4506744. PMID 26044054.
  11. Tanaydin V, Conings J, Malyar M, van der Hulst R, van der Lei B (2016). "The Role of Topical Vitamin E in Scar Management: A Systematic Review". Aesthet Surg J. 36 (8): 959–965. doi:10.1093/asj/sjw046. PMID 26977069.
  12. Kosari P, Alikhan A, Sockolov M, Feldman SR (2010). "Vitamin E and allergic contact dermatitis". Dermatitis. 21 (3): 148–153. doi:10.2310/6620.2010.09083. PMID 20487657.
  13. Sun, Lena (September 6, 2019). "Contaminant found in marijuana vaping products linked to deadly lung illnesses, tests show". Washington Post. Retrieved 2019-09-09.
  14. "Three Companies Subpoenaed in Weed Vape Illness Investigation". Rolling Stone. September 10, 2019.
  15. Wu, D; O'Shea, DF (24 March 2020). "Potential for release of pulmonary toxic ketene from vaping pyrolysis of vitamin E acetate". Proceedings of the National Academy of Sciences of the United States of America. 117 (12): 6349–6355. doi:10.1073/pnas.1920925117. PMC 7104367. PMID 32156732.
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