Chemistry:α-Tocopheryl acetate
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| Preferred IUPAC name
(2R)-2,5,7,8-Tetramethyl-2-[(4R,8R)-4,8,12-trimethyltridecyl]-3,4-dihydro-2H-1-benzopyran-6-yl acetate | |
| Other names
α-Tocopherol acetate
Vitamin E acetate | |
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| 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] |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
 verify (what is   ?)
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| Infobox references | |
α-Tocopheryl acetate (alpha-tocopherol acetate), also known as vitamin E acetate, is a form of vitamin E with D-Alpha Tocpheryl Acetate as the natural form and DL-Alpha Tocopheryl Acetate as the synthetic form. DL-indicates the synthetic form where as D- indicates the natural form. 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] Vaporization of this ester produces toxic pyrolysis products.[6]
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.[7] 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.[8] Tocopheryl acetate was first synthesized in 1963 by workers at Hoffmann-La Roche.[9]
Although there is widespread use of tocopheryl acetate as a topical medication, with claims for improved wound healing and reduced scar tissue,[10] reviews have repeatedly concluded that there is insufficient evidence to support these claims.[11][12] 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.[13]
Misuse
Ingredient in vape liquids
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 the recent vaping-related lung disease outbreak in the United States, tested positive for vitamin E acetate[14] which had been used as a thickening agent by illicit THC vape cartridge manufacturers.[15] 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.[6]
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 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
- ↑ 1.0 1.1 1.2 1.3 1.4 The Merck index (12th ed.). Merck. 1996. pp. 1580. ISBN 9780911910124.
- ↑ 2.0 2.1 2.2 2.3 2.4 "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.
- ↑ 3.0 3.1 3.2 "Transcript of CDC Telebriefing: Update on Lung Injury Associated with E-cigarette Use, or Vaping". Centers for Disease Control and Prevention. November 8, 2019. https://www.cdc.gov/media/releases/2019/t1108-telebriefing-vaping.html.
This article incorporates text from this source, which is in the public domain.
- ↑ 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.
- ↑ 5.0 5.1 "Outbreak of Lung Injury Associated with E-Cigarette Use, or Vaping". Centers for Disease Control and Prevention. November 8, 2019. https://www.cdc.gov/tobacco/basic_information/e-cigarettes/severe-lung-disease.html. This article incorporates text from this source, which is in the public domain.
- ↑ 6.0 6.1 Wu, D; O'Shea, DF (March 24, 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. PMID 32156732. Bibcode: 2020PNAS..117.6349W.
- ↑
- ↑ "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. 1995. doi:10.1016/1011-1344(95)90251-1. PMID 7472802.
- ↑ 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.
- ↑ "Topical alpha-tocopherol acetate in the bulk phase: eight years of experience in skin treatment". Ann. N. Y. Acad. Sci. 1031 (1): 443–447. 2004. doi:10.1196/annals.1331.069. PMID 15753192. Bibcode: 2004NYASA1031..443P.
- ↑ "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. 2015. doi:10.1007/s00403-015-1572-0. PMID 26044054.
- ↑ "The Role of Topical Vitamin E in Scar Management: A Systematic Review". Aesthet Surg J 36 (8): 959–965. 2016. doi:10.1093/asj/sjw046. PMID 26977069.
- ↑ "Vitamin E and allergic contact dermatitis". Dermatitis 21 (3): 148–153. 2010. doi:10.2310/6620.2010.09083. PMID 20487657.
- ↑ Sun, Lena (September 6, 2019). "Contaminant found in marijuana vaping products linked to deadly lung illnesses, tests show" (in en). Washington Post. https://www.washingtonpost.com/health/2019/09/05/contaminant-found-vaping-products-linked-deadly-lung-illnesses-state-federal-labs-show/.
- ↑ "Three Companies Subpoenaed in Weed Vape Illness Investigation" (in en). Rolling Stone. September 10, 2019. https://www.rollingstone.com/culture/culture-features/vaping-honey-cut-mystery-thickener-vitamin-e-acetate-vapes-881896/.
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