Retinyl acetate

{{Chembox

| ImageFile = Retinyl acetate.svg

| ImageSize = 200px

| IUPACName = (2E,4E,6E,8E)-3,7-Dimethyl-9-(2,6,6-trimethylcyclohex-1-en-1-yl)nona-2,4,6,8-tetraen-1-yl acetate

| OtherNames = Retinol acetate; Vitamin A acetate; Vitamin A₁ acetate; Acetylretinol; all-trans-Retinol acetate; all-trans-Retinyl acetate; all-trans-Vitamin A acetate;

|Section1={{Chembox Identifiers

| CASNo = 127-47-9

| CASNo_Ref = {{cascite|correct|}}

| Beilstein = 1915439

| ChEBI = 32095

| ChEMBL = 486193

| PubChem = 638034

| ChemSpiderID = 553599

| EC_number = 204-844-2

| KEGG = D01621

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 3LE3D9D6OY

| SMILES = O=C(OC/C=C(/C=C/C=C(/C=C/C1=C(/CCCC1(C)C)C)C)C)C

| InChI = 1/C22H32O2/c1-17(9-7-10-18(2)14-16-24-20(4)23)12-13-21-19(3)11-8-15-22(21,5)6/h7,9-10,12-14H,8,11,15-16H2,1-6H3/b10-7+,13-12+,17-9+,18-14+

| InChIKey = QGNJRVVDBSJHIZ-QHLGVNSIBE

| StdInChI = 1S/C22H32O2/c1-17(9-7-10-18(2)14-16-24-20(4)23)12-13-21-19(3)11-8-15-22(21,5)6/h7,9-10,12-14H,8,11,15-16H2,1-6H3/b10-7+,13-12+,17-9+,18-14+

| StdInChIKey = QGNJRVVDBSJHIZ-QHLGVNSISA-N

}}

|Section2={{Chembox Properties

| C=22|H=32|O=2

| Appearance =

| Density =

| MeltingPtC = 57 to 58

| MeltingPt_ref = [http://www.sigmaaldrich.com/catalog/product/sigma/r4632?lang=en®ion=US Retinyl acetate] from Sigma-Aldrich

| BoilingPtC =

| Solubility =

}}

|Section3={{Chembox Hazards

| NFPA-H = 1

| NFPA-F = 1

| NFPA-R = 0

| MainHazards =

| FlashPt =

| AutoignitionPt =

| GHSPictograms = {{GHS07}}{{GHS08}}

| GHSSignalWord = Warning

| HPhrases = {{H-phrases|315|361|413}}

| PPhrases = {{P-phrases|201|202|264|273|280|281|302+352|308+313|321|332+313|362|405|501}}

}}

Retinyl acetate (also called vitamin A acetate or all‑trans‑retinol acetate) is a synthetic, fat‑soluble retinyl ester often used to supply vitamin A in food fortification, dietary supplements, and topical cosmetic products.{{cite encyclopedia |year=2014 |title=Vitamin A |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |publisher=Wiley‑VCH |doi=10.1002/14356007.a27_381.pub2 |author=Rutter W, Sommer S|doi-broken-date=6 May 2025 }}{{cite web |date=12 January 2025 |title=Vitamin A – Fact Sheet for Health Professionals |url=https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional |access-date=5 May 2025 |publisher=National Institutes of Health, Office of Dietary Supplements}}

Because the acetyl group protects the alcohol functionality, the compound is markedly more stable to heat, oxygen and light than free retinol, yet is rapidly hydrolyzed in the human intestine to active retinol after ingestion.{{cite journal |last1=O'Byrne |first1=S M |last2=Blaner |first2=W S |year=2013 |title=Retinol and retinyl esters: biochemistry and physiology |journal=Journal of Lipid Research |volume=54 |issue=7 |pages=1731–1743 |doi=10.1194/jlr.R037648|doi-access=free |pmc=3679378 }}

Commercially, retinyl acetate is the second most common retinyl ester after retinyl palmitate.

Chemical structure and properties

Retinyl acetate is the acetate ester of all‑trans‑retinol. Its polyene side chain makes the molecule highly lipophilic and sensitive to photo‑oxidation; antioxidants (e.g., tocopherol) and opaque packaging are therefore used to limit degradation in finished products.

The compound melts at ~59 °C and is practically insoluble in water but miscible with edible oils and most organic solvents.{{cite web |title=Retinyl acetate |url=https://pubchem.ncbi.nlm.nih.gov/compound/445354 |access-date=5 May 2025 |website=PubChem |publisher=National Center for Biotechnology Information}}

Metabolism and biochemistry

Dietary retinyl acetate is hydrolyzed in the intestinal lumen by pancreatic triglyceride lipase and by brush‑border phospholipase B, releasing free retinol. The retinol is absorbed, re‑esterified mainly with long‑chain fatty acids by lecithin‑retinol acyltransferase (LRAT) inside enterocytes, and secreted in chylomicrons to the liver, where 50–80 % of total‑body vitamin A is stored as retinyl palmitate in hepatic stellate cells. Mobilization of these stores releases retinol bound to retinol‑binding protein 4 (RBP4) for delivery to peripheral tissues.

Industrial production and stability

Large‑scale vitamin A manufacture couples a C15 β‑ionone fragment with a C5 acetate side chain via a series of Wittig‑Horner and Grignard reactions, followed by final esterification or trans‑esterification to retinyl acetate. Modern processes achieve >95 % all‑trans selectivity and include crystallization or column purification under nitrogen to minimize isomerization.

Applications

= Food fortification =

The United States Food and Drug Administration lists retinyl acetate as "Generally Recognized as Safe" (GRAS) for use as a nutrient supplement in foods (21 CFR 184.1930).{{cite web |title=21 CFR § 184.1930 – Vitamin A |url=https://www.ecfr.gov/current/title-21/section-184.1930 |access-date=5 May 2025 |publisher=U.S. Food and Drug Administration}}

It is commonly added to margarine, plant‑based milk, breakfast cereals and staple oils in low‑ and middle‑income countries to prevent vitamin A deficiency.{{cite book |title=Guidelines on Food Fortification with Micronutrients |publisher=World Health Organization & Food and Agriculture Organization |year=2006 |location=Geneva |pages=31–54 |chapter=Vitamin A}}

= Dietary supplements =

Multivitamin tablets typically supply 600–900 μg retinol activity equivalents (RAE) from retinyl acetate or retinyl palmitate. The U.S. National Institutes of Health sets a Tolerable Upper Intake Level (UL) of 3 000 μg RAE day⁻¹ for adults.

= Cosmetics =

Retinyl acetate is used in "anti‑aging" skin‑care formulations as a milder, more photo‑stable alternative to retinol. The EU Scientific Committee on Consumer Safety (SCCS) concluded in 2017, and reaffirmed in 2023, that leave‑on products are safe at concentrations providing up to 0.3 % retinol equivalents, while body lotions for children aged 1–3 years should not exceed 0.05 % retinol equivalents.{{cite report |url=https://health.ec.europa.eu/system/files/2021-07/sccs_o_191_0.pdf |title=Opinion on Vitamin A (Retinol, Retinyl Palmitate and Retinyl Acetate) in cosmetic products |date=6 October 2017 |pages=1–55 |access-date=5 May 2025 |institution=Scientific Committee on Consumer Safety |id=SCCS/1584/17}}

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Safety and toxicity

Excess pre‑formed vitamin A from supplements or fortified foods can cause hypervitaminosis A, characterized acutely by nausea and raised intracranial pressure and chronically by liver injury and teratogenicity.

Retinyl acetate shares these dose‑dependent toxicities because it is quantitatively hydrolyzed to retinol. Phototoxicity and photo‑isomerization are significantly lower than for unesterified retinol but can occur in formulations lacking UV stabilizers.{{cite journal |year=2015 |title=Scientific opinion on Dietary Reference Values for vitamin A |journal=EFSA Journal |publisher=European Food Safety Authority |volume=13 |issue=3 |pages=4012 |doi=10.2903/j.efsa.2015.4012|doi-access=free }}

Regulation

United States: GRAS nutrient supplement (21 CFR 184.1930); dietary‑supplement labelling expresses content in μg RAE or International Units.

European Union: Permitted as vitamin A source in fortified foods under Regulation (EC) 1925/2006; cosmetic concentrations limited as per SCCS opinion.