Retinyl palmitate, or vitamin A palmitate, is the ester of retinol (vitamin A) and palmitic acid, with formula C36H60O2. An alternate spelling, retinol palmitate, which violates the -yl organic chemical naming convention for esters, is also frequently seen. Retinyl palmitate is a synthetic alternate for retinyl acetate in vitamin A supplements, and is available in oily or dry forms. It is a common vitamin supplement, available in both oral and injectable forms for treatment of vitamin A deficiency, under the brand names Aquasol A, Palmitate A and many others. It is a constituent of intra ocular treatment for dry eyes at a concentration of 138 µg/g (VitA-Pos) by Ursapharm. It is a pre-formed version of vitamin A; therefore, the intake should not exceed the Recommended Dietary Allowance (RDA). Overdosing preformed Vitamin A forms such as retinyl palmitate leads to adverse physiological reactions (hypervitaminosis A). Retinyl palmitate is used as an antioxidant and a source of vitamin A added to low fat milk and other dairy products to replace the vitamin content lost through the removal of milk fat.
Palmitate is attached to the alcohol form of vitamin A, retinol, in order to make vitamin A stable in milk. Retinyl palmitate is also a constituent of some topically applied skin care products. After its absorption into the skin, retinyl palmitate is converted to retinol, and ultimately to retinoic acid (the active form of vitamin A present in Retin-A). The Environmental Working Group (EWG) and New York Senator Chuck Schumer have called attention to the fact that high doses of topical retinyl palmitate were shown to accelerate cancer in lab animals,[2] fueling the sunscreen controversy in the popular press.[3] One toxicological analysis determined that "there is no convincing evidence to support the notion that [retinyl palmitate] in sunscreens is carcinogenic."[4] EWG disputed the findings, calling the report "faulty" and "misleading."[5] A technical report issued thereafter by the National Toxicology Program concluded that diisopropyl adipate increased incidence of skin tumors in mice, and the addition of either retinoic acid or retinyl palmitate both exacerbated the rate and frequency of tumors.
World Health Organization recommendation on Maternal Supplementation During Pregnancy states that "health benefits are expected for the mother and her developing fetus with little risk of detriment to either, from a daily supplement not exceeding 10,000 IU [preformed] vitamin A (3000 µg RE) at any time during pregnancy."[7] Preformed Vitamin A refers to retinyl palmitate and retinyl acetate. ^ Vitamin A, Linus Pauling Institute ^ National Toxicology Program. (2012). NTP technical report on the photocarcinogenesis study of retinoic acid and retinyl palmitate [CAS Nos. 302-79-4 (All-trans-retinoic acid) and 79-81-2 (All-trans-retinyl palmitate)] in SKH-1 mice (Simulated solar light and topical application study). Accessed September 19, 2013.The file you have requested, "/cgi/cbook.cgi?ID=79-81-2" is not available on this server.message Invalid path was requesteddescription The requested resource (Invalid path was requested) is not available.IdentificationTaxonomyOntologyPhysical propertiesSpectraBiological propertiesConcentrationsLinksReferencesenzymes (4) Show 4 proteinsXML Enzyme Details1.
Diacylglycerol O-acyltransferase 1General function:Involved in diacylglycerol O-acyltransferase activitySpecific function:Catalyzes the terminal and only committed step in triacylglycerol synthesis by using diacylglycerol and fatty acyl CoA as substrates. In contrast to DGAT2 it is not essential for survival. May be involved in VLDL (very low density lipoprotein) assembly. In liver, plays a role in esterifying exogenous fatty acids to glycerol. Functions as the major acyl-CoA retinol acyltransferase (ARAT) in the skin, where it acts to maintain retinoid homeostasis and prevent retinoid toxicity leading to skin and hair disorders. Gene Name:DGAT1Uniprot ID:O75907 Molecular weight:55277.735Reactionshexadecanoyl-CoA + Vitamin A → Coenzyme A + Retinyl palmitatedetails Enzyme Details2. Lecithin retinol acyltransferaseGeneral function:Involved in phosphatidylcholine-retinol O-acyltransferaSpecific function:Transfers the acyl group from the sn-1 position of phosphatidylcholine to all-trans retinol, producing all-trans retinyl esters.
Retinyl esters are storage forms of vitamin A. LRAT plays a critical role in vision. It provides the all-trans retinyl ester substrates for the isomerohydrolase which processes the esters into 11-cis-retinol in the retinal pigment epithelium; due to a membrane-associated alcohol dehydrogenase, 11 cis-retinol is oxidized and converted into 11-cis-retinaldehyde which is the chromophore for rhodopsin and the cone photopigments. Gene Name:LRATUniprot ID:O95237 Molecular weight:25702.635 Enzyme Details3. Acyl-CoA wax alcohol acyltransferase 1General function:Involved in transferase activity, transferring acyl groups other than amino-acyl groupsSpecific function:Acyltransferase that predominantly esterify long chain (wax) alcohols with acyl-CoA-derived fatty acids to produce wax esters. Wax esters are enriched in sebum, suggesting that it plays a central role in lipid metabolism in skin. Has a preference for arachidyl alcohol as well as decyl alcohol, demonstrating its relatively poor activity using saturated long chain alcohols (C16, C18, and C20).
Gene Name:AWAT1Uniprot ID:Q58HT5 Molecular weight:37758.815 Enzyme Details4. Acyl-CoA wax alcohol acyltransferase 2General function:Involved in transferase activity, transferring acyl groups other than amino-acyl groupsSpecific function:Acyltransferase that predominantly esterify long chain (wax) alcohols with acyl-CoA-derived fatty acids to produce wax esters. Has no activity using decyl alcohol and significantly prefers the C16 and C18 alcohols. May also have 2-acylglycerol O-acyltransferase (MGAT) and acyl-CoA:retinol acyltransferase (ARAT) activities, to catalyze the synthesis of diacylglycerols and retinyl esters; however this activity is unclear in vivo. Gene Name:AWAT2Uniprot ID:Q6E213 Molecular weight:38093.25Reactionshexadecanoyl-CoA + Vitamin A → Coenzyme A + Retinyl palmitatedetailsJ AOAC Int. 2013 Nov-Dec;96(6):1407-13.Thompson LB, Schimpf K, Baugh S.AbstractThe method presented is for quantification of alpha-tocopherol (vitamin E), vitamin E acetate, vitamin A acetate, and vitamin A palmitate in infant formula and adult/pediatric nutritionals.
The entire lipid fraction, including vitamins A and E, is extracted from product with iso-octane after products are mixed with methanol, which precipitates proteins and disrupts micelles freeing lipids for extraction. Vitamin A palmitate, vitamin A acetate, and vitamin E acetate are separated from alpha-tocopherol on a 3 cm silica column with a 1% methylene chloride, 0.06% isopropanol in iso-octane mobile phase; eluted onto a 20 cm silica column; and, after a column switch, further separated on the 20 cm column before UV detection at 325 nm (vitamin A palmitate and vitamin A acetate) and 285 nm (vitamin E acetate). Alpha-Tocopherol is further separated from other extraneous compounds on the 3 cm silica column and detected by fluorescence at excitation and emission wavelengths of 295 and 330 nm, respectively. Quantification limits in ready-to-feed products were estimated to be 80 IU/L for vitamin A palmitate, 207 International Units (IU)/L for vitamin A acetate, 2.4 mg/L for vitamin E acetate, and < 0.15 mg/L for alpha-tocopherol.
Over-spike recoveries and intermediate precision averaged 100.4 and 2.09% RSD for vitamin A palmitate, 100.4 and 1.52% RSD for vitamin E acetate, and 99.6 and 3.02% RSD for alpha-tocopherol. Vitamin A acetate spike recovery data averaged 96.6%, and the intermediate precision for the only product fortified with vitamin A acetate was 2.75% RSD.PMID: 24645522 [Indexed for MEDLINE] MeSH termsAcetates/analysisAdultChromatography, High Pressure Liquid/methods*Chromatography, Liquid/methodsEquipment DesignFood, Formulated/analysis*HumansInfantInfant Formula/chemistry*Lipids/chemistryPowdersReproducibility of ResultsSpectrometry, Fluorescence/methods*Spectrophotometry, Ultraviolet/methods*Vitamin A/analogs & derivativesVitamin A/analysis*Vitamin E/analysis*alpha-Tocopherol/analysisSubstancesAcetatesLipidsPowdersVitamin AVitamin Eretinol palmitateretinol acetatealpha-TocopherolFull Text SourcesIngenta plcMedicalInfant and Newborn Nutrition - MedlinePlus Health InformationVitamin A - MedlinePlus Health InformationVitamin E - MedlinePlus Health InformationMiscellaneousVITAMIN A - Hazardous Substances Data BankVITAMIN E - Hazardous Substances Data Bank