Retinyl-palmitate

Fig. 1. Vitamin A and derivatives retinol (1), retinyl acetate [127-47-9] (2), retinyl palmitate [79-81-2] (3), and retinyl propionate [7069-42-3] (4).

Property Retinol Retinyl acetate Retinyl palmitate Retinyl propionate o p-carotene... 

Spectroscopic methods such as uv and fluorescence have rehed on the polyene chromophore of vitamin A as a basis for analysis. Indirectly, the classical Carr-Price colorimetric test also exploits this feature and measures the amount of a transient blue complex at 620 nm which is formed when vitamin A is dehydrated in the presence of Lewis acids. For uv measurements of retinol, retinyl acetate, and retinyl palmitate, analysis is done at 325 nm. More sensitive measurements can be obtained by fluorescence. Excitation is done at 325 nm and emission at 470 nm. Although useful, all of these methods suffer from the fact that the method is not specific and any compound which has spectral characteristics similar to vitamin A will assay like the vitamin... 

Retinal (Vitamin A aldehyde). Retinoic acid (Vitamin A acid), Retinyl acetate, Retinyl palmitate see entries in Chapter 4. 

Retinyl Palmitate Topical 0.5-5% Emulsions Cosmetic agents ... 

Cosmetic Ingredient Review (1987) Final report on the safety assessment of retinyl palmitate and retinol. J Am Coll Toxicol 6 279-320... 

Borel, P. et al.. Chylomicron (3-carotene and retinyl palmitate responses are dramatically diminished when men ingest (3-carotene with medinm-chain rather than long-chain triglycerides, J. Nutr, 128, 1861, 1998. 

Sharpless, K.E. et al., Valne assignment of retinol, retinyl palmitate, tocopherol, and carotenoid concentrations in standard reference material 2383 (baby food composite), J. AOAC Int., 82, 288, 1999. 

The overall metabolism of vitamin A in the body is regulated by esterases. Dietary retinyl esters are hydrolyzed enzymatically in the intestinal lumen, and free retinol enters the enterocyte, where it is re-esterified. The resulting esters are then packed into chylomicrons delivered via the lymphatic system to the liver, where they are again hydrolyzed and re-esterified for storage. Prior to mobilization from the liver, the retinyl esters are hydrolyzed, and free retinol is complexed with the retinol-binding protein for secretion from the liver [101]. Different esterases are involved in this sequence. Hydrolysis of dietary retinyl esters in the lumen is catalyzed by pancreatic sterol esterase (steryl-ester acylhydrolase, cholesterol esterase, EC 3.1.1.13) [102], A bile salt independent retinyl-palmitate esterase (EC 3.1.1.21) located in the liver cell plasma hydrolyzes retinyl esters delivered to the liver by chylomicrons. Another neutral retinyl ester hydrolase has been found in the nuclear and cytosolic fractions of liver homogenates. This enzyme is stimulated by bile salts and has properties nearly identical to those observed for... 

Some esters of palmitic acid are well known, e.g., chloramphenicol pal-mitate and retinyl palmitate (8.76) [108][109], The latter is a provitamin of... 

J. Boehnlein, A. Sakr, J. L. Lichtin, R. L. Bronaugh, Characterization of Esterase and Alcohol Dehydrogenase Activity in Skin. Metabolism of Retinyl Palmitate to Retinol (Vitamin A) During Percutaneous Absorption , Pharm. Res. 1994, 11, 1155-1159. 

Fio. 35. HPLC record of a standard mixture of retinol and retinyl esters. Conditions column, 10 un octadecyl silica flowrate, I ml/min . mobile phase, (A) CHtOH/58.9 x I0- Af [Ag ], (B) CHsOH/23.5 x lO" W [Ag ], (C) CH,OH detection 330 hm. Peak identity (I) retinol (2) retinyl propionate (3) retinyl linoleate (4) retinyl lauratc (S) retinyl oleate (6) retinyl myristate (7) retinyl palmitate and (8) retinyl stearate. Reprinted with permission from DeRuyter and DeLeenheer (242), Anal. Chem. Copyright 1979 by the American Chemical Society. 

Biesalski, H. K., Reifen, R., Ftirst, P., and Edris, M. (1999). Retinyl palmitate supplementation by inhalation of an aerosol improves vitamin A status of preschool children in Gondar (Ethiopia). Br.. Nutr. 82,179-182. 

Bitzen, U., Winquist, M., Nilsson-Ehle, P., and Fex, G. (1994). Retinyl palmitate is a reproducible marker for chylomicron elimination from blood. Scand. J. Clin. Lab. Invest. 54, 611-613. 

Sobeck, U., Fischer, A., and Biesalski, H. K. (2003). Uptake of vitamin A in buccal mucosal cells after topical application of retinyl palmitate A randomised, placebo-controlled and double-blind trial. Br. J. Nutr. 90, 69-74. 

In the body retinol can also be made from the vitamin precursor carotene. Vegetables like carrots, broccoli, spinach and sweet potatoes are rich sources of carotene. Conversion to retinol can take place in the intestine after which retinyl esters are formed by esterifying retinol to long chain fats. These are then absorbed into chylomicrons. Some of the absorbed vitamin A is transported by chylomicrons to extra-hepatic tissues but most goes to the liver where the vitamin is stored as retinyl palmitate in stellate cells. Vitamin A is released from the liver coupled to the retinol-binding protein in plasma. 

Some conversion into the anhydrovitamin (112) occurs during silica gel t.l.c. of retinyl palmitate in non-polar solvents. Some new colour reactions of vitamin A are reported to be better than the Carr-Price reaction. The kinetics and mechanism of acid-catalysed isomerization of retinyl acetate into the trans-retro-derivative (113) have been studied. Oppenauer oxidation of kitol (39) results in specific cyclopentanol-cyclopentanone oxidation. ... 

Retinyl palmitate [79-81-2] M 524.9, e m (all-trans) 1000 (325 nm) in EtOH. Separate from retinol by column chromatography on water-deactivated alumina with hexane containing a very small percentage of acetone. Also chromatographed on TLC silica gel G, using pet ether/isopropyl ether/acetic acid/water (180 20 2 5) or pet ether/acetonitrile/acetic acid/water (190 10 1 15) to develop the chromatogram. Then recrystd from propylene. 

As vitamin A and carotene are in the fat portion of milk, the vitamin A activity is removed with the milk fat during separation into cream and lowfat and skim milks. Consequently, standards of identity established by the U.S. Food and Drug Administration (FDA) mandate the addition of vitamin A (e.g., retinyl palmitate) to fluid lowfat and skim milks and to nonfat dry milk to a level approximating that found in whole milk from cows on summer pasture. That is, at least 2000 IU of vitamin A must be present in each quart of lowfat and skim milk (FDA... 

Chase, G.W. Jr. and Long, A.R. 1998. Liquid chromatographic method for analysis for all-rac-al-pha-tocopheryl acetate and retinyl palmitate in milk-based infant formula using matrix solid-phase dispersion. J. AOAC Int. 81 582-586. 

Foods are supplemented with vitamin A in the form of standardized preparations of synthetic fatty acyl esters, nowadays chiefly retinyl palmitate. The preparations are available commercially as either dilutions in high-quality vegetable oils containing added vitamin E as an antioxidant or as dry, stabilized beadlets in which the vitamin A is dispersed in a solid matrix of gelatin and sucrose or gum acacia and sucrose. The oily preparations are used to supplement fat-based foods such as margarines the dry preparations are used in dried food products such as milk powder, infant formulas, and dietetic foods (24). 

Enzymatic hydrolysis is a nondestructive alternative to saponification for removing triglycerides in vitamin K determinations. For the simultaneous determination of vitamins A, D, E, and K in milk- and soy-based infant formulas and dairy products fortified with these vitamins (81), an amount of sample containing approximately 3.5-4.0 g of fat was digested for 1 h with lipase at 37°C and at pH 7.7. This treatment effectively hydrolyzed the glycerides, but only partially converted retinyl palmitate and a-tocopheryl acetate to their alcohol forms vitamin D and phyllo-quinone were unaffected. The hydrolysate was made alkaline in order to precipitate the fatty acids as soaps and then diluted with ethanol and extracted with pentane. A final water wash yielded an organic phase containing primarily the fat-soluble vitamins and cholesterol. 

Phylloquinone has been extracted from powdered infant formula using supercritical carbon dioxide at 8000 psi and 60°C for 15 min (65). The extracted material was readily recovered by depressurization of the carbon dioxide across an adsorbent trap and then washed from the trap with a small volume of dichloromethane/acetone (1 + 1) to give a sample suitable for direct HPLC analysis. Trial experiments gave recoveries of 92% of phylloquinone from a Chro-mosorb W matrix. A similar technique was applied to the extraction of retinyl palmitate from cereal products (90). 

Fig. 7 Comparative HPLC separations of a standard solution of six vitamins using (A) 250 X 4.0-mm-ID standard-bore and (B) 250 X 2.0-mm-ID narrow-bore columns. Stationary phase (both columns), 5-/tm Nu-cleosil-120-5 C8 (octyl) mobile phase, methanol/water (92 8). Flow rate (A) 0.7 ml/min, (B) 0.2 ml/min. Injection volume, 1 fi 1. Wavelength-programmed absorbance detection. Peaks (1) retinol (2) retinyl acetate (3) vitamin D3 (4) a-tocopherol (5) a-tocopheryl acetate (6) retinyl palmitate. (From Ref. 108.)...

Fortified fluid milk (whole, semiskimmed, skimmed) Mix 2 ml milk and 5 ml absolute EtOH in a centrifuge tube, let stand 5 min. Vortex-mix with 5 ml hexane, let stand 2 min. Repeat mixing and standing procedure twice. Add 3 ml water, mix by inversion, centrifuge. LiChrosorb Si-60 5 pm 250 X 3.2 mm Hexane/diethyl ether, 98 2 All-trans-retinyl palmitate UV 325 nm 83... 

Schneiderman et al. (90) extracted retinyl palmitate from commercial breakfast cereals using supercritical C02 and determined the vitamin by means of reversed-phase HPLC and electrochemical detection. Chromatograms of an unfortified wheat sample and a fortified bran-based cereal product are shown in Fig. 10. 

Fig. 10 HPLC chromatograms of supercritical fluid extracts of (A) an unfortified wheat sample and (B) a vitamin A-fortified bran-based ready-to-eat breakfast cereal. Column, 5-/rm Altex C8 (octyl) (150 X 4.6-mm ID) mobile phase, acetonitrile/2-propanol/aqueous 25 mM sodium perchlorate (45 45 10), 2.0 ml/min amperometric detection (oxidative mode), glassy carbon electrode, +1.2 V, vs saturated calomel electrode. Peak (1) retinyl palmitate. (Reprinted from Ref. 90, Copyright 1997, with the kind permission of Elsevier Science-NL, Sara Burgerhartstraat 25, 1055 KV Amsterdam, The Netherlands.)...

Breakfast cereals Extract sample with a sol- /rPorasil 10 pm Hexane/CHCl i con- Retinyl palmitate, a-to- UV 280 nm 249... 

Milk, milk powder, cream, 150 X 4.6 mm acetic acid in retinyl palmitate 13-... 

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