Vitamin palmitate, activity

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... 

Oil from wheat germ (the embryo of the seed of Triticum aestivuni) is rich in linoleic acid (ca. 60%), also contains a-linolenic acid (ca. 5%), 16% palmitic acid, and 14% oleic acid. The oil is rich in tocopherols and shows high vitamin E activity. ... 

Vitamin A-active compounds [1] are present in foods of animal origin as retinoids (retinol, retinyl esters, retinylaldehyde, retinoic acid) and in those of plant origin as carotenoids (only carotenoids with one unsubstituted P-ionone ring and with an 11-carbon polyene chain at least are provitamins A). Retinyl palmitate is the main form used as a food supplement [4]. 

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. 

AIDS therapeutic effects. Water extract of the dried rhizome taken orally by adults was active. A pharmaceutical solution containing fruit bodies of Tremella fuciformis, Daucus carota rhizome. Astragalus mongho licus root, and Zizyphus jujuba fruits, honey, vitamin A palmitate, zinc sulfate, and vitamin C was useful for controlling acquired immunodifficiency syndrome (AIDS), cancer, and infections . 

Structurally, vitamin A and many synthetic retinoids consist of a (3-ionone ring, a polyunsaturated polyene chain, and a polar end group. The polar end group can exist in several oxidation states, as retinol, retinal, or retinoic acid. Retinol and retinyl esters are the most abundant vitamin A forms found in the body (Blaner and Olson, 1994). Retinol can be esterified with long-chain fatty acids (mainly palmitate, oleate, and stearate) to form retinyl esters, which are the body s storage form of vitamin A. Retinol also can undergo oxidation to retinal, which can be oxidized further to retinoic acid. The active... 

Free retinol is chemically unstable and does not occur to any significant extent in foods or tissues. Rather, it is present as a variety of esters, mainly retinyl palmitate. Retinyl acetate is generally used as an analytical standard and in pharmaceutical preparations. Dehydroretinol (vitamin A2) is found in freshwater fishes and amphibians it has about half the biological activity of retinol. 

Vitamin A with its five conjugated double bonds oxidizes to 5,8-epoxides (15) with subsequent loss of UV absorption at 325 nm. Thus, vitamin A was studied with the addition of various antioxidants (Table XI) in open bottles in thin layers. Although EMQ was the best, it is limited to use in vitamin A for animal feeds. AP activity was not great, but when added to a mixture of tocopherol, BHT, and diethanolamide, AP gave excellent protection. Klaui (16) has shown stability of vitamin A palmitate with tocopherol, AP, and an amine equal to 1300 h, compared to a control equal to 100 h. However, the antioxidants in the dry market form (beadlets) protect the vitamin A in the beadlets as well as the end use of the product. For example, spray-dried vitamin A can be pro-... 

Vitamin A, U5P. Vitamin A (Aquasol A) contains retinol (vitamin A alcohol) or its esters from edible fatty acids (chiefly acetic and palmitic acids), whose activity is not less than 9S% of the labeled amount a dosage of 0..T yrg of vitamin A alcohol (retinol) equals I USP unit. 

Chemistry. The commercial form cf vitamin A is all-trans retinol, usually formulated as the acetate or palmitate ester. The active forms are the two oxidation products (Fig. 8.1, (l)retinal, which is a structural component of the visual pigment rhodopsin, and (2)retinoic acid, which is required for cell differentiation. There are specific nuclear receptors for retinoic acid. Although the vitamin is marketed in the all-trans form, retinal and retinoic acid are present, in vivo in cis forms. There are also commercial forms related to the retinoic acid structure that have cis stereochemistry. 

This class of vitamins comprises a group of molecules which are also known as retinoids and also includes certain carotenes which display vitamin A-like activity (particularly a-, and y-carotene from plants). Many derivatives of these compounds are found naturally and include the alcohol, the acetate and the palmitate. The best chromatographic mode for the resolution of the vitamin A class is often determined by the conditions used for the extraction. For example, saponification to remove lipids is often followed by extraction into solvents, such as hexane, which are compatible with aqueous reversed phase HPLC using either a Cg or C,g siUca-based stationary phase (Fig. 11.8.1). An alternative system has been reported using a Cjg support and a mobile phase of 0.5% acetic acid in acetonitrile (Annesley et al., 1984). 

Boehnlein, J., Sakr, S., Lichtin, J.L., and Bronaugh, R.L., 1994, Characterization of esterase and alcohol dehydrogenase activity in skin. Metabolism of retinyl palmitate to retinol (vitamin A) in skin during percutaneous absorption, Pharm. Res., 11 1155-1159. 

By this synergistic mechanism, tocopherols and ascorbic acid can mutually reinforce one another by regenerating the oxidized form of the other. Radical exchange reactions among lipid radicals, tocopherols, and ascorbic acid are the basis of numerous approaches for stabilizing oil and foods with their mixtures. It is however important to note that vitamin C is not soluble in the lipid phase that is most susceptible to oxidation. This was the reason why L-ascorbic esters were developed, e.g., ascorbyl palmitate that has a lipid solubility superior to that of ascorbic acid. Mixtures of ascorbyl palmitate with tocopherols are well known for their synergistic activity. 

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