Vitamin palmitate

L-Ascorbic acid biosynthesis in plants and animals as well as the chemical synthesis starts from D-glucose. The vitamin and its main derivatives, sodium ascorbate, calcium ascorbate, and ascorbyl palmitate, are officially recognized by regulatory agencies and included in compendia such as the United S fates Pharmacopeia/National Formula (USP/NF) and the Food Chemicals Codex (FCC). 

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).

Vitamin A palmitate [79-81-2] (3), a commercially important form of the vitamin, is produced from vitamin A acetate (2) via a transesterification reaction with methyl palmitate. En2ymatic preparation of the palmitate from the acetate has also been described (22). 

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... 

Ethoxylated castor ods or ethoxylated castorwaxes are used as solubilizers of hydrophobic substances in cosmetics. Examples are Cremophor EL (ethyoxylated castor od) and Cremophor RH (40/60 ethoxylated hydrogenated castor od). Other ethoxylated triglycerides are not as effective as castor od. Ethoxylated castor od is also a good solubilizer for vitamin A palmitate (121). 

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

The selection of an appropriate antioxidant depends on factors such as stability, toxicity, efficiency, odor, taste, compatibility with other ingredients, and distribution phenomena between the two phases. Antioxidants that give protection primarily in the aqueous phase include sodium metabisulfite, ascorbic acid, thioglycerol, and cysteine hydrochloride. Oil-soluble antioxidants include lecithin, propyl gal-late, ascorbyl palmitate, and butylated hydroxytoluene. Vitamin E has also been used, but its virtue as a natural antioxidant has been the subject of some controversy. 

The effects of antioxidants on protein oxidation were also studied in animal experiments. Barja et al. [73] demonstrated that feeding guinea pigs with vitamin C decreased endogenous protein oxidative damage in the liver. Administration of the mixture of antioxidants containing Trolox C, ascorbic palmitate, acetylcysteine, (3-carotene, ubiquinones 9 and 10, and (+)-catechin in addition to vitamin E and selenium to rats inhibited heme protein oxidation of kidney homogenates more efficiently than vitamin E + selenium [74]. 

Fig. 2.37. Gradient LC separation of the retinoid solution components and retinoic acid isomers by (A) UV-DAD detection (350 nm) and (B) fluorescence detection with on-line photoreactor switched (a) off and (b) on with irradiation at 366 nm. Peak identification 1 = 13-civ retinoic acid 2 = 9-civ retinoic acid 3 = all-fraws retinoic acid 4 = vitamin A palmitate 5 = /1-carotene. Reprinted with permission from R. Gatti el al. [85].

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... 

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. 

The provision of fat-soluble vitamins and lipids is difficult, if not impossible, in various diseases. This is especially true for diseases that are accompanied by a lot of oxidative stress, for example, mucoviscidosis. The requirements of fat-soluble antioxidative substances are certainly high in these cases and can barely be covered by intramuscular injections because fat-soluble vitamins can hardly, if at all, be absorbed from oily preparations. Alternatively, the vitamins can administered via the buccal mucosa the fat-soluble substances have to be packaged in such a way that they can be transported in a watery compartment and are thus able to largely dissolve in the saliva. When they have an adequate size, they can then penetrate the buccal mucosa. One approach is the development of the so-called nanocolloids, that is, particles with a polar nucleus, in which the fat-soluble vitamin is dissolved, and an apolar wrapping (monolayer). This structure makes an oral application of fat-soluble substances possible. First tests demonstrated that vitamin A palmitate, a-tocopherol, as well as coenzyme Qio are thus able to enter the systemic circulation via the buccal mucosa. 

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. 

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. 

This class includes both vitamin A and the provitamin A carotenoids. All the compounds related to all-trani-retinol (Figure 19.11) are known as vitamin A. These compounds, together with their metabolites and synthetic derivatives, exhibiting the same properties are called retinoids. Vitamin A is found in animal products as retinyl esters (mainly palmitate). 

The main sources of vitamin C are green vegetables and citrus fruit. Animal tissue contains vitamin C, mainly in the kidneys and liver. The level of vitamin C in food is rapidly reduced during cooking or storage due to oxidation or water dissolution. It is added to food as an antioxidant (with no specified limit on the level of use) or as a supplement (with a maximum recommended daily intake of 3000mg/day). The forms admitted are L-ascorbic acid (AA), L-ascorbyl 6-palmitate, sodium, calcium, or potassium L-ascorbate [403]. 

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. 

Vitamin A, vitamin E and their acetate and palmitate esters were determined in tablets. The tablet powder was mixed with sand and loaded into the extraction vessel CO2 alone was used for extraction at 40°C for 15 min. The CO2 was vented to... 

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 . 

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. ... 

Tamarindus indicus L. Luo Huang Zi (Tamarind) (stem, fruit) Tannins, beta-amyrin, campesterol, beta-sitosterol, palmitic acid, oleic acid, linoleic acid, eicosanoic acid, arabinose, xylose, galactose, glucose, uronic acid, pectins, mucilage, vitamin B.60-216 Diuretic, purgative, for liver disorders, inappetence, digestion, and hypoglycemic, hypocholesterolemic properties. 

---