Vitamin ester, application

Cholesterol Esterase. This enzyme (EC 3.1.1.13 CAS 9026-00-0) physiologically catalyzes the hydrolysis of cholesterol esters, monoacylglycerols, and vitamin esters. It has also been used for several cyclie and noncyclic substrates with variable enantioselectivity. The resolution of racemic esters has been reported and an interesting example is the application to the racemic acetate of an hemiacetal (eq 14). ... 

When the enamine is in conjugation with a carbonyl function, as in a-aminomethylene aldehydes (528,529), ketones (530), or esters (531), a Michael addition is found in vinylogous analogy to the reactions of amides. An application to syntheses in the vitamin A series employed a vinyl lithium compound (532). 

Niacin (vitamin B3) has broad applications in the treatment of lipid disorders when used at higher doses than those used as a nutritional supplement. Niacin inhibits fatty acid release from adipose tissue and inhibits fatty acid and triglyceride production in liver cells. This results in an increased intracellular degradation of apolipoprotein B, and in turn, a reduction in the number of VLDL particles secreted (Fig. 9-4). The lower VLDL levels and the lower triglyceride content in these particles leads to an overall reduction in LDL cholesterol as well as a decrease in the number of small, dense LDL particles. Niacin also reduces the uptake of HDL-apolipoprotein A1 particles and increases uptake of cholesterol esters by the liver, thus improving the efficiency of reverse cholesterol transport between HDL particles and vascular tissue (Fig. 9-4). Niacin is indicated for patients with elevated triglycerides, low HDL cholesterol, and elevated LDL cholesterol.3... 

Another application is the esterification of menahydroquinone-4, a water-insoluble vitamin K, with V,A-dimethylglycine [144], The 1-mono, 4-mono, and 1,4-bis esters were found to be water-soluble and rapidly hydrolyzable by liver and plasma esterases. A rapid pharmacodynamic response was seen after intravenous administration of the prodrugs. 

These results show that retinyl esters in respiratory epithelium and in alveolar cells form a pool of vitamin A, which can be used physiologically by the tissue. The formation of retinol and at least RA from retinyl esters is strictly controlled. So far an unphysiological formation of RA and a subsequent toxicity seems not possible. Retinyl esters, however, are biochemically inert with respect to gene expression or vitamin A activity as long as they are not hydrolyzed. Consequently, the inhalative application, especially in cases of insufficient lung development, could represent a true alternative. The oral contribution is hardly successful because of the poor RBP s)mthesis of the liver and the lack of availability of a parenteral solution is currently not available. 

The obtained results confirm earlier findings where vitamin A-deficient rats were used to prove the uptake of retinyl esters into lung, liver, kidney, and plasma after inhalation thereof (Biesalski, 1996). However, long-term topical administration of high vitamin A concentrations is a well-established therapy in atrophic rhinitis, rhinitis sicca, and metaplastic changes in the nasal or ocular epithelium (Deshpande et ah, 1997 Simm, 1980). The application leads to the normalization of mucous membranes and reappearance of a normal function with no side effects. 

Gerlach, T., Biesalski, H. K., Weiser, H., Haeussermann, B., and Baessler, K. H. (1989). Vitamin A in parenteral nutrition Uptake and distribution of retinyl esters after intravenous application. Am. ]. Clin. Nutr. 50,1029-1038. 

Uses. Although cyanoacetic acid can be used in applications requiring strong organic acids, its principal use is in the preparation of malonic esters and other reagents used in the manufacture of pharmaceuticals. See also Alkaloids and Vitamin. 

A few individual terpenoids, as well as less expensive mixtures of these compounds, find practical applications. Some examples are the tli terpenoid Vitamin A, the sesquiterpenoid santonin (as an anthelmintic), and the pyrcthnns, pyrctholonc esters of the monoterpenoid chrysanthcmic acid (used as an insecticide). A number of sesquiterpenoid lactones of the germacranolide. guaianolide and elemanolide types have shown promise as rumor inhibitors. 

One of the main problems of topical application of vitamin C is that it is extremly unstable, so hydrophilic derivatives like sodium ascorbyl phosphate and lipophilic esters with fatty acids were synthesized to improve stability.43,44 However, an efficient increase in vitamin C levels after topical application of different ascorbic acid derivatives including magnesium ascorbyl phosphate, ascorbyl-6-palmitate, and dehydroascorbic acid to porcine skin could not be shown.42... 

Soybean tocopherols are the major source of natural fat-soluble antioxidants and Vitamin E. The Vitamin E activity of natural d-cx-tocopherol is much greater that that of synthetic Vitamin E, which is a mixture of eight stereoisomers (203). Phytosterols are used as raw materials for over 75% of the world s steroid production. The more recent application of phytosterol, phytostanol, and their fatty acid esters in margarine and table spreads is based on the blood cholesterol-lowering effect of these compounds (204,205). The recent development of functional foods containing phytosterols has been reviewed by Hollingsworth (206) and Hicks and Moreau (207). 

The quantitative analysis of the fat-soluble vitamins (A, E, D and K) and their esters by reversed-phase partition in water/alcohol solvents on Zipax columns has been reported [255]. The applicability of gas and high pressure liquid chromatography of vitamin A was discussed by Vecchi, Vesely and Oesterhelt [256] who concluded that HPLC was superior in this application. 

Both normal-phase and reversed-phase HPLC have been applied in vitamin E analysis. Reversed-phase HPLC is unable to completely separate all tocopherols and toco-trienols. Because (1- and y-vitamers have very similar structures, their separation cannot be obtained with reversed-phase HPLC. It is, however, applicable when only tocopherols or a-tocopheryl esters are analyzed (Gimeno et al., 2000 Iwase, 2000). There are reversed-phase methods to analyze tocopherols together with other lipid constituents from biological and food samples such as carotenoids (Epler et al., 1993 Salo-Vaananen et al., 2000), ubiquinols and ubiquinones (Podda et al., 1996) or sterols (Warner and Mounts, 1990). 

Determination of four tocopherols and four tocotrienols in vegetable oils and fats by the official American Oil Chemists Society method is based on separation by normal-phase HPLC and fluorescence detection (AOCS, 1990). Oil samples are dissolved in hexane, whereas margarines and other fats containing vitamer esters need a cold saponification step to liberate the vitamers. The American Association of Cereal Chemists has a method to analyze vitamin E in various foods. This method (AACC, 1997) is applicable to a vitamin E range of 1 x 10" - 100%, and it includes hot saponification and separation by reversed-phase HPLC. Results are calculated as a-tocopherol acetate. The Royal Society of Chemistry has approved a method to analyze vitamin E in animal feedstuffs by normal-phase HPLC after the vitamers have been liberated by hot saponification (Analytical Methods Committee, 1990). 

The application of SCF to the extraction of vitamins has been widely reported. Thus, retinyl palmitate and tocopherol acetate have been extracted from a hydrophobic ointment with supercritical CO2 at 40°C and 196 bar for 4 min, the extract analysis being performed by SFC (137). The calibration graphs were linear from 0.5 to 2.5 pg and the recoveries were quantitative. On the other hand, water-soluble vitamins can be extracted mixing them with low substituted hydroxypropil cellulose. Portions were placed in a column to which a reversed micellar extractant was delivered (138). Extraction of vitamins A and E and their esters from tablet preparations prior to FIPLC was performed in the dynamic mode with CO2 at 40°C and 253 bar for 15 min (139). Calibration graphs were linear from 0.02 to 0.8 and from 0.005 to 0.2 mg/mL of vitamins E and A, respectively. The corresponding RSDs (six... 

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