Vitamins lipophilic

For some drugs that, for physiological and anatomical reasons, mainly follow a passive absorption mechanism, a satisfactory colonic absorption was demonstrated. Similar absorption rates from the small and large intestine were found for oxprenolol, metoprolol, isosorbide-5-mononitrate, and glibenclamide [9], It has also been known for many years, that some lipophilic vitamins, as well as bile salts and some steroids, that undergo enterohepatic circulation show satisfactory colonic absorption [2],... 

With exceptions, including halofantrine, DDT, and the lipophilic vitamins, the extent of lymphatic transport (as a proportion of the dose) is generally low. However, the compounds described in Table 5 are hydrophobic (as evidenced by the high log Ps), and their bioavailability is often low. Therefore, although the absolute extent of lymphatic transport may be low, the lymphatic contribution to the small fraction that is absorbed may be high, and alterations in the extent of lymphatic transport may have a significant effect on the extent of oral bioavailability. 

C4. Cano, A., Acosta, M., and Arnao, M. B., A method to measure antioxidant activity in organic media Application to lipophilic vitamins. Redox Report 5,365—370 (2000). 

To prevent this sun-induced cascade of oxidative injuries, topical preparations containing antioxidants have been developed in the past several decades. Initially, such antioxidants were added as stabilizers to various dermatologic and cosmetic preparations. In particular, lipophilic Vitamin E has been the favorite as a stabilizing agent. However, following oxidation, Vitamin E is degraded into particularly harmful prooxidative metabolites.177... 

The lipophilic vitamin A is a cyclic polyene alcohol (Figure 29.4). The recommended daily allowance is 700 to 900 /u. g, increasing to 1300 /xg during lactation (1 /xg of vitamin A equals 12 /xg of p-carotcnc or 24 jig of other provitamin A carotenoids).26,71... 

It has long been known that the body seems capable of metabolizing and disposing of "lipophilic vitamins by trapping them in fatty acids in the digestive system, somehow prohibiting their access to the gpnadaland brain... 

Superoxide dismutase and catalase are remarkably efficient, performing their reactions at or near the diffusion-limited rate (Section 8.4.2). Other cellular defenses against oxidative damage include the antioxidant vitamins, vitamins E and C. Because it is lipophilic, vitamin E is especially useful in protechng membranes from lipid peroxidahon. 

Lipophilic Vitamins by Thin-Layer Chromatography Alina Pyka... 

Lipophilic vitamins A, D2, and E (a-tocopherol) (Rp values 0.34, 0.44, and 0.62, respectively) are separated on silica gel plates and a mixture of benzene-chloroform-acetone (88.5 8.8 2.7, by volume) applied [8]. Table 1 gives information about detection and the hRp values of Upohilic vitamins in mixtures, using the various layers and solvents. 

Table 1 hRp Values of Lipophilic Vitamins Using Various Separation Systems and Detection of Lipophilic Vitamins... 

A. P. de Leenheer and W. E. Lambert, Lipophilic vitamins, in Handbook of Thin-Layer Chromatography (J. Sherma and B. Fried, eds.). Chromatographic Science Series Vol. 71, Marcel Dekker, Inc., New York, 1996, pp. 1055-1077. 

This concept allows the classification of molecules such as carotenoids, lipophilic vitamins, steroids, terpenes etc, as lipoids . Most researchers consider those molecules as separate groups and confine the term lipid to fatty acids, their derivatives and to substances that are closely related to their synthesis and function [1,2],... 

Eand C. Because it is lipophilic, vitamin E is especially useful in protecting membranes from lipid peroxidation. 

Foods and food raw materials primarily consist of hydrophilic substances compatible with the aqneons medinm of plant and animal tissues. Lipids, lipophilic vitamins, terpenes, and other nonpolar water-insoluble substances should thus be emulsified or converted into hydrophilic snbstances by formation of complexes with other food constitnents. The most important complex-forming food components are proteins and carbohydrates — or, more correctly stated, saccharides. 

Selective enzymic acylation and deacylation of nucleosides have been reviewed. Cordycepin (3 -deoxyadenosine) has been linked to various lipophilic vitamins and to diacylglycerols via dicarboxylic acid spacers at 0-2 and 0-5, and similar conjugates have been made to the cordycepin trimer core, with linkages at either the 5 - or the 2 -end. 3 -(9-Aminoacyl-2 -deoxynucleosides have been made using Fmoc aminoacid fluorides as acylating agents. ... 

Hinze was the first to investigate the capabilities of micellar bile salt mobile phases [11, 12]. He found that a significant amount ( 5% v/v) of a long chain n-alcohol (pentanol, hexanol or heptanol) was useful to minimize the bile salt adsorption on the C18 stationary plmse. A wide range of solutes could be separated by these phases, PAHs, quinones, steroids, indoles, polar and lipophilic vitamins. These phases were also able to resolve optically big enantiomers such as binaphthyl derivatives [12]. Such compounds are... 

De Leenheer AP, Nelis HJ, and Lambert WE (1993) Lipophilic vitamins. In Mukherjee KD and Weber N (eds.) CRC Handbook of Chromatography Analysis of Lipids, pp. 261-283. Boca Raton, FL CRC Press. 

Generally, TLC is useful for the investigation of a wide range of lipophilic vitamin applications, i.e., purification of samples, qualitative detection, quantitative determination, and the use of new visualizing agents, and also for separation of some optical isomers. ... 

The aim of this entry is to present selected works that describe the analytical separation of lipophilic vitamins by means of TLC. 

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