Lipophilic vitamins vitamin

Reduction, alteration of nucleic acids by, 944-945 Relative abundance (RA), 242 Retinol. See Lipophilic vitamins, vitamin A Reversed phase (RP) TLC, 18 of dyes, 1026-1027 separation of peptides by, 440,441 solvents for, 25 of steroids, 976-977 Riboflavin (vitamin Ba), 1048 Ribonucleic acids, 956 Ribonucleosides, 956 Riboses, identification of, 937 Rifamycin, 476-478 Robotics, 381-382,384,959 Rolitetracycline, 468-473 Rotachrom (RPC instrumentation), 328-329 Rotation planar chromatography (RPC), 29-30, 172, 307, 324-325 applicability, 335... 

Toxopherols. See Lipophilic vitamins, vitamin E Triacetylcellulose thin-layer plates, enantiomeric separation on, 630-631 Triazines, 774-779 Troleandomycin, 463-468 Tubular TLC-FID systems, 362-364 applications, 365... 

The possible prooxidant effects of a major lipophilic antioxidant vitamin E (a-tocopherol) have already been discussed in Chapter 25. Yamashita et al. [82] showed that a-tocopherol induced extensive DNA damage including base modification and strand breakage in the... 

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. 

Table 6 Relative Distribution of Some Lipophilic Drugs, Vitamins, and Xenobiotics between Different Lipoprotein Fractions in the Lymph... 

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... 

Chang CY, Chen JY, Ke D, Hu ML (2005) Plasma levels of lipophilic emtioxidant vitamins in acute ischemic stroke patients correlation to inflammation markers and neurological deficits. Nutrition 21(10) 987-993... 

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. 

Due to its lipophilic nature, vitamin E accumulates in cellular membranes, fat deposits and other circulating lipoproteins. 

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. 

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