Bile acids and their derivatives

M. Mikov, J. P. Fawcett, K. Kuhajda and S. Kevresan, Pharmacology of bile acids and their derivatives Absorption promoters and therapeutic agents, Eur. J. Drug Metab. Pharmacokinet., 2006, 31, 237. 

Hara, S. and Takeuchi, M., Systematic analysis of bile acids and their derivatives by thin layer chromatography, J. Chromatogr., 11, 565, 1963 Chem. Abs., 60, 838f, 1964. 

Chromatography.—Considerable attention is being paid to chromatographic methods for the separation and recognition of bile acids and their derivatives. The analysis (g.l.c.) of mixtures of bile acids and their conjugates is reported to be simplified by direct conversion into heptafluorobutyrate derivatives, which occurs with simultaneous deconjugation.The carboxyl function is apparently converted into its volatile mixed cholanyl-heptafluorobutyryl anhydride. Ethyl-dimethylsilyl ethers of bile acid ethyl esters are also reported to be suitable for... 

Porous host substructures with parallel channels are typical of many inclusion compounds formed by bile acids and their derivatives (see Deoxycholic, Cholic, and Apocholic Acids). In this class of compounds, host molecules are always optically active, and the resulting host networks are chiral. The best known among them are inclusion compounds of deoxycholic acid (DCA) (also known as choleic acidsj. With most guests. DCA molecules assemble via hydrogen bonds into a coiTugated... 

INCLUSION COMPOUNDS OF BILE ACIDS AND THEIR DERIVATIVES... 

Table 2 Formation of the inclusion compounds of bile acids and their derivatives with their host-guest ratios... 

Designing the robust host molecules is one of the fascinating researches for future chemistry. In this article, we demonstrated that the bile acids and their derivatives serve as host molecules for various guest compounds. Each derivative exhibits individual characteristic that vary from one case to another. Finally, bile acids tell us their information and expression through their molecular assemblies. that we should listen from them. 

Bile Acids. XXVIII. Gas Chromatography of New Bile Acids and Their Derivatives... 

TLC has been used to separate free bile acids and their derivatives. With the use of commercial reversed-phase layers, convenient methods are now available for the resolution of conjugated bile acids (Touchstone, 1986). 

Sarbu, C., Kuhajda, K., and Kevresan, S. 2001, Evaluation of the lipophUicity of bile acids and their derivatives by thin-layer chromatography and principal components analysis. J Chromatogr. A 917, 361. 

Lipids have been dehned on the basis of their stmctnre and solnbility. Lipids are natnrally occnrring componnds consisting of fatty acids and their derivatives, bile acids, pigments, vitamins, and steroids, as well as terpenoids, which are usually soluble in organic solvents such as benzene, chloroform, ether, and alcohol, etc., with variable solubility depending on the stmctnre of the lipid compound. 

Much of the cholesterol synthesis in vertebrates takes place in the liver. A small fraction of the cholesterol made there is incorporated into the membranes of he-patocytes, but most of it is exported in one of three forms biliary cholesterol, bile acids, or cholesteryl esters. Bile acids and their salts are relatively hydrophilic cholesterol derivatives that are synthesized in the liver and aid in lipid digestion (see Fig. 17-1). Cholesteryl esters are formed in the liver through the action of acyl-CoA-cholesterol acyl transferase (ACAT). This enzyme catalyzes the transfer of a fatty acid from coenzyme A to the hydroxyl group of cholesterol (Fig. 21-38), converting the cholesterol to a more hydrophobic form. Cholesteryl esters are transported in secreted lipoprotein particles to other tissues that use cholesterol, or they are stored in the liver. 

The heterogeneous class of compounds marked by solubility in so-called lipid solvents (acetone, hydrocarbons, ether, etc.) and relative insolubility in water, has traditionally been called lipids (3). This historical classification, based upon isolation procedures from natural products, is obviously too broad for simple generalizations since it includes triglycerides, fatty acids, phospholipids, sterols, sterol esters, bile acids, waxes, hydrocarbons, fatty ethers and hydrocarbons. For the purposes of this chapter, we will consider lipids to be fatty acids and their derivatives. 

Beside the bile salts, the anionic surfactants investigated for enhanced intestinal delivery were mainly sodium salts of fatty acids and their derivatives. These include sodium salts of saturated and unsaturated fatty acids (C8-Ci8), SLS, dioctyl sodium sulfossuccinate (DOSS), and others. 

In each form of cholestasis, atypical bile adds, such as monohydroxy bile acids, aUo-bile adds, 1- or 6-hydroxylated bile acids and their sulphated or glucuronidated derivatives, are found in the sermn and/or urine. In cholestasis, the increase in the neosynthesis of atypical bile adds that pass into the kidney can be seen as a compensatory mechanism which eliminates potentially hepatotoxic bile acids by renal clearance. The highest renal excretion quota is demonstrated by tetrahydroxy bile acids. 

B7. Barnes, S., Pritchard, D. G., Settine, R. L., and Geckle, M., Preparation and characterisation of permethylated derivatives of bile acids and their applications to gas chromatographic studies. /. Chromatogr. 183, 269-276 (1980). 

Stiehl, A., Becker, M., Czyan, P., Frohling, W., Kommerell, B.. Rottfaauwe, H. W., and Senn, M., Bile acids and their sulphated and glucuronidated derivatives in bile, plasma and urine of children with intrahepalic cholestasis Effects of phenobarbital treatment. Ear. J. CUn. Incest. 10, 307-316 (1980). 

The term lipid is frequently used to denote a wide variety of natural products fatty , oily or waxy substances of animal and vegetable origin that are easily soluble in organic solvents readily satisfy this loose definition. Thus, such diverse compounds as fatty acids and their derivatives, triglycerides, sterols, phosphatides and sphingolipids, carotenoids, bile acids, vitamins A, D, E, and K, long-chain alcohols, terpenes, etc., may be included. Studies of these substances by GC are indeed numerous a comprehensive survey of this field is beyond the scope of this... 

The structures of certain uncommon bile acids and their ethyl esters have abo been studied (79, 81), and incomplete crystal data of certain bile acid derivatives given in a brief note (72). The crystalline structures of most of the common bile acids and their alkaline salts have not yet been defined. 

Christie (2) noted that a variety of diverse eompounds generally soluble in organic solvents are usually classified as lipids, i.e., fatty acids and their derivatives, steroids, terpenes, carotenoids, and bile acids. He suggested that many of these diverse compounds have little in the way of structure or function to make them related, and that many substances regarded as lipids may be more soluble in water, e.g., glycolipids, gangliosides, than in organic solvents. Table 1 provides a list of diverse lipophilic substances that have been examined by TLC. It includes typical sorbents, solvent systems, and references for these lipophilic substances. 

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