Of cholic acid

Steroids are another class of natural products with multiple chirality centers One such compound is cholic acid which can be obtained from bile Its structural formula IS given m Figure 7 12 Cholic acid has 11 chirality centers and so a total (including cholic acid) of 2" or 2048 stereoisomers have this constitution Of these 2048 stereoiso mers how many are diastereomers of cholic acid s Remember Diastereomers are stereoisomers that are not enantiomers and any object can have only one mirror image Therefore of the 2048 stereoisomers one is cholic acid one is its enantiomer and the other 2046 are diastereomers of cholic acid Only a small fraction of these compounds are known and (+) cholic acid is the only one ever isolated from natural sources... 

The structure of cholic acid helps us understand how bile salts such as sodium tauro cholate promote the transport of lipids through a water rich environment The bot tom face of the molecule bears all of the polar groups and the top face is exclusively hydrocarbon like Bile salts emulsify fats by forming micelles m which the fats are on the inside and the bile salts are on the outside The hydrophobic face of the bile salt associates with the fat that is inside the micelle the hydrophilic face is m contact with water on the outside... 

As we have seen in this chapter steroids have a number of functions in human physiology Cholesterol is a component part of cell mem branes and is found in large amounts in the brain Derivatives of cholic acid assist the digestion of fats in the small intestine Cortisone and its derivatives are involved in maintaining the electrolyte balance in body fluids The sex hormones responsible for mascu line and feminine characteristics as well as numerous aspects of pregnancy from conception to birth are steroids... 

Bile acids, which exist mainly as bile salts, are polar carboxylic acid derivatives of cholesterol that are important in the digestion of food, especially the solubilization of ingested fats. The Na and salts of glycocholic acid and tauro-cholic acid are the principal bile salts (Ligure 25.41). Glycocholate and tauro-cholate are conjugates of cholic acid with glycine and taurine, respectively. 

The following mode) is that of cholic acid, a constituent of human bile. Locate the three hydroxyl groups, and identify each as axial or equatorial. Is cholic acid an A-B trans steroid or an A-B cis steroid ... 

Smith MG, RJ Park (1984) Effect of restricted aeration on catabolism of cholic acid by two Pseudomonas species. Appl Environ Microbiol 48 108-113. 

An IMER immobilizing 3 a-hydroxysteroid dehydrogenase was employed for HPLC determination of cholic acid and a detection limit of 2 pmol was achieved [44], This approach has the advantage of permitting a repeatable use of the enzyme. 

Experiments—Dissolve 0-02 g. of cholic acid in 0-5 c.c. of alcohol and add to the solution 1 c.c. of 0-1 A-iodine solution. On cautious dilution with water the blue crystalline iodine compound of cholic acid, comparable to starch iodide, separates. 

Wilkins and coworkers have redesigned both the sensitizer and the matrix resin (78-79). They have tested a variety of o-nitrobenzyl esters of cholic acid as sensitizers. These substances, like the diazoquinones, are insoluble in aqueous base but undergo a photo-reaction that yields base soluble products. The matrix resin chosen for the new sensitizer materials is a copolymer of methyl methacrylate and methacrylic acid that is far more transparent than novolac resins in the DUV. The new resist materials are reported to have useful sensitivity (ca. 00mJ/cm ) and extremely high contrast. The resist formulation is essentially aliphatic in nature and would be expected to be less stable to dry etching environments than the aromatic-based novolac resin materials (24). 

P. K. Baijal, E. P. Clow, D. W. Fitzpatrick and R. P. Bird, Tumourenhancing effects of cholic acid are exerted on the early stages of colon carcinogenesis via induction of aberrant crypt foci with enhanced growth phenotype. Can. J. Physiol. Pharmacol, 1998, 76, 1095. 

J. P. Cruse, M. R. Lewin and C. G. Clark, The effects of cholic acid and bile salt binding agents on 1,2-dimethylhydrazine-induced colon carcinogenesis in the rat. Carcinogenesis, 1981, 2, 439. 

The approach is used to show the shape of cholic acid, one of the bile acids secreted into the gut to emulsify fats and encourage digestion. Cholic acid is characterized by a cis fusion of rings A and B. 

In a first set of experiments [52], the methyl ester of cholic acid 66a (Structures 8) was reacted with diphenylketene (59a) in the presence and in the absence of catalysts [pyridine (50), concave pyridine 3r]. But in all experiments, only the equatorial group in 3-position could be acylated (66b). No functionalization of the axial OH-groups in 7- and 12-position was found (66c, 66d). 

Important alterations in hepatic drug excretion and metabolism also occur. Estrogens in the amounts seen during pregnancy or used in oral contraceptive agents delay the clearance of sulfobromophthalein and reduce the flow of bile. The proportion of cholic acid in bile acids is increased while the proportion of chenodeoxycholic acid is decreased. These changes may be responsible for the observed increase in cholelithiasis associated with the use of these agents. 

Oxidation of 5/3-cholestane, but not 5a-cholestane, gave an acid that turned out to be identical with cholanic acid obtained by dehydration of cholic acid at 300° followed by hydrogenation ... 

Deep-UV resists have also been prepared by changing both sensitizer and matrix resin. For example, materials combining o-nitrobenzyl ester derivatives of cholic acid with a P(MMA-MAA) matrix resin (Scheme V) have been reported (59-61). Upon photolysis, the nitrobenzyl ester dissolution... 

Salts of cholic acid and its derivatives are known as bile salts. Bile salts are unlike traditional surfactants in that they are rigid and have multiple polar moieties on one side of the molecule thus exhibiting surface activity. 

During the past few decades, a number of important studies were published on the effect of cholic acid derivatives on the absorption of macromolecules [81]. Guarini and Ferrari [84—86] compared simultaneous oral dosing of NaDOC and heparin to pretreatment with NaDOC by oral gavage in dogs followed by oral heparin administration at a 0.5-24-h interval. In all pretreatment regimens, NaDOC enhanced heparin absorption, with the maximum effect observed when heparin was administered 1 h after NaDOC. 

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