Naturally Occurring Bile Acids

Artificial analogues of the chloride transporter prodigiosin are effective symport HC1 carriers as exemplified in the model systems developed by the groups of Gale [39] and Davis [40], Biological inspiration is also behind another Cl- carrier. Cholic acid is a naturally occurring bile acid that functions as a surfactant in the intestine. Derivatives with three binding sites known as cholapods are able to transport isolated anions across lipid bilayers [41],... 

Ursodeoxycholic acid A naturally occurring bile acid (originally isolated from the bile of bears) that is present in minor concentrations in the bile (approximately 1 to 10 percent). When administered orally, it helps to dissolve cholesterol gallstones. 

The most successful therapy for cholestasis of pregnancy has been ursodeoxycholic acid (Figure 33-1). Ursodeoxycholic acid is a naturally occurring bile acid, which, when administered, relieves both pruritus and liver function abnormalities. Experimental evidence suggests that it protects hepa-tocytes and cholangiocytes from bile acid-induced cytotoxicity and improves hepatobiliary excretion. Additionally, it decreases bile salt transfer to the fetus and improves the secretory function of placental trophoblast cells. Ursodeoxycholic acid is recycled through the enterohepatic circulation. 

Matschiner, J. T., Naturally occurring bile acids and alcohols and their origins. In The Bile Acids (P. P. Nair and D. Kritchevsky, eds.), Vol. 1, pp. 11-46. Plenum, New York, 1971. 

Desoxycorticosterone was the first naturally occurring corticoid to be synthesized. It was prepared, before its isolation from the adrenal cortex, by Steiger and Reichstein (32). As a result of his synthesis of 11-desoxycorticosterone and other early work with corticoids, Reichstein later shared the Nobel Prize with Kendall, another chemist who was instrumental in carrying out early steroid syntheses, and with Hench, a rheumatologist who in 1929 discovered that cortisone is effective in the treatment of rheumatoid arthritis. Kendall s basic research ultimately led to the synthesis of cortisone from naturally occurring bile acids (33). 

Li, W. Sorensen, RW. 1997. Highly independent olfactory receptor sites for naturally occurring bile acids in the sea lamprey, Petromyzon marinus. J. Comp. Physiol. A., /59,429—438... 

The most abundant naturally occurring bile acids in higher vertebrates are derivatives of cholanic acid (1) (Fig. 1), a 24-carbon-atom steroid possessing the characteristic cyclopentanophenanthrene nucleus. The structure and nomenclature of this class of compounds have been described in detail by Fieser and Fieser (25), Kritchevsky (26), and Van Belle (27). 

Naturally Occurring Bile Acids and Alcohols and Their Origins... 

A thorough review of the chemistry of many of the naturally occurring bile acids and related substances may be found in the monograph by Fieser and Fieser (1). A tabulation of known acids and alcohols, their properties, and a brief description of their origins is presented in the next section of this chapter. Identifications in some cases have not been confirmed but the burden of accuracy has been left with the original authors. 

The alio bile acids are the 5a-cholanoic acids, i.e., derivatives of cholanoic acid in which the hydrogen at C5 is alpha-oriented rather than beta-oriented as in the large number of naturally occurring bile acids. The sequence of numbering in the cholane nucleus is the same as in the normal series. The... 

The spectra of 12-ketocholanoates also show a peak at mje 121 in almost all cases studied. The nature of this ion is not known it may be asumed to contain the C-ring with the carbonyl group and two additional carbon atoms. The presence of this ion is also support for a 12-keto group, at least when naturally occurring bile acids are studied. 

Now, although none of these compounds is a true steroid, they all contain polycyclic nuclei, and, furthermore, the fact that methyl colanthrene has been prepared from a naturally occurring bile acid suggests that they must be considered as possible types of compounds produced in abnormal sterol metabolism. 

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