Abstract
A method for the determination of total bile acids in human feces that is suitable for routine application is described and discussed. Bile acids are extracted from freeze-dried feces with acetic acid and toluene, in the presence of the internal standard 23-nordeoxycholic acid. After saponification of the extract, bile acids and the internal standard are methylated and converted by mild chromic acid oxidation into their ketonic derivatives. The resultant mixture of a few stable compounds can be separated and measured quantitatively by gas-liquid chromatography on a methylsiloxane polymer. A reference bile acid mixture including the internal standard is also taken through the entire procedure with each series of samples. It has been demonstrated that, in spite of the omission of the usual purification steps, the method is specific for bile acids.
Highlights
A method for the determination of total bile acids in human feces that is suitable for routine application is described and discussed
Because fecal bile acids are numerous [6,7,8] and their composition may vary with changes of the intestinal flora [8], interference from nonbile acid contaminants is probably best avoided when several purification steps are included in the preparation of samples ( 5 ) and identification work is carried out with each type of pattern encountered (6, 7, 9-11)
The unusual procedure for extraction of bile acids from feces is not considered an essential feature of the present method
Summary
A method for the determination of total bile acids in human feces that is suitable for routine application is described and discussed. The feasibility of determining the total human feca bile acids in a few steps seemed, in our judgment, greater with a method that includes mild chromic acid oxidation of hydroxyl groups carried out with the methyl esters, after extraction of the samples and alkaline hydrolysis. Experiments in this laboratory indicated the formation, under these conditions, of a few ketonic esters whose behavior on several gaschromatographic phases was identical with that of the methyl esters of 3-keto-5@-cholanoic, 3,12-(or 3,7-)diketo-5/3-cholanoic, and 3,7,12-triketo-5~-cholanoiacid. Chromic acid in acetic acid [12] was made by dissolving chromium trioxide (20 g) in a mininum of water, and making the solution up to 100 ml with acetic acid
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