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Thin-Layer Chromatography in Clinical Chemistry
Published in Bernard Fried, Joseph Sherma, Practical Thin-Layer Chromatography, 2017
The determination of bile acids is done in various biological specimens,32 e.g., bile, serum, duodenal contents, and crude fecal extracts. Thin-layer chromatography (TLC) has been used extensively for the separation of bile acids. Prior to TLC analysis of bile acid, purification of the specimen is essential. Sample cleanup steps would, however, depend upon the type of biological specimens being analyzed. Isolation of individual free bile acids in serum involves protein separation, alkaline hydrolysis, solvolysis of conjugated bile acids, and purification of lipids. Kindel et al.33 published a very useful paper in 1989 for separation of bile acids by TLC. These authors separated five predominant bile acids (cholic, chenodeoxycholic acid, deoxycholic acid, lithocholic acid, and ursodeoxycholic acid) in human stool specimens on a silica gel plate using two different solvent systems. The plate was first developed in isooctane-2-propanol–acetic acid (30:10:1, v/v) for 40 min, dried, and developed again with isooctane–ethyl acetate–acetic acid (10:10:2, v/v) for 65 min. For quantitative analysis, the plate was dipped in 0.2% 2,7-dichlorofluorescein ethanolic solution, and bile acid fluorescence was measured by TLC with direct scanning fluorometry (TLC–DSF). In clinical practice, this TLC procedure constitutes a reliable, simple, and time-saving alternative to gas chromatography.
New non-conventional lithocholic acid derivatives: synthesis and characterisations for mesogenic properties
Published in Liquid Crystals, 2020
A large amount of work has been carried out for the formation of liquid crystals (LC) using cholesterol, but not using lithocholic acid. These are naturally occurring bile acid complex molecules and it is hard to change their structure and morphology. Cholesterol derivatives are basically the class of cholestanes and cholic acid derivatives are the class of cholanes. These are made of cells either from sterols, i.e. lanosterol (animals and fungi), or from cycloartenol (plants). These molecules possess chirality and are thus optically active. Bile acids and their derivatives display self-association in aqueous solutions [1–4] and the chemical structure of each bile acid is responsible for the extent to which it aggregates [5]. Due to their unique assembling properties, bile acids and bile salts have gained importance in supramolecular chemistry [6,7]. The lithocholic acid and cholesterol molecule contain a steroid backbone like all bile acids and ends in a four-carbon chain containing carboxyl group (i.e. lithocholic acid). It also has a hydroxyl group on the far end of the molecule as can be seen in the chemical structures given below.