CONICET | Buscador de Institutos y Recursos Humanos

The analysis of feces is a useful tool for ecological studies. However, it is difficult to identify them by their external characteristics. Fecal bile acids and their relative concentration follow patterns that are species specific and can be characterized by different chromatographic techniques such as TLC and HPLC. Feces from wild and captive individuals of T. matacus and E. sexcinctus were analyzed. Bile acids were extracted with benzene:methanol. For TLC bile acids were spotted on silicagel plates, eluted with toluene:acetic acid:water and revealed with anisaldehyde:glacial acetic acid:sulphuric acid. An HPLC equipped with an UV-visible detector set at 200 and 210 nm was used. The separation was achieved using a C-18 column. Mobile phase consisted of ammonium carbonate 0.3%:acetonitrile in a gradient, at a flow of 0.8 ml/min. Bile acids were identified by comparison with standard retention factor and retention times in TLC and HPLC respectively. Both species were differentiated by their bile acid patterns, having taurocholic, glycocholic, chenodeoxycholic, dehydrocholic, deoxycholic and lithocholic acids, as well as cholesterol. In TLC, T. matacus showed deoxycholic and chenodeoxycholic acids as one spot (Rf:0.32) in the plates, while in E. sexcinctus they appeared as two separate spots (Rf:0.47, Rf:0.43). In HPLC, T. matacus showed a majority peak for chenodeoxycholic acid (Rt:20.6 min) which is not detected in E. sexcinctus; this species showed a majority peak for cholic acid (Rt:9.6 min) while this compound is minority for T matacus. In HPLC, conjugated bile acids showed more absorbance at UV than no conjugated bile acids; and most compounds showed greater absorbance at 200 than 210 nm. Feces of T. matacus and E. sexinctus were differentiated in this work; thus, demonstrating the usefulness of TLC and HPLC to identify wild-collected feces of those species by their bile acid pattern.

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