Abstract
This study aimed to analyze the bile acid patterns in commercially available oxgall powders used for evaluation of the bile tolerance ability of probiotic bacteria. Qxgall powders purchased from Sigma-Aldrich, Oxoid and BD Difco were dissolved in distilled water, and analyzed. Conjugated bile acids were profiled by ion-pair high-performance liquid chromatography (HPLC), free bile acids were detected as their p-bromophenacyl ester derivatives using reversed-phase HPLC after extraction with acetic ether, and total bile acids were analyzed by enzymatic-colorimetric assay. The results showed that 9 individual bile acids (i.e., taurocholic acid, glycocholic acid, taurodeoxycholic acid, glycodeoxycholic acid, taurochenodeoxycholic acid, glycochenodeoxycholic acid, cholic acid, chenodeoxycholic acid, deoxycholic acid) were present in each of the oxgall powders tested. The content of total bile acid among the three oxgall powders was similar; however, the relative contents of the individual bile acids among these oxgall powders were significantly different (P < 0.001). The oxgall powder from Sigma-Aldrich was closer to human bile in the ratios of glycine-conjugated bile acids to taurine-conjugated bile acids, dihydroxy bile acids to trihydroxy bile acids, and free bile acids to conjugated bile acids than the other powders were. It was concluded that the oxgall powder from Sigma-Aldrich should be used instead of those from Oxoid and BD Difco to evaluate the bile tolerance ability of probiotic bacteria as human bile model.
Highlights
Bile acids are synthesized from cholesterol in liver hepatocytes in humans and most animals, stored in the gallbladder, secreted into the small intestine after ingestion of a fatty meal, efficiently reabsorbed by the distal small intestine and returned to the liver via the portal vein [1]
The liquid chromatograms obtained from the analysis of the bile acid compositions of the three oxgall powders showed baseline separation and symmetrical sharp peaks for most the conjugated bile acids (S1 Fig) and the free bile acids modified as p-bromophenacyl esters (S2 Fig) under the present chromatographic conditions
The major conjugated bile acids in the oxgall powders were identified as taurocholic acid (TCA), glycocholic acid (GCA), taurodeoxycholic acid (TDCA), glycodeoxycholic acid (GDCA), taurochenodeoxycholic acid (TCDCA) and glycochenodeoxycholic acid (GCDCA), whereas the major free bile acids were characterized as cholic acid (CA), deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA)
Summary
Bile acids are synthesized from cholesterol in liver hepatocytes in humans and most animals, stored in the gallbladder, secreted into the small intestine after ingestion of a fatty meal, efficiently reabsorbed by the distal small intestine and returned to the liver via the portal vein [1]. Bile acids are a digestive secretion that plays an important physiological role in the elimination of cholesterol from the body and in the intestinal solubilization and absorption of lipids [2]. Bile acid concentration ranges from *8% in the gallbladder to *0.2–2% in the intestine. These values are not absolute, though, as person-to-person variations in bile acid levels exist due to factors such as dietary intake [3].
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