MATERIALS AND METHODS

General TLC was performed on silica gel precoated TLC aluminum sheets (0.2 mm thickness, Merck, Germany). NMR spectra were measured at 600MHz on a JEOL ECA-600 spectrometer using chloroform-d5 as a solvent and tetramethylsilane as internal standard. GC-MS was carried out on GCMS-QP2010 (Shimadzu, Kyoto, Japan) under the following conditions: column, DB-1MS (0.25 mm15. 0 m); column oven temperature, 70—250 C at a rate of 20 C/min with initial time of 1 min, followed by 250—290 C at a rate of 2 C/min with final time of 2 min; injection port temperature, 300 C; ion source temperature, 200 C; pressure of helium carrier gas, 150 kPa; ionizing voltage, 70 V. Bile acid samples were treated with freshly prepared ethereal diazomethane solution at room temperature for 1 h, and the resulting methyl esters were chromatographed as their trimethylsilyl (TMS) ether derivatives.