Determination of Fecal Sterols Following a Diet with and without Plant Sterols.

The aim of this study was to develop a method for neutral fecal sterols determination in subjects receiving a normal diet with or without a plant sterols-enriched beverage using gas chromatography-mass spectrometry (GC/MS). Sample preparation conditions (homogenization of lyophilized feces with water) were evaluated. Sterol determination required direct hot saponification, unsaponifiable extraction with hexane, and the formation of trimethylsilyl (TMS) ether derivatives. The method allows the quantification of cholesterol, plant sterols and their metabolites (coprostanol, coprostanone, cholestanol, cholestanone, methylcoprostanol, methylcoprostanone, ethylcoprostenol, stigmastenol, ethylcoprostanol and ethylcoprostanone). Good linearity was obtained (r > 0.96) and interference was only observed for coprostanone, where the standard addition method proved necessary for quantification. The limits of detection (LOD) ranged from 0.10 to 3.88 µg/g dry feces and the limits of quantitation (LOQ) from 0.34 to 12.94 µg/g dry feces. Intra- and inter-assay precision (RSD %) were 0.9-9.2 and 2.1-11.3, respectively. Accuracy, expressed as percentage recovery (80-119%) was obtained for all determined sterols.