ABSTRACT
Although PSE should be handled by the various efficient esterases in the first part of the GI tract to result in the free sterols and fatty acids, a volunteer trial with stoma patients was conducted to confirm this. To understand the kinetics of the process, human trials have been conducted with otherwise healthy patients, ileostomized at different places in the GI tract (unpublished results). Determination of the levels of the free sterols and the sterols esters gives the desired information on the degree of hydrolysis as a function of GI tract transit time. Such studies require reliable methods for the determination of free vs. esterified sterols in the complex ileostomy excreta. From Table 5 it is clear that sample pretreatment should start with an extraction step. Saponification evidently cannot be used. The stoma fluid is a good example for the different and sometimes difficult matrices encountered in sterol analysis. Mild extraction conditions should be used, i.e., hexane extraction at ambient temperature under slow shaking overnight. Low temperatures have to be used to avoid reactions such as transesterification or oxidation of the compounds catalyzed by the stoma matrix as well as to minimize coextraction of other compounds that might interfere in subsequent quantification steps. The approach for sample clean-up as outlined in Table 5 resulted in the typical chromatograms as shown in Fig. 13. On average the study samples showed only low amounts of sterol esters still present at the end of the small intestine, indicating an efficient action of the GI enzymes (unpublished results). A similar approach can be used for the analysis of sterols in human or animal plasma. Plasma sterol analysis might be required to understand the absoption and uptake of sterols other than cholesterol. From the literature it is known that plant sterols, in contrast to
