Abstract:

The actual mechanism of cholesterol redn. by phytosterols is yet to be explored. One hypothesis states that cholesterol and phytosterols compete on the solubilization locus within gastric bile salt micelles. In this study competitive solubilization within microemulsions as vehicles for dietary intake of cholesterol and phytosterols was studied by pulse gradient spin-echo NMR. The loaded microemulsions undergo phase transitions as a function of diln., the type of solubilized sterol, and the wt. ratio of the cosolubilized sterols. Microemulsions contg. 10-20 wt% of aq. phase, show similar diffusivity of the oil and aq. phases in all examd. systems (excluding PS-loaded one) reflecting the minor influence of these solubilizates on the structure of the inner and the outer phases. The closeness of these structures enables the mobility of water mols. between them. Upon further diln. (\textgreater20 wt% aq. phase), significant differences in decrease rate of the oil and increase of the water phases mobilities (occurring upon inversion), were detected within the studied systems. It was concluded that the solubilized sterols influence the structural transitions based on their location within the structures and their competitive solubilization. The phytosterols solubilized mostly in the continuous oil phase and between the surfactant tails. Cholesterol is solubilized in the vicinity of the surfactant headgroups and affects the surface curvature. In mixts. of cholesterol and phytosterols, structural changes are dictated mostly by the presence of the cholesterol. [on SciFinder(R)]