Exploring how changes to the steroidal core alter oleogelation capability in sterol: gamma-oryzanol blends

Oleogels based on sterols such as beta-sitosterol blended with the sterol ester gamma-oryzanol are a very interesting class of systems, but there are aspects of their formation and structure that remain elusive. It has previously been shown that a methyl group on the C30 position of the sterol-ester plays an important role in gelation. This work explored the effect that having C30 methyl groups on both the sterol and the sterol-ester had on the gelation process and subsequent gel structure. Lanosterol and saponified gamma-oryzanol (which was synthesized as part of this study) were identified as materials of interest, as both feature a methyl group on the C30 position of their steroidal cores. It was observed that both sterols formed gels when blended with gamma-oryzanol, and also that lanosterol gelled sunflower oil without the addition of gamma-oryzanol. All of these gels were significantly weaker than that formed by beta-sitosterol blended with gamma-oryzanol. To explore why, molecular docking simulations along with AFM and SAXS were used to examine these gels on a broad range of length scales. The results suggest that saponified gamma-oryzanol-gamma-oryzanol gels have a very similar structure to that of beta-sitosterol-gamma-oryzanol gels. Lanosterol-gamma-oryzanol gels and pure lanosterol gel, however, form with a totally different structure facilitated by the head-to-tail stacking motif exhibited by lanosterol. These results give further evidence that relatively slight changes to the molecular structure of gelators can result in significant differences in subsequent gel properties.