Synthesis, Physical Properties, and In Vitro-Simulated Gastrointestinal Digestion of Hydrophilic β-Sitosterol Sugar Esters

Hydrophilic β-sitosterol sugar esters were synthesized by a two-step biocatalytic approach using β-sitosterol vinyl adipate as an intermediate. The maximum conversion (above 90%) of β-sitosterol vinyl adipate was achieved using the saccharides glucose, sucrose, and raffinose. The chemical structure of the synthesized esters was confirmed by various techniques. The investigation of physical properties revealed that β-sitosterol sugar esters had enhanced water solubility (3.0-8.0 mM at 35 °C), reduced crystallinity, and high wettability. Their lyotropic liquid crystal properties were observed by polarized light microscopy. Furthermore, β-sitosterol sugar esters could be hydrolyzed into β-sitosterol adipate under simulated intestinal conditions at a low rate (2.83-18.14%). Most β-sitosterol sugar esters probably entered into intestinal bile salt micelles with ester bonds intact and showed up to 10-fold higher in vitro bioaccessibility than free β-sitosterol in non-fat systems. The excellent physical and functional characteristics of β-sitosterol sugar esters suggested their great potential application in the food industry.