β-Sitosterol Loaded Nanostructured Lipid Carrier: Physical and Oxidative Stability, In Vitro Simulated Digestion and Hypocholesterolemic Activity

The objective of the present study was to explore the potential of nanostructured lipid carriers (NLCs) for improving the oral delivery of β-sitosterol, a poorly water-soluble bioactive component with hypocholesterolemic activity. Two β-sitosterol formulations with different solid lipid compositions were prepared by melt emulsification, followed by the sonication technique, and the effect of storage conditions and simulated digestion on the physical, chemical and oxidative stability, bioaccessibility and release were extensively studied. Both NLC preparations remained relatively stable during the four weeks of storage at different conditions (4, 25 and 40 °C), with more superior stability at lower temperatures. The in vitro digestion experiment indicated a high physical stability after exposure to the simulated mouth and stomach stages and an improved overall β-sitosterol bioaccessibility at the end of the digestion. The NLCs presented an increased solubility and gradual release which could be justified by the remarkable affinity of β-sitosterol to the complex lipid mixture. An in vivo study demonstrated an improved reduction in the total cholesterol and low-density lipoprotein cholesterol plasma levels in mice compared with the drug suspension. These investigations evidenced the potential of the developed NLC formulations for the enhancement of solubility and in vivo performance of β-sitosterol.