Improved stability and aqueous solubility of β-carotene via encapsulation in self-assembled bioactive oleanolic acid nanoparticles

Poor water solubility and stability of β-carotene (Car) greatly hinder its application in foods. Herein, naturally occurring bioactive oleanolic acid (OA) was used as a nanocarrier to overcome these shortcomings by fabricating Car-loaded OA nanoparticles (Car/OA NPs). Through optimization, the encapsulation efficiency and loading capacity reached 80.7% and 32.6%, respectively. Systematic characterization suggested that Car was successfully encapsulated, and hydrogen bonding and hydrophobic interactions are the main forces facilitating the self-assembly and encapsulation. Compared with free Car, Car/OA NPs exhibited significantly improved water dispersibility and enhanced stability against UV radiation, heat, ionic strength, and acidic conditions. Further, Car/OA NPs provided gastric protection, delayed-release in simulated gastric fluid (SGF) and controlled release in simulated intestinal fluid (SIF). Additionally, both OA NPs and Car/OA NPs showed markedly inherent hepatoprotective effects. This work demonstrates that OA NPs can be used as inherent bioactive nanocarriers to deliver hydrophobic nutrients and bioactive food components.