Delivery of Curcumin Using Colloidal Complexes Formed from Ammonium Chitosan and Acid Treated Soybean Protein

Curcumin (CUR) is found to exhibit a broad spectrum of potentially beneficial biological activities, which make it suitable as a nutraceutical ingredient in functional foods and supplements. But its application for this purpose is often limited by its low water-solubility, chemical stability, and bioavailability. In this study, acid-treated soybean protein isolate (SPI) and chitosan quaternary ammonium salt (CQAS) were used to assemble colloidal carriers for CUR to form soybean protein isolate-curcumin-chitosan quaternary ammonium salt nanoparticles (SPI-CUR-CQAS NPs). The nanoparticles formed were relatively small (< 400 nm), approximately spherical, and strongly positively charged (> 45 mV). Fluorescence spectroscopy demonstrated that the dominant interaction between CUR and SPI was hydrophobic attraction, while the dominant interaction between CQAS and SPI was electrostatic attraction. The encapsulation efficiency (95.4%) and loading capacity (14%) of the SPI-CUR-CQAS NPs (pH 1.5) were relatively high. The vitro digestion experiments showed that the CUR was progressively released from the nanoparticles under stomach, small intestine, and colon conditions. Moreover, the final bioavailability of the encapsulated CUR (63%) was much higher than for free CUR (18.5%). The SPI-CQAS NPs developed in this study can therefore be used as an effective delivery system for CUR in functional foods.