Isolation and Characterization of Bioactive Proteoglycan–Lipid Nanoparticles from Freshwater Clam (Corbicula fluminea Muller) Soup

Nanoparticles can be prepared by several sophisticated processes but until now, it cannot be prepared by simple home cooking. Here, we report that two incidental food nanoparticles (iFNPs) consisting of proteoglycans and phytosterols were isolated from soup made from freshwater clam (Corbicula fluminea Muller), a renowned folk remedy for liver problems in China and other parts of East Asia. These two bioactive iFNPs were obtained and characterized by anionic exchange chromatography coupled with multi-angle laser light scattering measurement. Their hydrodynamic diameters and ζ-potentials were 50 ± 0.2 nm and -28.0 mV and 67 ± 0.4 nm and -9.96 mV, respectively. FT-IR revealed that the proteoglycans in the particles contained α-type heteropolysaccharides. Both iFNPs were resistant to pH changes and separation by mechanical force but responsive to temperature changes. They effectively inhibited cholesterol uptake in vitro, which resonates with the traditional belief that freshwater clam soup provides hepatoprotective benefits. This study suggests that these two proteoglycan-lipid iFNPs are the active moieties and offers a supramolecular structure-based approach to study the function of such complex matrices derived from food.