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.

Hepatoprotective mechanism of freshwater clam extract alleviates non-alcoholic fatty liver disease: elucidated in vitro and in vivo models.

Freshwater clams (Corbicula fluminea) have long been used as a folk remedy in Chinese tradition. Their hot-water extract has been commercialized as a functional drink for liver protection. The objective of this study was to develop a product of the residual clam meat (FCR) and assess its functional compounds. The ethanol extract of FCR, designated FCRE, was identified to comprise phytosterols, polyunsaturated fatty acids (PUFAs) and carotenoids. FCRE significantly reduced lipid accumulation and cell death in HepG2 cells via decreased fatty acid synthase (FAS) activity and increased activities of carnitine palmitoyltransferase (CPT) and acyl-CoA oxidase (ACO), indicative of suppressed lipogenesis and increased ß-oxidation of fatty acids. In tilapia fed with high-fat diet (HFD), FCRE mitigated nonalcoholic steatohepatitis (NASH), which was evidenced by decreased levels of plasma aspartate transaminase (AST) and alanine transaminase (ALT), in addition to reduced total cholesterol and accumulation of triacylglycerols, particularly those of saturated and monounsaturated fatty acids. FCRE also suppressed stearoyl-CoA desaturase-1 (SCD-1) index, increased the PUFAs' n3/n6 ratio, and reduced prostaglandin E2 (PGE2) and inflammatory infiltrates in tilapia liver. Tilapia fed with HFD for 2 weeks displayed NASH symptoms, while mice took 10 weeks to display NASH symptoms. No previous study has been reported on the potential use of tilapia as an NASH model for pre-screening hepatoprotective-functional foods.

Phenolic acids identified in sorghum distillery residue demonstrated antioxidative and anti-cold-stress properties in cultured tilapia, Oreochromis mossambicus.

This study aimed to identify the bioactive compounds and evaluate the anti-cold-stress function of the sorghum distillery residue (SDR) using tilapia as an alternative animal model. The highest contents of water-soluble bioactive compounds in SDR were polyphenols, followed by tannins, anthocyanins, and flavonoids. SDR was extracted with double-distilled water, 95% ethanol, and ethyl acetate, separately. The ethanol extract (SDR-E) yielded the highest polyphenol content [15.03 mg/g of SDR dry weight (dw)], of which the EC50 value of R,R-diphenyl-ß-picrylhydrazyl (DPPH) radical scavenging efficiency was 0.56 ± 0.04 mg/mL. The SDR-E suppressed the oxidation of low-density lipoproteins (LDLs) more efficiently than that of other extracts. Tilapia fed a diet containing 3.6% SDR-E decreased accumulative mortality during cold stress, of 46.2%. The accumulative morality of the control was 92.9%. The phenolic acids identified in SDR included gallic acid (0.36 ± 0.08 mg/g of SDR dw), 3,4-dihydroxybenzoic acid (0.16 ± 0.12 mg/g of SDR dw), and 4-hydroxybenzoic acid (0.49 ± 0.23 mg/g of SDR dw). Diets supplemented with 0.5% 4-hydroxybenzoic acid fed to tilapia showed a lower mortality rate than that fed 1.0% 4-hydroxybenzoic acid, comparable to that of the tilapia fed 20% SDR. The latter showed lower mortality than that of the control. These results suggested that 4-hydroxybenzoic acid is one of the major anti-cold-stress compounds in SDR.