Binding affinity, antioxidative capacity and in vitro digestion of complexes of grape seed procyanidins and pork, chicken and fish protein.

Studies have reported that procyanidins can interact with proteins, thereby affecting their structure, function, and bioaccessibility. In this paper, we investigated the interaction between grape seeds procyanidins (GSP) and animal source protein (from pig, chicken and fish), and the effects on the protein structure, antioxidant capacity and bioaccessibility of GSP. Fluorescence results showed that the binding constant of GSP-protein complex was 10-104 M-1, and the main forces were van der Waals force, hydrogen bonds and hydrophobic interactions. The antioxidant capacity of GSP was masked by GSP-protein complexes formed. The circular dichroism indicated that GSP had an effect on the content of α-helix and ß-sheet in the secondary structure of pork and chicken proteins, but had little effect on the secondary structure of fish protein. The results showed that the protein can bind to GSP and affect its antioxidant activity and bioaccessibility. This study can provide reference for further study on the digestion and absorption of the complexes and offer health guidance in the preparation of diets.

Subcritical water extraction of polyphenolic compounds from sorghum (Sorghum bicolor L.) bran and their biological activities.

Subcritical water extraction (SWE), an environment-friendly technique, was applied to extract polyphenolics from sorghum bran. Extraction temperatures (°C), time (min), and solid-liquid ratio (mL/g) were investigated and optimized by Box-Behnken design. The optimized conditions for SWE was 144.5 °C of temperature, 21 min of time, and 35 mL/g of solid-liquid ratio, with a polyphenolics yield of 47.253 ±â€¯0.375 mg GAE/g dw, which was in good agree with the predicted value. Comparing with hot water extraction (HWE), SWE resulted in a higher yield of polyphenolics, higher radical scavenging activities, and more efficient antiproliferative activity. Furthermore, major polyphenolic compositions of the extracts were identified and quantified by HPLC-ESI-MS/MS. Taxifolin, taxifolin hexoside, oligomeric procyanidins, and epicatechin were the most abundant polyphenolic compounds in the extracts. Taken together, SWE can be used as a effective extraction method for polyphenolics from sorghum bran, which could be used as a potential source of natural antioxidants.