Trypsin-hydrolyzed Corn Silk Proteins: Antioxidant Activities, in vitro Gastrointestinal and Thermal Stability, and Hematoprotective Effects

The aim of this study was to examine the antioxidant capacity of Trypsin-hydrolyzed corn silk proteins, specifically radical scavenging, ferric reducing and anti-lipid peroxidation activities, as well as stability after heating and simulated gastrointestinal digestion. Among the 1-5-h hydrolysates, the 1-h Trypsin hydrolysate (T1H) was the strongest. T1H exhibited stronger H2O2 [half maximal effective concentration (EC50) = 156.44 mu g/mL] and superoxide (EC50 = 0.33 mg/mL) scavenging activities than glutathione, carnosine and N-acetylcysteine. Radical scavenging activities of T1H were heat-stable (25-100 degrees C), although lost by 20-58% after gastrointestinal digestion. Ferric reducing activity of T1H was heat-stable, even enhanced by 20% after gastrointestinal digestion. Lecithin liposome assay found anti-lipid peroxidation activity of T1H resistant to gastrointestinal peptidases. By contrast, 100 degrees C incubation reduced anti-lipid peroxidation activity of 0.5 mg/mL T1H to 3.5-fold lower than that of 25 degrees C incubation. At 30 mu g/mL, T1H (3% hemolysis) was stronger than glutathione (32% hemolysis) in protecting human red blood cells. T1H was 1.5-fold more potent than glutathione and carnosine in alleviating lipid peroxidation in the cells. Overall, T1H demonstrated strong, heat-stable radical scavenging activities, besides partial resistance to gastrointestinal peptidases. T1H was also hematoprotective. T1H is a promising antioxidant for the development of functional food ingredients and nutraceuticals. (c) 2020 International Association of Dietetic Nutrition and Safety. Publishing services by Atlantis Press International B.V. This is an open access article distributed under the CC BY-NC 4.0 license (http://creativecommons.org/licenses/by-nc/4.0/).