Antioxidant activity of soluble proteins and their peptic hydrolysates from commercially available corn flakes

The antioxidant activity of soluble proteins from commercially available corn flakes was determined using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and compared with their corresponding enzymatic hydrolysates using pepsin. Qualitative test using Bradford reagent showed positive results for the presence of proteins for all protein samples (i.e. crude extract, crude protein, and dialyzed crude protein) and their hydrolysates. Bradford assay showed the highest protein concentration for the crude extract followed by the crude protein. Dialyzed crude protein had the lowest soluble protein content which might indicate loss of low molecular weight proteins upon dialysis. SDS-PAGE gel of the protein samples showed faint bands indicating that certain peptides that are higher in molecular weight than BSA are present in the sample. While, the SDS-PAGE of the protein hydrolysates showed no bands indicating that effective hydrolysis using pepsin was performed. In the DPPH assay, the protein samples generally had higher antioxidant activity than the peptic hydrolysates ranging from 90.41% to 95.84%. The crude extract showed the highest antioxidant activity followed by the crude protein and lastly, the dialyzed crude protein. Peptic hydrolysates showed lower antioxidant activity ranging from 42.48% to 50.50% and around 40-50% reduction in antioxidant activity compared to their corresponding intact proteins. Increasing the incubation time for enzymatic hydrolysis using pepsin led to an increase in the antioxidant activity of the hydrolysates. Electrophoretic profiling of the protein samples showed single disctinct protein band while non was observed for the peptic hydrolysates