Frationation of hydrolysate from corn germ protein by ultrafiltration: In vitro antidiabetic and antioxidant activity

In the present work, defatted corn germ was hydrolyzed by three proteases and further separated by sequential ultrafiltration with different molecular weight cutoff (100, 10, 2 kDa). Corn germ protein hydrolysate (CGPH) and their fractions were investigated for antioxidant activity, alpha-glucosidase, alpha-amylase, and DPP-IV inhibitory activity. The degree of hydrolysis (DH) after 2 hr was 17.5%, 11.14%, and 2.05% for alcalase, trypsin, and flavourzyme, respectively. Trypsin hydrolysate showed the highest DPPH and ABTS(+) radical scavenging and Fe2+ chelating activity, but a lower alpha-glucosidase inhibitory activity. F1 fraction (<2 kDa) exhibited highest radical scavenging and alpha-glucosidase inhibitory activity. While F2 fraction (2-10 kDa) showed the higher Fe2+ chelating and alpha-amylase inhibitory activity, F1 fraction of flavourzyme showed the highest alpha-glucosidase inhibitory and F2 fraction of alcalase and flavourzyme exhibited highest alpha-amylase inhibitory activity. Hydrolysate and F1 fraction of alcalase and F2 fraction of trypsin showed the highest DPP-IV inhibitory activity. RP-HPLC results showed that trypsin hydrolysate had higher levels of high-hydrophobic peptides. The amino acid composition of the F1 fractions showed high levels of hydrophobic amino acids. Thus, CGPHs may be used as a potential source of antioxidant and antidiabetic peptides in food industry and pharmaceutical application.