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, α‐glucosidase, α‐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 Fe(2+) chelating activity, but a lower α‐glucosidase inhibitory activity. F1 fraction (<2 kDa) exhibited highest radical scavenging and α‐glucosidase inhibitory activity. While F2 fraction (2–10 kDa) showed the higher Fe(2+) chelating and α‐amylase inhibitory activity, F1 fraction of flavourzyme showed the highest α‐glucosidase inhibitory and F2 fraction of alcalase and flavourzyme exhibited highest α‐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.