Antioxidant activity of enzymatic hydrolysates from eggshell membrane proteins and its protective capacity in human intestinal epithelial Caco-2 cells

Eggshell membrane (ESM) hydrolysate was prepared by Alcalase and Protease S (AL-PS) sequentially and was ultrafiltered as fractions AL-PS-I (<5 kDa), AL-PS-II (5-10 kDa), and AL-PS-III (>10 kDa). The antioxidant activity of ESM hydrolysate was evaluated using chemical assays and its protective ability against oxidative stress was investigated using human intestinal epithelial Caco-2 cell-based assay. AL-PS-I possessed the highest scavenging activity against DPPH and hydroxyl radicals. AL-PS-III demonstrated the best Fe2+ chelating activity. AL-PS and AL-PS-I had higher cellular antioxidant activity to inhibit the formation of DCF. The secretion of IL-8 was inhibited significantly (P < 0.05) at 2 h post pretreatment with AL-PS, AL-PS-I and AL-PS-II (0.1 and 0.5 mg/mL) and at 6 h post stimulation with 1 mM H2O2. In addition, AL-PS, AL-PS-I and AL-PS-II (0.5 mg/mL) increased glutathione (GSH) level significantly (P < 0.05) in H2O2-treated Caco-2 cells.