Antioxidant Peptides Identified from Ovotransferrin by the ORAC Method Did Not Show Anti-Inflammatory and Antioxidant Activities in Endothelial Cells

Oxygen radical absorbance capacity (ORAC) is a widely used method of measuring antioxidant capacities of various antioxidant components. Surprisingly, 16 antioxidant peptides previously identified from egg protein ovotransferrin using the ORAC method did not show any anti-inflammatory and antioxidant activities in cells. After simulated gastro-intestinal digestion (GID), several peptide digests significantly reduced the expression of tumor necrosis factor-alpha (TNF-alpha)-induced proinflammatory intercellular cell adhesion molecule-1 (ICAM-1) by 65.7 +/- 10.4% and vascular cell adhesion molecule-1 (VCAM-1) by 53.5 +/- 9.6% to 61.0 +/- 14.5%, but only GWNI reduced TNF-alpha-activated superoxide generation by 71.0 +/- 12.9% when tested with dihydroethidium (DHE) assay. Mass spectrometer analysis identified two new peptides, GWN and GW, in the GWNI digest; however, only GW reduced TNF-alpha-induced VCAM-1 expression (64.3 +/- 20.6%) significantly compared to the TNF-a treated cells. Our study suggested that ORAC lacked biological relevance in assessing bioactive peptides.