Pepsin Digested Oat Bran Proteins: Separation, Antioxidant Activity, and Identification of New Peptides

The aim of this study was to determine pepsin hydrolysis conditions to produce digested oat bran proteins with higher radical scavenging activities and separate and identify peptides. Isolated proteins were then digested with different concentrations of pepsin and incubation times. Hydrolysates produced with 1 : 30 enzyme substrate (E/S) ratio and 2 h possessed the highest peroxyl radical scavenging activity, 608 +/- 17 mu M TE/g (compared to 456-474 mu M TE/g for other digests), and was therefore subsequently fractionated into eight fractions (F1-F8) by high performance liquid chromatography (HPLC). F1 and F2 had little activity because of their low protein contents. Activities of F3-F8 were 447-874 mu M TE/g, 20-36%, and 10-14% in the peroxyl, superoxide anion, and hydroxyl radical tests, respectively. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify a total of fifty peptides that may have contributed to the activity of F3, a fraction that better scavenged radicals.