Fractionation and evaluation of radical scavenging peptides from in vitro digests of buckwheat protein

Buckwheat protein (BWP) isolate was subjected to a two-stage in vitro digestion (1 h pepsin followed by 2-h pancreatin at 37 °C). The antioxidant potential of the BWP digests was compared by assessing their capacity to scavenge 2,2′-azinobis (3-ethylbenzothiszoline-6-sulphonic acid) (ABTS+) and hydroxyl (OH) radicals. The 2-h pancreatin digest, which demonstrated the strongest activity against both radicals, was subjected to Sephadex G-25 gel filtration. Of the six fractions collected, fractions IV (456 Da) and VI (362 Da) showed the highest ABTS+ scavenging activity and were 23–27% superior to mixed BWP digest (P < 0.05). Fraction VI was most effective in neutralising OH and was 86% and 24% more efficient (P < 0.05) than mixed BWP digest and fraction IV, respectively. LC–MS/MS identified Trp-Pro-Leu, Val-Pro-Trp, and Val-Phe-Pro-Trp (IV), Pro-Trp (V) and tryptophan (VI) to be the prominent peptides/amino acid in these fractions.