Structural Characteristics and in vitro Antioxidative Activity of Wheat Oligopeptides
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Abstract:
The structural characteristics of wheat oligopeptides were elucidated using scanning electron microscopy imaging as well as analyses of their basic physicochemical composition, relative molecular weight distribution, amino acid composition, and ultraviolet and circular dichroism spectra. The in vitro antioxidative activity of the oligopeptides was investigated by determining their oxygen radical absorbance capacity (ORAC) and their abilities to scavenge hydroxyl, DPPH, and ABTS free radicals. The wheat oligopeptides were in the form of spherical granules and had irregular folds and pores on the surface. Their protein and peptide contents were 95.86% and 83.74% (both on a dry basis), respectively, and 92.22% of the components had a molecular weight of less than 1000 u. Their contents of essential amino acids and hydrophobic amino acids were 20.46% and 33.38%, respectively. The maximum absorption peak was at 270 nm. The α-helix, parallel β-fold, antiparallel β-fold, β-turn, and random coil contents of the oligopeptides were 5.83%, 3.14%, 37.57%, 20.32%, and 33.14%, respectively, indicating the coexistence of multiple secondary structures. The IC50 values of wheat oligopeptides for hydroxyl and DPPH free radicals were 9.6 and 1.5 mg/mL, respectively. Moreover, their ABTS free radical-scavenging activity was 3.53 mmol Trolox/g and their ORAC was 1035.52 μmol Trolox/g. In summary, these findings indicating the strong antioxidative capacity of wheat oligopeptides provide a theoretical basis for their use in the development of antioxidant-containing foods.
