Flaxseed protein-derived peptide fractions: Antioxidant properties and inhibition of lipopolysaccharide-induced nitric oxide production in murine macrophages

A protein isolate was produced from cellulase-treated defatted flaxseed meal followed by hydrolysis with seven proteases and evaluation of the hydrolysates for antioxidant and anti-inflammatory properties. The flaxseed protein hydrolysates (FPH) were processed by ultrafiltration and ion-exchange chromatography to isolate low molecular weight (LMW) and cationic peptide fractions, respectively. The peptides showed antioxidant properties in scavenging 2,2-diphenyl-1-picrylhydrazyl radical, superoxide anion radical, electron-spin resonance-detected hydroxyl radical and nitric oxide. In addition, all peptide fractions inhibited semicarbazide-sensitive amine oxidase activity. Antioxidant activities of these peptides were dependent on the specificity of proteases and size of the resulting peptides. The LMW fractions from pepsin, ficin and papain FPH also inhibited lipopolysaccharide-induced nitric oxide productions in RAW 264.7 macrophages without apparent cytotoxicity; thus, these peptides may act as anti-inflammatory agents. Thus, flaxseed protein hydrolysates may serve as potential ingredients for the formulation of therapeutic products.