Abstract: In order to obtain peptide fractions, duck liver proteins were recovered by isoelectric precipitation, and then hydrolyzed simultaneously by alcalase and flavorzyme. The molecular mass distribution of the hydrolysate was determined by using a gel permeation chromatography (GPC) system followed by fractionation using a combination of gel filtration chromatography (GFC) and reversed phase-high performance liquid chromatography (RP-HPLC). Ten novel peptides with molecular mass less than 1 300 Da were identified from the subfraction with high inhibitory effect on cytokine release from macrophages using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The anti-inflammatory activity of the synthetic peptides was tested in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. Peptides LVYPFPGPI and VIESPPEI inhibited the release of NO from inflammatory cells in a dose-dependent manner, with inhibition percentages of 48.24% and 56.32% at the concentration of 100 μg/mL, respectively. VIESPPEI at the concentration of 100 μg/mL inhibited TNF-α release by 42.48%. Notably, IDVSPDSPDHY showed the strongest ability to inhibit the release of IL-6, with an inhibition percentage of 27.04% at the concentration of 25 μg/mL. This study may provide new ideas for the high-valued comprehensive utilization of duck by-products and their application in safe treatment of inflammation.

Key words: duck liver proteins; enzymatic hydrolysis; anti-inflammatory peptides; RAW264.7 macrophages