In vitro immunomodulatory and antioxidant effects of oligopeptides and four characteristic peptides in black‐bone silky fowl (Gallus gallus domesticus Brisson)

Black‐bone silky fowl (Gallus gallus domesticus Brisson) is considered to have strengthening effect on the body and immunomodulatory effects. The black‐bone silky fowl peptide (BSFP) was produced by enzymatic digestion of the whole black‐bone silky fowl (including the head and claws) after removal of the viscera. Afterwards, the four of the characteristic peptides Glu‐Phe (EF), Glu‐Glu‐Leu (EEL), Glu‐His‐Pro‐Thr (EHPT), Ala‐Gly‐Gly‐His (AGGF) of the BSFP were identified by HPLC‐MS/MS. The preventive effects of BSFP and the four characteristic peptides on antioxidant and immunomodulation were investigated. The antioxidant capacity was assessed by in vitro HepG2 intracellular reactive oxygen species (ROS). The immunomodulatory experiments were conducted by measuring the effects of the BSFP and four peptides on the proliferation of splenocytes, T and B lymphocytes cells, the CD4+/CD8+ T lymphocytes ratio, and the phagocytic capacity of macrophages and the nitric oxide (NO) content of macrophages. The four peptides of BSFP showed strong antioxidant capacity, with the most potent peptide for intracellular ROS being AGGF, with 56% inhibition. AGGF, EF, and BSFP showed highly positive effects on splenocyte proliferation and when Concanavalin A (ConA) was used as a stimulus for T lymphocytes and lipopolysaccharide (LPS) as a stimulus for B lymphocytes, the peptides stimulated cell proliferation in a dose‐dependent manner. Of these, EF, AGGF, and BSFP promoted the proliferation of T lymphocytes; EF, EHPT, and BSFP significantly promoted the proliferation of B lymphocytes. EHPT and BSFP increased the CD4+/CD8+ ratio of T cells. Needle aspiration of neutral red was significantly promoted by macrophages treated with peptides other than EF. In addition, EEL, EHPT, AGGF, and BSFP had a promotive effect on NO production in phagocytes. The results indicate that BSFP is a peptide product with good immunomodulatory functions, four peptides identified from BSFP show outstanding effects in terms of antioxidant properties and immunomodulation. Practical applications In this study, the amino acid composition and relative molecular masses of the black‐bone silky fowl peptide were analyzed, while the four peptides with significant effects on antioxidant and immunomodulatory properties in black‐bone silky fowl peptide were identified by HPLC‐MS/MS technique. Positive effects of black‐bone silky fowl peptide and its four peptides on antioxidant capacity and immunomodulatory ability