The Synergistic Anti-inflammatory Activity and Interaction Mechanism of Ellagic Acid and a Bioactive Tripeptide (Phe-Pro-Leu) from Walnut Meal

The anti-inflammatory effect of the interaction between ellagic acid (EA) and a bioactive tripeptide (FPL) from walnut meal was investigated in this study. We found that lipopolysaccharide (LPS) -induced expression of nitric oxide, tumor necrosis factor-α, interleukin-6, and interleukin-1β were significantly inhibited by the interaction of EA and FPL in RAW264.7 macrophage cells. Cell viability assays and CompuSyn simulations predicted the highest synergistic effect of the combination at doses of EA-25 µM and FPL-100 µM, with the lowest combination index (CI) values reaching 0.56. Fluorescence spectra revealed the intrinsic fluorescence of phenylalanine in FPL was quenched by interaction with EA. Fourier transform infrared spectroscopy indicated FPL had electrostatic and hydrophobic interactions with EA through N–H, C = O, C-N bonds and the secondary structure of FPL had effectively changed, with a decrease in α-helix when interacting with EA. Our results demonstrated that the synergistic anti-inflammatory effect of EA and FPL as potential inflammatory inhibitors in food industry.