Free and Bound Phenolics of Laird Lentil (Lens culinaris) Hulls and the Anti-inflammatory Activity of their Digestive Products via Crosstalk between NF-κB and Keap1-Nrf2 Signaling Pathways in HT-29 Cells

Polyphenol-rich Laird lentil hulls are a byproduct of lentil processing. In the present study, free and bound polyphenols in lentil hulls were analyzed with UHPLC-LTQ-OrbiTrap-MS², and the anti-inflammatory mechanism of their digestive products was explored based on the NF-κB and Keap1-Nrf2 signaling pathways in the HT-29 cell model. In summary, a total of 27 polyphenols and 5 nonphenolic constituents were identified in free and bound fractions, and among them, catechin glucoside, kaempferol tetraglucoside, procyanidin dimer, and dihydroxybenzoic acid-O-dipentoside were the main polyphenols in the digestive products. These digestive products could reduce inflammatory mediators and exert anti-inflammatory activity by inhibiting NF-κB and activating Keap1-Nrf2 signaling pathways, and there was crosstalk between them, which was a mutual inhibition effect. The results show that polyphenols in lentil hulls are a good source of anti-inflammatory ingredients and have a promising development potential.