Anti-inflammatory effect of lentil hull (Lens culinaris) extract via MAPK/NF-κB signaling pathways and effects of digestive products on intestinal barrier and inflammation in Caco-2 and Raw264.7 co-culture

Abstract

• RLE and GLE inhibit the MAPK and NF-κB signaling pathways to exert anti-inflammatory activity. • 5 main chemical substances were quantified in RLD. • RLD can be absorbed by the intestine and maintain the intestinal barrier and exert anti-inflammatory effects. • Polyphenol-rich lentil hulls may be a potentially valuable functional dietary resource. The polyphenol-rich lentil hulls are the by-product of lentils hulling process. In this manuscript, in vitro digestion, Caco-2 cell monolayer and Caco-2/RAW264.7 cell co-culture model were established to explore their anti-inflammatory mechanism, absorption of digestive products (RLD), and impact on the intestinal barrier. Results shown that high dose RLE and GLE could significantly inhibit the secretion of NO (30.23% and 31.08%, respectively), IL-6 (81.48% and 56.82%, respectively) and IL-1β (88.05% and 91.67%, respectively), and down-regulate the protein and mRNA expression of iNOS (56.46% and 45.69%, respectively) and COX-2 (76.53% and 46.65%, respectively), and inhibit the activation of MAPK and NF-κB signaling pathways. Polyphenols can be released from lentil hulls and protocatechuic acid glycoside derivative has the highest content (2205.09 ± 7.02 μg/g DW). Digestive products can be absorbed by intestine to maintain intestinal barrier and play anti-inflammatory effect. Above all, lentil hulls may be a potentially valuable functional dietary resource.