Pea protein and p-coumaric acid conjugates: New evidence on in vitro digestion, modulation of gut microbiota, and anti-inflammatory activity

• Covalent bonds formed between PPI and p-CA at the C8 position of p-CA. • PPI-p-CA conjugates reversed native PPI’s inhibitory effect on the beneficial bacterium. • PPI-p-CA conjugates further enhanced native PPI’s promoting effect on the beneficial bacterium. • Covalent modification by p-CA weakened the anti-inflammatory potential of PPI but did not induce pro-inflammatory effects. This study aimed to investigate the gut health benefits and anti-inflammatory property of pea protein isolates (PPI) as affected by conjugating with p-coumaric acid (p-CA). 13 C NMR analysis confirmed the newly formed covalent bonds between PPI and p-CA occurred at the C8 position of p-CA. Results showed that after in vitro digestion, the conjugates exhibited higher protein digestibility compared to PPI. Dialysis was conducted to simulate small intestinal absorption and obtain non-absorbable fraction, which were utilized for human fecal fermentation and for the evaluation of anti-inflammatory activity in RAW 264.7 cells. Gut microbiota analysis revealed that PPI reduced the abundance of Bifidobacterium and increased Lactobacillus. However, after conjugation with p-CA, the inhibitory effect of PPI on Bifidobacterium was diminished, while its promotive effect on Lactobacillus was further strengthened. Meanwhile, PPI exhibited anti-inflammatory potential, as evidenced by the significant suppression of nitric oxide (NO) production and IL-6 expression. While the conjugates induced higher NO production compared to PPI, the levels remained lower than those induced by LPS alone, suggesting a partial reduction in anti-inflammatory potential after conjugation. Overall, this study provides new evidence that conjugation with phenolics can enhance pea protein's potential to positively influence gut microbiota composition, albeit with a reduced anti-inflammatory potential.