Synergistic and Antagonistic ACE Inhibition by Food-Derived Tripeptide-Polyphenol Pairs: Roles of Binding Stability and Peptide Dissociation

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Interactions between food-derived angiotensin-I-converting enzyme (ACE)-inhibitory peptides and polyphenols may influence multicomponent inhibitor performance. Enzymatic assays and Chou-Talalay combination index analysis evaluated leucyl-alanyl-phenylalanine (LAF), leucyl-leucyl-leucine (LLL), quercetin (QU), chlorogenic acid (CA), epigallocatechin gallate (EGCG), and their mixtures at five peptide-to-polyphenol molar ratios. EGCG-containing mixtures showed synergistic inhibition, with mean CI values of 0.89 and 0.81 for LAF-EGCG and LLL-EGCG, respectively, whereas LAF-QU and LLL-QU were antagonistic (mean CI: 1.51 and 1.19). LAF-CA and LLL-CA showed mean CI values of 0.81 and 0.72, respectively, although these values remain provisional due to the limited characterization of CA’s individual dose–effect relationship. Simulations associated CA- and EGCG-containing systems with persistent peptide contacts, more compact active-pocket conformations, and higher calculated peptide-dissociation barriers; QU-containing systems showed greater pocket overlap and lower barriers. These in vitro and computational results provide a target-level framework for prioritizing peptide-polyphenol pairs for further food-matrix, digestion, transport, and in vivo validation.