An antihypertensive heptapeptide from tree bean (Parkia timoriana) seeds: isolation, mechanism, and stability

This study investigated the antihypertensive potential of bioactive peptides derived from the underutilized tree bean seed proteins (TBSP) via angiotensin-I converting enzyme (ACE) inhibition. ACE inhibition is a common therapeutic strategy for managing hypertension. Among the enzymatic hydrolysates, the TBSP simulated gastrointestinal (SGI) hydrolysate (80% inhibition at 0.17 mg/mL) and the TBSP thermolysin hydrolysate (78% inhibition at 0.17 mg/mL) exhibited strong ACE-inhibitory (ACEi) activity, with the SGI hydrolysate showing the lowest IC₅₀ (31.8 ± 2.6 µg/mL). Sequential fractionation using strong cation exchange and RP-HPLC yielded FY7 (FVLNSPY), a novel heptapeptide exhibiting potent ACEi activity with an IC₅₀ value of 72.3 ± 1.7 µM. Enzyme kinetics and molecular docking indicated a non-competitive inhibition pattern and revealed stable interactions between FY7 and ACE allosteric sites. FY7 also withstood ACE pre-incubation and remained largely intact after 6 h of simulated gastrointestinal digestion, highlighting its oral stability. Collectively, these findings highlight FY7 as a promising natural antihypertensive candidate for incorporation into functional foods or nutraceutical formulations, warranting further in vivo validation.