Digesting proteins from three legume types produced peptides with stronger antioxidant and ACE-inhibitory activity than the phenolic compounds the legumes are known for.
IC50 = 64 µg/mLBlack soybean peptides showed the strongest ACE inhibition after purification, improving up to 9-fold from crude hydrolysate
What the researchers found
After simulated digestion and purification, peptides from all three legumes showed potent ACE-inhibitory activity. The IC50 values (concentration needed to block 50% of ACE activity) improved two- to nine-fold after gel-permeation chromatography purification, reaching approximately 85 µg/mL for lentil, 64 µg/mL for black soybean, and 93 µg/mL for black turtle bean.
A total of 210 peptides were sequenced from the small (<3 kDa) fractions, with chain lengths from 6 to 18 amino acids. Lentil had the shortest average peptide length at 7.7 amino acids. Overall, the bioactive peptides contributed more antioxidant capacity and ACE inhibition than the phenolic compounds in these legumes. Black turtle bean proteins required more heating to achieve comparable digestibility to lentil and soy proteins.
Why it matters
ACE inhibitors are among the most prescribed blood pressure medications worldwide. Finding natural ACE-inhibiting peptides in common foods like lentils and beans suggests dietary protein — not just phenolics or fiber — may contribute to the cardiovascular benefits of legume-rich diets. This research supports the development of functional foods and supplements based on legume-derived bioactive peptides.
How the study worked
Proteins were isolated from lentils, black soybeans, and black turtle beans, then cooked and digested in vitro using pepsin, trypsin, and chymotrypsin to simulate human digestion. The resulting peptides were separated by ultrafiltration, anion-exchange chromatography, and gel-permeation chromatography. Peptides under 3 kDa were sequenced, and their antioxidant and ACE-inhibitory activities were measured at each purification step.
What this study cannot tell us
This is entirely an in vitro study — proteins were digested in a lab, not in actual human stomachs. Real digestion involves variable pH, enzyme levels, and transit times that could produce different peptide profiles. The ACE inhibition was measured in a test tube, not as blood pressure reduction in living organisms. Whether these peptides survive intestinal absorption intact and reach the bloodstream in active form is unknown.
How to read the evidence
This is a laboratory food science study using simulated digestion and in vitro assays. It provides proof-of-concept for bioactive peptide generation from legumes but has no human clinical data.
When this study was published
Published in 2025, this is a very recent study contributing to the rapidly growing field of food-derived bioactive peptides.
The bigger picture
Food-derived bioactive peptides are a growing research area bridging nutrition and pharmacology. This study adds to evidence that the health benefits of legumes extend beyond their famous fiber and phenolic content — the proteins themselves generate bioactive fragments during digestion. As the functional food industry grows, legume-derived ACE-inhibitory peptides could become ingredients in blood-pressure-lowering supplements, similar to how lactotripeptides from milk are already sold commercially.
Questions still open
- Do these legume-derived ACE-inhibitory peptides survive intact through human digestion and absorption to actually lower blood pressure?
- How do these peptide IC50 values compare to pharmaceutical ACE inhibitors like lisinopril?
- Could cooking methods be optimized to maximize bioactive peptide production from these legumes?
Common questions
Can eating lentils and beans actually lower your blood pressure?
Which legume produced the most potent blood-pressure-lowering peptides?
Read the original research
Structures, antioxidant, and angiotensin I-converting enzyme (ACE)-inhibitory activities of peptides derived from protein hydrolysates of three phenolics-rich legume genera.
Journal of food science, 90(2), e70069
Citation
Chang, Sam K C; Zhang, Yan; Pechan, Tibor. (2025). Structures, antioxidant, and angiotensin I-converting enzyme (ACE)-inhibitory activities of peptides derived from protein hydrolysates of three phenolics-rich legume genera.. Journal of food science, 90(2), e70069. https://doi.org/10.1111/1750-3841.70069