Two novel peptides isolated from rice bran protein effectively inhibited ACE (a key blood pressure-regulating enzyme) and promoted nitric oxide release in blood vessel cells, suggesting rice bran could be a source of natural antihypertensive compounds.
IC50 of 0.079 mg/mLThe peptide FDGSPVGY inhibited 50% of ACE activity at this concentration, demonstrating meaningful enzyme-blocking capability from a food-derived peptide.
What the researchers found
Two novel peptides were identified from rice bran protein hydrolysate: FDGSPVGY (840.4 Da) with an ACE-inhibitory IC50 of 0.079 mg/mL (94.05 μM), and VFDGVLRPGQ (1086.6 Da) with an IC50 of 0.093 mg/mL (85.59 μM).
Molecular docking analysis revealed that both peptides interact with the ACE receptor protein through hydrogen bonding and hydrophobic interactions, providing a structural explanation for their inhibitory activity.
In EA.hy926 endothelial cells, both peptides promoted nitric oxide (NO) release and reduced endothelin-1 (ET-1) levels — two complementary mechanisms that would lower blood pressure by relaxing blood vessels and reducing vasoconstriction.
Why it matters
Hypertension affects over a billion people worldwide and is a leading risk factor for heart disease and stroke. While pharmaceutical ACE inhibitors are effective, they can cause side effects like chronic cough. Bioactive peptides from food sources like rice bran could offer natural alternatives or complementary approaches to blood pressure management, while also adding value to an agricultural byproduct that is often discarded or underutilized.
How the study worked
Rice bran protein hydrolysate was separated using ultrafiltration to isolate small peptide fractions, then further purified by reversed-phase HPLC. Peptide sequences were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). ACE inhibitory activity was measured in vitro to determine IC50 values. Molecular docking simulations modeled how the peptides interact with the ACE enzyme. Cellular effects were tested in EA.hy926 human endothelial cells, measuring nitric oxide release and endothelin-1 levels.
What this study cannot tell us
This is entirely an in vitro and cell-based study — no animal or human trials were conducted. ACE inhibition in a test tube does not guarantee blood pressure reduction in a living organism, as peptides may be degraded during digestion or fail to reach the bloodstream. The IC50 values, while measurable, are relatively high compared to pharmaceutical ACE inhibitors. The EA.hy926 cell line is an approximation of human blood vessel cells and may not fully represent in vivo vascular biology. Bioavailability of these peptides after oral consumption is unknown.
How to read the evidence
This is a preliminary in vitro and cell-based study. While the peptide identification is solid and the dual-mechanism evidence (ACE inhibition plus NO/ET-1 modulation) is encouraging, no animal or human data exist. The evidence supports the concept but cannot establish clinical antihypertensive efficacy.
When this study was published
Published in 2023, this is a recent study. Food-derived ACE-inhibitory peptides remain an active research area, and follow-up studies may have tested bioavailability or in vivo effects since publication.
The bigger picture
Food-derived bioactive peptides are a growing area of research at the intersection of nutrition science and pharmacology. Many common foods — including milk, fish, soybeans, and grains — contain proteins that release health-promoting peptides during digestion. ACE-inhibitory peptides from food sources have attracted particular interest because of the global burden of hypertension. This study adds rice bran to the list of promising sources and provides both in vitro and cellular evidence of antihypertensive activity.
Questions still open
- Would these rice bran peptides survive digestion and reach the bloodstream in sufficient concentrations to inhibit ACE in vivo?
- How do these IC50 values compare to those of established food-derived ACE-inhibitory peptides from milk or fish protein?
- Could rice bran hydrolysate be developed as a functional food ingredient for blood pressure management?
Common questions
What is ACE and why do blood pressure drugs target it?
Can eating rice bran lower blood pressure?
Read the original research
Two Novel Angiotensin I-Converting Enzyme (ACE) Inhibitory Peptides from Rice (Oryza sativa L.) Bran Protein.
Journal of agricultural and food chemistry, 71(9), 4153-4162
Citation
Zhang, Lingyu; Miao, Jianyin; Guo, Junbin; Liu, Jie; Xia, Zhen; Chen, Bingbing; Ma, Feng; Cao, Yong. (2023). Two Novel Angiotensin I-Converting Enzyme (ACE) Inhibitory Peptides from Rice (Oryza sativa L.) Bran Protein.. Journal of agricultural and food chemistry, 71(9), 4153-4162. https://doi.org/10.1021/acs.jafc.2c07270