Fish Skin Waste Yields Bioactive Peptides with Blood Pressure-Lowering and Antioxidant Properties | Research

The takeaway

Peptides extracted from Priacanthus hamrur fish skin waste achieved 57.45% ACE inhibition at 2 mg/mL, demonstrating significant antihypertensive and antioxidant potential from a sustainable waste source.

57.45% ACE inhibition
The fish skin waste hydrolysate achieved significant ACE-blocking activity at just 2 mg/mL, alongside strong antioxidant properties — from a material otherwise discarded as waste

What the researchers found

The optimized protamex-mediated protein hydrolysate (PrMPH) from fish skin waste showed high protein content with essential amino acids. ACE inhibitory activity reached 57.45 ± 0.53% at 2 mg/mL protein concentration. Antioxidant capability increased significantly (p < 0.05) with increasing protein content. Optimal hydrolysis conditions were 1.77% enzyme concentration, 35.33 min duration, 50.75°C, and pH 7.40. Physical characterization confirmed the material as amorphous with characteristic peptide bond signatures.

Why it matters

Fish processing generates enormous amounts of skin and collagen waste globally — turning this into bioactive peptides addresses both environmental sustainability and human health. The ACE inhibitory activity suggests potential as a natural antihypertensive ingredient in functional foods or supplements. Unlike synthetic ACE inhibitors (which cause side effects like dry cough), food-derived peptides may offer gentler blood pressure support, though at lower potency.

How the study worked

Fish skin waste from Priacanthus hamrur was hydrolyzed using protamex enzyme. Process conditions were optimized using a quadratic model. The resulting hydrolysate was characterized by UV-Vis spectroscopy, FTIR, X-ray diffraction, and differential scanning calorimetry. Bioactivity was assessed through antioxidant assays and ACE inhibition testing. Amino acid composition and protein content were determined.

What this study cannot tell us

This is entirely an in vitro study — ACE inhibition in a test tube does not guarantee blood pressure-lowering effects in humans, as peptides may be degraded during digestion or poorly absorbed. The hydrolysate is a complex mixture; specific active peptide sequences were not identified. No animal or human studies were conducted. The antioxidant assays used (likely DPPH, ABTS) may not reflect in vivo antioxidant activity. Taste and sensory properties for food applications were not evaluated.

How to read the evidence

This is an in vitro characterization study. While the bioactivity results are promising, no biological validation in cells, animals, or humans was performed. The evidence supports the material's potential but not its clinical effectiveness.

When this study was published

Published in 2025, this study aligns with the growing research trend of extracting bioactive peptides from food processing waste streams, relevant to both sustainability and health product development.

The bigger picture

The global trend toward sustainable food production and circular economy principles is driving interest in valorizing food processing waste. Fish skin — rich in collagen and protein — is an ideal source of bioactive peptides. This study joins a growing body of research showing that enzymatic hydrolysis of food waste proteins can yield peptides with genuine health benefits. As the functional food and nutraceutical markets expand, these sustainable peptide sources could become increasingly commercially important.

Questions still open

Which specific peptide sequences within the hydrolysate are responsible for the ACE inhibitory activity?
Does the ACE inhibitory activity survive gastrointestinal digestion to produce blood pressure-lowering effects in vivo?
Could fish skin-derived peptides be commercially viable as a functional food ingredient or supplement?

Common questions

How can fish waste produce health-promoting peptides?

Fish skin is rich in collagen and other proteins. When these proteins are broken down using specific enzymes (like protamex), they release smaller peptide fragments. Some of these peptides happen to have biological activities — like blocking the ACE enzyme that raises blood pressure or neutralizing harmful free radicals. This turns environmental waste into potentially valuable health ingredients.

Could eating these peptides lower blood pressure?

The peptides showed strong ACE inhibition in lab tests, but whether eating them would actually lower blood pressure depends on whether they survive digestion and get absorbed into the bloodstream. Many food-derived ACE-inhibitory peptides are broken down during digestion. Human studies would be needed to confirm any blood pressure benefit, and effects would likely be much milder than prescription ACE inhibitors.

Read the original research

Eco-sustainable production of bioactive peptides: Antioxidant and antihypertensive potential of Priacanthus hamrur fish skin waste hydrolysate using protamex enzyme.

International journal of biological macromolecules, 320(Pt 4), 146129

View on PubMed ↗Publisher’s paper ↗

Citation

Baraiya, Ravi; Renuka, Vijayakumar; Rabindranath, Radhika Rajasree Santha; George, Joshy Chalil. (2025). Eco-sustainable production of bioactive peptides: Antioxidant and antihypertensive potential of Priacanthus hamrur fish skin waste hydrolysate using protamex enzyme.. International journal of biological macromolecules, 320(Pt 4), 146129. https://doi.org/10.1016/j.ijbiomac.2025.146129