Angiotensin-converting enzyme, or ACE, sits at the heart of the renin-angiotensin system, the hormonal cascade that regulates blood volume and vascular tone. When the enzyme clips a small peptide fragment from angiotensin I, it generates angiotensin II, one of the most potent vasoconstrictors in the human body. Angiotensin II narrows blood vessels, prompts the release of aldosterone, and drives up blood pressure. Blocking this conversion is therefore a proven pharmacological strategy, and the degree to which a substance can hamper the enzyme is conventionally expressed as an IC50 value, the concentration needed to halve the enzyme’s activity. In the new study, the 80 percent methanol extract of P. posumbu leaves achieved an IC50 of 298.46 micrograms per millilitre, a figure the authors describe as significant and consistent with a possible role in hypertension management.

The plant itself is far from a household name outside its native range. Polygonum posumbu belongs to the buckwheat family, Polygonaceae, a group of flowering plants known for producing phenolic compounds. In the traditional medicine systems of Manipur and neighbouring regions, preparations of the plant have been used to treat elevated blood pressure, among other ailments. Ethnomedicinal records like these have increasingly become starting points for drug discovery, on the logic that generations of observed use can point researchers toward plants whose chemistry genuinely interacts with human physiology. The Manipur team set out to test that logic rigorously, examining not only antihypertensive activity but also antioxidant and antimicrobial properties, and then asking which molecules in the extract might be responsible.

Preliminary phytochemical screening confirmed the presence of major classes of secondary metabolites, including tannins and alkaloids, both of which are chemically capable of interacting with proteins such as ACE. Tannins, in particular, are polyphenolic compounds that can bind to enzyme active sites, and many dietary polyphenols have been shown in laboratory studies to modulate blood pressure through multiple mechanisms. To go beyond these broad chemical categories, the researchers turned to ultra-high-performance liquid chromatography coupled to Orbitrap mass spectrometry, an analytical platform capable of separating complex mixtures and identifying individual molecules with high precision based on their mass and fragmentation patterns.

The metabolite profiling paid off. The team tentatively identified thirteen compounds with known antihypertensive associations, a list that reads like a highlight reel of plant pharmacology: gallic acid, rosmarinic acid, naringenin, ferulic acid, luteolin, oleanolic acid, quercetin, neochlorogenic acid, kaempferol, caryophyllene oxide, chrysin, ursolic acid, and apigenin. Several of these are flavonoids, a family of polyphenols abundant in fruits, vegetables, and teas that has been repeatedly linked to cardiovascular benefits in dietary studies. Quercetin and kaempferol, for example, have been investigated for their ability to relax blood vessels and reduce oxidative stress, while rosmarinic acid and gallic acid are well-documented antioxidants. The presence of this chemical ensemble, the authors argue, provides a plausible mechanistic foundation for the ACE inhibition and radical-scavenging behaviour observed in their assays.

Antioxidant activity was assessed through six complementary in vitro tests, each probing a different facet of how a substance handles reactive molecules. The extract neutralised the ABTS radical cation with an IC50 of 134.96 micrograms per millilitre and scavenged superoxide anion radicals at an IC50 of 181.98 micrograms per millilitre, both indicating strong free radical quenching capacity. Hydroxyl radical scavenging required a higher concentration, with an IC50 of 482.64 micrograms per millilitre, while nitric oxide scavenging was comparatively weaker at 11.53 milligrams per millilitre. The ferric reducing antioxidant power assay registered 18.66 micromoles of Fe2+ equivalents, and the phosphomolybdenum assay yielded 126 milligrams of ascorbic acid equivalents per gram of extract, confirming substantial overall reducing capacity. Statistical analysis found significant differences across the tested parameters, with p values below 0.001.

Why does antioxidant capacity matter in the context of blood pressure? Oxidative stress, the imbalance created when reactive oxygen species overwhelm cellular defences, is closely intertwined with hypertension. Free radicals can deactivate nitric oxide, a signalling molecule that tells blood vessels to relax, and can damage the endothelial lining of arteries, promoting stiffness and inflammation. A plant extract that both inhibits ACE and mops up reactive radicals would, in principle, attack hypertension from two directions at once, easing vascular constriction while protecting the vessels themselves. This dual action is precisely what the chemical profile of P. posumbu suggests, though the authors are careful to frame these as in vitro findings that warrant further investigation.

The study also documented antibacterial effectiveness against specific microbial strains, adding a third dimension to the extract’s broad-spectrum therapeutic profile. While antimicrobial activity is tangential to blood pressure control, it reinforces the picture of a plant rich in bioactive secondary metabolites, since many of the same phenolic compounds that scavenge radicals and inhibit ACE also disrupt bacterial membranes and metabolism. The authors note that these combined properties point to P. posumbu as a prospective source of naturally occurring bioactive chemicals with antihypertensive, antibacterial, and antioxidant qualities.

As with any laboratory study of a plant extract, important caveats apply. The experiments were conducted entirely in vitro, using plant extracts and purified enzymes rather than living organisms, and the authors explicitly state that no human or animal experiments were involved. An IC50 measured in a test tube does not translate directly into a dose for a patient, because absorption, metabolism, and distribution within the body can dramatically alter how much of each compound actually reaches its target. The identification of the thirteen antihypertensive compounds is described as tentative, meaning the assignments rest on mass spectrometric evidence rather than isolated, purified standards for every molecule. The authors themselves call for further in vivo studies and for the isolation of the active constituents as the necessary next steps.

Nevertheless, the research exemplifies a productive model for modernising ethnobotanical knowledge. By pairing traditional use records with quantitative enzyme assays and high-resolution metabolomics, the Manipur team has converted a folk remedy into a chemically characterised candidate for future drug development. If subsequent animal and clinical studies confirm that the polyphenols in P. posumbu can meaningfully lower blood pressure in living systems, the plant could join the growing roster of botanical sources informing cardiovascular therapeutics. For now, the study stands as a rigorous first step, demonstrating that a plant valued by traditional healers in Northeast India carries a measurable, mechanistically plausible arsenal against hypertension, one of the leading risk factors for death worldwide.

Subject of Research: ACE-inhibitory and antioxidant activity of Polygonum posumbu leaf extract with LC-MS/MS metabolite profiling

Article Title: Polygonum posumbu (an ethnomedicinal plant) extract shows antihypertensive potential via ACE inhibition supported by antioxidant activity and LC-MS/MS metabolite profiling

Article References: Pukhrambam, P. D., Chanu, W. K., Maisnam, J., & Singh, C. B. (2026). Polygonum posumbu (an ethnomedicinal plant) extract shows antihypertensive potential via ACE inhibition supported by antioxidant activity and LC-MS/MS metabolite profiling. BMC Complementary Medicine and Therapies. https://doi.org/10.1186/s12906-026-05552-7

Image Credits: AI Generated

DOI: 10.1186/s12906-026-05552-7

Keywords: Polygonum posumbu, hypertension, ACE inhibition, antioxidant activity, LC-MS/MS, phytochemistry, ethnomedicine, polyphenols, natural products, blood pressure, flavonoids, BMC Complementary Medicine and Therapies

The research team, led by Hikaru Ogi and Yoko Ichikawa of the University of Shizuoka together with colleagues at Tokoha University and Sagami Women’s University, obtained heart, stomach, liver, spleen, small intestine, large intestine, loin, and round samples from five wild-caught female sika deer and five wild-caught female wild boar, each estimated at three years of age, processed at a licensed facility in western Shizuoka Prefecture. The animals had been captured by licensed hunters as part of legally authorized population management, entirely independently of the study. For comparison, the researchers purchased matching tissues from three cattle and three pigs from a Shizuoka meat supplier. All samples were freeze-dried, pulverized, and stored frozen before analysis.

To simulate what happens when meat is cooked and eaten, the team applied a standardized in vitro digestion pipeline. Half a gram of each freeze-dried sample was mechanically disrupted with beads, heated at 70 degrees Celsius for 30 minutes to mimic cooking, and then subjected to two hours of gastric digestion with pepsin at pH 1.8, followed by two hours of intestinal digestion with trypsin and pancreatin. Enzymes were added at a nominal enzyme-to-protein ratio of 1:1,000, with the protein estimate derived from ultraviolet absorbance at 280 nanometers. After digestion, enzymes were heat-inactivated, and the soluble fraction was filtered for analysis. This common framework meant that every tissue from every species passed through exactly the same cooking and digestive gauntlet, allowing apples-to-apples comparisons across thirty-two species-tissue combinations.

The researchers measured three things: how much soluble protein and peptide material each digest released, how effectively that material scavenged DPPH free radicals, and how strongly it inhibited angiotensin-converting enzyme, or ACE, the enzyme that raises blood pressure. Soluble protein and peptide concentrations were estimated using the Waddell spectrophotometric method, which calculates concentration from the difference in absorbance at 215 and 225 nanometers. Both biological activities were expressed as IC50 values, the concentration of estimated soluble protein or peptide needed to achieve fifty percent of maximal effect, with lower values indicating greater potency. Statistical comparisons used Kruskal-Wallis tests followed by Dunn’s multiple-comparison tests with Holm adjustment, treating each tissue-outcome pair as a separate exploratory endpoint.

The yield results were strikingly tissue dependent. Wild boar stomach released roughly 27 milligrams of estimated soluble protein or peptide per gram of wet tissue, nearly triple the roughly 10 milligrams from sika deer stomach. Wild boar liver yielded about 34 milligrams per gram, significantly more than both sika deer liver at around 11 and cattle liver at under 10. Wild boar round outperformed pig round by nearly sevenfold, at about 34 versus 5 milligrams per gram. Yet the pattern reversed elsewhere: wild boar small intestine yielded less soluble material than pig small intestine, and sika deer spleen yielded less than both wild boar and cattle spleen. No significant differences appeared in heart or large intestine. An enzyme-only blank run through the same procedure produced a negligible concentration of 0.059 milligrams per milliliter, suggesting the digestive enzymes themselves contributed little to the measured signal.

When it came to antioxidant activity, wild boar emerged as the clear winner. The DPPH IC50 for wild boar liver digest was 9.38 milligrams per milliliter, significantly lower than the 44.02 milligrams per milliliter observed for cattle liver, meaning far less material was needed to neutralize half of the synthetic radicals. Wild boar loin also outperformed, with an IC50 of 16.53 milligrams per milliliter compared with 35.82 for sika deer loin and 58.10 for cattle loin. These findings align with a growing body of literature showing that meat proteins generate antioxidant peptides during digestion, and that such peptides are rich in hydrophobic and aromatic amino acids like leucine, tryptophan, and histidine, which can donate electrons or hydrogen atoms to radicals. The authors caution, however, that because sample-specific absorbance at 520 nanometers was not corrected with blanks, pigments in colored visceral digests may have influenced the measurements.

ACE inhibition told a different story. Here the standout was sika deer spleen, whose digest showed an IC50 of 3.10 milligrams per milliliter, significantly lower than the 19.48 milligrams per milliliter of wild boar spleen. Notably, sika deer spleen had produced less soluble material than wild boar spleen, yet inhibited ACE far more potently, a mismatch that underscores a central theme of the study: quantity of digestible protein does not predict bioactivity. ACE-inhibitory potency depends heavily on peptide molecular weight, hydrophobicity, charge, and especially the amino acid sequence near the C-terminus, which determines how well a peptide fits into the enzyme’s active site. Previous work has identified ACE-inhibitory peptides such as KAPVA and PTPVP in pork digests, and antihypertensive effects have been demonstrated in hypertensive rats, so the possibility that wild-game digests contain similar sequences is plausible, though not yet proven.

Indeed, the disconnect between yield and activity is perhaps the study’s most important conceptual contribution. Screening tissues solely on how much soluble protein they release would have missed sika deer spleen, a low-yield, high-activity tissue, and would have overrated others. The authors argue that this justifies activity-guided fractionation as the next step: isolating the active components from wild boar liver, wild boar loin, and sika deer spleen, identifying peptide sequences by liquid chromatography-tandem mass spectrometry, confirming activity with synthetic peptides, and eventually testing physiological effects in cells and animals. For a peptide to lower blood pressure in a living body, it must survive intestinal digestion, cross the epithelial barrier, remain stable in circulation, and reach its target, hurdles that many in vitro hits never clear.

The study is candid about its limitations. Sample sizes were small and unequal, with five wild animals but only three cattle and three pigs per tissue, limiting statistical power, and non-significant comparisons cannot be read as evidence of equivalence. The wild and domesticated groups also differed in diet, rearing conditions, and postmortem handling, so differences cannot be attributed to species alone. Enzyme dosing was based on an absorbance estimate rather than a direct protein measurement, the Waddell method can be confounded by UV-absorbing compounds in organ digests, and no reference compounds like Trolox or captopril were run alongside. Some undiluted samples even produced calculated ACE inhibition above one hundred percent, though IC50 values were computed only from concentrations bracketing the fifty percent mark.

Even with those caveats, the study opens a genuinely novel avenue. Japan’s deer and boar culls produce a vast, underused biomass, and if organs like wild boar liver or deer spleen can be shown to contain functional peptides, they could become ingredients for health-oriented foods rather than waste. The authors are explicit that this was a screening exercise, not a demonstration of health benefits, but it provides the systematic baseline that future characterization work can build on. In a country grappling simultaneously with wildlife overpopulation, food sustainability, and an aging population’s cardiovascular health, the idea that pest control could feed a functional-food industry is exactly the kind of unexpected connection that makes food science worth watching.

Subject of Research: Bioactive peptide yield and antioxidant and ACE-inhibitory activities of in vitro digests of wild sika deer and wild boar tissues compared with cattle and pig tissues in Japan

Article Title: Exploratory screening of wild-game tissues in Japan toward value-added utilization: estimated soluble protein/peptide yields and DPPH radical-scavenging and ACE-inhibitory activities after in vitro digestion

Article References: Exploratory screening of wild-game tissues in Japan toward value-added utilization: estimated soluble protein/peptide yields and DPPH radical-scavenging and ACE-inhibitory activities after in vitro digestion. (n.d.). https://doi.org/10.1007/s44463-026-00118-0

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00118-0

Keywords: wild game meat, sika deer, wild boar, bioactive peptides, in vitro digestion, DPPH radical scavenging, ACE inhibition, visceral organs, value-added utilization, functional foods, food science, Japan

Blood is a surprisingly protein-dense material. Whole blood typically contains 17 to 22 percent protein, split between the cellular fraction dominated by hemoglobin and a plasma fraction rich in albumins, globulins, and fibrinogen. These compositions vary by species: bovine and porcine blood contain the highest total protein concentrations at 7.9 to 8.7 and 7.7 to 8.9 grams per 100 milliliters respectively, while goat blood sits lower at 6.8 to 7.2 grams per 100 milliliters. Avian blood, particularly from ducks, is lower still at 12 to 13 percent total protein. These differences matter because the starting protein mix determines which peptides emerge during enzymatic hydrolysis, and the review shows that species-specific peptide profiles translate directly into distinct bioactivities.

The core technology is proteolysis. Enzymes such as alcalase, trypsin, chymotrypsin, pepsin, and papain cleave blood proteins into short peptide chains, each enzyme leaving its own signature. Alcalase, a serine protease with a Ser-His-Asp catalytic triad, broadly generates antioxidant, ACE-inhibitory, and DPP-IV inhibitory peptides. Trypsin cuts specifically after lysine and arginine residues, producing C-terminal basic peptides that often bind well to the angiotensin-converting enzyme active site. Papain, a cysteine protease with a Cys-His catalytic dyad, has been used to extract antioxidant peptides from poultry hemoglobin, while pepsin’s aspartic protease mechanism cleaves preferentially at hydrophobic and aromatic residues under acidic conditions that mimic the stomach. Chemical hydrolysis with acids or alkalis is faster and suited to industrial scale, though it sacrifices the sequence precision that enzymatic cleavage provides.

The resulting peptides display a remarkable range of biological activities. Bovine hemoglobin-derived peptides such as LRVSV inhibit ACE with an IC50 of just 0.15 micromolar, while the chicken blood cell peptide VSKRLNGDA showed antihypertensive effects in vivo in a rat model at 26.46 micromolar. Antioxidant sequences abound as well: duck plasma peptides RCLQ and EVGK showed strong ferric reducing power and iron chelation, and chicken blood peptides achieved metal chelation rates of 65 to 80 percent at 1.0 milligram per milliliter. For type 2 diabetes, blood-derived peptides such as AAATP and LPVPQ from bovine blood inhibit dipeptidyl peptidase IV, the enzyme that degrades the incretin hormones GLP-1 and GIP, with IC50 values in the range of 100 to 150 micromolar. Anti-inflammatory peptides from goose and Siamese crocodile blood act through the TLR4/NF-kB/iNOS pathway and shift macrophages from pro-inflammatory M1 to anti-inflammatory M2 phenotypes.

One of the review’s most significant contributions is its treatment of gastrointestinal stability as a structural question rather than an afterthought. Peptides face a brutal journey: gastric pH of 1.5 to 3.5, pepsin cleavage, pancreatic enzymes in the alkaline intestine, brush border peptidases, and finally plasma peptidases after absorption. Overall bioavailability of most food peptides is estimated at less than 1 to 2 percent of the administered dose. The authors identify proline as a key protective residue. Its unique pyrrolidine ring constrains rotation around the peptide backbone, creates kinks that block enzyme binding, and its capacity to switch between cis and trans configurations confounds aminopeptidases. Peptides rich in hydrophobic amino acids like leucine, isoleucine, and valine also show superior resistance to gastric digestion compared with sequences dominated by polar residues. These structural markers allow researchers to predict, from sequence alone, which peptides are likely to survive digestion and reach their targets intact.

Some peptides are even designed to be activated by digestion. Certain blood-derived sequences act as pro-peptides that release their bioactive fragments only after partial enzymatic breakdown in the gut, a sequential activation mechanism that inverts the conventional view of digestion as purely destructive. Absorption occurs mainly through peptide transporters PEPT1 and PEPT2, with peptides below 1000 daltons showing absorption rates of roughly 5 to 15 percent in Caco-2 cell models. Once in circulation, interaction with albumin can shield peptides from plasma peptidases and extend their half-life, and blood-derived peptides may enjoy enhanced circulation stability because their structures resemble endogenous blood proteins.

A major practical barrier to using hemoglobin in food has always been its intense red color. The review devotes detailed attention to decolorization strategies, ranging from solvent extraction of heme to enzymatic degradation of the porphyrin ring to chemical oxidation with food-grade hydrogen peroxide, peracetic acid, or ozone. Oxidation works by converting the heme iron from Fe2+ to Fe3+ and destroying the conjugated porphyrin system responsible for visible-light absorption. The authors caution, however, that because blood color resides in the heme-porphyrin itself, decolorization necessarily exposes globin and plasma proteins to oxidative conditions that can crosslink alpha-globin and oxidize sensitive amino acids, so mild, dose-controlled treatment with prompt catalase quenching is essential. Importantly, ACE- and DPP-IV-inhibitory activity depends on primary sequence rather than tertiary structure, so mild decolorization is not expected to diminish those potencies, though antioxidant peptides built on oxidation-sensitive residues such as cysteine, methionine, and tryptophan require experimental verification after treatment.

Purification and delivery technologies round out the industrial toolkit. Membrane filtration achieves 80 to 95 percent recovery of target peptides, chromatographic methods reach 60 to 90 percent with higher selectivity, and electrophoresis offers superior resolution for analytical work. Encapsulation technologies can improve stability of bioactive compounds by up to 80 percent during processing and storage, and microencapsulation of blood-derived peptides in maltodextrin carriers has maintained ACE-inhibitory and antioxidant activities over six-month storage periods. Spray-dried blood protein ingredients with neutral flavor and shelf life exceeding 12 months are already commercially feasible under controlled temperature and humidity.

The regulatory and commercial hurdles remain substantial. Blood is a high-risk substrate for pathogens including Salmonella and E. coli O157:H7, and ruminant blood carries transmissible spongiform encephalopathy risk that demands age- and tissue-restricted sourcing. Allergenicity is a further complication: the alpha-gal carbohydrate on mammalian blood glycoproteins survives both heat and proteolysis, making hydrolysis alone insufficient to eliminate allergy risk for sensitized consumers. Halal and kosher dietary law categorically prohibits blood consumption, excluding those markets entirely, and consumer perception of blood-derived ingredients constrains adoption elsewhere. Economic analyses suggest that production costs of purified blood peptides still exceed those of plant-derived alternatives, though integrated abattoir collection and high-throughput purification could narrow the gap.

Despite these challenges, the review positions blood-derived peptides as a cornerstone technology for circular economy food production. Proof of concept for oral antihypertensive peptides already exists in clinical data for milk-derived lactotripeptides, which consistently reduced systolic blood pressure in randomized trials across European and Asian populations. What remains is dedicated clinical validation of blood-derived preparations, scale-up of pilot processes such as the duck blood hydrolysate platform demonstrated by the same research group, and rational design pipelines that use proline content and hydrophobicity as predictive markers for peptide performance. If those pieces come together, the red liquid that slaughterhouses currently pay to dispose of could become a sustainable raw material for cardiovascular support, diabetes management, and next-generation functional foods.

Subject of Research: Bioactive peptides derived from slaughter blood proteins and their structure-function relationships, gastrointestinal stability, and applications in functional foods

Article Title: Slaughter blood-derived bioactive peptides: structure-function relationships, species-specific bioactivities, gastrointestinal stability, and sustainable applications in food systems

Article References: Laosam, P., Yue, Y., Rouabhia, M., Suwanangul, S., Pinyo, J., Katemala, S., Paengkoum, P., Nakharuthai, C., Pongsetkul, J., Pongsamai, N., & Sangsawad, P. (2026). Slaughter blood-derived bioactive peptides: structure-function relationships, species-specific bioactivities, gastrointestinal stability, and sustainable applications in food systems. Food Science of Animal Resources, 46(1), Article 104. https://doi.org/10.1007/s44463-026-00107-3

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00107-3

Keywords: slaughter blood, bioactive peptides, enzymatic hydrolysis, ACE inhibition, DPP-IV inhibition, gastrointestinal stability, proline, hemoglobin decolorization, functional foods, circular economy, food science, protein hydrolysates