Activity Of Peptide Fractions Research Articles

Mitigating aluminum chloride-induced toxicity in Drosophila melanogaster with peptide fractions from Euphorbia species

This study assessed the antioxidative and protective effects of peptide extracts from selected Euphorbia species on Aluminum Chloride (AlCl3)-induced toxicity in Drosophila melanogaster. Euphorbia humifusa (EHU), Euphorbia hirta (EHI), and Euphorbia graminae (EHG) were screened for bioactive peptides. The crude peptide extract and partially purified peptide fractions of all the plants were subjected to preliminary antioxidants activities through 2, 2-diphenyl-1-picrylhyhdrazyl (DPPH), and nitric oxide (NO) scavenging activities. The most active peptide fraction was subjected to biochemical studies using Drosophila melanogaster. Flies were treated with AlCl3 (100 mg/kg diet), peptide fraction (5 and 10 mg/kg diet), and cotreatment of AlCl3 and the fraction, respectively. After treatment, flies were homogenized for the determination of total thiol and Glutathione (non-protein thiol) content, catalase and Glutathione-S-transferase activities, and nitric oxide (nitrite/nitrate) and hydroperoxide levels. The antioxidant screening revealed that the peptide fraction from Euphorbia humifusa (PEHU) was the most significant compared to the control (ascorbic acid). The PEHU (5 and 10 mg/kg diet) maintained the redox status of the flies in the biochemical study. The PEHU significantly counteracted AlCl3-induced reduction in antioxidants (catalase, GST, GSH and Total thiol), increased nitric oxide levels, and acetylcholinesterase activity and prevented behavioral deficits flies. Hence, the peptide fraction of Euphorbia humifusa may shield against the life-threatening effects of free radicals associated with aluminum chloride toxicity.

Isolation of Bacillus altitudinis 5-DSW with Protease Activity from Deep-Sea Mineral Water and Preparation of Functional Active Peptide Fractions from Chia Seeds.

In this study, we successfully isolated Bacillus strains with high protease activity from deep-sea mineral water in Korea and used them to obtain functional peptide fractions from chia seeds. The obtained Bacillus strains showed a high similarity of 99% with B. altitude with a long rod type (named B. altitudinis 5-DSW) and high protease activity at 40 °C, and 70% of the activity remained even at 70 °C. The defatted chia seed protein (15-50 kDa) was treated with crude protease from B. altitudinis 5-DSW and digested into small peptides below 20 kDa. The obtained chia seed peptides showed 3 times and 1.5 times higher antioxidant activity in DPPH and ABT radical scavenging assays, respectively. Moreover, chia seed peptides showed enhanced AChE inhibitory activity with an IC50 value of 14.48 ± 0.88 μg/mL and BChE inhibition activity with an IC50 value of 10.90 ± 0.80 μg/mL. Our results indicate that the newly isolated B. altitudinis 5-DSW and chia seed protein hydrolysates have potential applications in biotechnology and functional food development, enhancing the nutritional quality and value-added utilization of chia byproducts.

Antifungal activity and identification of bioactive peptide from Etawa crossbreed goat (Capra hircus) milk protein hydrolyzed using trypsin enzyme

There had been a growing interest in biopreservation in recent years due to the increasing demand for food products that were free of synthetic preservatives and therefore safer to consume. This made it necessary to explore natural bioactive with antifungal properties that can inhibit microbial spoilage and extend shelf life. Etawa crossbreed goat milk (Capra hircus) peptide fraction has antifungal activity. Therefore, this study aimed to determine the peptide with antifungal activity resulting from the casein and whey proteins of goat milk hydrolysis by trypsin. The hydrolyzate was fractionated using a Strong Cationic Exchange (SCX) catridge and the antifungal activity test was performed against Aspergillus sp. using the disc diffusion method. The most active peptide fraction with the highest antifungal activity was identified using Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS). Based on the results, the ratio of the enzyme substrates used to hydrolyze casein and whey proteins is 1:10; 1:20; 1:30 and 1:40. The greatest degree of hydrolysis of casein and whey proteins was obtained at a 1:40 enzyme-substrate ratio of 66.8% and 75.4%, respectively. The analysis of Sodium Dodecylsulfate - Polyacrylamide Gel Electrophoresis (SDS PAGE) showed that goat milk casein contained αS1-casein and β-casein, while the whey proteins contained beta-lactoglobulin and α-lactalbumins. The casein and whey protein hydrolysates were fractionated using an SCX with pH variations of 3–9. The Goat Milk Casein (GMC) 5, 6, 7 dan 8 peptide fractions inhibited Aspergillus sp, and the most active was a fraction from GMC6 with an inhibition zone of 26.95 ± 0.63 mm and Minimum Inhibitory Concentration (MIC) value of 31.25 μg/mL. Furthermore, the morphology of Aspergillus sp. mycelia after treatment with peptide fraction showed that the mycelia were wrinkled and withered. The fractions with the highest antifungal activity contained 4 peptide sequences, namely YNVPQLEIVPK, KENNINELSK, GLSPEVPNENLLR, and YLGYLEQLLK. These results showed that peptide from goat milk had potential applications as a natural antifungal compound.

Characterization and biological properties of peptides isolated from dried fermented cow milk products by RP‐HPLC: Amino acid composition, antioxidant, antihypertensive, and antidiabetic properties

This study aimed to assess the biological properties of peptide fractions isolated from dried fermented dairy products (jameed) as influenced by processing. Peptide fractions were separated by reversed-phase high-performance liquid chromatography (RP-HPLC) from salted (Sa) and unsalted (Us) cow milk jameed after drying the fermented curd by sun drying (Sd) or freeze-drying (Fd) and were characterized for their antioxidant capacity and inhibitory activity toward angiotensin I-converting enzyme (ACE) and α-amylase. Sd samples showed more numerous peptide peaks in RP-HPLC chromatograms than Fd samples, regardless of the salt content. High antioxidant activity was evidenced in several peptide fractions from FdUs jameed (including fractions 1, 2, 4, 7, 8, 9, and 10), SdUs jameed (1, 2, 5, 7, and 9), and FdSa jameed (2, 5, 6, and 9). By contrast, peptide fractions from SdSa (1, 2, 3, 5, 8, and 9), SdUs (4, 5, and 10), and FdUs (5, 6, and 8) jameed displayed the highest ACE inhibitory activity. Similarly, the highest inhibition of α-amylase was obtained with fractions from SdSa (1, 2, 3, 4, 5, 6, 8, and 9), SdUs (2 and 6), and FdUs (1, 7 and 9) jameed. A significant negative correlation was evidenced between antioxidant activity and anti-α-amylase activity of peptide fractions from SdSa jameed. These findings demonstrate that cow milk jameed is a source of bioactive peptides with antioxidant, anti-ACE, and anti-α-amylase properties in vitro, which can be tailored by adjusting the salt content and the drying conditions. PRACTICAL APPLICATION: This study shows that cow milk jameed, a staple fermented food in several Mediterranean countries, can serve as a useful source of multifunctional bioactive peptides with potential antioxidant, hypotensive, and hypoglycemic effects, which may help prevent and manage chronic health conditions such as hypertension, type 2 diabetes, and the metabolic syndrome. The bioactivities of certain peptide fractions were enhanced by lowering the salt content of jameed or by the drying method. The relatively simple RP-HPLC method described in this study can be used to isolate the peptide fractions of interest for further characterization and use as functional ingredients.

Characterisation of Biologically Active Hydrolysates and Peptide Fractions of Vacuum Packaging String Bean (Phaseolus vulgaris L.).

The aim of the study is to characterise biologically active hydolysates and peptide fractions obtained from vacuum-packed string beans (Phaseolus vulragis L.) (PB). Unpacked beans were a control sample. The influence on human squamous carcinoma cell line SCC-15 (ATCC CRL-1623) was determined. Packed bean (PB) and unpacked bean (UB) extracts were found to exert no effect on the tongue squamous carcinoma cells. The results of the study indicated that the packing process contributed to the retention of protein, soluble dietary fibre, and free sugar (2.36, 3.5, and 1.79 g/100 d.m., respectively). PB was characterised by higher antioxidant activity (expressed as neutralisation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS ABTS•+) and 2,2-diphenyl-1-picrylhydrazyl (DPPH·) free radicals) as well as Fe2+ chelation and reducing power (IC50 = 54.56, 0.46, 3.85 mg mL−1; 0.088 A700/peptide content, respectively) than the UB samples before hydrolysis. The hydrolysis process enhanced these properties. The IC50 value of lipase and α-amylase inhibitory activity of the hydrolysates obtained from UB was reduced. The PB and UB fractions exhibited a certain level of antimicrobial activity against S. aureus and E. coli. Candida albicans were not sensitive to these peptide fractions.

Effect of flavorzyme digestion on the antioxidant capacities of ultra‐filtrated rice bran protein hydrolyzates

The antioxidant capacities of rice bran protein hydrolyzates (RBPH) using the flavorzyme digestion system were studied. The hydrolyzates were fractioned by ultrafiltration membranes into three fractions (FI: molecular weight (MW) >10 kDa, FII: MW 3–10 kDa, and FIII: MW < 3 kDa). Furthermore, free amino acids, amino acid composition, and SDS-PAGE of obtained hydrolyzates and its active peptide fractions were evaluated. The results showed that fraction FIII with MW < 3 kDa possessed the greatest antioxidant activity: DPPH of 31.65% ± 0.18%, ABTS of 52.03% ± 0.32%, and metal chelating activity of 71.06% ± 0.38%, and was further purified by RP-HPLC. Five sub-peptide fractions (F1, F2, F3, F4, and F5) were collected and their antioxidant abilities were evaluated. The data exhibited that the F2 sub-peptide fraction possessed a higher metal chelating activity (82.13% ± 0.51%) than other fractions. The RBPH using flavorzyme could be utilized as an antioxidant source in functional foods. Practical applications The high activity of <3 kDa fraction and its sub-peptide fractions in these antioxidant assays might be associated with the high proportion of hydrophobic and aromatic amino acids. The results from this work confirm that rice bran proteins are rich in bioactive peptides, which could be employed as a prospective source for natural antioxidant components, therefore, can be useful for future food applications.

Kokumi Taste Active Peptides Modulate Salt and Umami Taste.

Kokumi taste substances exemplified by γ-glutamyl peptides and Maillard Peptides modulate salt and umami tastes. However, the underlying mechanism for their action has not been delineated. Here, we investigated the effects of a kokumi taste active and inactive peptide fraction (500–10,000 Da) isolated from mature (FIIm) and immature (FIIim) Ganjang, a typical Korean soy sauce, on salt and umami taste responses in humans and rodents. Only FIIm (0.1–1.0%) produced a biphasic effect in rat chorda tympani (CT) taste nerve responses to lingual stimulation with 100 mM NaCl + 5 μM benzamil, a specific epithelial Na+ channel blocker. Both elevated temperature (42 °C) and FIIm produced synergistic effects on the NaCl + benzamil CT response. At 0.5% FIIm produced the maximum increase in rat CT response to NaCl + benzamil, and enhanced salt taste intensity in human subjects. At 2.5% FIIm enhanced rat CT response to glutamate that was equivalent to the enhancement observed with 1 mM IMP. In human subjects, 0.3% FIIm produced enhancement of umami taste. These results suggest that FIIm modulates amiloride-insensitive salt taste and umami taste at different concentration ranges in rats and humans.

Angiotensin Converting Enzyme (ACE) Inhibitory Activity of Peptide Fraction of Germinated Pigeon Pea (&lt;i&gt;Cajanus cajan&lt;/i&gt; (L.) Millsp.)

During the germination process, seeds can release various types of peptides due to the degradation of storage proteins. Some of these peptides can have biological activity (bioactive peptides). The objective of this study was to determine the ACE inhibitory activity of germinated pigeon pea peptide extract at various germination times and to carry out the fractionation to the extract to get the most active peptide fraction. The results showed that the highest activity of peptide extract was found on the 4th-day germination of pigeon pea with an IC50 value of 63.46 μg/mL. The peptide extract was further fractionated by centrifugal ultrafiltration method and it was found that the peptide fraction &lt; 3 kDa had the highest ACE inhibitory activity with an IC50 value of 57.79 μg/mL. The result of identification with the LCMS method to the fraction was able to detect 4 types of the peptide with a molecular weight of 230.304, 294.303, 441.436, and 570.591 Da. These results suggested that the peptide fraction of germinated pigeon pea has the potency as an ACE inhibitory nutraceutical.

Evaluation of the Antioxidant and Antimicrobial Activity of Protein Hydrolysates and Peptide Fractions Derived from Colossoma macropomum and Their Effect on Ground Beef Lipid Oxidation

ABSTRACTThe objective of this study was to obtain protein hydrolysate from the mechanically separated meat of blackfin pacu to evaluate the influence by ultrafiltration in the antioxidant and antimicrobial activities of the peptide fractions obtained and to apply in ground beef to evaluate the lipid stability. The enzymatic hydrolysis was performed using the enzyme Protamex (pH 7.0, 60°C) for 240 min. The protein hydrolysate was fractionated by ultrafiltration. Then, the antioxidant capacity of the protein hydrolysate and the peptide fractions were evaluated in vitro by the methods of 2,2’-azinobis (3-ethylbenzothiazoline sulfonic acid) radical capture, 2,2-diphenyl-1-picrylhydrazyl radical-scavenging assay, reducing power, and hydroxyl radical scavenging activity. The antimicrobial activity of the samples was evaluated by disc-diffusion against Staphylococcus aureus and Escherichia coli. After evaluation, the peptide fractions did not present higher bioactivities than that shown for the hydrolysate. The protein hydrolysate was applied to ground beef, where the substances reactive to thiobarbituric acid and color were evaluated during 7 days of storage at 4°C. Lipid oxidation was reduced up to 60.9% and there was no modification of the natural coloration. Thus, the protein hydrolysate can be used as an alternative source of antioxidant for the preservation of refrigerated meats.

Changes in structural integrity of sodium caseinate films by the addition of nanoliposomes encapsulating an active shrimp peptide fraction

A shrimp peptide fraction (ST1) with biological activity (ABTS radical scavenging capacity, angiotensin-converting enzyme and dipeptidyl-peptidase-IV inhibitory activities), was encapsulated in partially purified soy phosphatidylcholine nanoliposomes (L-ST1) using glycerol to preserve the bilayer during the film-forming dehydration step. The z-average, zeta potential and encapsulation efficiency of L-ST1 were, respectively, 99.98 nm, −53.87 mV and 52.37%. Transmisssion Electron Microscopy images showed that the liposomes incorporated in sodium caseinate films caused film matrix disruption, but vesicle structure was well preserved and uniformly distributed along the film matrix. The films with liposomes became more water soluble, adhesive and mucoadhesive, with no changes in thickness or transparency. The film showed a very favourable taste perception, regardless the presence or type of liposomes, while the buccal dissolution was faster with the films carrying the liposomes. The film could be used in different food designs without distorting the sensory acceptance of the final product.

Peptides and isoflavones in gastrointestinal digests contribute to the anti-inflammatory potential of cooked or germinated desi and kabuli chickpea (Cicer arietinum L.)

It is largely unknown how processing affects bioactive potential of chickpea proteins to prevent bowel inflammatory diseases. The aim was to investigate the anti-inflammatory activity of protein concentrates from germinated and cooked chickpeas (GC and CC, respectively) and its relationship with protein and isoflavone composition before and after in vitro gastrointestinal digestion and absorption. Anti-inflammatory activity of GC digests was almost 2-fold higher than CC digests (p < 0.05), which was associated to greater content of peptides, formononetin and biochanin A (p < 0.05). Anti-inflammatory activity of phenolic fraction in digests was 7-fold higher than the protein fraction (p < 0.05). The most active peptide fraction from GC digest (IC50 = 93 µg/mL) contained a total of 24 peptides derived from legumin and vicilin. In conclusion, this study stands out the potential of germinated chickpea proteins concentrates to exert anti-inflammatory effects in the lower gut which may contribute to the prevention of bowel inflammatory diseases.

Identification of antioxidant and anti‐inflammatory peptides obtained by simulated gastrointestinal digestion of three edible insects species (Gryllodes sigillatus, Tenebrio molitor, Schistocerca gragaria)

AbstractThe aim of this study was to determine the effect of heat treatment of edible insects on antioxidant and anti‐inflammatory activities of peptide fractions from hydrolysates obtained by in vitro gastrointestinal digestion thereof. Identification of bioactive peptides from the edible insects and their chemical synthesis were carried out as well. The highest antiradical activity against ABTS•+ and DPPH• was noted for the peptide fraction from the Gryllodes sigillatus protein preparation (EC50 value 2.75 and 6.91 μg mL−1, respectively). This fraction exhibited the strongest LOX and COX‐2 inhibitory activity (IC50 value 0.13 and 0.26 μg mL−1, respectively). The peptide fraction from the Tenebrio molitor protein preparation showed the highest Fe2+ chelating ability (EC50 value 2.21 μg mL−1) and the highest reducing power (0.198). The heat treatment process has a positive effect on the antioxidant and anti‐inflammatory properties of peptides. All identified and synthesised peptides from insect protein showed antioxidant and anti‐inflammatory activity.

Alanine rich peptide from Populus trichocarpa inhibit growth of Staphylococcus aureus via targetting its extracellular domain of Sensor Histidine Kinase YycGex protein

BackgroundDue to growing concern towards microbial resistance, ongoing search for developing novel bioactive compounds such as peptides is on rise. The aim of this study was to evaluate antimicrobial effect of Populus trichocarpa extract, chemically identify the active peptide fraction and finds its target in Staphylococcus aureus. MethodsIn this study the active fraction of P. trichocarpa crude extract was purified and characterized using MS/MS. This peptide PT13 antimicrobial activity was confirmed by in-vitro agar based disk diffusion and in-vivo infection model of G. mellonella. The proteomic expression analysis of S. aureus under influence of PT13 was studied using LTQ-Orbitrap-MS in-solution digestion and identity of target protein was acquired with their quantified expression using label-free approach of Progenesis QI software. Docking study was performed with peptide PT13 and its target YycG protein using CABS-dock. ResultsThe active fraction PT13 sequence was identified as KVPVAAAAAAAAAVVASSMVVAAAK, with 25 amino acid including 13 alanine having M/Z 2194.2469. PT13 was uniformly inhibited growth S. aureus SA91 and MIC was determined 16 μg/mL for SA91 S. aureus strain. Sensor histidine kinase (YycG) was most significant target found differentially expressed under influence of PT13. G. mellonella larvae were killed rapidly due to S aureus infection, whereas death in protected group was insignificant in compare to control. The docking models showed ten docking models with RMSD value 1.89 for cluster 1 and RMSD value 3.95 for cluster 2 which is predicted to be high quality model. ConclusionAlanine rich peptide could be useful in constructing as antimicrobial peptide for targeting extracellular Domain of Sensor Histidine Kinase YycG from S. aureus used in the study.

Isolation, Characterization, and Antimicrobial Activity of Extracellular Polypeptides from Diazotrophic Strain Rhizobium radiobacter

Antimicrobial polypeptide fractions were isolated from Rhizobium radiobacter culture medium and purified. Mass-spectrometric analysis showed that the most active biocidal peptide fraction contained 24 components with molecular masses in the range 1171.14–3626.78 Da. The isolated peptide fractions contained 60 and 56% protein, respectively, and inhibited the growth of test pathogens Candida albicans (CA) and Escherichia coli (EC). These polypeptides demonstrated protective properties.

Synthesis and antibacterial activity of new peptides from Alfalfa RuBisCO protein hydrolysates and mode of action via a membrane damage mechanism against Listeria innocua

In this work we evaluated the mode of action of six new synthesized peptides (Met-Asp-Asn; Glu-leu-Ala-Ala-Ala-Cys; Leu-Arg-Asp-Asp-Phe; Gly-Asn-Ala-Pro-Gly-Ala-Val-Ala; Ala-Leu-Arg-Met-Ser-Gly and Arg-Asp-Arg-Phe–Leu), previously identified, from the most active peptide fractions of RuBisCO peptic hydrolysate against Listeria innocua via a membrane damage mechanism. Antibacterial effect and the minimum inhibitory concentrations (MIC) of these peptides were evaluated against six strains and their hemolytic activities towards bovine erythrocytes were determined. Prediction of the secondary structure of peptides indicated that these new antibacterial peptides are characterized by a short peptide chains (3–8 amino acid) and a random coli structure. Moreover, it was observed that one key characteristic of antibacterial peptides is the presence of specific amino acids such as cysteine, glycine, arginine and aspartic acid. In addition the determination of the extracellular potassium concentration revealed that treatment with pure RuBisCO peptides could cause morphological changes of L. innocua and destruction of the cell integrity via irreversible membrane damage. The results could provide information for investigating the antibacterial model of antibacterial peptides derived from RuBisCO protein hydrolysates.

Identification of potential inhibitory peptides of enzymes involved in the metabolic syndrome obtained by simulated gastrointestinal digestion of fermented bean (Phaseolus vulgaris L.) seeds

The aim of this study was to determine the conditions of bean fermentation carried out by Lactobacillus plantarum to obtain biologically active peptide fractions after in vitro digestion.The results suggest that optimum process conditions should be selected according to the specific activity of peptides. Only a fraction with a molecular mass of 3.5–7kDa obtained after fermentation at 22°C for 3h had α-amylase inhibitory activity. The optimal fermentation conditions for bean seeds to release peptide fractions with a molecular mass of 3.5–7.0kDa and the highest lipase or ACE inhibitory activity (IC50 1.19 and 0.28mg mL−1, respectively) were determined as 30°C and 3days. The fractions with the highest inhibitory activity were identified by LC-MS/MS and the sequences of the peptide derived from bean proteins were determined as INEGSLLLPH, FVVAEQAGNEEGFE, SGGGGGGVAGAATASR, GSGGGGGGGFGGPRR, INEGSLLLPH, GGYQGGGYGGNSGGGYGNRG, GGSGGGGGSSSGRRP, and GDTVTVEFDTFLSR.

Evaluation of the Antioxidant and Antiproliferative Effects of Three Peptide Fractions of Germinated Soybeans on Breast and Cervical Cancer Cell Lines.

Soybeans are an important source of bioactive molecules, such as peptides, which generation can improve through germination. In this study, the antioxidant and antiproliferative activities of three peptide fractions (>10kDa, 5-10kDa and <5kDa) that were obtained by ultrafiltration of soybean protein hydrolysate after sixdays of germination were evaluated. The antioxidant activities of the peptide fractions were assessed by reducing power, Cu+2 and Fe+2 chelation and OH· scavenging assays, whereas their antiproliferative effects against cervical (HeLa, SiHa, CasKi) and breast (MCF7 and MDA-MB-231) cancer cell lines were evaluated by the MTT assay. Apoptosis was determined by Hoechst-PI staining. The most active peptide fraction (MAPF) was the >10kDa fraction, which showed the greatest antioxidant and antiproliferative activity. The most sensitive cancer cell lines were the HeLa, CasKi and MDA-MB-231 cells, which had IC50 values of 16.2, 14.3 and 15.2mg/mL, respectively, and apoptotic indices above 50% after 6 or 8h of exposure. The effect of MAPF on normal cells (HaCaT) was minimal. The amino acid composition of MAPF was characterized by high proline, phenylalanine and tyrosine content, and MALDI-TOF/TOF analysis showed six signals with molecular weights of 12 to 42kDa.

Peptides of amaranth were targeted as containing sequences with potential anti-inflammatory properties

The immunomodulatory effect of amaranth peptides on epithelial cells activated through the NF-κB signalling pathway was examined. Results showed that extensive protein hydrolysis from amaranth (23 and 30% degree of hydrolysis) reduced the emission of light in bacterial flagellin-activated Caco-2 CCL20: luc cells (Caco-2 cells transfected with a luciferase reporter under the control of the CCL20 promoter) compared with the non-hydrolysed protein. Purification of the most active peptide fractions by HPLC chromatography and sequencing showed that the peptide SSEDIKE possessed a modulatory capacity on activated cells to suppress the expression of mRNA coding for CCL20. This peptide was non-toxic for cells. These findings indicated that the peptide SSEDIKE derived from proteins of amaranth attenuated the activation of human intestinal epithelial cell, and hence amaranth proteins could be included in functional foods as a source of bioactive peptides with health promoting properties.

Functional and potential therapeutic ACE-inhibitory peptides derived from bromelain hydrolysis of trevally proteins

In a view to produce physiologically active peptides, soluble and insoluble fish protein fractions from trevally (Pseudocaranx sp.) were hydrolysed with bromelain and the hydrolysates were used in a systematic screening for angiotensin I-converting enzyme (ACE)-inhibitory peptides. The IC50 values of hydrolysates from soluble protein substrate ranged from 1.99 to 3.34 mg/mL, while the values for hydrolysates from insoluble protein substrate ranged from 2.45 to 4.74 mg/mL. Fractionation with RP-HPLC gave three most active peptide fractions labelled as TBS1, TBS2, and TBI2 which showed high potential as ACE-inhibitory agents. The primary structures of the three stable and active peptide fractions are AR, AV, and APER, with molecular weights of 245.28, 188.23, and 471.51 Da, respectively. Simulated gastrointestinal enzyme degradation of the three selected peptide fractions revealed their stability in the gut. In addition the <5 kDa fractions derived from the hydrolysates labelled TSB6h and TIB2h have potential to be used in functional foods.

Antioxidant, ACE-Inhibitory, and Antimicrobial Activities of Peptide Fractions Obtained From Dried Giant Squid Tunics

ABSTRACTSquid tunics were divided in two batches: freeze-dried and air-dried. Dried squid tunics were directly hydrolyzed with pepsin, Alcalase, and Esperase. Freeze-dried tunics showed better aptitude for hydrolysis than air-dried tunics. Pepsin showed the lowest efficiency in protein breakdown and gave hydrolysates with low antioxidant activity, whereas Alcalase and Esperase peptide fractions showed strong radical scavenging ability, ACE-inhibitory activity, and noticeable antimicrobial properties. B. cereus, B. coagulans, and D. hansenii were found to be the most sensitive bacteria. Dried squid tunics proved to be an alternative to a previously extracted gelatin for obtaining bioactive peptides.