Source Of Bioactive Peptides Research Articles

Pearl millet protein hydrolysates exhibiting effective in‐vitro antioxidant, antidiabetic and anti‐lipidemic properties as potential functional food ingredient

SummaryMillets are well‐known for protein with high nutritional value and a range of health benefits. Millet‐derived proteins can thus be a rich source of bioactive peptides with multiple bioactive properties. In this study three proteolytic enzymes, i.e. alcalase, bromelain, and chymotrypsin were used to generate pearl millet protein hydrolysates (PMPHs) and explored for multifunctional bioactive properties. Degree of hydrolysis (DH) ranged between 28.69% and 59.21% with maximum DH observed for PMPs hydrolysed with bromelain for 9 h. The PMPs digested with alcalase exhibited enhanced in‐vitro anti‐diabetic potential with greater inhibition towards α‐amylase and dipeptidyl peptidase‐IV (DPP‐IV) with IC50 inhibitory concentration of 5.06 and 3.44 μg mL−1, respectively. Alcalase PMPHs demonstrated the strongest ABTS radical scavenging activity (976 mM TEAC) while chymotrypsin‐generated PMPHs showed significant scavenging of DPPH free radicals (222.3 mM TEAC). In addition, bromelain‐treated hydrolysates displayed the highest α‐glucosidase inhibitory activity (6.71 μg mL−1) and Ferric reducing anti‐oxidant power (585.7 mM TEAC). Moreover, PMPHs generated by alcalase showed potential anti‐lipidemic activity by inhibiting pancreatic lipase and cholesteryl esterase with maximum IC50 values of 3.46 and 3.61 μg mL−1, respectively. These findings suggest that PMPs could be used as a potential source for bioactive hydrolysates with improved anti‐diabetic, anti‐lipidemic, and anti‐oxidant activities.

Soybean-Derived Tripeptide Leu-Ser-Trp (LSW) Protects Human Vascular Endothelial Cells from TNFα-Induced Oxidative Stress and Inflammation via Modulating TNFα Receptors and SIRT1.

Soybean is a rich source of high-quality proteins and an excellent food source of bioactive peptides. A tripeptide, Leu-Ser-Trp (LSW), was previously identified from soybean as an angiotensin-converting enzyme inhibitory peptide. In the present work, we further studied its antioxidant and anti-inflammatory activities in human vascular endothelial cells (EA.hy926) and elucidated the mechanisms underlying these biological activities. In tumor necrosis factor alpha (TNFα)-stimulated EA.hy926 cells, LSW significantly inhibited oxidative stress, both reduced superoxide and malondialdehyde levels (p < 0.001), owing to its free-radical-scavenging ability. LSW treatment also mitigated the elevated protein expression of vascular adhesion molecule-1 (p < 0.001) and cyclooxygenase 2 (p < 0.01) via inhibition of NF-κB and p38/JNK signaling, respectively. Additionally, LSW also inhibited the endogenous formation of TNFα and attenuated the expression of its two receptors in EA.hy926 cells. Furthermore, LSW upregulated sirtuin-1 level, which partially contributed to its anti-inflammatory activity. These results demonstrate the multiple roles of LSW in ameliorating vascular endothelial oxidative stress and inflammatory responses, which support its uses as a nutraceutical or functional food ingredient for combating endothelial dysfunction and cardiovascular diseases.

Bioactive Peptides Obtained from Legume Seeds as New Compounds in Metabolic Syndrome Prevention and Diet Therapy

Currently, food is regarded not only as a source of nutrients, vitamins, and minerals but also as a source of bioactive compounds that can play a significant role in the prevention and diet therapy of many diseases. Metabolic syndrome (MS) is a complex disorder defined as a set of interrelated factors that increase the risk of cardiovascular disease, atherosclerosis, type 2 diabetes, or dyslipidemia. MS affects not only adults but also children. Peptides are one of the compounds that exhibit a variety of bioactive properties. They are derived from food proteins, which are usually obtained through enzymatic hydrolysis or digestion in the digestive system. Legume seeds are a good source of bioactive peptides. In addition to their high protein content, they contain high levels of dietary fiber, vitamins, and minerals. The aim of this review is to present new bioactive peptides derived from legume seeds and showing inhibitory properties against MS. These compounds may find application in MS diet therapy or functional food production.

Fractionation and purification of antioxidant peptides from Chinese sturgeon (Acipenser sinensis) protein hydrolysates prepared using papain and alcalase 2.4L

Protein hydrolysates have the potential to be natural and safer sources of bioactive peptides. In this study, two proteases were used to hydrolyze Chinese sturgeon (Acipenser sinensis) protein, and the hydrolysates were then purified to yield antioxidant peptides. The degree of hydrolysis of 23.56 % and 18.14 % was obtained using papain and alcalase 2.4L, respectivly, and hydrolysates had 96.80 % and 87.24 % total amino acid content, respectivly. The papain hydrolysate (PH) and alcalase 2.4L hydrolysate (AH) showed good antioxidant activity against DPPH• (IC50 of 3.64 and 3.15 mg/mL) and ABTS•+ (IC50 of 1.92 and 1.58 mg/mL), respectively. The low-molecular-weight (<1000 Da) fraction of both hydrolysates demonstrated the highest antiradical activity (IC50 of 2.59 and 2.31 mg/mL, DPPH) and (IC50 of 1.54 and 1.36 mg/mL, ABTS), respectively. Nine peptides were separated from both hydrolysates using reverse phase high performance liquid chromatography (RP-HPLC). The IC50 for ABTS•+ scavenging activity of peptide P5 with valine, glycine and asparagine (MW of 282.13 Da) from PH, and peptide P3 with histidine, glycine and alanine (MW of 302.74 Da) from AH was 0.89 and 0.72 mg/mL, respectively. The fractions and purified peptides obtained from Chinese sturgeon hydrolysates could be utilized as natural antioxidant substitutes in pharmaceuticals and food products.

In Silico Approach of Glycinin and Conglycinin Chains of Soybean By-Product (Okara) Using Papain and Bromelain.

This study explores utilization of a sustainable soybean by-product (okara) based on in silico approach. In silico approaches, as well as the BIOPEP database, PeptideRanker database, Peptide Calculator database (Pepcalc), ToxinPred database, and AllerTop database, were employed to evaluate the potential of glycinin and conglycinin derived peptides as a potential source of bioactive peptides. These major protein precursors have been found as protein in okara as a soybean by-product. Furthermore, primary structure, biological potential, and physicochemical, sensory, and allergenic characteristics of the theoretically released antioxidant peptides were predicted in this research. Glycinin and α subunits of β-conglycinin were selected as potential precursors of bioactive peptides based on in silico analysis. The most notable among these are antioxidant peptides. First, the potential of protein precursors for releasing bioactive peptides was evaluated by determining the frequency of occurrence of fragments with a given activity. Through the BIOPEP database analysis, there are several antioxidant bioactive peptides in glycinin and β and α subunits of β-conglycinin sequences. Then, an in silico proteolysis using selected enzymes (papain, bromelain) to obtain antioxidant peptides was investigated and then analyzed using PeptideRanker and Pepcalc. Allergenic analysis using the AllerTop revealed that all in silico proteolysis-derived antioxidant peptides are probably nonallergenic peptides. We also performed molecular docking against MPO (myeloperoxidases) for this peptide. Overall, the present study highlights that glycinin and β and α subunits of β-conglycinin could be promising precursors of bioactive peptides that have an antioxidant peptide for developing several applications.

Heating affects protein digestion of skimmed goat milk under simulated infant conditions

The objective of this research was to analyse the effects of heating on digestion of skimmed goat milk proteins. Most previous goat milk digestion studies evaluated the digestion only based on the supernatant. In this study, digestion of skimmed goat milk was studied in both supernatant and gastric clot. The results indicated that, compared to mild temperature heated samples (≤75 °C), samples heated at ≥80 °C showed more extensive gastric clot formation with a higher protein digestion rate, but also resulted in a larger amount of undigested whey proteins due to its severe aggregation. For the peptidome, β-casein was the major source of bioactive peptides. The samples heated at 65 °C showed higher bioactive peptide abundances, whereas at temperatures higher than 75 °C, it was reduced due to cleavage into smaller peptides. Overall, this study showed that different heating temperatures induced different whey protein denaturation degrees, which affected their digestion in skimmed goat milk..

Electrospinning Pullulan to Nanoencapsulate Milk Derived Peptides

Background: Milk proteins are a source of bioactive peptides, which are concealed until released and activated. There is a growing interest and necessity for the use of biologically active milk protein-derived peptides with health-promoting properties in food. Despite several health benefits and functionalities, consumption of bioactive peptides through foods is poor due to their unfavorable flavour or bitter taste, low solubility, poor stability during processing and poor oral bioavailability. Electrospinning is an adaptable process for encapsulation since it does not involve severe temperature and requirement of chemicals for the preparation of encapsulate in the form of nanofibres. Methods: The peptide-loaded electrospun nanofibres are characterized for its surface morphology, encapsulation efficiency, zeta potential and interaction between wall material and peptides. In vitro release studies by dialysis bag technique and antioxidant property by DPPH method. Result: Pullulan at 10, 12 and 14% (w/w) concentrations was used for electrospinning of peptides. Scanning electron micrograph revealed the formation of clean beadfree peptides-loaded pullulan nanofibres at 12 and 14% concentrations. Encapsulation efficiency ranged from 73.00-86.00%. FTIR spectrum and XRD diffractograms showed the nonappearance of interactions between the functional groups of biopolymer pullulan and peptides in the electrospun nanofibres. The peptides from electrospun nanofibres showed sustained release. The antioxidant activity of peptides and those which are in the nanofibres was comparable. The physico-chemical and sensory analysis of milk fortified with peptide loaded nanofibres did not show noticeable difference.

Mechanistic Insights into Angiotensin I-Converting Enzyme Inhibitory Tripeptides to Decipher the Chemical Basis of Their Activity.

Food proteins are an important source of bioactive peptides, and the angiotensin I-converting enzyme (ACE) inhibitors are worthy of attention for their possible beneficial effects in subjects with mild hypertension. However, the chemical basis underpinning their activity is not well-understood, hampering the discovery of novel inhibitory sequences from the plethora of peptides encrypted in food proteins. This work combined computational and in vitro investigations to describe precisely the chemical basis of potent inhibitory tripeptides. A substantial set of previously uncharacterized tripeptides have been investigated in silico and in vitro, and LCP was described for the first time as a potent ACE inhibitory peptide with IC50 values of 8.25 and 6.95 μM in cell-free and cell-based assays, respectively. The outcomes presented could serve to better understand the chemical basis of already characterized potent inhibitory tripeptides or as a blueprint to design novel and potent inhibitory peptides and peptide-like molecules.

Exploitation of Olive (Olea europaea L.) Seed Proteins as Upgraded Source of Bioactive Peptides with Multifunctional Properties: Focus on Antioxidant and Dipeptidyl-Dipeptidase-IV Inhibitory Activities, and Glucagon-like Peptide 1 Improved Modulation.

Agri-food industry wastes and by-products include highly valuable components that can upgraded, providing low-cost bioactives or used as an alternative protein source. In this context, by-products from olive production and olive oil extraction process, i.e., seeds, can be fostered. In particular, this work was aimed at extracting and characterizing proteins for Olea europaea L. seeds and at producing two protein hydrolysates using alcalase and papain, respectively. Peptidomic analysis were performed, allowing to determine both medium- and short-sized peptides and to identify their potential biological activities. Moreover, an extensive characterization of the antioxidant properties of Olea europaea L. seed hydrolysates was carried out both in vitro by 2,2-diphenyl-1-picrylhydrazyl (DPPH), by ferric reducing antioxidant power (FRAP), and by 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) assays, respectively, and at cellular level by measuring the ability of these hydrolysates to significant reduce the H2O2-induced reactive oxygen species (ROS) and lipid peroxidation levels in human intestinal Caco-2 cells. The results of the both hydrolysates showed significant antioxidant properties by reducing the free radical scavenging activities up to 65.0 ± 0.1% for the sample hydrolyzed with alcalase and up to 75.7 ± 0.4% for the papain hydrolysates tested at 5 mg/mL, respectively. Moreover, similar values were obtained by the ABTS assays, whereas the FRAP increased up to 13,025.0 ± 241.5% for the alcalase hydrolysates and up to 12,462.5 ± 311.9% for the papain hydrolysates, both tested at 1 mg/mL. According to the in vitro results, both papain and alcalase hydrolysates restore the cellular ROS levels up 130.4 ± 4.24% and 128.5 ± 3.60%, respectively, at 0.1 mg/mL and reduce the lipid peroxidation levels up to 109.2 ± 7.95% and 73.0 ± 7.64%, respectively, at 1.0 mg/mL. In addition, results underlined that the same hydrolysates reduced the activity of dipeptidyl peptidase-IV (DPP-IV) in vitro and at cellular levels up to 42.9 ± 6.5% and 38.7 ± 7.2% at 5.0 mg/mL for alcalase and papain hydrolysates, respectively. Interestingly, they stimulate the release and stability of glucagon-like peptide 1 (GLP-1) hormone through an increase of its levels up to 660.7 ± 21.9 pM and 613.4 ± 39.1 pM for alcalase and papain hydrolysates, respectively. Based on these results, olive seed hydrolysates may represent new ingredients with antioxidant and anti-diabetic properties for the development of nutraceuticals and functional foods for the prevention of metabolic syndrome onset.

Lipid-lowering effect of microencapsulated peptides from brewer's spent grain in high-sucrose diet-fed rats

Brewer's spent grain (BSG) -a byproduct generated from the processing of beer-brewing industry-is currently recognized as an important source of bioactive peptides with potential health benefits. In previous studies we demonstrated that peptides obtained from BSG (BSG-P) can exert in vitro biofunctional activities including hypolipidemic effects. However, there are no studies about the effects of gastrointestinal digestion on BSG lipid-lowering peptides and it is unknown whether the bioactive properties observed in vitro remain in vivo. The aims of this work were to evaluate the microencapsulation as strategy to preserve hypolipidemic BSG-P under a simulated gastrointestinal digestion, and the bioavailability of microencapsulated BSG-P using a rodent model of hyperlipidemia and other metabolic-related disorders induced by the consumption of a high-sucrose diet. In vitro studies showed that microencapsulation improved the BSG-P reduced hypolipidemic activity observed under a simulated gastrointestinal digestion by increasing the inhibition of the fat digestion enzymes, pancreatic lipase and cholesterol esterase. Furthermore, in vivo studies demonstrated that microencapsulated BSG-P were also able to reduce the increased serum lipid levels (triglycerides-TG- cholesterol and free fatty acids), energy intake, visceral adipocytes size and TG content observed in sucrose-rich diet-fed rats. This was accompanied by reduced liver lipids levels and the activities of key enzymes involved in dietary fat absorption. Therefore, our findings show that microencapsulation is a useful strategy to preserve the hypolipidemic activity of BSG-P and support the concept that microencapsulated BSG-P would be an interesting and cheaper natural source to prevent hyperlipidemias and its related-disorders.

Anti-Melanogenesis Activity of Crocodile (Crocodylus siamensis) White Blood Cell Extract on Ultraviolet B-Irradiated Melanocytes.

Ultraviolet (UV) radiation generates a range of biological effects in the skin, which includes premature skin aging, hyperpigmentation, and cancer. Therefore, the development of new effective agents for UV-related skin damage remains a challenge in the pharmaceutical industry. This study aims to test the inhibitory effect of crocodile white blood cell (cWBC) extract, a rich source of bioactive peptides, on ultraviolet B (UVB)-induced melanocyte pigmentation. The results showed that cWBC (6.25-400 μg/mL) could inhibit tyrosinase without adduct formation by 12.97 ± 4.20% on average. cWBC pretreatment (25-100 μg/mL) had no cytotoxicity and reduced intracellular melanin to 111.17 ± 5.20% compared with 124.87 ± 7.43 for UVB condition. The protective role of cWBC pretreatment against UVB was exhibited by the promotion of cell proliferation and the prevention of UVB-induced morphological change as observed from F actin staining. The decrease of microphthalmia-associated transcription factor expression levels after cWBC pretreatment might be a mechanism by which cWBC suppresses UVB-induced pigmentation. These results suggest that cWBC could be beneficial for the prevention of UVB-induced skin pigmentation.

Review on Bioactive Peptides in Milk and Dairy Products, and Their Health Benefits

Bioactive peptides (BAPs) are defined as peptides with hormone or drug like activity that bind to specific receptors leading to induction of physiological responses. The objective of this seminar is to summarize literature reports on the bioactive peptides in milk and dairy products, and their health-benefits on human body. Milk and milk products are important source of bioactive peptides. The bioactive peptides in milk are encrypted in the structure of the parent proteins; therefore it requires enzymatic hydrolysis or food processing to make them active. Different BAPs released from milk protein have different physiological functions which improve the problem of different chronic diseases. Keywords : Milk protein, Bioactive peptides, Generating methods, Health benefits DOI: 10.7176/FSQM/118-02 Publication date: August 31 st 2022

A review on the application of bioactive peptides as preservatives and functional ingredients in food model systems

The rising demand for health-promoting foods has led to the search for alternative, sustainable, and multifunctional peptide sources. Unconventional though promising sources such as agro-industrial wastes and by-products, insects, marine, and plant RuBisCo could be the future sources of bioactive peptides. Bioactive peptides derived from various proteins are biologically active regulators that can be used as food additives to prevent oxidation and microbial spoilage. Therefore, bioactive peptides have been applied to maintain the quality and microbial safety of food products. Besides, peptides can be used as functional ingredients to treat or prevent chronic and lifestyle diseases. The present review highlights the recent findings of alternative sources of bioactive peptides, technological improvements in bioactive peptides identification and isolation, and some obstacles to the widespread application and uses of bioactive peptides. Especially, the present review discusses the application of bioactive peptides in food model systems as food additives and functional ingredients. Novelty impact statement Recent research shows that high-quality unconventional proteins could be the future alternatives to animal proteins to derive bioactive peptides. Bioactive peptides not only play a significant role in human health but also prevent lipid oxidation and microbial growth in foods. Hence, protein hydrolysates and peptides can replace synthetic preservatives to extend the shelf life of food products. Innovative research dedicated to the purification, isolation, and application of bioactive peptides to foods could bring multiple benefits to consumers, food processors, nutraceutical industries, and other stakeholders.

IN SILICO ANALYSIS OF EDIBLE BIRD’S NEST PROTEINS AS POTENTIAL PRECURSORS FOR BIOACTIVE PEPTIDES

The present study aimed to perform an in silico evaluation of edible bird’s nest protein as potential precursors of bioactive peptides, as well as to determine whether such peptides can be released by selected proteolytic enzymes. Six edible bird’s nest (EBN) protein sequences from a previous study were chosen as potential precursors to produce bioactive peptides via in silico method using the BIOPEP database. AMCase protein sequences gave the highest number of bioactivities (16 to 18) and nucleobindin-2 protein gave the lowest number of bioactivities (9) among the other protein sequences. It was found that the most potential bioactive peptides from EBN proteins are angiotensin-converting enzyme (ACE) inhibitors and dipeptidyl peptidase-IV (DPPIV) inhibitors. Furthermore, in silico proteolysis using six selected enzymes was employed to release both dominant bioactivities in EBN proteins, which were ACE and DPP-IV inhibitors. This study shows that a combination of enzymes, chymotrypsin, and papain, produced the highest number of activities for both ACE and DPP-IV inhibitor peptides with the frequency of occurrence of bioactive peptides of 0.0968 and 0.1104, respectively. The toxic prediction tool, ToxinPred, found that all EBN peptides derived by in silico analysis were non-toxic. The current study proposed that EBN can serve as a potential source of bioactive peptides.

Expeller-Pressed Pomegranate Seed (Punica granatum L.) as a Protein Source for the Production of Antioxidant Peptides

Because of health concerns regarding synthetic antioxidants, natural antioxidant compounds are being considered by scientists. Bioactive peptides have been shown to have various physiological functions, such as antioxidative activity. Pomegranate seed protein, the by-product of the pomegranate seed oil industry, can be a good source of bioactive peptides. The optimum conditions for enzymatic hydrolysis of pomegranate seed protein with alcalase were determined using a response surface methodology. The influence of different temperatures (45–55 °C), times (30–180 min), and enzyme to substrate (E/S) ratio (1–3% w/w) on DPPH scavenging power and ferric reducing activity as the responses, were studied. Also, the degree of hydrolysis and the surface hydrophobicity of samples were determined. Moreover, using scanning electron microscopy and electrophoresis technique, microscopic structure and molecular weight of hydrolysate, were studied respectively. Alcalase-derived hydrolysates showed a DPPH scavenging activity (88 ± 0.97%) and ferric reducing power (0.5 ± 0.83) at optimum conditions of hydrolysis (48.8 °C, 97.5 min, E/S ratio 1.3%w/w). The degree of hydrolysis coincided with 36 ± 1.2%. An increase in the surface hydrophobicity of the protein during hydrolysis confirmed the unfolding of the pomegranate seed protein structure. The presence of low-molecular-weight peptides was evidenced by the electrophoresis technique. As well as the SEM showed that protein fragments had been reduced to small sizes following enzymatic treatments. According to the results of this study, pomegranate seed protein hydrolysate can be considered a suitable source of antioxidants with an aggregate market value in food formulations.

Identification of peptides of cinobufacini by gel filter chromatography and peptidomics.

Aqueous extract of toad skin (named as Cinobufacini or Huachansu) provides plentiful sources of bioactive peptides that remain undetected and unidentified. High-resolution mass spectrometry-based peptidomics platforms have developed into a major approach to the discovery of natural peptides, with data-dependent acquisition modes providing a wealth of peptide profiling information. In this study, we used a gel- and HLB (a solid phase extraction cartridge)-based two-dimensional separation and purification system and nano-liquid chromatography-tandem mass spectrometry-based peptidomic studies with homology matching for the identification of peptides from Cinobufacini. We evaluated 232 multi-charged peptides and found several specific peptides, some of which were validated by target parallel reaction monitoring mode. These peptides are the first to be identified in Cinobufacini and are completely different from ones identified in toad venom. So, this mapping provides key peptide information for the quality control of Bufo bufo gargarizans skin and its preparation.

Differential effects of oilseed protein hydrolysates in attenuating inflammation in murine macrophages

Proteins from underutilized defatted oilseed meals have been proposed as promising sources of bioactive peptides. This study was conducted to determine the anti-inflammatory activities of five oilseed proteins (flaxseed, rapeseed, sunflower, sesame and soybean) hydrolysed via alcalase, pepsin (at pH 1.3 and pH 2.1), respectively, and to compare these against two dairy proteins (whey, casein). The potential of protein hydrolysates of three different molecular weight fractions (Mw > 10 kDa, 3–10 kDa, < 3 kDa) to modulate nuclear factor kappa B (NF-κB) signalling was screened via RAW-Blue™ reporter cells. Fractions with Mw < 3 kDa of pepsin (pH 1.3)-treated protein hydrolysates were subsequently selected to validate anti-inflammatory properties in RAW 264.7 macrophages. Rapeseed fractions showed greatest potency to attenuate inflammation, via efficiently down-regulating the expression of IL-6 (−49.1%), IL-1β (−58.6%), iNOS (−41.9%) and COX-2 (−58.7%) and up-regulating the IL-10 (+47.2%) mRNA level at 2000 μg peptides/mL. Rapeseed, sesame and casein demonstrated marked repression of NF-κB pathway, through down-regulating NF-κB1, p65 and/or IκBα mRNA levels. In addition, rapeseed, sesame and soybean reduced the expression of TLR4 and/or CD14 associated with attenuated LPS recognition. In addition, it was confirmed that rapeseed and soybean hydrolysates showed capabilities to bind 43.9 and 52.4% of LPS in solution, thereby weakening inflammatory response; an effect that could at least partially be related to the presence of hydrophobic amino acids. To summarize, current data demonstrate differing capacity of plant protein hydrolysates to interact with inflammatory signalling, indicating the need for further research into the molecular mechanisms of peptide action.

Integrated Evaluation of the Multifunctional DPP-IV and ACE Inhibitory Effect of Soybean and Pea Protein Hydrolysates.

Nowadays, notwithstanding their nutritional and technological properties, food bioactive peptides from plant sources garner increasing attention for their ability to impart more than one beneficial effect on human health. Legumes, which stand out thanks to their high protein content, represent valuable sources of bioactive peptides. In this context, this study focused on the characterization of the potential pleotropic activity of two commercially available soybean (SH) and pea (PH) protein hydrolysates, respectively. Since the biological activity of a specific protein hydrolysate is strictly correlated with its chemical composition, the first aim of the study was to identify the compositions of the SH and PH peptides. Peptidomic analysis revealed that most of the identified peptides within both mixtures belong to storage proteins. Interestingly, according to the BIOPEP-UWM database, all the peptides contain more than one active motive with known inhibitory angiotensin converting enzyme (ACE) and dipeptidyl-dipeptidases (DPP)-IV sequences. Indeed, the results indicated that both SH and PH inhibit DPP-IV and ACE activity with a dose-response trend and IC50 values equal to 1.15 ± 0.004 and 1.33 ± 0.004 mg/mL, and 0.33 ± 0.01 and 0.61 ± 0.05 mg/mL, respectively. In addition, both hydrolysates reduced the activity of DPP-IV and ACE enzymes which are expressed on the surface of human intestinal Caco-2 cells. These findings clearly support that notion that SH and PH may represent new ingredients with anti-diabetic and hypotensive effects for the development of innovative multifunctional foods and/or nutraceuticals for the prevention of metabolic syndrome.

Purification and Identification of an ACE-Inhibitory Peptide from Gracilaria tenuistipitata Protein Hydrolysates

Edible marine species are valuable sources of bioactive peptides. This study investigated the ACE-inhibitory activity of protein hydrolysates from the red algae Gracilaria tenuistipitata. Fifteen groups of protein hydrolysates were prepared by a two-step enzymatic hydrolysis of G. tenuistipitata: initial hydrolysis with several glycolytic enzymes, followed by three separate proteolytic reactions (Alcalase, Neutrase and Flavourzyme) for 2–10 h. Results showed that the hydrolysate GTN4H had the highest ACE-inhibitory activity in vitro. Furthermore, oral administration of GTN4H significantly reduced systolic blood pressure in spontaneously hypertensive rats. Fraction A derived from GTN4H displayed the highest ACE-inhibitory activity among fractions. Further purification of fraction A by RP-HPLC obtained a purified peptide (MW: 1776 Da) with 17 amino acids and 95.4% ACE-inhibitory activity.

Picturins and Pictuseptins, two novel antimicrobial peptide families from the skin secretions of the Chachi treefrog, Boana picturata

The Imbabura treefrog (Boana picturata) is an underexplored source of bioactive peptides. The combination of molecular cloning and mass spectrometry allowed us to identify three new peptide families, named “Picturins” (PTR), “Pictuseptins” (PTS), and “Boanins” (BNS). PTR is composed of three 25-mer peptides, characterized by the N-terminal sequence: GVFKDALKQ and the C-terminal sequence: AANALKPK. The sequences of PTR-1, −2 and − 3 are highly conserved only showing two divergent sites: (L/F) in position 10 and (K/Q) in position 17. PTS gathers six peptides. PTS -1, −2 and − 4 have 22 amino acid residues in length, while PTS -3, −5 and − 6 are composed of 26 residues. Whereas BNS are four 28–37 mer peptides, showing two conserved regions: the N-terminal sequence FLGAL and the C-terminal sequence KALNP. PTR-1 to 3 and PTS -1 to −3 were chemically synthetized and their antimicrobial and haemolytic activity was assessed. PTR displayed moderate activity against Escherichia coli (MIC 24.80 to 48.95 μM), while PTS showed a broad antimicrobial and antifungal effect. PTS-1 was the most active peptide against E. coli (6.8 μM) followed by PTS-3 (11.7 μM) and PTS-2 (14.24 μM). These peptides also showed low haemolytic activity, pointing to a favorable selectivity. Overall, new unique non-hemolytic and cationic peptide sequences were characterized that could be valuable for the next-generation of anti-infective drugs. Future functional studies should explore the pharmacological potential of Boanins to include them as antimicrobial scaffolds. Biological significanceNature-inspired solutions have shown their importance mainly for the development of the pharmaceutical industry. Frog skin peptides are excellent examples of the biomedical potential of naturally evolved molecules for specific targets, including multi-resistant bacteria. The characterization of new chemical entities from poorly studied skin secretions of Ecuadorian biodiversity, such as B. picturata, represents an unprecedented opportunity to identify candidates to tackle global concerns, for instance, antibiotic resistance.