Exploration of bioactive peptides from various origin as promising nutraceutical treasures: In vitro, in silico and in vivo studies

In Silico Prospecting for Novel Bioactive Peptides from Seafoods: A Case Study on Pacific Oyster (Crassostrea gigas)

Pacific oyster (Crassostrea gigas), an abundant bivalve consumed across the Pacific, is known to possess a wide range of bioactivities. While there has been some work on its bioactive hydrolysates, the discovery of bioactive peptides (BAPs) remains limited due to the resource-intensive nature of the existing discovery pipeline. To overcome this constraint, in silico-based prospecting is employed to accelerate BAP discovery. Major oyster proteins were digested virtually under a simulated gastrointestinal condition to generate virtual peptide products that were screened against existing databases for peptide bioactivities, toxicity, bitterness, stability in the intestine and in the blood, and novelty. Five peptide candidates were shortlisted showing antidiabetic, anti-inflammatory, antihypertensive, antimicrobial, and anticancer potential. By employing this approach, oyster BAPs were identified at a faster rate, with a wider applicability reach. With the growing market for peptide-based nutraceuticals, this provides an efficient workflow for candidate scouting and end-use investigation for targeted functional product preparation.

Isolation of a Novel Anti-Diabetic α-Glucosidase Oligo-Peptide Inhibitor from Fermented Rice Bran

At present, the incidence rate of diabetes is increasing gradually, and inhibiting α-glucosidase is one of the effective methods used to control blood sugar. This study identified new peptides from rice bran fermentation broth and evaluated their inhibitory activity and mechanism against α-glucosidase. Rice bran was fermented with Bacillus subtilis MK15 and the polypeptides of <3 kDa were isolated by ultrafiltration and chromatographic column, and were then subjected to LC-MS/MS mass spectrometry analysis. The results revealed that the oligopeptide GLLGY showed the greatest inhibitory activity in vitro. Docking studies with GLLGY on human α-glucosidase (PDB ID 5NN8) suggested a binding energy of −7.1 kcal/mol. GLLGY acts as a non-competitive inhibitor and forms five hydrogen bonds with Asp282, Ser523, Asp616, and His674 of α-glucosidase. Moreover, it retained its inhibitory activity even in a simulated digestion environment in vitro. The oligopeptide GLLGY could be developed into a potential anti-diabetic agent.

Antioxidant peptides: Overview of production, properties, and applications in food systems

In recent years, several studies have reported the beneficial effects of antioxidant peptides in delaying oxidation reactions. Thus, a growing number of food proteins have been investigated as suitable sources for obtaining these antioxidant peptides. In this study, some of the most critical developments in the discovery of peptidic antioxidants are discussed. Initially, the primary methods to release, purify, and identify these antioxidant peptides from various food-derived sources are reviewed. Then, computer-based screening methods of the available peptides are summarized, and methods to interpret their structure-activity relationship are illustrated. Finally, approaches to the large-scale production of these bioactive peptides are described. In addition, the applications of these antioxidants in food systems are discussed, and gaps, future challenges, and opportunities in this field are highlighted. In conclusion, various food items can be considered promising sources to obtain these novel antioxidant peptides, which present various opportunities for food applications in addition to health promotion. The lack of in-depth data on the link between the structure and activity of these antioxidants, which is critical for the prediction of possible bioactive amino acid sequences and their potency in food systems and in vivo conditions (rather than in vitro systems), requires further attention. Consequently, future collaborative research activities between the industry and academia are required to realize the commercialization objectives of these novel antioxidant peptides.

Screening and Identification of Novel Soluble Epoxide Hydrolase Inhibitors from Corn Gluten Peptides

The objective of this study was to investigate the soluble epoxide hydrolase (sEH) inhibitory properties of corn gluten peptides. In total, 400 dipeptides and 8000 tripeptides were first virtually screened by molecular docking and 30 potential sEH inhibitory peptides were selected. Among them, WEY, WWY, WYW, YFW, and YFY showed the highest sEH inhibitory activities with IC₅₀ values of 55.41 ± 1.55, 68.80 ± 7.72, 70.66 ± 9.90, 96.00 ± 7.5, and 94.06 ± 12.86 μM, respectively. These five peptides all behaved as mixed-type inhibitors and were predicted to form hydrogen bond interactions mainly with Asp333, a key residue located in the catalytic active site of sEH. Moreover, it was found that the corn gluten hydrolysates of Alcalase, Flavourzyme, pepsin and pancreatin all exhibited high sEH inhibitory activities, with IC₅₀ values of 1.07 ± 0.08, 1.19 ± 0.24, and 1.46 ± 0.31 mg/mL, respectively. In addition, the sEH inhibitory peptides WYW, YFW, and YFY were successfully identified from the corn gluten hydrolysates by Alcalase using nano-LC-MS/MS. This study demonstrated the sEH inhibitory capacity of peptides for the first time and corn gluten might be a promising food protein source for discovering novel natural sEH inhibitory peptides.

Unconventional microbial proteases as promising tools for the production of bioactive protein hydrolysates

Enzymatic hydrolysis is the most prominent strategy to release bioactive peptides from different food proteins and protein-rich by-products. Unconventional microbial proteases (UMPs) have gaining increased attention for such purposes, particularly from the 2010s. In this review, we present and discuss aspects related to UMPs production, and their use to obtain bioactive protein hydrolysates. Antioxidant and anti-hypertensive potentials, commonly evaluated through in vitro testing, are mainly reported. The in vivo bioactivities of protein hydrolysates and peptides produced through UMPs action are highlighted. In addition to bioactivities, enzymatic hydrolysis acts by modulating the functional properties of proteins for potential food uses. The compiled literature indicates that UMPs are promising biocatalysts to generate bioactive protein hydrolysates, adding up to commercially available enzymes. From the recent interest on this topic, continuous and in-depth research is needed to advance toward the applicability and commercial utility of both UMPs and obtained hydrolysates.

Separation and purification of antioxidant peptides from purple speckled kidney bean by macroporous adsorption resin and analysis of amino acid composition

The protein hydrolysate of purple speckled kidney bean (PSKB) was used as the raw material in this study, and the antioxidant peptide of the PSKB protein hydrolysate was purified using macroporous resin. The XAD-7HP macroporous resin was selected as the best purification material, and the static adsorption-desorption of the purified PSKB antioxidant peptide was optimized. The optimum static adsorption and desorption conditions were as follows: the adsorption capacity reached 11.93 ± 0.11 mg/ml at pH 7 for 24 h, and the desorption capacity was 5.24 ± 0.04 mg/ml with 60% ethanol for 30 min. Under this condition, the amount of antioxidant peptide obtained by adsorption-desorption was the highest. The optimum process conditions were as follows: the appropriate flow rate was 1 ml/min, and the optimal injection volume was 40 ml. The adsorption amount at this time can reach 12.19 ± 0.15 mg/ml. The components with an elution time of 10-30 min were separated using the reversed-phase high-performance liquid chromatography (RP-HPLC) technique to obtain three main components, namely, RP₁, RP₂, and RP₃. The DPPH free radical scavenging ability reached 56.26 ± 0.56, 66.42 ± 0.56, and 78.57 ± 0.56%, respectively, which were 36.65, 46.34 ± 0.56, and 54.39 ± 0.56% higher than those before purification. The amino acid sequences of the three components were identified as Phe-Leu-Val-Asp-Arg-Ile, Phe-Leu-Val-Ala-Pro-Asp-Asp, and Lys-Asp-Arg-Val-Ile-Ser-Glu-Leu.

Effects of autochthonous strains mixture on gut microbiota and metabolic profile in cobia (Rachycentron canadum)

The fish immune system is a topic or subject that offers a unique understanding of defensive system evolution in vertebrate heredity. While gut microbiota plays several roles in fish: well-being, promoting health and growth, resistance to bacterial invasion, regulation of energy absorption, and lipid metabolism. However, studies on fish gut microbiota face practical challenges due to the large number of fish varieties, fluctuating environmental conditions, and differences in feeding habits. This study was carried out to evaluate the impacts of supplemented three autochthonous strains, Bacillus sp. RCS1, Pantoea agglomerans RCS2, and Bacillus cereus RCS3 mixture diet on cobia fish (Rachycentron canadum). Also, chromatography, mass spectrometry and high throughput sequencing were combined to explore composition and metabolite profile of gut microbiota in juvenile cobia fed with supplemented diet. In the trial group, juvenile cobia received diets supplemented with 1 × 10¹² CFU mL^-1 autochthonous strains for ten weeks and a control diet without supplementation. Juvenile cobia receiving diets supplementation exhibited significantly improved growth than those without additives (control). Haematological indices, such as red blood cells, white blood cells, corpuscular haemoglobin concentration, mean corpuscular volume, haemoglobin, and mean corpuscular haemoglobin, were higher in the supplemented group. Similarly, digestive enzymes (trypsin, lipase, amylase, pepsin and cellulose, activities) activities were higher in supplemented diet with an indigenous isolates mixture. Serum biochemical parameters albumin, globulin, and total protein were significantly higher, while triglyceride, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and cholesterol showed no significant difference. On the other hand, glucose was significantly (P < 0.05) higher in the group without supplementation. On gene expression in the midgut, Immunoglobulin, Colony-stimulating factor receptor 1, major histocompatibility complex 1 were up-regulated by native isolates while T cell receptor beta, and Major histocompatibility complex 2 showed no significant difference. Gut bacterial composition was altered in fish receiving supplemented diet with autochthonous strains. Metabolomics also revealed that some metabolic pathways were considerably enriched in fish fed with supplemented diet; pathway analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment revealed that differentially expressed metabolites were involved in galactose metabolism, tryptophan metabolism, carbohydrate digestion and absorption, purine metabolism, and ABC transporters. Functional analysis of bacterial community showed that differences in enriched metabolic pathways generally comprised carbohydrate and its metabolites, nucleotide and its metabolites, amino acid and its metabolites, heterocyclic compounds, and tryptamines, cholines, pigments. The current investigation results showed that autochthonous strains mixture has significantly enhanced the growth, survival, and innate and adaptive immunities of juvenile cobia.

Theragra chalcogramma Hydrolysates, Rich of Fragment Gly-Leu-Pro-Ser-Tyr-Thr, Ameliorate Alcohol-Induced Cognitive Impairment via Attenuating Neuroinflammation and Enhancing Neuronal Plasticity in Sprague-Dawley Rats

Chronic alcohol abuse induces the cognitive deficits and is associated with low-grade inflammation and neurodegeneration. Currently, by virtue of the immunomodulatory and neuroprotective properties, nutrients represent a promising strategy to attenuate cognitive impairments. We previously prepared the hydrolysates from Theragra chalcogramma skin (TCH), and this study aims to evaluate the neuroprotection of TCH on alcohol-induced cognitive impairment (AICI) and to elucidate the associated mechanism. Behavioral results showed that TCH effectively ameliorated AICI and this amelioration was highly associated with the decrease of IL-1β and the increase of BDNF, CREB, and PSD95 in AICI rats (P < 0.05). Furthermore, TCH restored the histopathological impairment in hippocampus by reactivating extracellular signal-regulated kinase and suppressing Caspase-3 apoptosis signal pathways and modulating the abnormality of neurotransmitters acetylcholine and γ-aminobutyric acid(P < 0.05 or 0.01). Therefore, TCH exhibits potent attenuation of neuroinflammation and represents a potential ingredient for prevention of AICI.

Peptides as Pharmacological Carriers to the Brain: Promises, Shortcomings and Challenges

Central nervous system (CNS) diseases are among the most difficult to treat, mainly because the vast majority of the drugs fail to cross the blood-brain barrier (BBB) or to reach the brain at concentrations adequate to exert a pharmacological activity. The obstacle posed by the BBB has led to the in-depth study of strategies allowing the brain delivery of CNS-active drugs. Among the most promising strategies is the use of peptides addressed to the BBB. Peptides are versatile molecules that can be used to decorate nanoparticles or can be conjugated to drugs, with either a stable link or as pro-drugs. They have been used to deliver to the brain both small molecules and proteins, with applications in diverse therapeutic areas such as brain cancers, neurodegenerative diseases and imaging. Peptides can be generally classified as receptor-targeted, recognizing membrane proteins expressed by the BBB microvessels (e.g., Angiopep2, CDX, and iRGD), "cell-penetrating peptides" (CPPs; e.g. TAT_47-57, SynB1/3, and Penetratin), undergoing transcytosis through unspecific mechanisms, or those exploiting a mixed approach. The advantages of peptides have been extensively pointed out, but so far few studies have focused on the potential negative aspects. Indeed, despite having a generally good safety profile, some peptide conjugates may display toxicological characteristics distinct from those of the peptide itself, causing for instance antigenicity, cardiovascular alterations or hemolysis. Other shortcomings are the often brief lifetime in vivo, caused by the presence of peptidases, the vulnerability to endosomal/lysosomal degradation, and the frequently still insufficient attainable increase of brain drug levels, which remain below the therapeutically useful concentrations. The aim of this review is to analyze not only the successful and promising aspects of the use of peptides in brain targeting but also the problems posed by this strategy for drug delivery.

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.

Production of Bioactive Peptides from Baltic Herring (Clupea harengus membras): Dipeptidyl Peptidase-4 Inhibitory, Antioxidant and Antiproliferative Properties

This study aimed to produce bioactive protein hydrolysates from undervalued fish, namely Baltic herring, and its filleting by-products. Protein hydrolysates were produced with Alcalase and Flavourzyme to achieve effective hydrolysis. The hydrolysates were evaluated for chemical composition, molecular weight distribution, antioxidant capacity, dipeptidyl-peptidase 4 (DPP4) inhibitory activity, effects on cell proliferation and surface hydrophobicity. The protein content of the hydrolysates was high, from 86% to 91% (dm), while the fat content was low, from 0.3% to 0.4% (dm). The hydrolysates showed high DPP4 inhibition activities with IC50 values from 5.38 mg/mL to 7.92 mg/mL. The scavenging activity of the hydrolysates towards DPPH was low, but an intermediate Folin–Ciocalteu reducing capacity and Cu2+ chelating ability was observed. The solid phase extraction with Sep-Pak C18 cartridges increased the DPP4 inhibition activity and antioxidant capacity, indicating peptides’ crucial role in the bioactivities. The cytotoxicity of the hydrolysates was evaluated on the HCT8, IMR90, and A549 cell lines. The hydrolysates inhibited cell growth in the cancer and normal cells, although they did not reduce cell viability and were not lethal. Overall, our results indicate that protein hydrolysates from Baltic herring have potential as health-promoting foods and nutraceuticals, especially for enhancing healthy blood glucose regulation.

Evaluation of Plant Protein Hydrolysates as Natural Antioxidants in Fish Oil-In-Water Emulsions

In this work, we evaluated the physical and oxidative stabilities of 5% w/w fish oil-in-water emulsions stabilized with 1%wt Tween20 and containing 2 mg/mL of protein hydrolysates from olive seed (OSM–H), sunflower (SFSM–H), rapeseed (RSM–H) and lupin (LUM–H) meals. To this end, the plant-based substrates were hydrolyzed at a 20% degree of hydrolysis (DH) employing a mixture 1:1 of subtilisin: trypsin. The hydrolysates were characterized in terms of molecular weight profile and in vitro antioxidant activities (i.e., DPPH scavenging and ferrous ion chelation). After incorporation of the plant protein hydrolysates as water-soluble antioxidants in the emulsions, a 14-day storage study was conducted to evaluate both the physical (i.e., ζ-potential, droplet size and emulsion stability index) and oxidative (e.g., peroxide and anisidine value) stabilities. The highest in vitro DPPH scavenging and iron (II)-chelating activities were exhibited by SFSM–H (IC₅₀ = 0.05 ± 0.01 mg/mL) and RSM–H (IC₅₀ = 0.41 ± 0.06 mg/mL). All the emulsions were physically stable within the storage period, with ζ-potential values below −35 mV and an average mean diameter D[4,3] of 0.411 ± 0.010 μm. Although LUM–H did not prevent lipid oxidation in emulsions, OSM–H and SFSM–H exhibited a remarkable ability to retard the formation of primary and secondary lipid oxidation products during storage when compared with the control emulsion without antioxidants. Overall, our findings show that plant-based enzymatic hydrolysates are an interesting alternative to be employed as natural antioxidants to retard lipid oxidation in food emulsions.

Nutraceuticals and Food-Grade Lipid Nanoparticles: From Natural Sources to a Circular Bioeconomy Approach

Nutraceuticals have gained increasing attention over the last years due to their potential value as therapeutic compounds formulated from natural sources. For instance, there is a wide range of literature about the cardioprotective properties of omega-3 lipids and the antioxidant value of some phenolic compounds, which are related to antitumoral activity. However, the value of nutraceuticals can be limited by their instability under gastric pH and intestinal fluids, their low solubility and absorption. That is why encapsulation is a crucial step in nutraceutical design. In fact, pharmaceutical nanotechnology improves nutraceutical stability and bioavailability through the design and production of efficient nanoparticles (NPs). Lipid nanoparticles protect the bioactive compounds from light and external damage, including the gastric and intestinal conditions, providing a retarded delivery in the target area and guaranteeing the expected therapeutic effect of the nutraceutical. This review will focus on the key aspects of the encapsulation of bioactive compounds into lipid nanoparticles, exploring the pharmaceutical production methods available for the synthesis of NPs containing nutraceuticals. Moreover, the most common nutraceuticals will be discussed, considering the bioactive compounds, their natural source and the described biological properties.

Identification of novel antioxidant peptides from sea squirt (Halocynthia roretzi) and its neuroprotective effect in 6-OHDA-induced neurotoxicity

Ocean life contains a wealth of bioactive peptides that could be utilized in nutraceuticals and pharmaceuticals. This study aimed to obtain neuroprotective antioxidant peptides in sea squirt (Halocynthia roretzi) through protamex enzymolysis. Fraction F4 (ultrafiltration generated four fractions) had a lower molecular weight (<500 Dalton (Da)) with greater 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radical scavenging activities (94.24 ± 2.50% and 91.80 ± 1.19%). After gel filtration, six peptides, including Phe-Gly-Phe (FGF), Leu-Gly-Phe (LGF), Leu-Phe-VAL (LFV), Val-Phe-Leu (VFL), Trp-Leu-Pro (WLP), and Ile-Ser-Trp (ISW), were identified and sequenced by liquid chromatography-mass spectrometry (LC-MS/MS). Peptides WLP and ISW showed higher oxygen radical absorbance capacity (ORAC) values (2.72 ± 0.47 and 1.93 ± 0.01 μmol L^-1 of Trolox equivalent (TE) per μmol L^-1 of peptide) than glutathione (GSH). Additionally, WLP effectively increased cell viability, dramatically attenuated 6-Hydroxydopamine (6-OHDA)-induced cell apoptosis and decreased reactive oxygen species (ROS) levels to nearly two-fold, and significantly boosted glutathione peroxidase (GSH-Px) activity in PC12 cells. Transcriptome sequencing revealed differential expression of genes associated with various oxidative stress pathways after WLP treatment, such as glutathione metabolism. These results suggest that the Halocynthia roretzi-derived tripeptide WLP could alleviate neurodegenerative diseases associated with oxidative stress.

Bioactivities of Mealworm (Alphitobius diaperinus L.) Larvae Hydrolysates Obtained from Artichoke (Cynara scolymus L.) Proteases

In this study, we aimed to obtain hydrolysates with bioactive peptides from mealworm (Alphitobius diaperinus L.) larvae using an artichoke (Cynara scolymus L.) enzyme extract. Two types of substrates were used: the raw larvae flour (LF) and its protein extract (PE). The hydrolysis yield, considering the peptide concentration of the hydrolysates, was higher in PE hydrolysates than in LF hydrolysates (6.39 ± 0.59 vs. 3.02 ± 0.06 mg/mL, respectively). However, LF showed a higher antioxidant activity against the DPPH radical than PE (59.10 ± 1.42 vs. 18.79 ± 0.81 µM Trolox Eq/mg peptides, respectively). Regarding the inhibitory activity of angiotensin-I-converting enzyme (ACE), an IC50 value of 111.33 ± 21.3 µg peptides/mL was observed in the PE. The identification of the peptide sequence of both hydrolysates was conducted, and LF and its PE presented 404 and 116 peptides, respectively, most with low molecular weight (<3 kDa), high percentage of hydrophobic amino acids, and typical characteristics of well-known antioxidant and ACE-inhibitory peptides. Furthermore, the potential bioactivity of the sequences identified was searched in the BIOPEP database. Considering the antioxidant and ACE-inhibitory activities, LF hydrolysates contained a larger number of sequences with potential bioactivity than PE hydrolysates.

Effect of extrusion and autoclaving on the biological potential of proteins and naturally-occurring peptides from common beans: Antioxidant and vasorelaxant properties

•

Postharvest hardening did not definitively affect bioactivity of bean peptides.

•

Peptides from hardened and non-hardened beans showed high vasorelaxant activity.

•

Thermal treatment positively affected the biological potential of hardened beans.

Aiming to understand the impact of hardening on the biological potential of bean protein and peptides, we evaluated the antioxidant and vasorelaxant properties of common beans after and before hardening. It was also evaluated the effect of extrusion and autoclaving in the biological potential of hardened beans. In general, hardening caused a reduction from 13.5 to 39.6% on the antioxidant activity of the peptide-rich fractions. On the other hand, hardening did not strongly interfere with the vascular reactivity in thoracic aorta rings, being observed maximal relation varying from 801% to 84.7%. The thermal treatment caused a general increase in the antioxidant and vasorelaxant potential of these fractions, being observed EC₅₀ values ranging from 0.22 mg mL⁻¹ to 0.26 mg mL⁻¹. We can conclude that hardening did not seem to affect definitively the bioactivity of the obtained peptide-rich fractions. Finally, this study allows suggesting practical applications of extrusion as a thermal process in the production of functional food ingredients, and as ready-to-eat products presenting nutraceutical potential. In addition, autoclaving can be used as a pre-treatment of the hardened grains aiming to use them as whole grains with potentialized benefits for human health.

Walnut protein hydrolysates ameliorate alcohol-induced cognitive impairment (AICI) by alleviating oxidative stress and inflammation in the brain and improving hippocampal synaptic plasticity in Sprague–Dawley rats

Walnut protein hydrolysate (WPH) ameliorates Alcohol-induced cognitive impairment (AICI) via alleviating oxidative stress and inflammation in brain tissue and improving the hippocampal synaptic plasticity.