Marine bioactive peptides: Types, structures, and physiological functions

Antioxidative and Anti-Atopic Dermatitis Effects of Peptides Derived from Hydrolyzed Sebastes schlegelii Tail By-Products

Atopic dermatitis (AD) is a chronic inflammatory skin disorder associated with significant morbidity, including pruritus, recurrent skin lesions, and immune dysregulation. This study aimed to investigate the antioxidative and anti-AD effects of peptides derived from hydrolyzed Sebastes schlegelii (Korea rockfish) tail by-products. Hydrolysates were prepared using various enzymes, including Alcalase, Flavourzyme, Neutrase, and Protamex. Among them, Protamex hydrolysates demonstrated the highest ABTS radical scavenging activity with an RC50 value of 69.69 ± 0.41 µg/mL. Peptides were further isolated from the Protamex hydrolysate using dialysis, fast protein liquid chromatography (FPLC), and high-performance liquid chromatography (HPLC). The most active peptide, STPO-B-II, exhibited a single peak and was identified as a sequence of Glu-Leu-Ala-Lys-Thr-Trp-His-Asp-Met-Lys, designated as MP003. In vivo experiments were conducted using a 2,4-dinitrochlorbenzene (DNCB)-induced AD model in NC/Nga mice. The isolated peptide, MP003, showed significantly reduced AD symptoms, including erythema, lichenification, and collagen deposition. Additionally, MP003 decreased epidermal and dermal thickness, eosinophil, and mast cell infiltration and downregulated the expression of pro-inflammatory cytokines IL-1β, IL-6, and IgE in serum and skin tissues. These findings suggest that peptides derived from Sebastes schlegelii tail by-products may serve as potential therapeutic agents for AD.

The Antioxidant Mechanism of Peptides Extracted from Tuna Protein Revealed Using a Molecular Docking Simulation

Tuna protein serves as a significant source of bioactive peptides, and its functional properties can be elucidated through predictive modeling, followed by experimental validation. In this study, the active polypeptides were obtained from tuna protein via enzymatic hydrolysis (TPP), and their peptide sequences were determined. Furthermore, the potential activity of these peptides was predicted, focusing on antioxidant peptides, and compared to the sequence library of known antioxidant peptides to identify common structural motifs. The accuracy of the prediction results was confirmed through in vitro antioxidant assays and molecular docking studies. We identified seven specific peptide segments derived from tuna protein that exhibit antioxidant potential, accounting for approximately 15% of all active peptides. Molecular docking and cell experiments were employed to provide compelling evidence for the presence of antioxidant peptides within tuna protein. This study not only lays a solid foundation for studying the structure of active peptides but also opens up a novel avenue for an expedited assessment of their properties.

The effects of hydrolyzed protein on macronutrient digestibility, fecal metabolites and microbiota, oxidative stress and inflammatory biomarkers, and skin and coat quality in adult dogs

Research on protein hydrolysates has observed various properties and functionalities on ingredients depending on the type of hydrolysate. The objective of this study was to evaluate the effects of hydrolyzed chicken protein that was incorporated into diets on digestibility, gut health, skin and coat health, oxidative stress, and intestinal inflammation markers in healthy adult dogs. Five complete and balanced diets were manufactured: (1) CONd: 25% chicken meal diet; (2) 5% CLHd: 5% chicken liver and heart hydrolysate plus 20% chicken meal diet; (3) CLHd: 25% chicken liver and heart hydrolysate diet; (4) 5% CHd: 5% chicken hydrolysate plus 20% chicken meal diet; (5) CHd: 25% chicken hydrolysate diet. A replicated 5 × 5 Latin square design was used which included 10 neutered adult Beagles. Each of the 5 periods consisted of a 7-d washout time and a 28-d treatment period. All diets were well accepted by the dogs. Fecal butyrate concentration was higher while fecal isovalerate and total phenol/indole were lower in dogs fed CLHd than CONd (P < 0.05). Dogs fed CHd had higher fecal immunoglobulin A concentration when compared with CLHd (P < 0.05); however, both groups were comparable to the CONd. There was no difference among groups in serum cytokine concentrations, serum oxidative stress biomarkers, or skin and coat health analyses (P > 0.05). Fecal microbiota was shifted by CLHd with higher abundance in Ruminococcus gauvreauii group as well as lower Clostridium sensu stricto 1, Sutterella, Fusobacterium, and Bacteroides when compared with CONd (P < 0.05). There was also a difference in beta diversity of fecal microbiota between CLHd and CHd (P < 0.05). In conclusion, chicken protein hydrolysate could be incorporated into canine extruded diets as a comparable source of protein to traditional chicken meal. The test chicken protein hydrolysates showed the potential to support gut health by modulating immune response and microbiota; however, functional properties of protein hydrolysates are dependent on inclusion level and source.

A critical review of a typical research system for food-derived metal-chelating peptides: Production, characterization, identification, digestion, and absorption

In the past decade, food-derived metal-chelating peptides (MCPs) have attracted significant attention from researchers working towards the prevention of metal (viz., iron, zinc, and calcium) deficiency phenomenon by primarily inhibiting the precipitation of metals caused by the gastrointestinal environment and exogenous substances (including phytic and oxalic acids). However, for the improvement of limits of current knowledge foundations and future investigation directions of MCP or their derivatives, several review categories should be improved and emphasized. The species' uniqueness and differences in MCP productions highly contribute to the different values of chelating ability with particular metal ions, whereas comprehensive reviews of chelation characterization determined by various kinds of technique support different horizons for explaining the chelation and offer options for the selection of characterization methods. The reviews of chelation mechanism clearly demonstrate the involvement of potential groups and atoms in chelating metal ions. The discussions of digestive stability and absorption in various kinds of absorption model in vitro and in vivo as well as the theory of involved cellular absorption channels and pathways are systematically reviewed and highlighted compared with previous reports as well. Meanwhile, the chelation mechanism on the molecular docking level, the binding mechanism in amino acid identification level, the utilizations of everted rat gut sac model for absorption, and the involvement of cellular absorption channels and pathway are strongly recommended as novelty in this review. This review makes a novel contribution to the literature by the comprehensive prospects for the research and development of food-derived mineral supplements.

Antimicrobial Peptides Originating from Expression Libraries of Aurelia aurita and Mnemiopsis leidyi Prevent Biofilm Formation of Opportunistic Pathogens

The demand for novel antimicrobial compounds is rapidly growing due to the rising appearance of antibiotic resistance in bacteria; accordingly, alternative approaches are urgently needed. Antimicrobial peptides (AMPs) are promising, since they are a naturally occurring part of the innate immune system and display remarkable broad-spectrum activity and high selectivity against various microbes. Marine invertebrates are a primary resource of natural AMPs. Consequently, cDNA expression (EST) libraries from the Cnidarian moon jellyfish Aurelia aurita and the Ctenophore comb jelly Mnemiopsis leidyi were constructed in Escherichia coli. Cell-free size-fractionated cell extracts (<3 kDa) of the two libraries (each with 29,952 clones) were consecutively screened for peptides preventing the biofilm formation of opportunistic pathogens using the crystal violet assay. The 3 kDa fraction of ten individual clones demonstrated promising biofilm-preventing activities against Klebsiella oxytoca and Staphylococcus epidermidis. Sequencing the respective activity-conferring inserts allowed for the identification of small ORFs encoding peptides (10-22 aa), which were subsequently chemically synthesized to validate their inhibitory potential. Although the peptides are likely artificial products from a random translation of EST inserts, the biofilm-preventing effects against K. oxytoca, Pseudomonas aeruginosa, S. epidermidis, and S. aureus were verified for five synthetic peptides in a concentration-dependent manner, with peptide BiP_Aa_5 showing the strongest effects. The impact of BiP_Aa_2, BiP_Aa_5, and BiP_Aa_6 on the dynamic biofilm formation of K. oxytoca was further validated in microfluidic flow cells, demonstrating a significant reduction in biofilm thickness and volume by BiP_Aa_2 and BiP_Aa_5. Overall, the structural characteristics of the marine invertebrate-derived AMPs, their physicochemical properties, and their promising antibiofilm effects highlight them as attractive candidates for discovering new antimicrobials.

Intranasal Lipid Nanoparticles Containing Bioactive Compounds Obtained from Marine Sources to Manage Neurodegenerative Diseases

Marine sources contain several bioactive compounds with high therapeutic potential, such as remarkable antioxidant activity that can reduce oxidative stress related to the pathogenesis of neurodegenerative diseases. Indeed, there has been a growing interest in these natural sources, especially those resulting from the processing of marine organisms (i.e., marine bio-waste), to obtain natural antioxidants as an alternative to synthetic antioxidants in a sustainable approach to promote circularity by recovering and creating value from these bio-wastes. However, despite their expected potential to prevent, delay, or treat neurodegenerative diseases, antioxidant compounds may have difficulty reaching the brain due to the need to cross the blood–brain barrier (BBB). In this regard, alternative delivery systems administered by different routes have been proposed, including intranasal administration of lipid nanoparticles, such as solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), which have shown promising results. Intranasal administration shows several advantages, including the fact that molecules do not need to cross the BBB to reach the central nervous system (CNS), as they can be transported directly from the nasal cavity to the brain (i.e., nose-to-brain transport). The benefits of using SLN and NLC for intranasal delivery of natural bioactive compounds for the treatment of neurodegenerative diseases have shown relevant outcomes through in vitro and in vivo studies. Noteworthy, for bioactive compounds obtained from marine bio-waste, few studies have been reported, showing the open potential of this research area. This review updates the state of the art of using SLN and NLC to transport bioactive compounds from different sources, in particular, those obtained from marine bio-waste, and their potential application in the treatment of neurodegenerative diseases.

Standardized amino acid digestibility and protein quality in extruded canine diets containing hydrolyzed protein using a precision-fed rooster assay

Protein hydrolysate has become a choice of alternative protein source in canine diets as it showed greater digestibility, lower allergenic responses, and various functional properties when compared with intact proteins. The objective of the study was to determine the effect of hydrolyzed protein inclusion on amino acid digestibility and protein quality in extruded canine diets when compared with a traditional protein source for adult dogs. Five treatment diets were formulated to have similar compositions except for the main protein source. The control diet was formulated with chicken meal (CM) as the primary protein source. Test hydrolyzed proteins, chicken liver and heart hydrolysate (CLH) and chicken hydrolysate (CH) were used to partially or completely substitute CM. The diets were: CONd: CM (30%) diet; 5%CLHd: 5% CLH with 25% CM diet; CLHd: CLH (30%) diet; 5%CHd: 5% CH with 25% CM diet; CHd: CH (30%) diet. A precision-fed rooster assay was used to determine standardized amino acid digestibility for the ingredients and diets. In addition, Digestible Indispensable Amino Acid Score (DIAAS)-like values were calculated for the protein ingredients. All protein ingredients had higher than 80% of digestibility for all indispensable amino acids with no difference among sources (P > 0.05). From the DIAAS-like values referencing AAFCO nutrient profile for adult dogs, CLH and CH did not have any limiting amino acid; on the other hand, CM has a lower DIAAS-like value (93.3%) than CLH and CH (P < 0.05) with tryptophan being the first-limiting amino acid. The DIAAS-like values were often lower when the amino acid combinations methionine + cysteine and phenylalanine + tyrosine were included in the calculation. When referencing NRC recommended allowances and minimal requirements, methionine was the first-limiting amino acid for all protein sources. Amino acid digestibility was mostly above 80% and comparable among the treatment diets. Regarding the digestible indispensable amino acid concentrations in the diets, all of them met the AAFCO nutrient profile for adult dogs at maintenance. In conclusion, both protein hydrolysates were highly digestible, high-quality protein sources, and a full substitution from CM to protein hydrolysate could result in greater protein quality, according to the DIAAS-like values of the ingredients, when compared with CM in extruded canine diets.

Therapeutic Potential of Marine Bioactive Peptides against Human Immunodeficiency Virus: Recent Evidence, Challenges, and Future Trends

Acquired immunodeficiency syndrome (AIDS) is a chronic and potentially fatal ailment caused by the human immunodeficiency virus (HIV) and remains a major health problem worldwide. In recent years, the research focus has shifted to a greater emphasis on complementing treatment regimens involving conventional antiretroviral (ARV) drug therapies with novel lead structures isolated from various marine organisms that have the potential to be utilized as therapeutics for the management of HIV-AIDS. The present review summarizes the recent developments regarding bioactive peptides sourced from various marine organisms. This includes a discussion encompassing the potential of these novel marine bioactive peptides with regard to antiretroviral activities against HIV, preparation, purification, and processing techniques, in addition to insight into the future trends with an emphasis on the potential of exploration and evaluation of novel peptides to be developed into effective antiretroviral drugs.

Protective Effect of Oyster Peptides Derived From Crassostrea gigas on Intestinal Oxidative Damage Induced by Cyclophosphamide in Mice Mediated Through Nrf2-Keap1 Signaling Pathway

Oyster peptide (OP) has exhibited useful biological activities and can be used in multi-functional foods. OP has been reported to play a significant role in intestinal protection, but its specific mechanism is still not completely understood. The aim of this study was to analyze the potential effect of OP on oxidative damage of mice intestine induced by cyclophosphamide (Cy). The experimental results revealed that intragastric administration of OP significantly increased average bodyweight, improved ileum tissue morphology and villus structure, as well as increased the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in oxidized mice serum and liver. The content of malondialdehyde (MDA) in the mice serum and liver homogenate was found to be markedly decreased. Moreover, OP significantly increased the relative mRNA expression levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-P_X), quinone oxidoreductase (NQO1) and heme oxidase-1 (HO-1) in ileum. Western-blot results indicated that prior administration of OP significantly up-regulated the Nrf2 production in ileum, and substantially decreased then Keap1 gene expression. In conclusion, intake of OP was found to markedly improve intestinal oxidative stress in vivo, and this effect was primarily mediated through the simulation of antioxidant Nrf2-Keap1 signaling pathway. This study is beneficial to the application of peptide nutrients in the prevention or mitigation of intestinal oxidative damage.

Microbial diversity of garden snail mucus

The search for new natural compounds for application in medicine and cosmetics is a trend in biotechnology. One of the sources of such active compounds is the snail mucus. Snail physiology and the biological activity of their fluids (especially the mucus) are still poorly studied. Only a few previous studies explored the relationship between snails and their microbiome. The present study was focused on the biodiversity of the snail mucus used in the creation of cosmetic products, therapeutics, and nutraceuticals. The commonly used cultivation techniques were applied for the determination of the number of major bacterial groups. Fluorescence in situ hybridization for key taxa was performed. The obtained images were subjected to digital image analysis. Sequencing of the 16S rRNA gene was also done. The results showed that the mucus harbors a rich bacterial community (10.78 × 1010  CFU/ml). Among the dominant bacteria, some are known for their ability to metabolize complex polysaccharides or are usually found in soil and plants (Rhizobiaceae, Shewanella, Pedobacter, Acinetobacter, Alcaligenes). The obtained data demonstrated that the snail mucus creates a unique environment for the development of the microbial community that differs from other parts of the animal and which resulted from the combined contribution of the microbiomes derived from the soil, plants, and the snails.

Bioactive Peptides: Synthesis, Sources, Applications, and Proposed Mechanisms of Action

Bioactive peptides are a group of biological molecules that are normally buried in the structure of parent proteins and become active after the cleavage of the proteins. Another group of peptides is actively produced and found in many microorganisms and the body of organisms. Today, many groups of bioactive peptides have been marketed chemically or recombinantly. This article reviews the various production methods and sources of these important/ubiquitous and useful biomolecules. Their applications, such as antimicrobial, antihypertensive, antioxidant activities, blood-lipid-lowering effect, opioid role, antiobesity, ability to bind minerals, antidiabetic, and antiaging effects, will be explored. The types of pathways proposed for bioactive applications will be in the next part of the article, and at the end, the future perspectives of bioactive peptides will be reviewed. Reading this article is recommended for researchers interested in various fields of physiology, microbiology, biochemistry, and nanotechnology and food industry professionals.

Can be marine bioactive peptides (MBAs) lead the future of foodomics for human health?

Marine organisms are considered a cache of biologically active metabolites with pharmaceutical, functional, and nutraceutical properties. Among these, marine bioactive peptides (MBAs) present in diverse marine species (fish, sponges, cyanobacteria, fungi, ascidians, seaweeds, & mollusks) have acquired attention owing to their broad-spectrum health-promoting benefits. Nowadays, scientists are keener exploring marine bioactive peptides precisely due to their unique structural and biological properties. These MBAs have reported ameliorating potential against different diseases like hypertension, diabetes, obesity, HIV, cancer, oxidation, and inflammation. Furthermore, MBAs isolated from various marine organisms may also have a beneficial role in the cosmetic, nutraceutical, and food industries. Few marine peptides and their derivative are approved for commercial use, while many MBAs are in various pre-clinical and clinical trials. This review mainly focuses on the diversity of marine bioactive peptides in marine organisms and their production procedures, such as chemical and enzymatic hydrolysis. Moreover, MBAs' therapeutic and biological potential has also been critically discussed herein, along with their status in drug discovery, pre-clinical and clinical trials.

Applying Seaweed Compounds in Cosmetics, Cosmeceuticals and Nutricosmetics

The interest in seaweeds for cosmetic, cosmeceutics, and nutricosmetics is increasing based on the demand for natural ingredients. Seaweeds offer advantages in relation to their renewable character, wide distribution, and the richness and versatility of their valuable bioactive compounds, which can be used as ingredients, as additives, and as active agents in the formulation of skin care products. Bioactive compounds, such as polyphenols, polysaccharides, proteins, peptides, amino acids, lipids, vitamins, and minerals, are responsible for the biological properties associated with seaweeds. Seaweed fractions can also offer technical features, such as thickening, gelling, emulsifying, texturizing, or moistening to develop cohesive matrices. Furthermore, the possibility of valorizing industrial waste streams and algal blooms makes them an attractive, low cost, raw and renewable material. This review presents an updated summary of the activities of different seaweed compounds and fractions based on scientific and patent literature.

Antiaging Potential of Peptides from Underused Marine Bioresources

Aging is a biological process that occurs under normal conditions and in several chronic degenerative diseases. Bioactive natural peptides have been shown to improve the effects of aging in cell and animal models and in clinical trials. However, few reports delve into the enormous diversity of peptides from marine organisms. This review provides recent information on the antiaging potential of bioactive peptides from underused marine resources, including examples that scavenge free radicals in vitro, inhibit cell apoptosis, prolong the lifespan of fruit flies and Caenorhabditis elegans, suppress aging in mice, and exert protective roles in aging humans. The underlying molecular mechanisms involved, such as upregulation of oxidase activity, inhibition of cell apoptosis and MMP-1 expression, restoring mitochondrial function, and regulating intestinal homeostasis, are also summarized. This work will help highlight the antiaging potential of peptides from underused marine organisms which could be used as antiaging foods and cosmetic ingredients in the near future.

Antimicrobial Peptides: Novel Source and Biological Function With a Special Focus on Entomopathogenic Nematode/Bacterium Symbiotic Complex

The rapid emergence of multidrug resistant microorganisms has become one of the most critical threats to public health. A decrease in the effectiveness of available antibiotics has led to the failure of infection control, resulting in a high risk of death. Among several alternatives, antimicrobial peptides (AMPs) serve as potential alternatives to antibiotics to resolve the emergence and spread of multidrug-resistant pathogens. These small proteins exhibit potent antimicrobial activity and are also an essential component of the immune system. Although several AMPs have been reported and characterized, studies associated with their potential medical applications are limited. This review highlights the novel sources of AMPs with high antimicrobial activities, including the entomopathogenic nematode/bacterium (EPN/EPB) symbiotic complex. Additionally, the AMPs derived from insects, nematodes, and marine organisms and the design of peptidomimetic antimicrobial agents that can complement the defects of therapeutic peptides have been used as a template.

Marine Bioactive Peptides in Supplements and Functional Foods - A Commercial Perspective

Many bioactive peptides have been described from marine sources and much marine biomass is still not explored or utilized in products. Marine peptides can be developed into a variety of products, and there is a significant interest in the use of bioactive peptides from marine sources for nutraceuticals or functional foods. We present here a mini-review collecting the knowledge about the value chain of bioactive peptides from marine sources used in nutraceuticals and functional foods. Many reports describe bioactive peptides from marine sources, but in order to make these available to the consumers in commercial products, it is important to connect the bioactivities associated with these peptides to commercial opportunities and possibilities. In this mini-review, we present challenges and opportunities for the commercial use of bioactive peptides in nutraceuticals and functional food products. We start the paper by introducing approaches for isolation and identification of bioactive peptides and candidates for functional foods. We further discuss market-driven innovation targeted to ensure that isolated peptides and suggested products are marketable and acceptable by targeted consumers. To increase the commercial potential and ensure the sustainability of the identified bioactive peptides and products, we discuss scalability, regulatory frameworks, production possibilities and the shift towards greener technologies. Finally, we discuss some commercial products from marine peptides within the functional food market. We discuss the placement of these products in the larger picture of the commercial sphere of functional food products from bioactive peptides.

Recent developments on production, purification and biological activity of marine peptides

Marine peptides are one of the richest sources of structurally diverse bioactive compounds and a considerable attention has been drawn towards their production and bioactivity. However, there is a paucity in consolidation of emerging trends encompassing both production techniques and biological application. Herein, we intend to review the recent advancements on different production, purification and identification technologies used for marine peptides along with presenting their potential health benefits. Bibliometric analysis revealed a growing number of scientific publications on marine peptides (268 documents per year) with both Asia (37.2%) and Europe (33.1%) being the major contributors. Extraction and purification by ultrafiltration and enzymatic hydrolysis, followed by identification by chromatographic techniques coupled with an appropriate detector could yield a high content of peptides with improved bioactivity. Moreover, the multifunctional health benefits exerted by marine peptides including anti-microbial, antioxidant, anti-hypertension, anti-diabetes and anti-cancer along with their structure-activity relationship were presented. The future perspective on marine peptide research should focus on finding improved separation and purification technologies with enhanced selectivity and resolution for obtaining more novel peptides with high yield and low cost. In addition, by employing encapsulation strategies such as nanoemulsion and nanoliposome, oral bioavailability and bioactivity of peptides can be greatly enhanced. Also, the potential health benefits that are demonstrated by in vitro and in vivo models should be validated by conducting human clinical trials for a technology transfer from bench to bedside.

Pepsin Hydrolysis of Orange By-Products for the Production of Bioactive Peptides with Gastrointestinal Resistant Properties

Recently, the use of bioactive compounds in improving human health has received more attention. The aim of the present study was to hydrolyze orange seed proteins using pepsin enzyme to obtain bioactive peptides as well as to study the stability of such activity after simulated gastrointestinal digestion conditions. The method was optimized using different enzyme concentrations from 1% to 3%, hydrolysis times between 2 and 5 h, and an optimal temperature of 33 °C. Biological activities including α-glucosidase inhibition, α-amylase inhibition, Angiotensin I-Converting Enzyme (ACEI) inhibition, ferric reducing antioxidant power, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity were evaluated. According to the results, a significant higher value of the biological activity (p < 0.05) was observed using an enzyme ratio of 0.03 E/S and hydrolysis time of 3.5 h. After size-exclusion chromatography separation, fractions 45–49 and 50–54 showed the highest biological roles such as antioxidant, ACEI inhibitory, and hypoglycemic. Fractions with the highest biological activity were purified using RP-HPLC and analyzed using nano-liquid chromatography and mass spectrometry. The results obtained after simulated gastrointestinal digestion indicated that peptide fractions obtained after chromatographic separation significantly maintain their activity.

Protein Recovery from Underutilised Marine Bioresources for Product Development with Nutraceutical and Pharmaceutical Bioactivities

The global demand for dietary proteins and protein-derived products are projected to dramatically increase which cannot be met using traditional protein sources. Seafood processing by-products (SPBs) and microalgae are promising resources that can fill the demand gap for proteins and protein derivatives. Globally, 32 million tonnes of SPBs are estimated to be produced annually which represents an inexpensive resource for protein recovery while technical advantages in microalgal biomass production would yield secure protein supplies with minimal competition for arable land and freshwater resources. Moreover, these biomaterials are a rich source of proteins with high nutritional quality while protein hydrolysates and biopeptides derived from these marine proteins possess several useful bioactivities for commercial applications in multiple industries. Efficient utilisation of these marine biomaterials for protein recovery would not only supplement global demand and save natural bioresources but would also successfully address the financial and environmental burdens of biowaste, paving the way for greener production and a circular economy. This comprehensive review analyses the potential of using SPBs and microalgae for protein recovery and production critically assessing the feasibility of current and emerging technologies used for the process development. Nutritional quality, functionalities, and bioactivities of the extracted proteins and derived products together with their potential applications for commercial product development are also systematically summarised and discussed.

Design, Synthesis and Biological Evaluation of Jahanyne Analogs as Cell Cycle Arrest Inducers

Jahanyne, a lipopeptide with a unique terminal alkynyl and OEP (2-(1-oxo-ethyl)-pyrrolidine) moiety, exhibits anticancer activity. We synthesized jahanyne and analogs modified at the OEP moiety, employing an α-fluoromethyl ketone (FMK) strategy. Preliminary bioassays indicated that compound 1b (FMK-jahanyne) exhibited decreased activities to varying degrees against most of the cancer cells tested, whereas the introduction of a fluorine atom to the α-position of a hydroxyl group (2b) enhanced activities against all lung cancer cells. Moreover, jahanyne and 2b could induce G0/G1 cell cycle arrest in a concentration-dependent manner.

Antiradical Activity of Hydrolysates and Extracts from Mollusk A. broughtonii and Practical Application to the Stabilization of Lipids

The antiradical properties of hydrolysates and hydrothermal extracts of bivalve mollusks (Anadara broughtonii) from the Far Eastern Region of Russia and their influence on lipid oxidation in mayonnaise were investigated. The radical binding activity of hydrolysates and extracts of A. broughtonii varies from 55% to 89%. The maximum radical-binding activity was observed for acid hydrolysates. The antiradical efficiency of acid hydrolysates is 35%–41% of the BHT (butylhydroxytoluene) index. The antiradical activity depends on the (method of) technological and biotechnological processing of raw materials. Acid and enzymatic hydrolysates and hydrothermal extracts of A. broughtonii in mayonnaise slow down the process of oxidation of lipids and hydrolysis of triglycerides. Acid hydrolysates reduce the speed of oxidation and hydrolysis of lipids in mayonnaise more efficiently than the enzymatic hydrolysates.

Calculation of the Global and Local Conceptual DFT Indices for the Prediction of the Chemical Reactivity Properties of Papuamides A-F Marine Drugs

A well-behaved model chemistry previously validated for the study of the chemical reactivity of peptides was considered for the calculation of the molecular properties and structures of the Papuamide family of marine peptides. A methodology based on Conceptual Density Functional Theory (CDFT) was chosen for the determination of the reactivity descriptors. The molecular active sites were associated with the active regions of the molecules related to the nucleophilic and electrophilic Parr functions. Finally, the drug-likenesses and the bioactivity scores for the Papuamide peptides were predicted through a homology methodology relating them with the calculated reactivity descriptors, while other properties such as the pKas were determined following a methodology developed by our group.

Fish-derived proteins and their potential to improve human health

Emerging evidence from studies evaluating the effect of lean fish consumption in humans suggests that proteins from fish have several beneficial metabolic effects. Rest, or waste, material from the fishing industry contains high-quality proteins, and utilization of this material offers novel possibilities for the development of protein-containing products that might be beneficial for human consumption. Fish-derived peptides containing bioactive amino acid sequences suggested to beneficially influence pathways involved in body composition, hypertension, lipid profile, and regulation of glucose metabolism are of particular interest, although the results of published studies are conflicting. This review aims to summarize current knowledge from animal studies and clinical interventions in humans evaluating the effects of lean fish, fish proteins, and fish-derived peptides on outcomes related to metabolic health. Fish proteins have a high content of taurine, and animal trials suggest that taurine mediates some of the beneficial effects observed thus far, although the mechanisms by which fish peptides exert their action are not yet elucidated. At this time, the literature is inconsistent, and there is insufficient mechanistic evidence to support a beneficial effect of fish-derived peptides on metabolic health.

Identification and Structure-Activity Relationship of Intestinal Epithelial Barrier Function Protective Collagen Peptides from Alaska Pollock Skin

The effect of collagen peptides (CPs) in intestinal mucosal protection has been approved in both cell and animal models. However, its structure–activity relationship and efficient peptide sequences are unclear, which hinders the in-depth study of its action mechanism and relative nutraceuticals and pharmaceuticals development. In this work, size exclusion chromatography, cation-exchange chromatography, and RP-HPLC were used to separate Alaska pollock skin-derived collagen hydrolysates based on their molecular weight, charge property, and hydrophobicity. The intestinal epithelial barrier function (IEBF) protective effect of separated peptide fractions were evaluated by tumor necrosis factor (TNF)-α-induced Caco-2 cell model. Results indicated that lower molecular weight (500–1000 Da) and higher hydrophilicity of CPs were related to better IEBF protective effect. Two high-efficiency IEBF protective peptide sequences, GPSGPQGSR and GPSGLLGPK with the corresponding molecular weights of 841.41 Da and 824.38 Da, were subsequently identified by UPLC-QToF-MS/MS. Their IEBF protective ability are comparable or even better than the currently used intestinal health supplements glutamine and arginine. The present findings suggested that the hydrophilic CPs, with molecular weight between 500 Da to 1000 Da, should be preferred in IEBF protective peptides preparation. GPSGPQGSR and GPSGLLGPK might have the potential of being IEBF protective ingredients used in intestinal health supplements and drugs.

Total Synthesis of the Highly N-Methylated Peptides Carmabin A and Dragomabin

The first total synthesis of carmabin A and dragomabin was achieved at 52.3 mg and 43.8 mg scale, respectively. The synthesis led to determination of the configuration of carmabin A and reassignment of the configuration of dragomabin at the stereogenic centre on the alkyne-bearing fragment.

Natural Peptides in Drug Discovery Targeting Acetylcholinesterase

Acetylcholinesterase-inhibitory peptide has gained much importance since it can inhibit acetylcholinesterase (AChE) and increase the availability of acetylcholine in cholinergic synapses, enhancing cholinergic transmission in pharmacological treatment of Alzheimer’s disease (AD). Natural peptides have received considerable attention as biologically important substances as a source of AChE inhibitors. These natural peptides have high potential pharmaceutical and medicinal values due to their bioactivities as neuroprotective and neurodegenerative treatment activities. These peptides have attracted great interest in the pharmaceutical industries, in order to design potential peptides for use in the prophylactic and therapy purposes. Some natural peptides and their derivatives have high commercial values and have succeeded in reaching the pharmaceutical market. A large number of peptides are already in preclinical and clinical pipelines for treatment of various diseases. This review highlights the recent researches on the various natural peptides and future prospects for AD management.

Natural Preservatives for Extending the Shelf-Life of Seafood: A Revisit

Consumer demand for minimally processed seafood that retains its sensory and nutritional properties after handling and storage is increasing. Nevertheless, quality loss in seafood occurs immediately after death, during processing and storage, and is associated with enzymatic, microbiological, and chemical reactions. To maintain the quality, several synthetic additives (preservatives) are promising for preventing the changes in texture and color, development of unpleasant flavor and rancid odor, and loss of nutrients of seafood during storage at low temperature. However, the use of these preservatives has been linked to potential health hazards. In this regard, natural preservatives with excellent antioxidant and antimicrobial properties have been extensively searched and implemented as safe alternatives in seafood processing, with the sole purpose of extending shelf-life. Natural preservatives commonly used include plants extracts, chitosan and chitooligosaccharide, bacteriocins, bioactive peptides, and essential oils, among others. This review provides updated information about the production, mode of action, applications, and limitations of these natural preservatives in seafood preservation.

Total Synthesis of the Highly N-Methylated Peptide Jahanyne

Total synthesis of jahanyne (1) was achieved from commercially available materials on a 38 mg scale. The Boc- N-Me- L-Val-OH fragment along with the HATU/DIPEA coupling condition was applied to avoid the diketopiperazine side reaction in solution phase synthesis.

Identification of Bioactive Peptides with α-Amylase Inhibitory Potential from Enzymatic Protein Hydrolysates of Red Seaweed (Porphyra spp)

Inhibition of α-amylase enzyme is one therapeutic approach in lowering glucose level in the blood to manage diabetes mellitus. In this study α-amylase inhibitory peptides were identified from proteolytic enzymes hydrolysates of red seaweed laver ( Porphyra species) using consecutive chromatographic techniques. In the resultant fractions from RP-HPLC (D₁-₁₀), D₂ inhibited α-amylase activity (88.67 ± 1.05%) significantly ( p ≤ 0.5) at 1 mg/mL protein concentration. A mass spectrometry (ESI-Q-TOF- MS) analysis was used to identify peptides from this fraction. Two novel peptides were identified as Gly-Gly-Ser-Lys and Glu-Leu-Ser. To validate their α-amylase inhibitory activity, these peptides were synthesized chemically. The peptides were demonstrated inhibitory activity at IC₅₀ value: 2.58 ± 0.08 mM (Gly-Gly-Ser-Lys) and 2.62 ± 0.05 mM (Glu-Leu-Ser). The inhibitory kinetics revealed that these peptides exhibited noncompetitive binding mode. Thus, laver can be a potential source of novel ingredients in food and pharmaceuticals in diabetes mellitus management.

Marine Natural Peptides: Determination of Absolute Configuration Using Liquid Chromatography Methods and Evaluation of Bioactivities

Over the last decades, many naturally occurring peptides have attracted the attention of medicinal chemists due to their promising applicability as pharmaceuticals or as models for drugs used in therapeutics. Marine peptides are chiral molecules comprising different amino acid residues. Therefore, it is essential to establish the configuration of the stereogenic carbon of their amino acid constituents for a total characterization and further synthesis to obtain higher amount of the bioactive marine peptides or as a basis for structural modifications for more potent derivatives. Moreover, it is also a crucial issue taking into account the mechanisms of molecular recognition and the influence of molecular three-dimensionality in this process. In this review, a literature survey covering the report on the determination of absolute configuration of the amino acid residues of diverse marine peptides by chromatographic methodologies is presented. A brief summary of their biological activities was also included emphasizing to the most promising marine peptides. A case study describing an experience of our group was also included.

Bioactive Peptides Derived from Seaweed Protein and Their Health Benefits: Antihypertensive, Antioxidant, and Antidiabetic Properties

Cardiovascular diseases and diabetes are the biggest causes of death globally. Therefore, prevention of these diseases is a focus of pharmaceuticals and functional food manufacturers. This review summarizes recent research trends and scientific knowledge in seaweed protein-derived peptides with particular emphasis on production, isolation and potential health impacts in prevention of hypertension, diabetes and oxidative stress. The current status and future prospects of bioactive peptides are also discussed. Bioactive peptides have strong potential for use in therapeutic drug and functional food formulation in health management strategy, especially cardiovascular disease and diabetes. Seaweeds can be used as sustainable protein sources in the production of these peptide-based drugs and functional foods for preventing such diseases. Many studies have reported that peptides showing angiotensin converting enzyme inhibition, antihypertensive, antioxidative and antidiabetics activities, have been successfully isolated from seaweed. However, further research is needed in large-scale production of these peptides, efficient isolation methods, interactions with functional foods and other pharmaceuticals, and their ease to digestion in in vivo studies and safety to validate the health benefits of these peptides.

Structural Diversity, Biological Properties and Applications of Natural Products from Cyanobacteria. A Review

Nowadays, various drugs on the market are becoming more and more resistant to numerous diseases, thus declining their efficacy for treatment purposes in human beings. Antibiotic resistance is one among the top listed threat around the world which eventually urged the discovery of new potent drugs followed by an increase in the number of deaths caused by cancer due to chemotherapy resistance as well. Accordingly, marine cyanobacteria, being the oldest prokaryotic microorganisms belonging to a monophyletic group, have proven themselves as being able to generate pharmaceutically important natural products. They have long been known to produce distinct and structurally complex secondary metabolites including peptides, polyketides, alkaloids, lipids, and terpenes with potent biological properties and applications. As such, this review will focus on recently published novel compounds isolated from marine cyanobacteria along with their potential bioactivities such as antibacterial, antifungal, anticancer, anti-tuberculosis, immunosuppressive and anti-inflammatory capacities. Moreover, various structural classes, as well as their technological uses will also be discussed.

Peptides, Peptidomimetics, and Polypeptides from Marine Sources: A Wealth of Natural Sources for Pharmaceutical Applications

Nature provides a variety of peptides that are expressed in most living species. Evolutionary pressure and natural selection have created and optimized these peptides to bind to receptors with high affinity. Hence, natural resources provide an abundant chemical space to be explored in peptide-based drug discovery. Marine peptides can be extracted by simple solvent extraction techniques. The advancement of analytical techniques has made it possible to obtain pure peptides from natural resources. Extracted peptides have been evaluated as possible therapeutic agents for a wide range of diseases, including antibacterial, antifungal, antidiabetic and anticancer activity as well as cardiovascular and neurotoxin activity. Although marine resources provide thousands of possible peptides, only a few peptides derived from marine sources have reached the pharmaceutical market. This review focuses on some of the peptides derived from marine sources in the past ten years and gives a brief review of those that are currently in clinical trials or on the market.

Alkynyl-Containing Peptides of Marine Origin: A Review

Since the 1990s, a number of terminal alkynyl residue-containing cyclic/acyclic peptides have been identified from marine organisms, especially cyanobacteria and marine mollusks. This review has presented 66 peptides, which covers over 90% marine peptides with terminal alkynyl fatty acyl units. In fact, more than 90% of these peptides described in the literature are of cyanobacterial origin. Interestingly, all the linear peptides featured with terminal alkyne were solely discovered from marine cyanobacteria. The objective of this article is to provide an overview on the types, structural characterization of these unusual terminal alkynyl fatty acyl units, as well as the sources and biological functions of their composed peptides. Many of these peptides have a variety of biological activities, including antitumor, antibacterial, antimalarial, etc. Further, we have also discussed the evident biosynthetic origin responsible for formation of terminal alkynes of natural PKS (polyketide synthase)/NRPS (nonribosome peptide synthetase) hybrids.