Marine active peptides are mainly extracted from molluscs, crustaceans, fish, algae, and some marine by-products (shellfish, fish skin, offal, and muscle). Algae is rich in protein, so it is a good source of bioactive peptides and has potential applications in the food, pharmaceutical, and cosmetics industries. Crustaceans and molluscs also contain 7%~23% protein, and marine molluscs are widely distributed around the world, and it is estimated that there are about 48,584 species of marine mollusks. Among them, mussels have high ornamental value and edible value, and the smaller or broken mussels are often discarded directly in the fishing process, and the processing of waste mussels is conducive to the sustainable development of the industry and the development of circular economy. In recent years, research on marine bioactive compounds has focused on the antibacterial activity, antihypertensive activity, and antioxidant activity of marine bioactive peptides, as well as bioactive peptides that are limited to specific sources, such as fish, mussels, and algae.
Bioavailability of Peptides
The activity of peptides in vitro may be different from that in vivo, and when peptides are ingested orally, the body's digestive system may reduce their biological activity, so the bioavailability of peptides is often analyzed by in vivo and in vitro experiments. In vitro experiments usually need to simulate the gastrointestinal environment, firstly, the peptide can be exposed to α-amylase, and the pH value can be controlled between 5.6~6.9 to simulate oral digestion, and then the gastric and intestinal digestion can be simulated by simulating gastric juice (containing pepsin, pH 2.0) and intestinal fluid (containing pancreatic enzyme and bile salt, pH 6.0). Subsequently, a semi-permeable membrane with a molecular cut-off size of 3 kDa was used for dialysis to analyze whether the peptides could be absorbed by the small intestine. Finally, peptides in solution inside and outside the cell membrane need to be tested for biological activity. In order to explore the mechanism of action of peptides on target targets, in vivo activity studies (animal experiments and clinical studies) are also necessary, mainly to verify the gastrointestinal digestibility and solubility, absorption, distribution, utilization rate, and optimal dose of peptides. In vivo studies of peptides can be modeled using different test animals, such as invertebrates (Caenorhabditis elegans and Drosophila), vertebrates (rats and mice), etc.
In order to improve the bioavailability of peptides, peptide microcapsules and peptide nanocapsules can usually be prepared to reduce the digestion of peptides by the gastrointestinal digestive system. Some common peptide embedding delivery systems are microemulsions (oil in water (O/W), water-in-oil (W/O)), emulsified microemulsions (water-in-oil-inwater (W/O/W)), emulsions (O/W or W/O), nanoemulsions (O/W or W/O), solid lipid nanoparticles, liposomes, and biopolymeric microgels. In anti-tumor studies, the embedding of peptides does not cause them to lose their anti-tumor activity. In addition, microencapsulation can also be applied to vaccine production, and these results point to the study of the bioavailability of active peptides. The embedding of peptides can prevent peptides from being digested and degraded after ingestion, or prevent degradation caused by other factors (such as oxidation), and can also control the release of peptides (rate and environmental conditions), enhance the stability of peptides, and reduce the toxicity of peptides. For peptide embedding, it is necessary to study the delivery system and final product characteristics of the peptide. For the active peptide itself, in addition to analyzing its molecular weight, electrical properties, polarity, solubility, surface activity, and stability, it is also necessary to study the composition, size and shape, interface properties, and aggregation state of the embedded peptide particles.
Biological Properties of Marine Bioactive Peptides
The main sources of marine bioactive peptides are algae, molluscs, fish, and crustaceans. The extraction methods include enzymatic hydrolysis, fermentation, acid-base extraction, hot water extraction or a combination of different technologies, among which the most commonly used method is enzymatic hydrolysis, and pepsin, papain, trypsin and alkaline protease are commonly used enzymes. A study categorized the molecular mass range of marine bioactive peptides from different sources, and found that the molecular mass of most bioactive peptides was less than 3 kDa, for example, among the 27 kinds of algae peptides, only 2 kinds of active peptides had a molecular mass of more than 3 kDa, 11 kinds of active peptides had a molecular mass of 1~3 kDa, and 14 kinds of active peptides had a molecular mass of less than 1 kDa. Among the 28 mollusc active peptides, 10 active peptides had a molecular mass of more than 4 kDa, 8 active peptides had a molecular weight of 1~4 kDa, and 6 active peptides had a molecular weight of less than 1 kDa. Among the 20 fish and crustacean active peptides, 13 active peptides had molecular mass less than 1 kDa, 3 active peptides had molecular mass of 1~3 kDa, and 7 active peptides had molecular mass greater than 3 kDa. In addition, mussel peptides tend to have a higher molecular mass than those of algae and other species.
Marine active peptides have anti-atherosclerosis, anti-cancer, anticoagulant, anti-diabetic, anti-inflammatory, anti-hypertensive, antibacterial and antioxidant activities, among which antihypertensive and antioxidant activities have been widely studied. Fewer anticancer and antimicrobial peptides (AMPs) have been isolated from algae, and antimicrobial and anti-inflammatory peptides are often derived from molluscs. In addition, some studies have shown that peptides often have multiple biological activities at the same time, as often as both antioxidant and antihypertensive effects.
Table.1 Anticancer peptides products at Creative Peptides.
Anti-Atherosclerotic Activity
Cardiovascular diseases (CVD) are the leading cause of death worldwide. Atherosclerosis is a multifactorial chronic disease with a complex pathogenesis that can lead to myocardial infarction, ischemic cardiomyopathy, stroke, and peripheral artery disease, making it the primary cause of CVD. In atherosclerosis, arterial obstruction is caused by the formation of lesions or plaques that reduce blood flow. These plaques are primarily caused by the accumulation of lipids, such as cholesterol, in the arterial wall space.
Recent studies on marine peptides' anti-atherosclerotic activity are limited. Research has shown that peptides extracted from spirulina can downregulate histamine-induced endothelial cell activation, exhibiting potential anti-atherosclerotic effects. Peptides (VGCTGPAAPGP) extracted from Chlorella demonstrated in vitro activity by reducing the production of endothelial cell selectins, key vascular adhesion molecules involved in atherosclerosis, as well as intercellular and vascular cell adhesion molecules. Additionally, hydrolysis of red algae using papain yielded a tetrapeptide with in vitro acetylcholinesterase inhibition and good water solubility, making it suitable for food and pharmaceutical applications.
Although some algae-derived peptides have been found to have anti-atherosclerotic activity, there have been few reports in recent years. As a promising field, it is feasible to search for active peptides from other algae that can inhibit acetylcholinesterase or vascular adhesion molecules.
Table.2 CVD related peptides product catalog at Creative Peptides.
Anticancer Activity
Cancer is one of the leading causes of death worldwide and a chronic disease that severely impacts human well-being. The number of cancer cases and death rates continue to rise, with 18.1 million new cancer cases and 9.89 million deaths globally in 2020. It is expected that cancer cases will increase by approximately 50% over the next 20 years. Over the years, some natural compounds, such as flavonoids, carotenoids, phenolic acids, isothiocyanates, curcumin, and resveratrol, have been proven to have anticancer effects. Around 3,491 peptides with anticancer activity are listed in the anticancer peptide and protein database, which exert their effects by binding to specific sites on cancer cells to inhibit cell division or induce apoptosis.
The efficacy and mechanisms of action of anticancer peptides (ACPs) have been widely studied. Natural host defense peptides with antimicrobial or antifungal activity have been found in various organisms. Compared to monoclonal antibodies and checkpoint inhibitors, ACPs are smaller in size, more soluble, with better pharmacokinetics and higher cell uptake rates, enhancing their potency and efficacy. Many natural peptides, such as plitidepsin, microtubule polymerization inhibitors, geodiamine B, and marine cyclic peptides, have been used in clinical trials for treating various cancers. Understanding the structure-activity relationship of these peptides helps in the design and development of peptide-based drugs.
In recent years, research on anticancer peptides from terrestrial plants and animals has advanced significantly. Bioactive peptides from wheat germ protein hydrolysates have demonstrated antioxidant, anticancer, and ACE-inhibitory activity. Peptides derived from hydrolyzed rice husk encapsulated in chitosan have also shown anticancer properties. Additionally, novel bioactive peptides with anticancer and antioxidant activity have been identified from pangolins. Extensive research has also been conducted on marine-derived drugs. The first marine-derived anticancer drug, cytarabine, was extracted from Caribbean sponges and approved in 1959. Currently, eight natural product-derived anticancer drugs have been approved by the U.S. FDA or the EMA, including two marine peptides.
Anticoagulation Activity
Coagulation factors can stop bleeding and repair damaged blood vessels, while anticoagulants, as therapeutic drugs, interfere with the coagulation mechanism by prolonging clotting time or preventing coagulation. The main commercial anticoagulant is heparin. however, it has numerous side effects, such as low platelet count and bleeding effects, which can lead to serious complications, limiting its long-term use. Aspirin and clopidogrel also have anticoagulant effects but carry bleeding risks as well, while marine bioactive peptides, with no cytotoxicity, have the potential to replace these drugs.
Activated partial thromboplastin time, prothrombin time, and thrombin time are common indicators of anticoagulant activity. In existing studies, marine anticoagulant compounds are mainly polysaccharides and proteoglycans. Currently, marine-derived peptides with anticoagulant activity primarily come from algae (Porphyra tenera), mussels (Mytilus edulis, Perna viridis), and polychaetes (Eunice aphroditois). All peptides tested in vitro showed an extension of activated partial thromboplastin time and exhibited a dose-response relationship. The activity of Perna viridis peptides is to inhibit the activation of factor X in the enzyme complex and the conversion of prothrombin in the prothrombinase complex to thrombin. Similarly, peptides extracted from Eunice aphroditois inhibit coagulation factor FXIa, and peptides derived from papain hydrolysis of Mytilus edulis (DFEEIPEEYLQ) inhibit thrombin activity by competing with fibrinogen, extending the activated partial thromboplastin time and thrombin time.
Marine-derived bioactive peptides could be good alternatives to heparin. Typically, peptides with anticoagulant activity have a molecular weight of less than 3.5 kDa, with most being below 2.5 kDa. Therefore, considering the low molecular weight of identified anticoagulant peptides, it is possible to filter and select peptides with anticoagulant activity that have a molecular weight of less than 3 kDa. Further studies are needed to assess whether they exhibit side effects similar to those of heparin.
Antidiabetic Activity
Bioactive peptides have the ability to inhibit glucosidase, α-amylase, or DPP-IV, opening new avenues for diabetes treatment. Antidiabetic peptides were first extracted from milk and soybean proteins, but research on marine-derived antidiabetic peptides has been increasing, especially from fish. Hydrolyzed peptides from grouper (IPVDM and IPV) have shown in vitro DPP-IV inhibition. In routine in vitro tests, the IC50 of IPVDM peptide for DPP-IV was (21.72±1.08) µmol/L, and in Caco-2 cell-based DPP-IV inhibition assays, the IC50 reached (44.26±0.65) µmol/L. Both peptides can stimulate insulin secretion. Peptides isolated from papain hydrolyzed carp egg (IPNVAVD) also exhibit DPP-IV inhibitory activity, with an IC50 of (777.35±5.50) μmol/L in Caco-2 and HepG2 cell models. In salmon byproduct trypsin hydrolysates, the peptide LDKVFR has DPP-IV inhibitory activity, with an IC50 of (0.10±0.03) mg/mL. Molecular docking revealed that six hydrogen bonds and eight hydrophobic interactions between LDKVFR and DPP-IV contribute to DPP-IV inhibition.
There is limited research on the antidiabetic activity of mussel peptides. Antidiabetic peptides (GGSK and ELS) isolated from seaweed can inhibit α-amylase activity, thereby controlling glucose levels in the blood. Almost all antidiabetic peptides have a small molecular weight, typically less than 1000 Da. Most of these peptides exhibit in vitro DPP-IV inhibition, and some antidiabetic peptides control blood glucose levels by inhibiting α-amylase activity.
Anti-Inflammatory Activity
Inflammation is the immune system's response to harmful stimuli, such as toxins or pathogens, and is a part of the body's defense mechanism. Multiple pathways are associated with inflammation, but they all involve the recognition of harmful stimuli by cell surface pattern receptors, the activation of inflammatory pathways, the release of inflammatory markers, and the recruitment of inflammatory cells. Macrophages play a crucial role in immune responses. Upon stimulation, macrophages secrete various inflammatory mediators, such as nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1. Additionally, interferon-γ, pro-inflammatory cytokines (TNF-α, IL-6, and IL-1b), and Gram-negative bacterial lipopolysaccharides (LPS) can activate macrophages.
Most anti-inflammatory active peptides are extracted from mollusks, with few reports on peptides isolated from algae, fish, and crustaceans. Anti-inflammatory active peptides (QCQQAVQSAV) obtained from the hydrolysis of Philippine clam basic proteinase inhibited LPS-induced inflammation in RAW264.7 mouse macrophages by reducing NO production. Similar anti-inflammatory active peptides were also isolated from thick-shelled mussels and long oysters. Anti-inflammatory peptides from salmon pectoral fins, obtained through pepsin hydrolysis, demonstrated multiple anti-inflammatory effects in LPS-induced RAW264.7 mouse macrophages, such as inhibiting the protein expression of inducible nitric oxide synthase and cyclooxygenase-2, and reducing the production of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1b).
Antiallergic Activity
Allergic reactions are immune system responses to normally harmless environmental substances. The severity of allergic reactions is unpredictable, ranging from mild itching and vomiting to life-threatening systemic allergic reactions, causing thousands of deaths each year. Mast cells, basophils, and eosinophils play key roles in the initiation and propagation of allergic reactions. Mast cells are crucial in the pathogenesis of allergic diseases, being activated by allergens mediated by immunoglobulin E. Histamine is an important mediator associated with acute inflammatory responses and is involved in various allergic reactions, such as vascular edema, increased vascular permeability, vasodilation, bronchoconstriction, mucus production, and hypothermia. Therefore, the main target for anti-allergic drugs is to inhibit mast cell degranulation and histamine production.
Marine peptides extracted from giant spirulina have been studied for their anti-allergic activity in vitro. The peptides LDAVNR (P1 peptide) and MMMLDF (P2 peptide) both exhibit dose-dependent anti-allergic effects. They reduce histamine release and the increase in intracellular Ca2+ levels, thereby inhibiting mast cell degranulation, as confirmed by morphological studies. The P1 peptide acts through calcium- and microtubule-dependent signaling pathways, while the P2 peptide inhibits the activation of phospholipase and the formation of reactive oxygen species. The anti-allergic properties of marine peptides have not yet been fully explored and require further research.
Antihypertensive Activity
Hypertension is a very common condition directly related to cardiovascular risk. Although it can be controlled with a healthy lifestyle and antihypertensive medications, some patients still have poor blood pressure control. The renin-angiotensin system plays an important role in regulating the body's water, electrolytes, and blood, and is involved in the development and progression of hypertension. ACE-I is involved in regulating blood pressure and catalyzing the formation of angiotensin II, a potent vasopressor. Therefore, inhibiting the activity of the two rate-limiting enzymes in the renin-angiotensin system (ACE-I or renin) can control hypertension. Existing synthetic antihypertensive drugs have many side effects, such as chronic cough, loss of taste, kidney damage, and angioedema. Therefore, it is important to find natural compounds with antihypertensive activity that do not have adverse side effects by inhibiting ACE-I or renin activity.
ACE inhibitory peptides derived from whey, mushrooms, walnuts, and other sources have been widely studied. In marine resources, antihypertensive peptides have been studied in fish, mussels, and algae. Most of the identified antihypertensive peptides have a molecular weight of less than 1.5 kDa, and the ACE inhibitory activity shows a dose-effect relationship. In addition, a peptide with in vitro renin inhibitory activity was isolated from red algae, a large marine alga, through enzymatic hydrolysis by papain. peptide VECYGPNRPQF was obtained from microalgae, Chlorella. peptide FQIN [M(O)] CILR and TGAPCR were obtained from the seaweed Gracilaria. and peptides YH, KY, FY, IY, YNKL, IY, and IW were obtained from the kelp Laminaria. These marine bioactive peptides all exhibited good in vitro ACE inhibitory activity. Peptides YH, KY, FY, and IY were prepared by hot water extraction, while the rest were obtained by enzymatic hydrolysis using pepsin or trypsin. Studies on the soldiers' fish and skipjack tuna also demonstrated potential activity, with their derived peptides AWW, IWW, WL, VRP, IKP, LRP, and IRP showing in vitro ACE inhibitory activity.
Antimicrobial Activity
AMPs are one of the main components of innate immune defense and are widely found in plants, mammals, and microorganisms. As the first line of defense against pathogenic microorganisms, antimicrobial factors play an important role. Typically, AMPs are cationic peptides composed of 12 to 50 amino acids, exhibiting amphipathic structural characteristics. The cationic nature of AMPs is the main reason for their activity, as they can specifically bind to the negatively charged LPS in microbial cell membranes through electrostatic attraction. The activity of cationic AMPs depends on their secondary structure, overall net charge, hydrophilicity, hydrophobicity, size, and the balance between hydrophobic and polar regions. Since the discovery of AMPs, their mechanisms of action have been widely studied. Understanding the mechanisms of AMPs is crucial for their future therapeutic development. AMPs mainly exert antibacterial effects through two different pathways: directly killing microorganisms and regulating the immune system. Direct killing of microorganisms is achieved through two different mechanisms based on the target site: non-membrane-targeting mechanisms and membrane-targeting mechanisms. Membrane-targeting peptides disrupt the cell membrane, while non-membrane-targeting peptides interfere with key intracellular metabolic processes such as nucleic acid and protein synthesis. AMPs can be classified based on their biological origin, physicochemical properties, biological functions, covalent bonding patterns, biosynthesis, molecular targets, and secondary structures.
Unlike vertebrates, marine invertebrates do not have adaptive immunity. For example, bivalves only have innate immunity. Therefore, they need to develop defense systems to adapt to their environment, which is often rich in pathogenic microorganisms and viruses. Their filter-feeding activity also increases their contact with pathogens. One of the defense mechanisms in invertebrates is antimicrobial peptides with antibacterial activity. Research on marine mussel AMPs is divided into eight categories: Defensin, Mytilin, Myticin, Mytimycin, Mytimacin, Bigdefensin, Mytichitin-CBD, and Myticusin-1. Several AMPs have been purified and identified from marine mussels. For example, Mytilus galloprovincialis-derived Myticin C, obtained by pepsin hydrolysis, has antiviral activity against human herpes simplex virus 1 and 2. In 2018, antimicrobial peptides (AMPs) were extracted from the bivalve Mytilus coruscus using hot water. The obtained peptide exhibited strong antibacterial activity against both Gram-positive and Gram-negative bacteria, as well as fungi. Subsequently, AMPs named Myticusin-beta were prepared from Mytilus coruscus. This active peptide has a molecular weight of approximately 11 kDa and demonstrates antibacterial activity against several pathogenic microorganisms, including Escherichia coli and Staphylococcus aureus.
In algae AMP research, a peptide mixture was obtained from the marine microalga Chlamydomonas through acid extraction, showing strong activity against both Gram-positive and Gram-negative bacteria. Additionally, an active peptide, TPDSEAL, with a molecular weight of 732 Da, was prepared from nori using pepsin hydrolysis. This peptide has been shown to damage the cell wall and cell membrane of Staphylococcus aureus.
Table.3 Antimicrobial peptides at Creative Peptides.
Antioxidant Activity
Reactive oxygen species and free radicals are involved in numerous metabolic processes and can cause cellular damage, leading to cancer, cardiovascular diseases, neurological disorders, lung diseases, rheumatoid arthritis, kidney diseases, eye conditions, and prenatal medical issues. Large algae are considered an important source of natural bioactive compounds, particularly those with antioxidant activities. Compounds identified in algae with antioxidant activity mainly include chlorophyll and its derivatives, carotenoids, vitamins E and C, xanthophylls, enzymes, cysteine-like amino acids, polysaccharides, and polyphenols. Although the exact mechanisms of antioxidant peptides have not been fully revealed, the most studied mechanisms include inhibiting lipid peroxidation, scavenging free radicals, and metal chelation ability.
Marine-derived antioxidant peptides have a low molecular weight, typically less than 3 kDa. Except for self-digested products from Pacific cod (Merluccius productus) and yeast fermentation products from Pavlova lutheri, most are produced by enzymatic hydrolysis, with pepsin being the commonly used enzyme for producing marine antioxidant peptides. Research has mainly focused on the ability to scavenge hydroxyl radicals, peroxide radicals, DPPH radicals, and ABTS cation radicals. Furthermore, only a few studies have evaluated the protective effects of peptides on DNA and cells and their ability to absorb oxygen free radicals.
Other Activity
In other studies, collagen hydrolysates extracted from fish or by-products are a promising functional food ingredient that promotes skin improvement by increasing skin collagen content and can prevent skin aging. In addition, studies have shown that Marine AMPs can play an anti-osteoporosis role by regulating the osteogenic synthesis pathway.
Functional Properties of Marine Active Peptides
The functional properties of a protein or protein hydrolysate are influenced by its molecular mass, physical structure, amino acid composition and sequence, charge, hydrophobicity/hydrophilic ratio, and interactions with other components. Although there are not many studies on the functional properties of specific marine peptides, however, some studies have shown the effect of protein hydrolysates on functional properties, such as emulsifying capacity and solubility. Enzymatic hydrolysis of marine proteins has been used to improve the functional properties of proteins, particularly fish by-products. The most important properties in food formulations are emulsifying ability and stability, solubility, and fat binding capacity, and proteolysis can enhance these properties.
Solubility
Solubility is one of the most important functional characteristics in food, and proteins with high solubility are more suitable for the food industry. Solubility affects other properties, such as emulsifying and foaming. The solubility of peptides increases with enhanced emulsifying and foaming abilities. The higher the degree of proteolysis, the better the solubility. A pH of 6 or 7 can increase the solubility of salmon byproduct hydrolysates. Sardine byproduct hydrolysates also showed similar results, with protein hydrolysates being more soluble than undigested hydrolysates. Hydrolysates with higher degrees of hydrolysis exhibit better solubility under pH conditions ranging from 6 to 10. Protein hydrolysates prepared from the golden-banded trevally fish using alkaline protease and flavor protease achieved protein solubility of over 85% under pH conditions from 2 to 12. Moreover, improving the solubility of protein hydrolysates through the Maillard reaction is an effective method for functional modification. Exploring the precise control of the Maillard reaction process between food-derived protein hydrolysates and sugars is also of significant importance for improving their solubility.
Emulsifying Properties and Foaming Properties
The emulsifying ability is measured using the emulsifying activity index (EAI), and the ability of the emulsion to resist degradation is assessed using the emulsion stability index (ESI). Therefore, the higher the ESI, the more stable the emulsion. The length of peptides is related to emulsifying ability because smaller peptides exhibit lower emulsifying performance. On the other hand, larger or more hydrophobic peptides tend to have higher ESI. Fish protein hydrolysates (FPH) extracted from fish muscle, skin, and byproducts (such as heads, viscera, fins, etc.) exhibit good solubility, foaming, and emulsifying properties. Emulsifying ability and emulsion stability do not increase with higher degrees of hydrolysis. The higher the hydrolysis, the smaller the peptide segments, and the weaker the emulsifying performance. The emulsifying properties of protein hydrolysates are influenced by factors such as solubility, peptide molecular weight, amino acid sequence, degree of hydrolysis, acetylation of peptides, type of enzymes used, extraction solvents, and environmental pH.
Peptides with molecular weights greater than 50 kDa, isolated from the brine of salted herring, exhibit good EAI and higher foaming abilities, whereas shorter peptide fragments lack this ability. The foaming ability of peptides with molecular weights greater than 50 kDa is strongest at pH 10 and weakest at pH 4, which may be related to their isoelectric point. In sardine hydrolysates, foam formation decreases as the degree of hydrolysis and pH increase. Compared to cod skin collagen peptides, the foaming and foam stability of cod skin collagen peptide-xylose covalent complexes are significantly enhanced.
Water Retention and Fat Binding Capacity
Water retention is an important processing property in the food industry, and once protein hydrolysates or peptides give food its ability to retain moisture, it often improves food texture. In FPH, high solubility reduces water holding capacity. FPH with lower molecular mass peptides exhibits higher water-holding capacity. The fat-binding capacity of peptides or protein hydrolysates is a property required for some foods (meat and confectionery) and it also affects the taste of the food. The bulk density, degree of hydrolysis, and enzyme-substrate specificity of the protein may all affect the activity of the enzyme. The results of the study of the two FPHs showed that the fat binding capacity decreased as the size of the peptide molecule increased.
Industrial Applications of Marine Active Peptides
Current Industrial Applications
Bioactive peptides can be used in various industrial fields, such as the food, cosmetics, or pharmaceutical industries. In the food industry, several dairy products containing bioactive peptides have already been commercialized. The application of microalgae in cosmetics is gaining increasing attention, especially spirulina and chlorella.
The application of antioxidant peptides in food packaging is also significant because lipid oxidation is one of the main causes of food spoilage, such as in nuts, fish, meat, and sauces. Lipid oxidation leads to rancidity, formation of toxic aldehydes, and loss of nutritional quality. To prevent this spoilage, antioxidants are used as food additives or to package food in controlled atmospheres to limit the presence of oxygen.
Several products containing FPH and peptides are already marketed in Japan as functional foods, such as beverages, soup powders, or dietary supplements. In the functional food market in the United States and Canada, peptides derived from enzymatic hydrolysis of deep-sea white fish proteins, as dietary supplements, help regulate intestinal function. Fish protein hydrolysates made by autolysis from Atlantic salmon are used in sports nutrition supplements. In the UK functional food market, peptides obtained from enzymatic hydrolysis of fish protein are used as dietary supplements to regulate mood-related stress symptoms.
More than 60 peptides have been approved by the FDA for medical applications, and numerous preclinical studies are ongoing. Some marine-based peptide drugs have already been approved by the FDA, while others are undergoing clinical trials. For example, a peptide, peptide, isolated from the monk's horn snail, is used to treat severe chronic pain. Peptides such as plipeptide and aplindin extracted from Utricularia asplundii are used for cancer treatment. However, most peptides or hydrolysates from marine species have only been tested in vitro, with few studies involving human trials.
Future Industrial Applications
Marine algae are abundant, easy to produce, high in biomass, rich in protein, and more readily available than common crops (wheat and soybeans), making the beneficial active peptides isolated from algae have great potential for industrial applications. Spirulina is a kind of cyanobacteria, its protein content (53%~62% of dry weight) is higher than that of other algae, contains all essential amino acids, and as a high-quality source of bioactive peptides, spirulina active peptides have a variety of biological activities, such as antibacterial, anti-allergic and anti-hypertensive, etc., which is very promising. In recent years, many marine peptides have been studied and some important biological activities have been characterized, but there are still many shortcomings in the current research, such as the change of algae protein content with the change of season, temperature and fishing location. Therefore, protein content is a key factor influencing the preparation of algae active peptides.
Applications in Pharmaceuticals and Nutrition
Peptides with antihypertensive, anticoagulant, antibacterial, and antioxidant effects may play a role in the prevention or treatment of diseases. Some peptides from the ocean have been tested in clinical trials, but most of the studies are based on in vitro experiments, and in vivo experiments must be conducted to understand their specific effects in order to further the use of peptides as nutraceuticals and medicines. For example, the development of peptide drugs with antihypertensive activity of marine origin must be carried out more in vivo experiments and pharmacokinetic studies. Marine antidiabetic active peptides are attracting attention for their ability to promote the treatment of type 2 diabetes.
Applications in the Food Industry
AMPs have an inhibitory effect on some bacterial and fungal strains, aid in food preservation, and have high potential as food preservatives. Microalgae cell walls are often difficult to digest due to their cellulose properties, resulting in inefficient consumption of proteins. However, protein hydrolysates prepared from microalgae show higher digestibility and higher peptide and amino acid bioavailability, increasing their value for food applications. Future development and research should highlight several advantages of marine biological peptides in human nutrition to increase their application in food, such as: they are more easily absorbed by the gastrointestinal tract than intact proteins or free amino acids. They have a variety of biological activities that enhance the benefits of food for human health. Can be used as a preservative. Contribution to sustainable development can be made by the use of marine by-products.
Application in the Cosmetics Industry
The development of antioxidant peptides is of great significance to the development of the cosmetics industry, on the one hand, antioxidant peptides can scavenge free radicals in the body and have the function of preventing skin aging and skin disorders. Antioxidant peptides, on the other hand, prevent lipid oxidation, which in turn extends the shelf life of the product. Peptides extracted from some algae can be used in cosmetic formulations for skin and hair care, such as body lotions, shampoos, hair restorators, hair dyes, soaps, etc.
Summary
As a source of bioactive compounds, marine species have a variety of biological activities and functions, and have potential applications in the pharmaceutical, food, nutrition and cosmetics industries. In addition, for a deeper understanding of peptide applications, issues such as bioavailability are enumerated in this article. Marine bioactive peptides are a promising field, but their applications in the field of marine bioactive peptides are still scarce. Therefore, there is a need for further research into the application of bioactive peptides in the final product to better understand their performance, potential, and consumer acceptance. The biodiversity of the ocean is high, and there is a large amount of waste with high protein content in related products, so the production of active peptides from marine species can promote the sustainable development of society and help promote their future development and application in functional foods, pharmaceutical products and cosmetics.
References
- Cunha, Sara Alexandra, and Manuela Estevez Pintado. Bioactive peptides derived from marine sources: Biological and functional properties. Trends in Food Science & Technology 119 (2022): 348-370.
- Jo, Cheorun, et al., Marine bioactive peptides: Types, structures, and physiological functions. Food Reviews International 33.1 (2017): 44-61.
- Ucak, Ilknur, et al., Functional and bioactive properties of peptides derived from marine side streams. Marine Drugs 19.2 (2021): 71.
