Purification, modification and inhibition mechanism of angiotensin I-converting enzyme inhibitory peptide from silkworm pupa (Bombyx mori) protein hydrolysate

Uncovering the Potential Somatic Angiotensin-Converting Enzyme (sACE) Inhibitory Capacity of Peptides from Acheta domesticus: Insights from In Vitro Gastrointestinal Digestion

Entomophagy is being proposed as a sustainable and nutritious alternative protein source. Additionally, insect consumption is also associated with some health benefits mediated by bioactive compounds produced during gastrointestinal (GI) digestion. The antihypertensive property resulting from the inhibition of the somatic angiotensin-converting enzyme (sACE) by small peptides is one of the most common bioactivities related to insect consumption. This study aimed to investigate the potential sACE-inhibitory capacity of six peptides (AVQPCF, CAIAW, IIIGW, QIVW, PIVCF, and DVW), previously identified by the in silico GI digestion of Acheta domesticus proteins, validate their formation after in vitro GI digestion of A. domesticus by LC-MS/MS, and assess the bioactivity of the bioaccessible digesta. The results showed that the IC50 values of AVQPCF, PIVCF, and CAIAW on sACE were 3.69 ± 0.25, 4.63 ± 0.16, and 6.55 ± 0.52 μM, respectively. The obtained digesta demonstrated a sACE-inhibitory capacity of 77.1 ± 11.8 µg protein/mL extract (IC50). This is the first report of the sACE-inhibitory capacity attributed to whole A. domesticus subjected to GI digestion without any pre-treatment or protein concentration. This evidence highlights the potential antihypertensive effect of both the digesta and the identified peptides.

Biological Activities of Soy Protein Hydrolysate Conjugated with Mannose and Allulose

The non-enzymatic conjugation of peptides through the Maillard reaction has gained attention as an effective method to enhance biological functions. This study focuses on two conjugate mixtures: crude soy protein hydrolysate (SPH) conjugated with mannose (SPHM) and crude soy protein hydrolysate conjugated with allulose (SPHA). These two mixtures were products of the Maillard reaction, also known as non-enzymatic glycation. In vitro experiments were conducted to evaluate the antioxidant, anti-pancreatic lipase, inhibition of Bovine Serum Albumin (BSA) denaturation, and anti-angiotensin converting enzyme (ACE) activities of these conjugated mixtures. The results indicate that conjugated mixtures significantly enhance the antioxidant potential demonstrated via the DPPH and FRAP assays. SPHA exhibits superior DPPH scavenging activity (280.87 ± 16.39 µg Trolox/mL) and FRAP value (38.91 ± 0.02 mg Trolox/mL). Additionally, both conjugate mixtures, at a concentration of 10 mg/mL, enhance the BSA denaturation properties, with SPHM showing slightly higher effectiveness compared to SPHA (19.78 ± 2.26% and 5.95 ± 3.89%, respectively). SPHA also shows an improvement in pancreatic lipase inhibition (29.43 ± 1.94%) when compared to the SPHM (23.34 ± 3.75%). Furthermore, both the conjugated mixtures and rare sugars exhibit ACE inhibitory properties on their own, effectively reducing ACE activity. Notably, the ACE inhibitory effects of the individual compounds and their conjugate mixtures (SPHM and SPHA) are comparable to those of positive control (Enalapril). In conclusion, SPHM and SPHA demonstrate a variety of bioactive properties, suggesting their potential use in functional foods or as ingredients in supplementary products.

Bioactive Peptides Derived from Edible Insects: Effects on Human Health and Possible Applications in Dentistry

Novel foods, including edible insects, are emerging because of their nutritional characteristics and low environmental impacts and could represent a valid alternative source of food in a more sustainable way. Edible insects have been shown to have beneficial effects on human health. Insect-derived bioactive peptides exert antihypertensive, antioxidant, anti-inflammatory, and antimicrobial properties and have protective effects against common metabolic conditions. In this review, the roles of edible insects in human health are reported, and the possible applications of these peptides in clinical practice are discussed. A special mention is given to the role of antimicrobial peptides and their potential applications in controlling infections in orthodontic procedures. In this context, insects' antimicrobial peptides might represent a potential tool to face the onset of infective endocarditis, with a low chance to develop resistances, and could be manipulated and optimized to replace common antibiotics used in clinical practice so far. Although some safety concerns must be taken into consideration, and the isolation and production of insect-derived proteins are far from easy, edible insects represent an interesting source of peptides, with beneficial effects that may be, in the future, integrated into clinical and orthodontic practice.

The current state of research and potential applications of insects for resource recovery and aquaculture feed

Concerns about fishmeal use and its ecological footprints must be addressed for the aquaculture industry to move on as a sustainable food production sector. Through recent research outcomes, the insect-based meals in fish diets have promise and harnessed promises for commercial applications. In this midst, the efficiency of the selected insects in valorizing biological waste, as well as the nutritional profile of the harvested insects for use in fish diets, will be the driving forces behind such an approach. More extensive research has been published on the suitability of the waste substrate, the nutritional profiling of the meals, the level of substitution, the effects on growth, the immune physiology, and the flesh quality of the animals. Previously, there are only a few reviews available in insect protein applications in aqua feed that focused particularly on the nutritional quality and substitution levels. Considering the dearth of available work, the goal of this review is to provide a more comprehensive account of the resource recovery potential of insects and its derivatives, with a special emphasis on quality as determined by substrate used and processing techniques. Suggestions and policy implications for a sustainable approach to achieving a circular bio-economy of insect farming and its application in aquaculture are discussed for progression and advancement of the existing state of the art.

Characteristics of enzymolysis of silkworm pupa protein after tri-frequency ultrasonic pretreatment: kinetics, thermodynamics, structure and antioxidant changes

As a by-product of the sericulture industry, the utilization rate of silkworm pupa resources is currently not high. Proteins are converted into bioactive peptides through enzymatic hydrolysis. Not only can it solve the utilization problem, but it also creates more valuable nutritional additives. Silkworm pupa protein (SPP) was pretreated with tri-frequency ultrasonic (22/28/40 kHz). Effects of ultrasonic pretreatment on enzymolysis kinetics, enzymolysis thermodynamics, hydrolysate structure as well as hydrolysate antioxidant of SPP were investigated. Ultrasonic pretreatment significantly increased the hydrolysis efficiency, showing a 6.369% decrease in k _m and a 16.746% increase in k _A after ultrasonic action (p < 0.05). The SPP enzymolysis reaction followed a second-order rate kinetics model. Evaluation of enzymolysis thermodynamics revealed that Ultrasonic pretreatment markedly enhanced the SPP enzymolysis, leading to a 21.943% decrease in E _a. Besides, Ultrasonic pretreatment significantly increased SPP hydrolysate's surface hydrophobicity, thermal stability, crystallinity, and antioxidant activities (DPPH radical scavenging activity, Fe²⁺ chelation ability, and reducing power). This study indicated that tri-frequency ultrasonic pretreatment could be an efficient approach to enhancing the enzymolysis and improving the functional properties of SPP. Therefore, tri-frequency ultrasound technology can be applied industrially to enhance enzyme reaction process.

Edible Insects as a Novel Source of Bioactive Peptides: A Systematic Review

The production of food and feed to meet the needs of the growing world's population will soon become a serious challenge. In search for sustainable solutions, entomophagy is being proposed as an alternative source of proteins, with economic and environmental advantages when compared to meat. Edible insects are not only a valuable source of important nutrients, but their gastrointestinal digestion also originates small peptides with important bioactive properties. The present work intends to provide an exhaustive systematic review on research articles reporting bioactive peptides identified from edible insects, as demonstrated by in silico, in vitro, and/or in vivo assays. A total of 36 studies were identified following the PRISMA methodology, gathering 211 potentially bioactive peptides with antioxidant, antihypertensive, antidiabetic, antiobesity, anti-inflammatory, hypocholesterolemia, antimicrobial, anti-severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), antithrombotic, and immunomodulatory properties, originated from the hydrolysates of 12 different insect species. From these candidates, the bioactive properties of 62 peptides were characterized in vitro and 3 peptides were validated in vivo. Data establishing the scientific basis of the health benefits associated with the consumption of edible insects can be a valuable contribution to overcoming the cultural issues that hinder the introduction of insects in the Western diet.

Insect biorefinery: A circular economy concept for biowaste conversion to value-added products

With rapid growing world population and increasing demand for natural resources, the production of sufficient food, feed for protein and fat sources and sustainable energy presents a food insecurity challenge globally. Insect biorefinery is a concept of using insect as a tool to convert biomass waste into energy and other beneficial products with concomitant remediation of the organic components. The exploitation of insects and its bioproducts have becoming more popular in recent years. This review article presents a summary of the current trend of insect-based industry and the potential organic wastes for insect bioconversion and biorefinery. Numerous biotechnological products obtained from insect biorefinery such as biofertilizer, animal feeds, edible foods, biopolymer, bioenzymes and biodiesel are discussed in the subsequent sections. Insect biorefinery serves as a promising sustainable approach for waste management while producing valuable bioproducts feasible to achieve circular bioeconomy.

Bioactive Peptide Discovery from Edible Insects for Potential Applications in Human Health and Agriculture

In the past decade, there has been fast-growing interest among researchers to discover bioactive peptides from edible insects and to evaluate their potential applications in the management of human, livestock, and plant health. This review summarizes current knowledge of insect-derived peptides and their potential role in tackling human health issues and solving agriculture problems by protecting crops and livestock against their pathogens. Numerous bioactive peptides have been identified from edible insect species, including peptides that were enzymatically liberated from insect proteins and endogenous peptides that occur naturally in insects. The peptides exhibited diverse bioactivities, encompassing antioxidant, anti-angiotensin-converting enzyme, anti-dipeptidyl peptidase-IV, anti-glucosidase, anti-lipase, anti-lipoxygenase, anti-cyclooxygenase, anti-obesity, and hepatoprotective activities. Such findings point to their potential contribution to solving human health problems related to inflammation, free radical damage, diabetes, hypertension, and liver damage, among others. Although most of the experiments were performed in vitro, evidence for the in vivo efficacy of some peptides is emerging. Evidence of the protective effects of insect-derived endogenous antimicrobial peptides in combating farm animal and plant pathogens is available. The ability of insect-derived endogenous neuropeptides to protect plants against herbivorous insects has been demonstrated as well. Nevertheless, the potency of peptides identified from insect protein hydrolysates in modulating livestock and plant health remains a knowledge gap to be filled.

Physicochemical properties and angiotensin-I converting enzyme inhibitory activity of lipid-free ribbon fish (Lepturacanthus savala) protein hydrolysate

The study aims at removal of lipid from ribbon fish protein hydrolysate (FPH) to enhance the protein content and analyse its physicochemical and bioactive properties. Ribbon fish protein hydrolysate was prepared using commercially available papain enzyme (1.5% w/v for 4 h). The resulting supernatant was further treated with lipase (0.5-2.0% w/v for 1-5 h). The treatment used in this study reduced ~ 98% of lipids depending on the enzyme concentration, temperature, pH, and duration of the treatment. Lipase treatment for 2 h increased the protein content from 62.87 to 94.11%. FPH after lipase treatment showed 1.21 folds increase in angiotensin-converting enzyme-I (ACE-I) inhibitory activity and 1.7 folds increase in standard amino acids composition (32.193 to 61.493 g/100 g). The physicochemical properties of FPH samples were analyzed by solubility, hygroscopicity, color, FT-IR, SEM, SDS-PAGE, and Zeta Potential. Use of lipase enzyme for separating the lipid content from protein hydrolysate without conferring any undesirable adverse effects on the physicochemical properties of protein hydrolysate. Lipid-free protein hydrolysates can be of commercial importance for their enhanced ACE-I inhibitory activity, replacing the side effect causing synthetic drugs for hypertension, and can have potential applications in developing functional food formulations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05620-z.

Recent Insight on Edible Insect Protein: Extraction, Functional Properties, Allergenicity, Bioactivity, and Applications

Due to the recent increase in the human population and the associated shortage of protein resources, it is necessary to find new, sustainable, and natural protein resources from invertebrates (such as insects) and underutilized plants. In most cases, compared to plants (e.g., grains and legumes) and animals (e.g., fish, beef, chicken, lamb, and pork), insect proteins are high in quality in terms of their nutritional value, total protein content, and essential amino acid composition. This review evaluates the recent state of insects as an alternative protein source from production to application; more specifically, it introduces in detail the latest advances in the protein extraction process. As an alternative source of protein in food formulations, the functional characteristics of edible insect protein are comprehensively presented, and the risk of allergy associated with insect protein is also discussed. The biological activity of protein hydrolyzates from different species of insects (Bombyx mori, Hermetia illucens, Acheta domesticus, Tenebrio molitor) are also reviewed, and the hydrolysates (bioactive peptides) are found to have either antihypertensive, antioxidant, antidiabetic, and antimicrobial activity. Finally, the use of edible insect protein in various food applications is presented.

Purification and Identification of a Novel Angiotensin Converting Enzyme Inhibitory Peptide from the Enzymatic Hydrolysate of Lepidotrigla microptera

In this study, Lepidotrigla microptera were hydrolyzed with four different proteolytic enzymes (Papain, neutrase, flavourzyme, and alcalase), and their distribution of molecular weights and ACE-inhibitory activity were tested. The alcalase hydrolysates showed the maximum ACE-inhibitory activity. A novel ACE-inhibitory peptide was isolated and purified from Lepidotrigla microptera protein hydrolysate (LMPH) using ultrafiltration, gel filtration chromatography, and preparative high performance liquid chromatography (prep-HPLC). The amino acid sequence of the purified peptide was identified as Phe-Leu-Thr-Ala-Gly-Leu-Leu-Asp (DLTAGLLE), and the IC50 value was 0.13 mg/mL. The ACE-inhibitory activity of DLTAGLLE was stable across a range of temperatures (<100 °C) and pH values (3.0−11.0) and retained after gastrointestinal digestion. DLTAGLLE was further identified as a noncompetitive inhibitor by Lineweaver−Burk plot. The molecular docking simulation showed that DLTAGLLE showed a high binding affinity with ACE sites by seven short hydrogen bonds. As the first reported antihypertensive peptide extracted from alcalase hydrolysate of Lepidotrigla microptera, DLTAGLLE has the potential to develop functional food or novel ACE-inhibitor drugs.

Isolation and characterization of ACE-I inhibitory peptides from ribbonfish for a potential inhibitor of the main protease of SARS-CoV-2: An in silico analysis

Recently, multifunctional fish peptides (FWPs) have gained a lot of attention because of their different biological activities. In the present study, three angiotensin-I converting enzyme (ACE-I) inhibitory peptides [Ala-Pro-Asp-Gly (APDG), Pro-Thr-Arg (PTR), and Ala-Asp (AD)] were isolated and characterized from ribbonfish protein hydrolysate (RFPH) and described their mechanism of action on ACE activity. As per the results, peptide PTR showed ≈ 2 and 2.5-fold higher enzyme inhibitory activity (IC₅₀ = 0.643 ± 0.0011 μM) than APDG (IC₅₀ = 1.061 ± 0.0127 μM) and AD (IC₅₀ = 2.046 ± 0.0130 μM). Based on experimental evidence, peptides were used for in silico analysis to check the inhibitory activity of the main protease (PDB: 7BQY) of SARS-CoV-2. The results of the study reveal that PTR (-46.16 kcal/mol) showed higher binding affinity than APDG (-36.80 kcal/mol) and AD (-30.24 kcal/mol) compared with remdesivir (-30.64 kcal/mol). Additionally, physicochemical characteristics of all the isolated peptides exhibited appropriate pharmacological properties and were found to be nontoxic. Besides, 20 ns molecular dynamic simulation study confirms the rigid nature, fewer confirmation variations, and binding stiffness of the peptide PTR with the main protease of SARS-CoV-2. Therefore, the present study strongly suggested that PTR is the perfect substrate for inhibiting the main protease of SARS-CoV-2 through the in silico study, and this potential drug candidate may promote the researcher for future wet lab experiments.

Insects as an Alternative Protein Source

The recent COVID-19 pandemic drastically affected food supply chains worldwide, showing the vulnerability of food security. Efforts to develop alternative protein sources that are sustainable and can help alleviate global food shortage problems should be prioritized. Insects have been part of our diet for thousands of years and still are today, and market trends show a global increase in the number of food-grade insect producers. The global market for edible insects has been forecasted to reach US$8 billion by the year 2030. Insects are highly nutritious and have bioactive peptides with potential therapeutic effects. This review provides an overview of the consumption of insects from ancient to modern times, discusses the rationale for using insects as alternative protein sources, and presents a summary of the major insects consumed worldwide as well as a brief description of the traditional and novel technologies currently used to process insects and/or extract their nutritional components. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

In Vitro Antioxidant and Antihypertensive Activity of Edible Insects Flours (Mealworm and Grasshopper) Fermented with Lactococcus lactis Strains

The objective of the present study was to evaluate the potential antioxidant and angiotensin converting enzyme inhibition (ACEI) activity of edible insect flours fermented with Lactococcus lactis strains. For the fermentation, mealworm and grasshoppers flours were dissolved (0.5% w/v) in buffer solution (pH 7.0) and individually inoculated (3%) with Lactococcus lactis strains (NRRL B-50571, NRRL B-50572). The samples were incubated for 72 h at 30 °C, and the pH was recorded. The degree of hydrolysis (DH) and protein content were determined. The total polyphenol compounds, antioxidant activity (ABTS, DPPH, ORAC, and FRAP), and ACEI of the <3 kDa fractions were analyzed. The pH of the fermented samples decreased to 3.5–3.9 (p < 0.05). The fermented grasshopper flour showed an increased DH (0.42%) and overall higher total polyphenol content (8.23 mg Gallic Acid Equivalent/mL). In general, the highest antioxidant activity was for the grasshopper fractions fermented for 24 h by Lactococcus lactis NRRL B-50572, which also showed 23.47% ACEI inhibition with an IC50 of 0.97 mg/mL. The peptide profile obtained increased after fermentation, being higher for the mealworm flour fermented sample. This study presents, for the first time, the use of specific strains of Lactococus lactis for fermenting edible insect-derived products in the production of bioactive compounds with potential antioxidant and antihypertensive activity.

Accurate prediction for adsorption rate of peptides with high ACE-inhibitory activity from sericin hydrolysate on thiophene hypercross-linked polymer using CoMSIA in 3D-QSAR model

Efficient screening of angiotensin converting enzyme inhibitory (ACE-I) peptides from agricultural or edible sources attract increasing attention. However, their purification process from the complex natural system is still semi-empirical or even uncontrollable, which has seriously reduced their screening efficiency. Herein, inspired by the prediction of ACE-I activity, 3D-QSAR was proposed to predict the adsorption performance of peptides from sericin hydrolysate (SH) having high ACE-I activity on porous hypercross-linked polymers according to their molecular structures. Thiophene hypercross-linked polymer (T-HCP) possessing better screening capacity for ACE-I peptides was chosen as our research object in this work. The sequence and relative adsorption rate of 101 peptides in SH were analyzed by LC-MS and was used as a database to construct the relationship of peptide's chemical structure and adsorption performance on T-HCP by Comparative molecular similarity indices analysis (CoMSIA) from 3D-QSAR. Optimum CoMSIA revealed that enhanced interaction of hydrophobicity and H-bond between T-HCP and the peptide was conducive to increase the adsorption performance of di- to hexa- peptides. Based on these relationships, the adsorption capability of 24 designed peptides with distinguished hydrophobic and H-bond fields was predicted on T-HCP by using optimum CoMSIA and the results of half of these were verified, which showed high consistency with their predicted adsorption rate. Interestingly, these peptides having higher adsorption capacities on T-HCP also possessed higher ACE-I activity. This can be attributed to the high concentration of aromatic surface with π-π interaction and weak-polar CSC group with H-bond interaction on T-HCP material, which is ideal for the selective adsorption of peptides with higher ACE-I activity from SH. This study provides important theoretical guidance for the industrial screening of bio-functional peptides from complex protein mixtures.

Dual-enzyme hydrolysis for preparation of ACE-inhibitory peptides from sesame seed protein: Optimization, separation, and identification

To prepare and identify ACE-inhibitory peptides originated from sesame seed protein, peptides with strong ACE-inhibitory activities were obtained via the optimization of protease and hydrolysis conditions, and these peptides were purified and identified by membrane separation, gel filtration, and liquid chromatography-mass spectrometry. Results showed that the dual-enzyme comprised alcalase and trypsin with the enzyme activity ratio of 3:7 was suitable to produce ACE-inhibitory peptides. The highest ACE-inhibitory activity of 98.10 ± 0.26% was obtained at the following parameters, pH 8.35, E/S ratio of 6,145 U/g, and hydrolysis time of 4.4 hr. ISGAQPSLR and VVISAPSK ranked the first and second ACE-inhibitory activity among 15 identified ACE-inhibitory peptides. Both peptides influenced ACE via binding with the S1 pocket, S2 pocket, and Zn²⁺ ion. ISGAQPSLR even impacted the S1' pocket. ISGAQPSLR and VVISAPSK acted as a competitive and noncompetitive inhibitor, respectively. ACE-inhibitory peptides derivated from sesame seed protein have potential applications in functional food. PRACTICAL APPLICATIONS: Although sesame seed protein is proven as the precursor of ACE-inhibitory peptide, preparing ACE-inhibitory peptide from sesame seed protein is still suffering from insufficient information on hydrolysis condition and the peptide sequence. Therefore, the performance of the typical protease on preparing ACE-inhibitory peptide from sesame seed protein has been evaluated, the effect of the amino acid composition of sesame seed protein and cleavage specificity of protease on the generation of ACE-inhibitory peptide has been investigated, hydrolysis conditions have been optimized, the peptide sequence has been identified to illuminate the effect of sesame seed protein fraction on the formation of ACE-inhibitory peptide and discuss the structural characteristics. ACE-inhibitory peptides originating from sesame seed protein could apply in functional food. It is promising for dual-enzyme hydrolysis to utilize in preparation of high-value bioactive peptides.

Insetos comestíveis como potenciais fontes de proteínas para obtenção de peptídeos bioativos

Resumo O consumo de insetos como uma fonte alternativa de proteínas é considerado uma tendência futura e uma estratégia viável, com potencial notório para garantia do fornecimento de alimentos em nível global. Os insetos são uma fonte não convencional de proteínas, seja para consumo humano direto ou indiretamente, como ingredientes em alimentos formulados. Além disso, estudos científicos têm demonstrado que a hidrólise enzimática destas proteínas resulta na produção de peptídeos com atividades biológicas de grande interesse, como atividade antioxidante, antidiabética, anti-hipertensiva e antimicrobiana. O uso desses peptídeos com fim nutracêutico pode substituir ou reduzir o uso de drogas sintéticas, as quais estão associadas a efeitos colaterais indesejáveis. O presente trabalho teve como objetivo abordar o uso de insetos na alimentação humana, destacando sua aplicação como substrato proteico na hidrólise enzimática para produção de peptídeos bioativos. As principais propriedades bioativas dos peptídeos foram relatadas.

Litter to Leaf: The Unexplored Potential of Silk Byproducts

Silk has remained the most preferred protein fiber since its discovery in 3000 BC. However, the cost, availability, and resources required to rear the silkworms and process silk are imposing considerable constraints on the future of silk. It is often unrealized that apart from the fibers, production and processing of silk are a source for a diverse range of sustainable, biodegradable, and biocompatible polymers. Hence, delineating itself from being the primary source of protein fibers for millenniums, the silk industry worldwide is transitioning into a biobased industry and as a source for pharmaceuticals, biomaterials, cosmetics, food, and energy. Toward this, byproducts (BPs) and co-products (CPs) that are inevitably generated are now being considered to be of immense economic value and could be up to 10 times more valuable than the silk fibers. Here, we elucidate the properties and potential applications of silk BPs and CPs to present the true potential of silkworms and to promote the establishment of silkworm-based bioeconomy and biorefineries.

Nutritional, Physiochemical, and Antioxidative Characteristics of Shortcake Biscuits Enriched with Tenebrio molitor Flour

Edible insects, due to their high nutritional value, are a good choice for traditional food supplementation. The effects of partial replacement of wheat flour and butter with mealworm flour (Tenebrio molitor) on the quality attributes of shortcake biscuits were studied. The approximate composition was analyzed, along with the physical properties and color. Moreover, the antioxidant properties, starch digestibility, and glycemic index were determined in vitro. The protein and ash contents in biscuits supplemented with mealworm flour increased, while the carbohydrates content decreased. The increasing insect flour substitution decreased the lightness (L*) and yellowness (b*) but increased the redness (a*), total color difference (ΔE), and browning index (BI). The spread factor for the sample with the highest proportion of mealworm flour was significantly higher than the other biscuits. Furthermore, higher additions of mealworm flour increased the antioxidant activity of the biscuits and contributed to an increase in the content of slowly digested starch, with a decrease in the content of rapidly digested starch. Therefore, the results of the research are promising and indicate the possibility of using edible insects to enrich food by increasing the nutritional and health-promoting values.

Effect of Thermal Processing on Physico-Chemical and Antioxidant Properties in Mulberry Silkworm (Bombyx mori L.) Powder

The mulberry silkworm (Bombyx mori L.) is a common edible insect in many countries. However, the impact of thermal processing, especially regarding Thai silkworm powder, is poorly known. We, therefore, determined the optimum time for treatment in hot water and subsequent drying temperatures in the production of silkworm powder. The silkworms exposed to 90 °C water for 0, 5, 10, 15, and 20 min showed values of Total Phenolic Compounds (TPCs), 2,2-Diphenyl-1-picrylhydrazyl free radical scavenging (DPPH) assay, 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assay, and Ferric Reducing Antioxidant Power (FRAP) assay that were significantly (p < 0.05) higher at the 5 min exposure time compared with the other times. The reduction of microorganisms based on log CFU/g counts was ≥3 log CFU/g (99%) at the 5 min treatment. To determine the optimum drying temperature, the silkworms exposed to 90 °C water for 5 min were subjected to a hot-air dryer at 80, 100, 120, and 140 °C. The TPC value was the highest (p < 0.05) at 80 °C. The silkworm powder possessed significantly (p < 0.05) higher DPPH, ABTS radical scavenging ability, and ferric ion reducing capability (FRAP assay) at 80 °C compared with other drying temperatures. This study indicates that shorter exposure times to hot water and a low drying temperature preserve the antioxidant activities. High antioxidant activities (in addition to its known protein and fat content) suggest that silkworms and silkworm powder can make a valuable contribution to human health.

Current Trends of Bioactive Peptides-New Sources and Therapeutic Effect

Generally, bioactive peptides are natural compounds of food or part of protein that are inactive in the precursor molecule. However, they may be active after hydrolysis and can be transported to the active site. Biologically active peptides can also be synthesized chemically and characterized. Peptides have many properties, including antihypertensive, antioxidant, antimicrobial, anticoagulant, and chelating effects. They are also responsible for the taste of food or for the inhibition of enzymes involved in the development of diseases. The scientific literature has described many peptides with bioactive properties obtained from different sources. Information about the structure, origin, and properties of peptides can also be found in many databases. This review will describe peptides inhibiting the development of current diseases, peptides with antimicrobial properties, and new alternative sources of peptides based on the current knowledge and documentation of their bioactivity. All these issues are part of modern research on peptides and their use in current health or technological problems in food production.

Evaluation of ACE, α-glucosidase, and lipase inhibitory activities of peptides obtained by in vitro digestion of selected species of edible insects

The objective of this study was to examine the inhibition of the activity of enzymes associated with development of the metabolic syndrome by peptide fractions received from simulated gastrointestinal digestion and absorption of heat-treated edible insects. The inhibitory activities of insect-derived peptides were determined against key enzymes relevant to the metabolic syndrome such as the angiotensin-converting enzyme (ACE), pancreatic lipase, and α-glucosidase. After the in vitro absorption process, all hydrolysates showed high inhibitory activity; however, the most effective metabolic syndrome-inhibitory peptides were received after separation on Sephadex G10. The best results were found for peptide fractions obtained from Schistocerca gregaria. The highest enzymes inhibitory activities were obtained for peptide fractions from S. gregaria: boiled for ACE (IC50 3.95 µg mL−1), baked for lipase (IC50 9.84 µg mL−1), and raw for α-glucosiadase (IC50 1.89 µg mL−1) S. gregaria, respectively. Twelve sequences of peptides from the edible insects were identified and their chemical synthesis was carried out as well. Among the synthesized peptides, the KVEGDLK, YETGNGIK, AIGVGAIR, IIAPPER, and FDPFPK sequences of peptides exhibited the highest inhibitory activity. Generally, the heat treatment process applied to edible insects has a positive effect on the properties of the peptide fractions studied.

Immobilized metal affinity chromatography matrix modified by poly (ethylene glycol) methyl ether for purification of angiotensin I-converting enzyme inhibitory peptide from casein hydrolysate

Purification of small bioactive peptides from complex biological samples is a difficult task due to the interference of concentrated large biomolecules. In this study, a magnetic immobilized metal affinity chromatography matrix modified by poly (ethylene glycol) methyl ether (IMACM@mPEG) was prepared and applied for the rapid purification of angiotensin I-converting enzyme (ACE) inhibitory peptides from casein hydrolysate. The proposed IMACM@mPEG considerably reduced the non-specific adsorption of large proteins and exhibited improved purification efficiency towards ACE inhibitory peptides. A novel peptide with moderate ACE inhibitory activity (IC₅₀ value of 274 ± 5 μM) was identified as LLYQEPVLGPVR. Lineweaver-Burk plot confirmed the non-competitive inhibition pattern of LLYQEPVLGPVR. The purified peptide was digested after simulated gastrointestinal digestion and produced shorter peptides which contributed to enhanced ACE inhibitory activity. These results indicated that the IMACM@mPEG is an effective method for the prepurification of ACE inhibitory peptide and the purified peptide LLYQEPVLGPVR may have potential as nutraceutical ingredient in functional foods for hypertension treatments.

Porous Fe@C Composites Derived from Silkworm Excrement for Effective Separation of Anisole Compounds

Silkworm excrement is a very useful biomass waste, composed of layer-structured fats and proteins, which are great precursors for carbon composite materials. In this work, new porous composites derived from silkworm excrement were prepared for selective separation of flavor 4-methylanisole from the binary 4-methylanisole/4-anisaldehyde mixture. In particular, the silkworm excrement, possessing a unique nanosheet structure, is converted into a graphite-like carbon by a simple calcination strategy followed by a metal-ion-doping procedure. This Fe@C composite exhibits a special nano-spongy morphology, anchoring Fe₃C/Fe₅C₂ on the carbon nanosheets. Density functional theory simulations showed that 4-methylanisole presents a stronger π-π interaction and attraction forces with sp² carbon nanosheets in Fe@C composites than 4-anisaldehyde. The selective adsorption experiments further confirmed that the Fe@C composites exhibited a 4-methylanisole capacity of 7.3 mmol/g at 298 K and the highest selectivity of 17 for an equimolar 4-methylanisole/4-anisaldehyde mixture among the examined adsorbents including MOFs and commercial activated carbon materials, which demonstrates the potential of this low-cost and eco-friendly porous carbon material as a promising sustainable adsorbent.

Novel Angiotensin-Converting Enzyme-Inhibitory Peptides From Fermented Bovine Milk Started by Lactobacillus helveticus KLDS.31 and Lactobacillus casei KLDS.105: Purification, Identification, and Interaction Mechanisms

Fermented milks with strong angiotensin I-converting enzyme (ACE)-inhibitory activity were obtained through a culture with Lactobacillus helveticus KLDS.31 and Lactobacillus casei KLDS.105 with a fermentation and storage temperature of 37 °C. Ultrafiltration fractions with a molecular weight less than 3 kDa in fermented milk whey exhibited the strongest inhibitory activity. Correspondingly, a gastrointestinal digestion experiment showed retention of the bioactivity of these fractions with pepsin and trypsin treatment. Four ACE-inhibitory peptides from fermented milk were isolated, purified by two-step reverse chromatography, and sequenced. Furthermore, the interaction mechanisms between ACE and four isolated peptides were investigated by a molecular docking method and the Independent Gradient Model. Experimental determination of IC50 was done to verify theoretical results. The inhibitory peptide interacted with ACE as follows: Lys-Pro-Ala-Gly-Asp-Phe > Lys-Ala-Ala-Leu-Ser-Gly-Met > Lys-Lys-Ala-Ala-Met-Ala-Met > Leu-Asp-His-Val-Pro-Gly-Gly-Ala-Arg.

Comparative Characterization of Protein Hydrolysates from Three Edible Insects: Mealworm Larvae, Adult Crickets, and Silkworm Pupae

A comparative characterization of proteins from three edible insects-Tenebrio molitor (mealworm) larvae, Gryllus bimaculatus (cricket), and Bombyx mori (silkworm) pupae-was performed in this study. Proteins were extracted from edible insects and their hydrolysates were prepared through enzymatic hydrolysis with commercial enzymes (Flavourzyme: 12%; Alcalase: 3%). Solubility was significantly higher following enzymatic hydrolysis, while foamability was lower compared to those of the protein control. Angiotensin-converting enzyme was significantly inhibited after enzymatic hydrolysis, especially following Alcalase treatment, with IC50 values of 0.047, 0.066, and 0.065 mg/mL for G. bimaculatus, T. molitor larvae, and B. mori pupae, respectively. Moreover, the Alcalase-treated group of B. mori pupae and the T. molitor larvae group treated with a mixture of enzymes showed the effective inhibition of α-glucosidase activity. The anti-inflammatory activity of the insect hydrolysates was assessed via nitric oxide production from macrophages, and B. mori pupae samples exhibited significant activity regardless of the method of hydrolysis. These results indicate the functional properties of protein and hydrolysates from three species of edible insects, which may be useful in their future exploitation.

Nitrogen-Doped Hollow Copolymer Tube via Template-Free Asynchronous Polymerization with Highly Selective Separation of Hydrophilic Dipeptide for Enhancing Inhibitory Activity of Angiotensin Converting Enzyme

A N-doped hollow copolymer tube (NHCT) was fabricated via template-free one-pot asynchronous polymerization strategy. Discrepancies of monomer polymerization speed and their hydrophilic-hydrophobic interaction resulted in the assembly of a hollow tube having inner diameter and double wall thickness of ∼230 and 40 nm, respectively. The formation and growth mechanism of NHCT analyzed via advanced characterization revealed that the unique growth processes tuned a demarcating surface layer between inner (hydrophilic) and outer (hydrophobic) layers. The screening and recognition ability of NHCT were determined for two specific dipeptides (WW and RR) possessing great discrepancies in hydrophilicity and angiotensin converting enzyme inhibitory (ACE-I) activity. NHCT realized high adsorption capacity (1.57 mmol/g) and selectivity (∼1274) for hydrophilic dipeptide RR (low ACE-I activity) from the mixture of RR/WW. As a result, ACE-I activity for residual solution were enhanced about 4.1 times as compared to original solution from natural silkworm pupae protein hydrolysate. Awarding to these results and its facile and discerning ability, NHCT can be envisioned to be of great value for the separation of small functional peptides from a natural edible source.

Amino Acid Imprinted UiO-66s for Highly Recognized Adsorption of Small Angiotensin-Converting-Enzyme-Inhibitory Peptides

Introduction of targeted defects into microporous UiO-66s for manipulating their three-dimensional size and surface properties can endow them with adsorption and separation areas involving angiotensin-converting-enzyme-inhibitory (ACE-inhibitory) peptides. Three hydrophobic amino acids (AAs) (i.e., proline (Pro), phenylalanine (Phe), and tryptophan (Trp)) having different physical/chemical properties were applied to in situ tailor defects in UiO-66 through targeted incoordination of missing linkers or missing nodes. Characterization results revealed a uniform oval shape of the developed defects with lengths ranging from 1.8 to 3.1 nm, which was also highly consistent with our molecular simulation. Among these three defective UiO-66s, Phe and Trp imprinted UiO-66s significantly promoted the adsorption affinity of small ACE-inhibitory peptides (uptake: 1.25 mmol g^-1 for DDFF and 1.37 mmol g^-1 for DDWW) and ultrahigh selectivity for DDFF (249) or DDWW (279) from inactive KKKK solution based on a lock-and-key mechanism. As a result, the imprinted UiO-66 showed an enrichment capacity for ACE-inhibitory peptides about eight times higher than that of pristine UiO-66. Therefore, the amino acid imprinting strategy endorsed by its facile and discerning ability can be envisioned to be of great value for small functional peptide separation and oriented enrichment in biomedicines.

Highly Advanced Degradation of Thiamethoxam by Synergistic Chemisorption-Catalysis Strategy Using MIL(Fe)/Fe-SPC Composites with Ultrasonic Irradiation

MIL(Fe)/Fe-doped nanospongy porous biocarbon (Fe-SPC) composite was fabricated from MIL-100(Fe) via in situ growth on a unique Fe-doped nanospongy porous biocarbon (Fe-SPC) and was used as Fenton-like catalyst for advanced degradation of thiamethoxam (THIA). Fe was loaded on silkworm excrement and calcined to Fe-SPC with nanospongy and high sp² C structure. The in situ growth strategy embedded the Fe-SPC into MIL-100(Fe) crystals and formed conductive heterojunctions with an intensified interface by Fe-bridging effect, which was confirmed by negative shift of Fe³⁺ binding energy in X-ray photoelectron spectroscopy. MIL(Fe)/Fe-SPC composites exhibited high degree of crystallinity and surface area (Brunauer-Emmett-Teller: 1730 m²/g). Liquid chromatography-mass spectrometry and density functional theory simulations demonstrated that THIA was converted to a relatively stable compound (C₄H₅N₂SCl), which could be captured by MIL-100(Fe) with strong chemical bonding energy (Fe-N, -587 kJ/mol), followed by a significant geometric distortion, resulting in a thorough degradation. Efficient charge separation and synergistic chemisorption-catalysis strategy resulted in the high catalytic activity of MIL(Fe)/Fe-SPC. The composite catalyst concurrently exhibited high mineralization ratio with 95.4% total organic carbon removal (at 25 °C and 180 min) and good recycling ability under wider neutral/alkaline conditions. Endorsing to these intriguing properties, MIL(Fe)/Fe-SPC can be deemed an efficient contender for removal of hard-degradable pesticides and other environmental pollutants in practical applications.

The potential peptides against angiotensin-I converting enzyme through a virtual tripeptide-constructing library

Peptides derived from food proteins are promising bioactive source for inhibiting Angiotensin-I converting enzyme (ACE) activity. Bioactive peptides (BP) have received much attention, particularly from the pharmaceutical industry. As they not only own potent properties but also possess less side-effects than synthetic drugs. In this work, an 8000 possible tripeptides library was constructed to predict the potential ACE inhibitory peptides by using in silico tools. GOLD molecular docking was then applied to determine the binding mode of action between ACE and each of tripeptide from this in-house library. The first 662 high-ranking tripeptides by ChemScore were chosen to create association rules of tripeptides-ACE complexes. An orientation pattern of amino acid in the binding tunnel of ACE has been examined by frequency analysis. The association rules (confident values over 90%) illustrated that hydrophobic factor has been displayed as main components in the ACE tripeptides inhibitor from four factors in equation, hydrophobic, aromatic, polar, charged. According to in silico output, five tripeptides were chosen to test in vitro study of ACE-inhibitory activity. The half-maximal inhibitory concentration (IC₅₀) of these selective five peptides, WCW, IWW, WWW, WWI and WLW for inhibiting ACE were 49.50 ± 3.88 μM, 489.14 ± 8.84 μM, 536.02 ± 38.57 μM, 752.91 ± 41.89 μM and 1783 ± 0.113 μM, respectively. Molecular dynamics simulations approach was applied to study the interaction of WCW (Trp-Cys-Trp) within ACE pocket site. This ligand was stabilized by strong hydrogen bonding interactions with ACE active site, Tyr523-Trp'1 (99.76%) and His353-Trp'1 (95.68%). Our computational protocol could be considered as a new tool for identifying active peptide against ACE from hydrolysated peptides of natural sources.

Novel Angiotensin-Converting Enzyme Inhibitory Peptides Derived from Oncorhynchus mykiss Nebulin: Virtual Screening and In Silico Molecular Docking Study

Excessive concentrations of angiotensin-converting enzyme (ACE) can give rise to high blood pressure, and is harmful to the body. ACE inhibitory peptides from food proteins are considered good sources of function food. However, the preparation of ACE inhibitory peptides by classical method faces many challenges. Three novel ACE inhibitory peptides were identified by in silico methods, and showed potent activity against ACE in vitro. The simulation hydrolysis of nebulin was performed with ExPASy PeptideCutter program. Potential activity, solubility, and absorption, distribution, metabolism, excretion, and toxicity properties of generated peptides were predicted using program online. Molecular docking displayed that EGF, HGR, and VDF were docked into the S₁ and S₂ pockets of ACE. Meanwhile, Phe and Arg at the C-terminal enhance ACE affinity. The IC₅₀ values of EGF, HGR, and VDF were 474.65 ± 0.08, 106.21 ± 0.52, and 439.27 ± 0.09 μM, respectively. Three peptides EGF, HGR, and VDF from Oncorhynchus mykiss nebulin were identified, and the molecular mechanism between ACE and peptides was clarified using in silico methods. The results suggested that Oncorhynchus mykiss nebulin would be an attractive raw material of antihypertensive nutraceutical ingredients.

PRACTICAL APPLICATION

This study has shown the potential of Oncorhynchus mykiss nebulin as good sources for producing ACE inhibitory peptides. According to this finding, in silico approach is the feasible way for prediction and identification of food-derived ACE inhibitory peptides in emerging nutraceutical field.

Effect of enzymatic hydrolysis on bioactive properties and allergenicity of cricket (Gryllodes sigillatus) protein

Food-derived bioactive peptides have gained attention for their role in preventing chronic diseases. Edible insects are viable sources of bioactive peptides owing to their high protein content and sustainable production. In this study, whole crickets (Gryllodes sigillatus) were alcalase-hydrolyzed to a degree of hydrolysis (DH) ranging from 15 to 85%. Antioxidant activity, angiotensin converting enzyme (ACE), and dipeptidyl peptidase-4 (DPP-IV)- inhibition of the cricket protein hydrolysates (CPH) were evaluated before and after simulated gastrointestinal digestion (SGD). Antioxidant activity was similar among CPH, whereas ACE and DPP-IV inhibition was greater (p < 0.05) in CPH with 60-85% DH. Bioactivity improved after SGD. CPH allergenicity was evaluated using human shrimp-allergic sera. All sera positively reacted to tropomyosin in the unhydrolyzed cricket and CPH with 15-50% DH, whereas 60-85% DH showed no reactivity. In conclusion, CPH (60-85% DH) had the greatest bioactive potential and lowest reactivity to tropomyosin, compared with other CPH and the unhydrolyzed control.

Generation of dipeptidyl peptidase IV (DPP-IV) inhibitory peptides during the enzymatic hydrolysis of tropical banded cricket (Gryllodes sigillatus) proteins

Cricket (Gryllodes sigillatus) protein hydrolysates inhibit dipeptidyl peptidase IV (DPP-IV) in vitro.

Ultrafast Screening of a Novel, Moderately Hydrophilic Angiotensin-Converting-Enzyme-Inhibitory Peptide, RYL, from Silkworm Pupa Using an Fe-Doped-Silkworm-Excrement-Derived Biocarbon: Waste Conversion by Waste

A novel, moderately hydrophilic peptide (RYL) with high ACE-inhibitory activity was screened ultrafast via a concept of waste conversion using waste. This novel peptide was screened from silkworm pupa using an Fe-doped porous biocarbon (FL/Z-SE) derived from silkworm excrement. FL/Z-SE possessed magnetic properties and specific selection for peptides due to Fe's dual functions. The selected RYL, which has moderate hydrophilicity (LogP = -0.22), exhibited a comparatively high ACE-inhibitory activity (IC₅₀ = 3.31 ± 0.11 μM). The inhibitory kinetics and docking-simulation results show that, as a competitive ACE inhibitor, RYL formed five hydrogen bonds with the ACE residues in the S1 and S2 pockets. In this work, both the screening carbon material and the selected ACE-inhibitory peptide were derived from agricultural waste (silkworm excrement and pupa), which offers a new way of thinking about the development of advanced uses of the silkworm byproducts and wastes.

High-Throughput and Rapid Screening of Novel ACE Inhibitory Peptides from Sericin Source and Inhibition Mechanism by Using in Silico and in Vitro Prescriptions

Several novel peptides with high ACE-I inhibitory activity were successfully screened from sericin hydrolysate (SH) by coupling in silico and in vitro approaches for the first time. Most screening processes for ACE-I inhibitory peptides were achieved through high-throughput in silico simulation followed by in vitro verification. QSAR model based predicted results indicated that the ACE-I inhibitory activity of these SH peptides and six chosen peptides exhibited moderate high ACE-I inhibitory activities (log IC₅₀ values: 1.63-2.34). Moreover, two tripeptides among the chosen six peptides were selected for ACE-I inhibition mechanism analysis which based on Lineweaver-Burk plots indicated that they behave as competitive ACE-I inhibitors. The C-terminal residues of short-chain peptides that contain more H-bond acceptor groups could easily form hydrogen bonds with ACE-I and have higher ACE-I inhibitory activity. Overall, sericin protein as a strong ACE-I inhibition source could be deemed a promising agent for antihypertension applications.

Graphitized Porous Carbon for Rapid Screening of Angiotensin-Converting Enzyme Inhibitory Peptide GAMVVH from Silkworm Pupa Protein and Molecular Insight into Inhibition Mechanism

A novel hydrophobic hexapeptide with high angiotensin-converting enzyme (ACE) inhibitory activity was screened from silkworm pupa protein (SPP) hydrolysate via graphitized porous carbon and reverse-phase high-performance liquid chromatography methods. Graphitized porous carbon derived from dopamine, possessing high surface area and high graphitic carbon, was used to rapidly screen and enrich hydrophobic peptides from SPP hydrolysate. The ACE inhibition pattern and mechanism of the purified peptide were also systematically studied by the classic Lineweaver-Burk model and by molecular docking/dynamic simulation. The novel hydrophobic hexapeptide was identified as Gly-Ala-Met-Val-Val-His (GAMVVH, IC₅₀ = 19.39 ± 0.21 μM) with good thermal/antidigestive stabilities. Lineweaver-Burk plots revealed that GAMVVH behaved as a competitive ACE inhibitor. It formed hydrogen bonds with S1 and S2 pockets of ACE and established competitive coordination with Zn(II) of ACE. The synergy of hydrogen bonds with active pockets and Zn(II) coordination efficiently changed the three-dimensional structure of ACE and thus inhibited bioactivity of ACE.