Characterization and analysis of antioxidant activity of walnut-derived pentapeptide PW5 via nuclear magnetic resonance spectroscopy

Recent advances in the effect of simulated gastrointestinal digestion and encapsulation on peptide bioactivity and stability

Food-derived bioactive peptides have garnered significant attention from researchers due to their specific biological functions, including antihypertensive, antioxidant, antidiabetic, anticancer, anti-inflammatory, and anti-osteoporosis properties. Despite extensive in vitro research, the bioactivity of these peptides may be compromised in the gastrointestinal tract due to enzymatic hydrolysis before reaching the bloodstream or target cells. Therefore, understanding the fate of bioactive peptides during digestion is crucial before advancing to clinical trials and commercial applications. To exert their health-promoting effects, these peptides must maintain their bioactivity throughout digestion. Encapsulation has emerged as a promising strategy for protecting peptides in the gastrointestinal tract. This review examines the effects of in vitro simulated gastrointestinal digestion on peptide bioactivity and stability, highlighting recent research on encapsulation strategies designed to enhance their gastrointestinal stability. Furthermore, the review addresses existing research gaps and suggests future research directions to advance our understanding and the application of bioactive peptides.

Bioactive oligopeptides and the application in skin regeneration and rejuvenation

Oligopeptides, composed of 2-10 amino acid residues, are protein fragments with unique structural characteristics, including small molecular size, high biocompatibility, and modifiable functional groups. These features endow oligopeptides with excellent permeability, safety, and versatile biological activities, making them widely applicable in disease treatment, drug delivery, and skincare. In particular, oligopeptides have emerged as advanced ingredients in skincare, offering anti-aging, anti-wrinkle, and whitening effects by regulating key biological processes such as collagen synthesis, antioxidant defense, and melanin production. This review comprehensively discusses the structural properties, functional mechanisms, and diverse applications of oligopeptides and their derivatives, highlighting their potential in skin regeneration, rejuvenation, and anti-aging medicine. By providing insights into the latest advancements, this review aims to serve as a valuable reference for future research and development in oligopeptide-based therapeutics and skincare innovations.

Antioxidative and mineral-binding food-derived peptides: Production, functions, metal complexation conditions, and digestive fate

The discovery of food-derived biopeptides is becoming increasingly prevalent in the scientific community. Some peptides possess multiple biological functions that can confer health benefits through various mechanisms following ingestion. The present review targets food-derived antioxidant and mineral-binding peptides (AMBPs) including their production procedure i.e., enzymolysis, separation, and purification (through membrane separation, gel filtration, ion exchange chromatography, and high-performance liquid chromatography), followed by mass spectrometry for identification. The most effective AMBPs exhibit radical scavenging activity, detoxification of excess metals, and reduction of lipid peroxidation to facilitate mineral bioavailability. The metal complexation of AMBPs necessitates an optimal metal-to-peptide ratio, specific ligands, precursors, and complexation reactions. The bioavailability and absorbability mechanisms of AMBPs are also elucidated, encompassing gastrointestinal stability, binding mode, and cell absorption machinery. Ultimately, further considerations regarding additional research on AMBPs are provided, which will assist researchers in conducting more comprehensive studies to promote the effective and safe use of AMBPs.

The role of gut microbiota in MP/NP-induced toxicity

Microplastics (MPs) and nanoplastics (NPs) are globally recognized as emerging environmental pollutants in various environmental media, posing potential threats to ecosystems and human health. MPs/NPs are unavoidably ingested by humans, mainly through contaminated food and drinks, impairing the gastrointestinal ecology and seriously impacting the human body. The specific role of gut microbiota in the gastrointestinal tract upon MP/NP exposure remains unknown. Given the importance of gut microbiota in metabolism, immunity, and homeostasis, this review aims to enhance our current understanding of the role of gut microbiota in MP/NP-induced toxicity. First, it discusses human exposure to MPs/NPs through the diet and MP/NP-induced adverse effects on the respiratory, digestive, neural, urinary, reproductive, and immune systems. Second, it elucidates the complex interactions between the gut microbiota and MPs/NPs. MPs/NPs can disrupt gut microbiota homeostasis, while the gut microbiota can degrade MPs/NPs. Third, it reveals the role of the gut microbiota in MP/NP-mediated systematic toxicity. MPs/NPs cause direct intestinal toxicity and indirect toxicity in other organs via regulating the gut-brain, gut-liver, and gut-lung axes. Finally, novel approaches such as dietary interventions, prebiotics, probiotics, polyphenols, engineered bacteria, microalgae, and micro/nanorobots are recommended to reduce MP/NP toxicity in humans. Overall, this review provides a theoretical basis for targeting the gut microbiota to study MP/NP toxicity and develop novel strategies for its mitigation.

Exploring the Ecological Implications, Gastronomic Applications, and Nutritional and Therapeutic Potential of Juglans regia L. (Green Walnut): A Comprehensive Review

The green walnut, which is frequently overlooked in favor of its more mature sibling, is becoming a topic of great significance because of its unique ecological role, culinary flexibility, and therapeutic richness. The investigation of the bioactive substances found in green walnuts and their possible effects on human health has therapeutic potential. Juglans regia L. is an important ecological component that affects soil health, biodiversity, and the overall ecological dynamic in habitats. Comprehending and recording these consequences are essential for environmental management and sustainable land-use strategies. Regarding cuisine, while black walnuts are frequently the main attraction, green walnuts have distinct tastes and textures that are used in a variety of dishes. Culinary innovation and the preservation of cultural food heritage depend on the understanding and exploration of these gastronomic characteristics. Omega-3 fatty acids, antioxidants, vitamins, and minerals are abundant in green walnuts, which have a comprehensive nutritional profile. Walnuts possess a wide range of pharmacological properties, including antioxidant, antibacterial, antiviral, anticancer, anti-inflammatory, and cognitive-function-enhancing properties. Consuming green walnuts as part of one's diet helps with antioxidant defense, cardiovascular health, and general well-being. Juglans regia L., with its distinctive flavor and texture combination, is not only a delicious food but also supports sustainable nutrition practices. This review explores the nutritional and pharmacological properties of green walnuts, which can be further used for studies in various food and pharmaceutical applications.

Difunctional AuNPs@PVP with oxidase-like activity for SERRS detection of total antioxidant capacity

Assessing the total antioxidant capacity (TAC) of foods plays a significant role in dietary guidance and disease risk reduction. Therefore, building a simple, rapid, and sensitive sensing method for detecting TAC possesses broad application prospects. Herein, we constructed a novel nanozyme catalyzed‒surface-enhanced Raman resonance scattering (SERRS) sensing strategy for analysis of TAC based on polyvinylpyrrolidone coated gold nanoparticles (AuNPs@PVP) that was synthesized by one step reduction method. AuNPs@PVP not only served as the SERRS substrate but also possessed high oxidase activity which can catalyze 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by generating hydroxyl radicals (•OH) and superoxide anion free radical (•O2-). According to the inhibiting effect of antioxidants, ascorbic acid (AA) was selected as the representative for TAC detection. The linear range and limit of detection (LOD) were determined to be 10-8‒10-5 M and 0.6 nM, respectively. More importantly, the proposed nanozyme catalyzed‒SERRS strategy has been successfully applied to the detection of TAC in fruit juices, demonstrating promising potential in the field of food supervision and healthcare applications.

Plant Protein-Derived Active Peptides: A Comprehensive Review

Active peptides are a class of physiologically active protein fragments, which can be prepared from different sources. In the past few decades, the production of peptides with various effects from different plant proteins continues to receive academic attention. With advances in extraction, purification, and characterization techniques, plant protein-derived active peptides continue to be discovered. They have been proven to have various functional activities such as antioxidant, antihypertensive, immunomodulatory, antimicrobial, anti-inflammatory, antidiabetic, antithrombotic, and so on. In this review, we searched Web of Science and China National Knowledge Infrastructure for relevant articles published in recent years. There are 184 articles included in this manuscript. The current status of plant protein-derived active peptides is systematically introduced, including their sources, preparation, purification and identification methods, physiological activities, and applications in the food industry. Special emphasis has been placed on the problems of active peptide exploration and the future trend. Based on these, it is expected to provide theoretical reference for the further exploitation of plant protein-derived active peptides, and promote the healthy and rapid development of active peptide industry.

Intestinal absorptivity-increasing effects of sodium N-[8-(2-hydroxybenzoyl)amino]-caprylate on food-derived bioactive peptide

Delivering bioactive peptides orally is hampered by poor absorption across the gastrointestinal barrier. Using the walnut-derived peptide PW5, PPKNW, we explored whether coformulation of peptides with absorption enhancer sodium N-[8-(2-hydroxybenzoyl)aminocaprylate] (SNAC) could improve the intestinal absorption of orally-administered bioactive peptides. Herein, the application of SNAC enhanced the absorption efficiency of PW5 in a non-everted gut sac model. Particle size distribution (1 027.8 ± 6.74 nm) and zeta potential (-2.89 ± 0.07 mV) of the PW5-SNAC complex were significantly greater than that of individual PW5 and SNAC. Scanning electron microscopy revealed that SNAC application could aggravate the surface roughness and reduce the compact structure of PW5. It further showed that PW5 and SNAC binds through an endothermic process underpinned by hydrogen bond and van der Waals forces and that SNAC could bound primarily to the internal calyx of PW5. These findings are helpful for the effective delivery of bioactive peptides.

The study of single‐cell dynamics contributes to the evaluation of food‐derived antioxidant capacity

Exploring potential food‐derived bioactive substances that relieve oxidative stress is considered an important goal for antioxidant research. We first used the long‐pair electron index and orbital fingerprint to predict the molecular interactions in a range of polyphenols and polypeptides. We found Rutin and peptide PW5 had the highest LPE index values. Subsequently, by D‐galactose (D‐gal)‐induced oxidative NIH3T3 cell model, we proved both Rutin and PW5 could effectively protect cells against D‐gal‐induced damage, through enhancement in cell proliferation and reduction in β‐galactosidase activity. Although Rutin displayed better performance than PW5 in the oxidative stress model, we confirmed Rutin stimulated obvious changes in the morphology and motility of normal NIH3T3 cells based on the real‐time dynamic images. Taken together, combined computational and typical model experiment methods, proved useful in efficiently screening food‐derived antioxidants. Moreover, the analytical results of cell morphology and movement may provide novel insights for the safety evaluation of antioxidants.

Inversion Theory Leveling as a New Methodological Approach to Antioxidant Thermodynamics: A Case Study on Phenol

Antioxidants are various types of compounds that represent a link between biology and chemistry. With the development of theoretical and computational methods, antioxidants are now being studied theoretically. Here, a novel method is presented that aims to reduce the estimated wall times for DFT calculations that result in the same or higher degree of accuracy in the second derivatives over energy than is the case with the regular computational route (i.e., optimizing the reaction system at a lower model and then recalculating the energies at a higher level of theory) by applying the inversion of theory level to the universal chemical scavenger model, i.e., phenol. The resulting accuracy and wall time obtained with such a methodological setup strongly suggest that this methodology could be generally applied to antioxidant thermodynamics for some costly DFT methods with relative absolute deviation.

Food Protein-Derived Antioxidant Peptides: Molecular Mechanism, Stability and Bioavailability

The antioxidant activity of protein-derived peptides was one of the first to be revealed among the more than 50 known peptide bioactivities to date. The exploitation value associated with food-derived antioxidant peptides is mainly attributed to their natural properties and effectiveness as food preservatives and in disease prevention, management, and treatment. An increasing number of antioxidant active peptides have been identified from a variety of renewable sources, including terrestrial and aquatic organisms and their processing by-products. This has important implications for alleviating population pressure, avoiding environmental problems, and promoting a sustainable shift in consumption. To identify such opportunities, we conducted a systematic literature review of recent research advances in food-derived antioxidant peptides, with particular reference to their biological effects, mechanisms, digestive stability, and bioaccessibility. In this review, 515 potentially relevant papers were identified from a preliminary search of the academic databases PubMed, Google Scholar, and Scopus. After removing non-thematic articles, articles without full text, and other quality-related factors, 52 review articles and 122 full research papers remained for analysis and reference. The findings highlighted chemical and biological evidence for a wide range of edible species as a source of precursor proteins for antioxidant-active peptides. Food-derived antioxidant peptides reduce the production of reactive oxygen species, besides activating endogenous antioxidant defense systems in cellular and animal models. The intestinal absorption and metabolism of such peptides were elucidated by using cellular models. Protein hydrolysates (peptides) are promising ingredients with enhanced nutritional, functional, and organoleptic properties of foods, not only as a natural alternative to synthetic antioxidants.

Novel Morpholine-Bearing Quinoline Derivatives as Potential Cholinesterase Inhibitors: The Influence of Amine, Carbon Linkers and Phenylamino Groups

A series of novel 4-N-phenylaminoquinoline derivatives containing a morpholine group were designed and synthesized, and their anti-cholinesterase activities and ABTS radical-scavenging activities were tested. Among them, compounds 11a, 11g, 11h, 11j, 11l, and 12a had comparable inhibition activities to reference galantamine in AChE. Especially, compound 11g revealed the most potent inhibition on AChE and BChE with IC₅₀ values of 1.94 ± 0.13 μM and 28.37 ± 1.85 μM, respectively. The kinetic analysis demonstrated that both the compounds 11a and 11g acted as mixed-type AChE inhibitors. A further docking comparison between the 11a- and 12a-AChE complexes agreed with the different inhibitory potency observed in experiments. Besides, compounds 11f and 11l showed excellent ABTS radical-scavenging activities, with IC₅₀ values of 9.07 ± 1.34 μM and 6.05 ± 1.17 μM, respectively, which were superior to the control, Trolox (IC₅₀ = 11.03 ± 0.76 μM). It is worth noting that 3-aminoquinoline derivatives 12a–12d exhibited better drug-like properties.

Preparation, characterization, and biological activity of Cinnamomum cassia essential oil nano-emulsion

To solve the problems of low bioavailability and unstable properties of Cinnamomum cassia Essential oil (CCEO), encapsulation technology was introduced as an effective means to improve its shortcomings. In this study, Cinnamomum cassia Essential oil nano-emulsion (CCEO-NE) was successfully synthesized by the oil-in-water method and characterized by standard analytical methods, including dynamic light scattering (DLS), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM). The results show that the synthesized CCEO is spherical, smooth in surface, and uniform in shape, with an average particle size of 221.8 ± 1.95 nm, which is amorphous. In this experiment, by simulating the digestion of CCEO-NE in the gastrointestinal tract, it was found that CCEO-NE was undigested in the oral cavity, mainly in the stomach, followed by the small intestine. By understanding the digestion of CCEO-NE, we can improve the potential of CCEO bioavailability in food and drug applications. In addition, through the study of ABTS and DPPH free radicals by CCEO and CCEO-NE, it was found that the antioxidant activity of CCEO-NE was more potent than that of CCEO. When the concentration of CCEO-NE and CCEO is 400 μg/mL, the DPPH free radical scavenging rate is 92.03 ± 0.548% and 80.46 ± 5.811%, respectively. In comparison, ABTS free radical scavenging rate is 90.35 ± 0.480% and 98.44 ± 0.170% when the concentration of CCEO- NE, and CCEO is 75 μg/mL, respectively. The antibacterial test shows that CCEO-NE can inhibit both Gram-positive and Gram-negative bacteria. Among them, CCEO-NE has a stronger antibacterial ability than CCEO, and the maximum inhibition zone diameter of CCEO can reach 15 mm, while that of CCEO-NE can reach 18 mm. Meanwhile, SEM and TEM showed that CCEO-NE treatment destroyed the ultrastructure of bacteria. Generally speaking, we know the situation of CCEO in the gastrointestinal tract. CCEO-NE has more potent antioxidant and antibacterial ability than CCEO. Our research results show that whey protein is an effective packaging strategy that can improve the effectiveness, stability, and even bioavailability of CCEO in various applications, including food and health care industries.

Production, bioactivities and bioavailability of bioactive peptides derived from walnut origin by-products: a review

Walnut-origin by-products obtained from walnut oil extraction industry are high in proteins with various physiological functions and pharmacological properties and an extensive potential for usage in producing bioactive peptides. This review presents the current research status of bioactive peptides derived from walnut by-products, including preparation, separation, purification, identification, bioactivities, and bioavailability. A plethora of walnut peptides with multiple biological activities, including antioxidative, antihypertensive, neuroprotective, antidiabetic, anticancer, and antihyperuricemia activities, were obtained from walnut-origin by-products by enzymatic hydrolysis, fermentation, and synthesis. Different bioactive peptides show various structural characteristics and amino acid composition due to their diverse mechanism of action. Furthermore, walnut protein and its hydrolysate present a high bioavailability in human gastrointestinal digestive system. Improving the bioavailability of walnut peptides is needful in the development of walnut industry. However, future research still needs to exploit energy conservation, high efficiency, environmentally friendly and low-cost production method of walnut bioactive peptide. The molecular mechanisms of different bioactive walnut peptides still need to be explored at the cell and gene levels. Additionally, the digestion, absorption, and metabolism processes of walnut peptides are also the focus of future research.

Physicochemical and molecular transformation of novel functional peptides from Baijiu

A novel strategy for screening and identifying peptides present in Baijiu was developed based on magnetic solid-phase extraction with magnetic S-doped graphene (M-G-S) as adsorbent combined with ultrahigh-performance liquid chromatography with high resolution tandem mass spectrometry. In total, 28 peptides consisting of amino acids from 3 to 9 were preliminarily identified, and significantly higher in the number than that of direct concentration and SPE with C₁₈ as the adsorbent. Six peptides were confirmed with their corresponding synthetic reference standards by comparing their retention time, high resolution MS/MS spectra, and NMR spectroscopic studies. Parallel reaction monitoring integrated with the internal standard method was utilized to quantify identified peptides with concentrations ranging from 1.14 to 10.25 ng mL^-1, and prediction results of bioactivity comprising antioxidation or ACE inhibitors were obtained. These discoveries were conducive to understanding the versatility benefit of Baijiu and paved the way to study the interaction between peptides and volatile substances.

Exploring the Mechanisms of Anti‐Aβ42 Aggregation Activity of Walnut‐derived Peptides using Transcriptomics and Proteomics in vitro

Inhibiting β‐amyloid (Aβ) aggregation is of significance in finding potential candidates for Alzheimer's disease (AD) treatment. Accumulating evidence suggests that nutrition is important for improving cognition and reducing AD risk. Walnut has been widely used as a functional food for brain health; however the underlying mechanisms remain unknown. Here, we investigated the molecular level alteration in Arctic mutant Aβ42 induced aggregation cell model by RNA‐seq and iTRAQ approaches after walnut‐derived peptides Pro‐Pro‐Lys‐Asn‐Trp (PW5) and Trp‐Pro‐Pro‐Lys‐Asn (WN5) interventions. PW5 or WN5 could significantly decrease abnormal Aβ42 aggregates. However, resultant alterations in transcriptome (substantially unchanged) were inconsistent with proteomic data (marked change). Proteomic analysis revealed 184 and 194 differentially expressed proteins unique to PW5 and WN5 treatment, respectively, for inhibiting Aβ42 protein production or increasing protein degradation via the mismatch repair pathways. Our study provides new insights into the effectiveness of food‐derived peptides for anti‐Aβ42 aggregation in AD.