Antioxidant hydrolyzed peptides from Manchurian walnut (Juglans mandshurica Maxim.) attenuate scopolamine-induced memory impairment in mice

Dual-modified starch micelles as nanocarriers for efficient encapsulation and controlled release of walnut-derived active peptides

Hydrophilic and hydrophobic modified nanomicelles might be more conducive to passage of the gastrointestinal barrier than walnut peptide (WP). In this study, a novel double modified starch polymer, SB-CST-DCA, was synthesized by grafting sulfabetaine (SB) and deoxycholic acid (DCA) onto corn starch (CST) molecules through etherification and esterification. The modification mechanism was discussed to determine its chemical structure, morphological properties, and thermal stability. Peptide-loaded nanomicelles (SB-CST-DCA-WP) were prepared using WP as the core material. The encapsulation efficiency and peptide loading amount reached 76.90 ± 1.52% and 18.27 ± 0.53%, respectively, with good stability and pH-responsive release behavior observed to effectively control WP release and enhance its antioxidant activity. The composite exhibited safety, non-toxicity, and good blood compatibility at concentrations below 125 μg/mL. Duodenum was identified as the main absorption site with an absorption ratio of 41.16 ± 0.36%.

Effect of bi-enzyme hydrolysis on the properties and composition of hydrolysates of Manchurian walnut dreg protein

Walnut dreg (WD) active peptides are an important source of dietary antioxidants; however, the products of conventional hydrolysis have limited industrial output owing to poor flavour and low bioactivity. To this end, in this study, we aimed to employ bvLAP, an aminopeptidase previously identified in our research, as well as commercially available Alcalase for bi-enzyme digestion. The flavour, antioxidant activity, and structures of products resulting from various digestion methods were compared. The results showed that the bi-enzyme digestion products had enhanced antioxidant activity, increased β-sheet content, and reduced bitterness intensity from 9.65 to 6.93. Moreover, bi-enzyme hydrolysates showed a more diverse amino acid composition containing 1640 peptides with distinct sequences. These results demonstrate that bi-enzyme hydrolysis could be a potential process for converting WD into functional food ingredients. Additionally, our results provide new concepts that can be applied in waste processing and high-value utilisation of WD.

Role of Corn Peptide Powder in Lipopolysaccharide-Induced Inflammatory Responses in 3T3-L1 Adipocytes

Corn peptide (CP) is a short, naturally occurring, and physiologically active peptide generated from corn-protease-catalyzed hydrolysis. CP plays a role in preventing obesity-related disorders, but its impact on reducing inflammation is unknown. Hence, this study examined the possible protective effects of corn peptide powder (CPP) against the harmful effects of lipopolysaccharide (LPS), with a particular emphasis on reducing oxidative damage and inflammation in adipocytes. Hence, mature 3T3-L1 adipocytes underwent exposure to 10 ng/mL LPS, with or without CPP (10 and 20 μg/mL). LPS stimulation increased reactive oxygen species and superoxide anion generation. However, this effect was reduced in a dose-dependent manner by pretreatment with CPP. CPP treatment elevated the mRNA expressions of the antioxidant enzymes manganese superoxide dismutase (mnSOD) and glutathione peroxidase 1 (Gpx1) while reducing the mRNA expressions of the cytosolic reactive oxygen species indicators p40 and p67 (NADPH oxidase 2). In addition, CPP inhibited the monocyte chemoattractant protein-1, tumor necrosis factor-alpha, Toll-like receptor 4, and nuclear factor kappa B mRNA expressions induced by LPS. These findings demonstrate that CPP may ameliorate adipocyte dysfunction by suppressing oxidative damage and inflammatory responses through a new mechanism known as Toll-like receptor 4/nuclear factor kappa B-mediated signaling.

Walnut-Derived Peptides Ameliorate Scopolamine-Induced Memory Impairments in a Mouse Model via Activation of Peroxisome Proliferator-Activated Receptor γ-Mediated Excitotoxicity

We investigated the protective effect of walnut peptides and YVPFPLP (YP-7) on scopolamine-induced memory impairment in mice and β-amyloid (Aβ)-induced excitotoxic injury in primary hippocampal neurons, respectively. Additionally, the protective mechanism of YP-7 on neuronal excitotoxicity was explored. Mouse behavioral and hippocampal slice morphology experiments indicate that YP-7 improves the learning and memory abilities of cognitively impaired mice and protects synaptic integrity. Immunofluorescence, western blotting, and electrophysiological experiments on primary hippocampal neurons indicate that YP-7 inhibits neuronal damage caused by excessive excitation of neurons induced by Aβ. HT-22 cell treatment with peroxisome proliferator-activated receptor γ (PPARγ) activators and inhibitors showed that YP-7 activates PPARγ expression and maintains normal neuronal function by forming stable complexes with PPARγ to inhibit the extracellular regulated protein kinase pathway. Therefore, YP-7 can ameliorate glutamate-induced excitotoxicity and maintain neuronal signaling. This provides a theoretical basis for active peptides to ameliorate excitotoxicity and the development of functional foods.

Novel strategy to the characterization and enhance the glycemic control properties of walnut-derived peptides via zinc chelation

This study aimed to utilize zinc coordination to promote the hypoglycemic and antioxidant properties of walnut-derived peptides, such as walnut protein hydrolysate (WPH) and Leu-Pro-Leu-Leu-Arg (LPLLR, LP5), of which LP5 was previously identified from WPH. The optimal conditions for the chelation were a peptide-to-zinc ratio of 6:1, pH of 9, duration of 50 min, and temperature of 50 °C. The WPH-Zn and LP5-Zn complexes increased the α-glucosidase inhibition, α-amylase inhibition, and antioxidant activity more than WPH and LP5 (p < 0.05). In particular, the antioxidant activity of WPH-Zn was superior to LP5-Zn. This is attributable to the WPH containing more aromatic amino acids, carboxylate groups and the imidazole groups, which implies its capacity to potentially coordinate with Zn2+ to form the WPH-Zn complex. Moreover, particle size, zeta potential, and scanning electron microscope indicated that the chelation of Zn2+ by peptides led to intramolecular and intermolecular folding and aggregation.

Isolation, Virtual Screening, and Evaluation of Hazelnut-Derived Immunoactive Peptides for the Inhibition of SARS-CoV-2 Main Protease

The aim of this study is to validate the activity of hazelnut (Corylus avellana L.)-derived immunoactive peptides inhibiting the main protease (Mpro) of SARS-CoV-2 and further unveil their interaction mechanism using in vitro assays, molecular dynamics (MD) simulations, and binding free energy calculations. In general, the enzymatic hydrolysis components, especially molecular weight < 3 kDa, possess good immune activity as measured by the proliferation ability of mouse splenic lymphocytes and phagocytic activity of mouse peritoneal macrophages. Over 866 unique peptide sequences were isolated, purified, and then identified by nanohigh-performance liquid chromatography/tandem mass spectrometry (NANO-HPLC-MS/MS) from hazelnut protein hydrolysates, but Trp-Trp-Asn-Leu-Asn (WWNLN) and Trp-Ala-Val-Leu-Lys (WAVLK) in particular are found to increase the cell viability and phagocytic capacity of RAW264.7 macrophages as well as promote the secretion of the cytokines nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β). Fluorescence resonance energy transfer assay elucidated that WWNLN and WAVLK exhibit excellent inhibitory potency against Mpro, with IC50 values of 6.695 and 16.750 μM, respectively. Classical all-atom MD simulations show that hydrogen bonds play a pivotal role in stabilizing the complex conformation and protein-peptide interaction. Molecular Mechanics/Generalized Born Surface Area (MM/GBSA) calculation indicates that WWNLN has a lower binding free energy with Mpro than WAVLK. Furthermore, adsorption, distribution, metabolism, excretion, and toxicity (ADMET) predictions illustrate favorable drug-likeness and pharmacokinetic properties of WWNLN compared to WAVLK. This study provides a new understanding of the immunomodulatory activity of hazelnut hydrolysates and sheds light on peptide inhibitors targeting Mpro.

Advances in Research on the Activity Evaluation, Mechanism and Structure-Activity Relationships of Natural Antioxidant Peptides

Antioxidant peptides are a class of biologically active peptides with low molecular weights and stable antioxidant properties that are isolated from proteins. In this review, the progress in research on the activity evaluation, action mechanism, and structure-activity relationships of natural antioxidant peptides are summarized. The methods used to evaluate antioxidant activity are mainly classified into three categories: in vitro chemical, in vitro cellular, and in vivo animal methods. Also, the biological effects produced by these three methods are listed: the scavenging of free radicals, chelation of metal ions, inhibition of lipid peroxidation, inhibition of oxidative enzyme activities, and activation of antioxidant enzymes and non-enzymatic systems. The antioxidant effects of natural peptides primarily consist of the regulation of redox signaling pathways, which includes activation of the Nrf2 pathway and the inhibition of the NF-κB pathway. The structure-activity relationships of the antioxidant peptides are investigated, including the effects of peptide molecular weight, amino acid composition and sequence, and secondary structure on antioxidant activity. In addition, four computer-assisted methods (molecular docking, molecular dynamics simulation, quantum chemical calculations, and the determination of quantitative structure-activity relationships) for analyzing the structure-activity effects of natural peptides are summarized. Thus, this review lays a theoretical foundation for the development of new antioxidants, nutraceuticals, and cosmetics.

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.

In silico prediction aided preparation of antioxidant soybean peptides by enzymatic hydrolysis for ameliorating lead exposure-induced toxicity

Food derived bioactive peptides are prominent dietary supplements to protect against oxidative stress induced by lead (Pb) exposure. This study aimed to develop a new strategy for rapid preparation of highly active antioxidant soybean polypeptides (ASPs) against Pb toxicity. In silico enzymatic hydrolysis simulation and antioxidant activity prediction showed that pepsin, chymotrypsin and bromelain can produce peptides with the highest activity. The preparation process was then optimized, and the obtained ASP showed good antioxidant and metal-chelating activities in vitro. An in vivo study showed that ASP exerted prominent protective effects against Pb-induced cognitive impairment and tissue damage in mice by reducing Pb deposition and enhancing the antioxidant capacity in tissues and was superior to Vc, DMSA or their combination in some aspects. ASP composition analysis demonstrated that its prominent antioxidant activity might be attributed to the high proportion of amino acid residues E, L, P and V in the peptide sequence and L, V and A at the C- and N-termini. In conclusion, in silico prediction could facilitate the preparation of ASP. And the ASP prepared with the new strategy exerted prominent protective effects against Pb toxicity.

Screening of the Active Substances for the Assessment of Walnut Kernel in the Treatment of Scopolamine-Induced AD Animals

SCOPE

Alzheimer's disease (AD) has been a challenge and hotspot in the field of neuroscience research due to the high morbidity. As we all know, walnut kernel (WK) ingestion has been linked to benefits to brain health and has the function of improving memory. This study follows the AD model induced by scopolamine to reveal the active fractions and substances of walnut in the treatment of AD.

METHODS AND RESULTS

The histopathological analysis and brain tissue biochemistry assay are revealed the active fractions of WK, and this result determines that walnut kernel organic acids have significant therapeutic effect on AD. The strategy of studying ingredients pointed at lesions is integrated to ascertain the selected brain-targeted effective substances of WK for blood-brain barrier by ultra-performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry, and a total of eight organic acids are figured out definite absorptivity in rat brains. Finally, the binding interaction between the effective substances and target proteins is analyzed by molecular docking, and the main function related active markers are ascertained as glansreginin A, glansreginic acid, ellagic acid, and ellagic acid 4-O-xyloside.

CONCLUSIONS

The comprehensive process is helpful to the clinical application of WK as a promising cholinesterase inhibitors for nutritional intervention.

Neuroprotective mechanisms of defatted walnut powder against scopolamine-induced Alzheimer's disease in mice revealed through metabolomics and proteomics analyses

ETHNOPHARMACOLOGICAL RELEVANCE

Defatted walnut powder (DWP), the byproduct remaining after extracting oil from the walnut kernel, has the actions of nourishing liver and the kidney, replenishing blood, and calming the nerves, which is believed to be a brain-nourishing in Chinese medicine. DWP is rich in phenolic substances with demonstrated anti-inflammatory, antioxidant, lipid-lowering and neuroprotective effects. Despite these promising properties of DWP, its effectiveness in treating Alzheimer's disease (AD) remains unclear, and further research is needed to understand the mechanism of action.

AIM OF THE STUDY

This study aimed to investigate the potential mechanism of DWP on AD by constructing the overall metabolic profile of mice with an anti-scopolamine AD model and verification of the highly correlated pathway.

MATERIALS AND METHODS

The neuroprotective efficacy of DWP in a mouse model of AD established by scopolamine injection was examined. Spatial memory performance in the Morris water maze (MWM), markers of cholinergic function in hippocampus and cortex, and neuropathological changes were compared among control, model, and DWP-consuming model group mice. In addition, combined metabolomic and proteomic analyses were conducted to investigate changes in metabolite and protein expression profiles in AD model mice induced by DWP consumption. Differentially expressed proteins and metabolites were then analyzed for KEGG pathway enrichment and results confirmed through targeted amino acid metabolomics.

RESULTS

The results showed that consumption of DWP improved spatial learning and memory in the MWM, enhanced cholinergic function, and reduced histopathological damage in the cortex and hippocampus of AD model mice. Based on differentially abundant metabolites and proteins, 43 metabolic pathways modulated by DWP were identified, mainly involving in amino acid metabolic pathways strongly associated with cellular energetics and antioxidant capacity, and targeted amino acid metabolomics confirmed that DWPE significantly elevated the levels of Arginine (Arg), Histidine (His), Proline (Pro), Serine (Ser), and Tyrosine (Tyr), while reducing the levels of Glutamate (Glu). This ultimately resulted in an improvement in the progression of AD.

CONCLUSION

This study identified numerous metabolic networks modulated by DWP that can mitigate scopolamine-induced AD neuropathology and cognitive dysfunction. DWP is a promising resource to identify AD-related pathogenic pathways and therapeutic strategies.

Research Progress on the Preparation and Function of Antioxidant Peptides from Walnuts

Food-derived peptides have good antioxidant activity and are highly safe for humans; consequently, there has been continuous growth in research on antioxidants, with potential applications in food, medicine, cosmetics, and other fields. Among food-derived peptides, walnut-derived peptides have attracted increasing attention as food-derived peptides rich in eight essential amino acids. This review summarizes the progress made in the development and identification of antioxidant peptides in walnut proteins. This article mainly describes the interaction between reactive oxygen species and cellular antioxidant products, modulation of enzyme content and activity, and regulation of the redox signaling pathways and analyzes the mechanisms of reduction in oxidative stress. Finally, the complex structure-activity relationships of walnut-derived peptides are analyzed based on their amino acid composition and secondary structure of the polypeptides. This review provides a theoretical basis for the production of walnut-derived antioxidant peptides and could help promote the development of the walnut industry.

Isolation, Identification, Activity Evaluation, and Mechanism of Action of Neuroprotective Peptides from Walnuts: A Review

As human life expectancy increases, the incidence of neurodegenerative diseases in older adults has increased in parallel. Walnuts contain bioactive peptides with demonstrated neuroprotective effects, making them a valuable addition to the diet. We here present a comprehensive review of the various methods used to prepare, isolate, purify, and identify the neuroprotective peptides found in walnuts. We further summarise the different approaches currently used to evaluate the activity of these peptides in experimental settings, highlighting their potential to reduce oxidative stress, neuroinflammation, and promote autophagy, as well as to regulate the gut microflora and balance the cholinergic system. Finally, we offer suggestions for future research concerning bioavailability and improving or masking the bitter taste and sensory properties of final products containing the identified walnut neuroprotective peptides to ensure successful adoption of these peptides as functional food ingredients for neurohealth promotion.

Synergistic Effect of Combined Walnut Peptide and Ginseng Extracts on Memory Improvement in C57BL/6 Mice and Potential Mechanism Exploration

This work aimed to investigate whether there are synergistic effects between walnut peptide (WNP) and ginseng extracts (GSE) treatments to ameliorate the memory impairment caused by scopolamine (SCOP). The Morris water maze trial, hippocampal neuron morphology, neurotransmitters, and synaptic ultrastructure were examined, along with brain-derived neurotrophic factor (BDNF)-related signaling pathway proteins. The results of the Morris water maze trial demonstrated that the combined administration of WNP and GSE effectively alleviated memory impairment in C57BL/6 rats caused by SCOP. Improvement in the morphology of hippocampal neurons, dendritic spines, and synaptic plasticity and upregulation of neurotransmitters AChE, ACh, ChAT, Glu, DA, and 5-HT supported the memory improvement effects of WNP + GSE. In addition, compared with the model group, WNP + GSE significantly enhanced the protein levels of VAChT, Trx-1, and the CREB/BDNF/TrkB pathway in hippocampal and PC12 cells induced by SCOP (p < 0.05). Notably, WNP + GSE boosted memory via multiple pathways, not only the BDNF/TrkB/CREB target.

Purification and Identification of Novel Antioxidant Peptides from Hydrolysates of Peanuts (Arachis hypogaea) and Their Neuroprotective Activities

Peanut (Arachis hypogaea) peptides have various functional activities and a high utilization value. This study aims to isolate and characterize antioxidant peptides from peanut protein hydrolysates and further evaluate their neuroprotection against oxidative damage to PC12 cells induced by 6-hydroxydopamine (6-OHDA). After the peanut protein was hydrolyzed with pepsin and purified using ultrafiltration and gel chromatography, six peptides were identified and sequenced by high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Out of these six peptides, Pro-Gly-Cys-Pro-Ser-Thr (PGCPST) exhibited a desirable antioxidant capacity, as determined using the 1,1-diphenyl-2-picrylhydrazyl, 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, and hydroxyl radical scavenging assays. Moreover, our results indicated that the peptide PGCPST effectively increased the cell viability and reduced the cell apoptosis in 6-OHDA-induced PC12. RNA sequencing further showed that the neuroprotective effect of the peptide PGCPST was mediated via sphingolipid metabolism-related pathways. With further research efforts, the peptide PGCPST was expected to develop into a new neuroprotective agent.

Pharmacotherapeutic potential of walnut (Juglans spp.) in age-related neurological disorders

Global and regional trends of population aging spotlight major public health concerns. As one of the most common adverse prognostic factors, advanced age is associated with a remarkable incidence risk of many non-communicable diseases, affecting major organ systems of the human body. Age-dependent factors and molecular processes can change the nervous system's normal function and lead to neurodegenerative disorders. Oxidative stress results from of a shift toward reactive oxygen species (ROS) production in the equilibrium between ROS generation and the antioxidant defense system. Oxidative stress and neuroinflammation caused by Amyloid-ß protein deposition in the human brain are the most likely pathogenesis of Alzheimer's disease (AD). Walnut extracts could reduce Amyloid-ß fibrillation and aggregation, indicating their beneficial effects on memory and cognition. Walnut can also improve movement disabilities in Parkinson's disease due to their antioxidant and neuroprotective effect by reducing ROS and nitric oxide (NO) generation and suppressing oxidative stress. It is noteworthy that Walnut compounds have potential antiproliferative effects on Glioblastoma (the most aggressive primary cerebral neoplasm). This effective therapeutic agent can stimulate apoptosis of glioma cells in response to oxidative stress, concurrent with preventing angiogenesis and migration of tumor cells, improving the quality of life and life expectancy of patients with glioblastoma. Antioxidant Phenolic compounds of the Walnut kernel could explain the significant anti-convulsion ability of Walnut to provide good prevention and treatment for epileptic seizures. Moreover, the anti-inflammatory effect of Walnut oil could be beneficial in treating multiple sclerosis. In this study, we review the pharmaceutical properties of Walnut in age-related neurological disorders.

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

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

A Two-Stage Enzymolysis Method and Its Application in Exerting Antioxidant Activity of Walnut Protein

Traditional enzymolysis method for producing bioactive peptides does not consider the utilization of digestive enzymes in the human gastrointestinal tract, leading to the possibility of excessive hydrolysis and higher production cost. Therefore, a two-stage enzymolysis method was established in this study based on in vitro limited enzymolysis and gastrointestinal digestion, and applied it to the research of walnut protein (WP) in exerting antioxidant activity. Results showed that WP could be well-digested by pepsin and pancreatin. WP with limited enzymolysis degree of 0% could achieve high antioxidant activity after the simulated gastrointestinal digestion, and the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and reducing power were 66.53% and 8.55 μmoL TE/mL, respectively. In vivo experimental results also exhibited that both WP and WP hydrolysate (WPH) could alleviate the oxidative damage induced by D-galactose in SD rats to some extent. Considering the digestive function of human body, in vitro limited enzymolysis, in vitro simulated gastrointestinal digestion and in vivo validation are necessary processes for the production of bioactive peptides.

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.

Walnut-Derived Peptide Enhances Mitophagy via JNK-Mediated PINK1 Activation to Reduce Oxidative Stress in HT-22 Cells

Mitophagy has a neuroprotective effect on reactive oxygen species (ROS)-induced neurodegenerative diseases. The walnut-derived polypeptide (TW-7) has antioxidant activity and protects nerves by promoting autophagy. However, its action mechanism against oxidative stress through mitophagy remains obscure. Therefore, we aimed to assess the effects of TW-7 on HT-22 cells under oxidative stress. Mitochondrial ultrastructure and cristae number were observed by transmission electron microscopy. The results showed that TW-7 (100 μM) restored the fluorescence intensity of the mitochondrial membrane potential to 0.99 ± 0.04 (P < 0.05), decreased H₂O₂-induced opening of mitochondrial permeability transition pores, and inhibited mitochondrial bioenergetic deficits. Moreover, it significantly increased activities of antioxidant enzymes to 186.88 ± 5.40 U/mgprot, 40.08 ± 0.87 mU/mgprot, and 23.57 ± 0.77 U/mgprot (P < 0.05), based on superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) assay results, respectively. Consistently, it decreased cellular and mitochondrial ROS levels by 51.71 ± 0.81 and 49.75 ± 0.69% (P < 0.05). TW-7 also downregulated C-Jun N-terminal kinase (JNK) phosphorylation and activated PTEN-induced putative kinase 1 (PINK1)-mediated mitophagy in H₂O₂-induced HT-22 cells treated with JNK activator (anisomycin) and inhibitor (SP600125). Furthermore, TW-7 inhibited the mitochondrial apoptosis pathway by downregulation of the cytoplasmic cytochrome C, caspase-9, and cleaved-caspase-3 expression. Additionally, BDNF and SNAP-25 levels significantly increased to protect the synaptic function. Collectively, TW-7 improved oxidative stress-mediated nerve cell injury via JNK-regulated PINK1-mediated mitophagy.

Sea Cucumber Peptides Attenuated the Scopolamine-Induced Memory Impairment in Mice and Rats and the Underlying Mechanism

Social stress and unhealthy diets lead to memory impairment, triggering health problems. This study aimed to determine the mitigating effect and regulation mechanism of sea cucumber peptides (SCP) against memory impairment. Here, scopolamine-induced memory impairment in mouse and rat models was used based on behavioral tests, a histological staining technique, Fourier transform infrared microscopy, and gas-chromatographic analysis as well as a Western blotting method. SCP improved the behavioral performance and regulated the disorder of the cholinergic system in mouse models in a dose-dependent manner. Therefore, the underlying mechanism was explored in high-dose SCP using mouse and rat models. SCP repaired damaged neuronal cells, enhanced the Nissl body number, increased the unsaturated lipid level, and activated the long-term potentiation (LTP) pathway (p-CaMKII, p-CREB, and BDNF), both in the mouse and rat hippocampus. The results indicated that SCP upregulated the LTP pathway and unsaturated lipid level to combat scopolamine-induced memory impairment, suggesting that SCP was a potential candidate for neurological recovery.

Neuroprotective effects of fermented yak milk-derived peptide LYLKPR on H2O2-injured HT-22 cells

This study explored the neuroprotective effect of the peptide LYLKPR derived from fermented yak milk by Lactiplantibacillus plantarum JLAU103 on H2O2-injured HT-22 cells.

Rapid qualitative profiling and quantitative analysis of Juglandis Mandshuricae Cortex and seven flavonoids by ultra-high performance liquid chromatography-quadrupole/orbitrap high-resolution mass spectrometry

Juglandis Mandshuricae Cortex is the bark of Juglans mandshurica Maxim., which has been used as a folk medicine plant in China and India. In this study, an ultra-high performance liquid chromatography-quadrupole/orbitrap high-resolution mass spectrometry method was developed to clarify and quantify the chemical profiling of Juglandis Mandshuricae Cortex rapidly. A total of 113 compounds were characterized. Among them, seven flavonoids were simultaneously quantified in 15 min, including myricetin, myricetrin, taxifolin, kaempferol, quercetin, quercitrin, and naringenin. The method was validated for accuracy, precision, and the limits of detection and quantification. All calibration curves showed a good linear relationship (r > 0.9990) within test ranges. The intra- and inter-day relative standard deviations were less than 2.16%. Accuracy validation showed that the recovery was between 95.6% and 101.3% with relative standard deviation values below 2.85%. The validated method was successfully applied to determine the contents of seven flavones in Juglandis Mandshuricae Cortex from seven sources and the contents of these places were calculated respectively. This method provides a theoretical basis for further developing the medicinal value of Juglandis Mandshuricae Cortex.

Walnut peptide WEKPPVSH in alleviating oxidative stress and inflammation in lipopolysaccharide-activated BV-2 microglia via the Nrf2/HO-1 and NF-κB/p38 MAPK pathways

The peptide WEKPPVSH from walnut protein hydrolyzate was used to evaluate the antioxidant and anti-inflammatory protective effect on lipopolysaccharide (LPS)-activated BV-2 microglia and its possible mechanism. The results indicated that WEKPPVSH significantly decreased nitric oxide (NO) and reactive oxygen species (ROS) generation in a dose-dependent manner, and significantly up-regulated superoxide dismutase and catalase activities (P < 0.01). Results of enzyme-linked immunosorbent assay (ELISA) showed that WEKPPVSH significantly mitigated the secretion of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) (P < 0.01). Immunofluorescence analysis exhibited that WEKPPVSH down-regulated p65 translocation to the cell nucleus. Western blotting showed that WEKPPVSH up-regulated the expression of nuclear factor erythroid 2-related factor (Nrf2) and heme oxygenase-1 (HO-1), and down-regulated the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), p-IκB/IκB, p-p65/p65 and p-p38/p38. In summary, WEKPPVSH might protect against oxidative stress and inflammation in LPS-stimulated BV-2 microglia by enhancing the Nrf2/HO-1 signaling pathway and blocking the nuclear factor-κB/p38 mitogen - activated protein kinase (NF-κB/p38 MAPK) signaling pathway. The results provided an experimental basis for the research and development of walnut peptide products.

Potential of plant-derived peptides for the improvement of memory and cognitive function

Recently, there has been an increased demand for functional foods, to reduce the risk of age-related cognitive impairment, dementia, and Alzheimer's disease. Among them, plant-derived bioactive compounds, such as phytochemicals and peptides, have notable potential in improving memory and cognitive functions. Many studies have provided potential data concerning the characteristics and structure-activity relationships of memory-enhancing peptides. When considering the proof of efficacy of these plant-based peptides in humans as neurological treatment options, it is necessary to accumulate evidence concerning their bioavailability and permeability through blood-brain barrier (BBB). This review focuses on the memory-enhancing effects of peptides derived from plant proteins and presents a current perspective on their structure-activity relationships and BBB permeability.

Pine nut antioxidant peptides ameliorate the memory impairment in a scopolamine-induced mouse model via SIRT3-induced synaptic plasticity

This study aimed to investigate the effects of a pine nut albumin hydrolysate (fraction <3 kDa) and of its short peptide derivative, Trp-Tyr-Pro-Gly-Lys (WYPGK), on synaptic plasticity and memory function in scopolamine-induced memory-impaired mice, as well as the potential underlying mechanism in PC12 cells. In the scopolamine-induced mouse model, the results revealed that the fraction <3 kDa and WYPGK enhanced synaptic plasticity and improved learning and memory function. H&E and Nissl staining analysis showed that the damage in hippocampal neurons was decreased. Golgi staining and transmission electron microscopy further revealed that the enhanced synaptic plasticity was associated with increased dendritic spine abundance and synaptic density. In an H₂O₂-induced PC12 cell model, treatment with mitochondrial sirtuin 3 (SIRT3) inhibitor and inducer molecules confirmed that the <3 kDa fraction and WYPGK activated SIRT3, leading to the decrease in Ace-SOD2 acetylation and increasing the expression of SYP, SYN-1, SNAP25, and PSD95, thus enhancing synaptic plasticity. The <3 kDa fraction and WYPGK also activated the ERK/CREB pathway and upregulated the expression of brain-derived neurotrophic factor. Our results show that fraction <3 kDa and WYPGK improve learning and memory ability through SIRT3-induced synaptic plasticity in vitro and in vivo.

Production and antioxidant capacity of bioactive peptides from plant biomass to counteract lipid oxidation

Preventing lipid oxidation, especially with the polyunsaturated fat-based products, is a major concern in sectors as agri-food and cosmetic. Even though the efficiency of synthetic antioxidants has been recognized, both consumers and manufacturers are looking for more innovative, healthy and quality products while rejecting synthetic additives due to their concern about safety, along with their environmental impact issues. In this context, plant biomass, which have shown to be rich in compounds, have raised interest for the isolation of novel naturally occurring antioxidants. Among their myriad of molecules, bioactive peptides, which are biologically active sequence of amino acid residues of proteins, seem to be of a great interest. Therefore, the number of identified amino acids sequences of bioactive peptides from plant biomass with potential antioxidant action is progressively increasing. Thus, this review provides a description of 129 works that have been made to produce bioactive peptides (hydrolysate, fraction and/or isolate peptide) from 55 plant biomass, along with the procedure to examine their antioxidant capacity (until 2019 included). The protein name, the process, and the method to concentrate or isolate antioxidant bioactive peptides, along with their identification and/or specificity were described. Considering the complex, dynamic and multifactorial physico-chemical mechanisms of the lipid oxidation, an appropriate in-vitro methodology should be better performed to efficiently probe the antioxidant potential of bioactive peptides. Therefore, the results were discussed, and perspective for antioxidant applications of bioactive peptides from plant biomass was argued.

Exploring Molecular Insights of Cereal Peptidic Antioxidants in Metabolic Syndrome Prevention

The prevalence of metabolic syndrome (MetS) is presently an alarming public health problem globally. Oxidative stress has been postulated to be strongly correlated with MetS, such as type 2 diabetes, obesity, hypertension, cardiovascular diseases, and certain cancers. Cereals are important staple foods which account for a huge proportion of the human diet. However, owing to recent growing demand and the search for natural antioxidants for the prevention and management of MetS, cereal peptides have gained increasing attention for developing functional ingredients or foods with substantial antioxidant properties. This review explores the current production techniques for cereal peptidic antioxidants and their potential mechanism of action in the prevention and management of MetS.

Walnut-Derived Peptide Activates PINK1 via the NRF2/KEAP1/HO-1 Pathway, Promotes Mitophagy, and Alleviates Learning and Memory Impairments in a Mice Model

Mitophagy has a pivotal protective function in the pathogenesis of neurological disorders. However, the mechanism of its modulation remains elusive, especially in PINK1-mediated mitophagy. Here, we investigated the neuroprotective effects of a walnut-derived peptide, YVLLPSPK, against scopolamine-induced cognitive deficits in mice and explored the underlying PINK1-mediated mitophagy mechanisms in H₂O₂-treated HT-22 cells. Using the Morris water maze, we showed that YVLLPSPK relieved the cognitive deficiency by alleviating oxidative stress. Mitochondrial morphology was observed in mice hippocampal tissues using transmission electron microscopy (TEM). Both Western blot and immunofluorescence analysis illustrated YVLLPSPK promoted the expression of mitophagy-related proteins and activated the NRF2/KEAP1/HO-1 pathway. Subsequently, an NRF2 inhibitor (ML385) was used to verify the contribution of the YVLLPSPK-regulated NRF2/KEAP1/HO-1 pathway in PINK1-mediated mitophagy in H₂O₂-treated HT-22 cells. These data suggested that YVLLPSPK improved learning and memory in scopolamine-induced cognitive-impaired mice through a mechanism associated with PINK1-mediated mitophagy via the NRF2/KEAP1/HO-1 pathway.

Juglans mandshurica Maxim.: A Review of Its Traditional Usages, Phytochemical Constituents, and Pharmacological Properties

Juglans mandshurica Maxim., also known as “Manchurian walnut” (Chinese) and “Onigurumi” (Japanese), is a medicinal plant widely distributed in Western and Central Asia, especially in China. It has been traditionally used to treat cancer, gastric ulcers, diarrhea, dysentery, dermatosis, uterine prolapse, and leukopenia. To date, more than 400 constituents including quinones (e.g. naphthoquinones, anthraquinones, naphthalenones, tetralones), phenolics, flavonoids, triterpenoids, coumarins, lignans, phenylpropanoids, diarylheptanoids, and steroids, were isolated and structurally identified from different plant parts of J. mandshurica. Among them, quinones, phenolics, triterpenoids, and diarylheptanoids, as the major bioactive substances, have been extensively studied and displayed significant bioactivity. Previous studies have demonstrated that J. mandshurica and a few of its active components exhibit a wide range of pharmacologically important properties, such as antitumor, immunomodulatory, anti-inflammatory, neuroprotective, anti-diabetic, antiviral, antimicrobial, and anti-melanogenesis activities. However, many investigations on biological activities were mainly based on crude extracts of this plant, and the major bioactive ingredients responsible for these bioactivities have not been well identified. Further in vitro and in vivo studies on the mechanisms of action of the pure bioactive compounds, and more elaborate toxicity studies as well as clinical studies are needed to ensure safety and effectiveness of the plant for human use. Taken together, the present review will provide some specific useful suggestions guide to further investigations and applications of this plant in the preparation of medicines and functional foods.

Protective effects of crimson snapper scales peptides against oxidative stress on Drosophila melanogaster and the action mechanism

Peptides derived from crimson snapper scales (CSSPs) were reported to possess excellent free radical scavenging activities in vitro. In present study, the anti-aging and anti-oxidative stress effects of CSSPs were evaluated in Drosophila melanogaster models. Results showed that the addition of CSSPs in the diets of normal Drosophila could effectively extend their lifespan and improve the motor ability of aged Drosophila. Moreover, CSSPs could protect Drosophila from oxidative damage induced by H₂O₂, paraquat and UV irradiation. The extension of lifespan was found to be associated with the effects of CSSPs in improving the antioxidant defense system of Drosophila, manifesting as the reduction of oxidation products MDA and PCO, the elevated activities of T-SOD, CAT and GSH-Px, and the upregulated expression of antioxidant related genes after CSSPs supplemented. Furthermore, CSSPs at 6 mg/mL significantly downregulated mTOR signaling pathway and activated autophagy in aged male Drosophila, and the inhibition on mTOR activation was probably mediated by the antioxidant effects of CSSPs. Our findings suggest that CSSPs have the potential in making dietary supplements against natural aging and oxidative stress in organisms.

A Walnut Diet in Combination with Enriched Environment Improves Cognitive Function and Affects Lipid Metabolites in Brain and Liver of Aged NMRI Mice

This in vivo study aimed to test if a diet enriched with 6% walnuts alone or in combination with physical activity supports healthy ageing by changing the oxylipin profile in brain and liver, improving motor function, cognition, and cerebral mitochondrial function. Female NMRI mice were fed a 6% walnut diet starting at an age of 12 months for 24 weeks. One group was additionally maintained in an enriched environment, one group without intervention served as control. After three months, one additional control group of young mice (3 weeks old) was introduced. Motor and cognitive functions were measured using Open Field, Y-Maze, Rotarod and Passive Avoidance tests. Lipid metabolite profiles were determined using RP-LC-ESI(-)-MS/MS in brain and liver tissues of mice. Cerebral mitochondrial function was characterized by the determination of ATP levels, mitochondrial membrane potential and mitochondrial respiration. Expression of genes involved with mito- and neurogenesis, inflammation, and synaptic plasticity were determined using qRT-PCR. A 6% walnut-enriched diet alone improved spatial memory in a Y-Maze alternation test (p < 0.05) in mice. Additional physical enrichment enhanced the significance, although the overall benefit was virtually identical. Instead, physical enrichment improved motor performance in a Rotarod experiment (p* < 0.05) which was unaffected by walnuts alone. Bioactive oxylipins like hydroxy-polyunsaturated fatty acids (OH-PUFA) derived from linoleic acid (LA) were significantly increased in brain (p** < 0.01) and liver (p*** < 0.0001) compared to control mice, while OH-PUFA of α-linolenic acid (ALA) could only be detected in the brains of mice fed with walnuts. In the brain, walnuts combined with physical activity reduced arachidonic acid (ARA)-based oxylipin levels (p < 0.05). Effects of walnut lipids were not linked to mitochondrial function, as ATP production, mitochondrial membrane potential and mitochondrial respiration were unaffected. Furthermore, common markers for synaptic plasticity and neuronal growth, key genes in the regulation of cytoprotective response to oxidative stress and neuronal growth were unaffected. Taken together, walnuts change the oxylipin profile in liver and brain, which could have beneficial effects for healthy ageing, an effect that can be further enhanced with an active lifestyle. Further studies may focus on specific nutrient lipids that potentially provide preventive effects in the brain.

Anti-Amnesic Effect of Walnut via the Regulation of BBB Function and Neuro-Inflammation in Aβ1-42-Induced Mice

This study was conducted to assess the protective effect of walnut (Juglans regia L.) extract on amyloid beta (Aβ)_1-42-induced institute of cancer research (ICR) mice. By conducting a Y-maze, passive avoidance, and Morris water maze tests with amyloidogenic mice, it was found that walnut extract ameliorated behavioral dysfunction and memory deficit. The walnut extract showed a protective effect on the antioxidant system and cholinergic system by regulating malondialdehyde (MDA) levels, superoxide dismutase (SOD) contents, reduced glutathione (GSH) contents, acetylcholine (ACh) levels, acetylcholinesterase (AChE) activity, and protein expression of AChE and choline acetyltransferase (ChAT). Furthermore, the walnut extract suppressed Aβ-induced abnormality of mitochondrial function by ameliorating reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and ATP contents. Finally, the walnut extract regulated the expression of zonula occludens-1 (ZO-1) and occludin concerned with blood–brain barrier (BBB) function, expression of tumor necrosis factor-alpha (TNF-α), tumor necrosis factor receptor 1 (TNFR1), phosphorylated c-Jun N-terminal kinase (p-JNK), phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor (p-IκB), cyclooxygenase-2 (COX-2), and interleukin 1 beta (IL-1β), related to neuroinflammation and the expression of phosphorylated protein kinase B (p-Akt), caspase-3, hyperphosphorylation of tau (p-tau), and heme oxygenase-1 (HO-1), associated with the Aβ-related Akt pathway.

Torularhodin from Sporidiobolus pararoseus Attenuates d-galactose/AlCl3-Induced Cognitive Impairment, Oxidative Stress, and Neuroinflammation via the Nrf2/NF-κB Pathway

Oxidative stress and neuroinflammation are considered as crucial culprits in Alzheimer's disease (AD). Torularhodin, a carotenoid pigment, possesses powerful antioxidant activity. This study aimed to elucidate the protective effects of torularhodin in the AD-like mouse model and investigated the underlying mechanisms. Behavioral and histopathological results suggested that torularhodin relieved cognitive impairments, attenuated Aβ accumulation, and inhibited glial overactivation in d-gal/AlCl₃-induced ICR mice. Simultaneously, torularhodin also markedly increased antioxidant enzyme capacities, lowered the contents of RAGE, and reduced levels of inflammatory cytokines. Western blot results showed that torularhodin ameliorated neuronal oxidative damage via activation of Nrf2 translocation, upregulation of HO-1, and inactivation of NF-κB in vivo and in vitro. Thus, torularhodin effectively ameliorated cognitive impairment, oxidative stress, and neuroinflammation, possibly through the Nrf2/NF-κB signaling pathways, suggesting torularhodin might offer a promising prevention strategy for neurodegenerative diseases.

Neuroprotection by Walnut-Derived Peptides through Autophagy Promotion via Akt/mTOR Signaling Pathway against Oxidative Stress in PC12 Cells

Natural-derived peptides are effective substances in attenuating oxidative stress. However, their specific mechanisms have not been fully elucidated, especially in peptide-mediated autophagy. In the present study, TWLPLPR, YVLLPSPK, and KVPPLLY, novel peptides from Juglans mandshurica Maxim, prevented reactive oxygen species (ROS) production, elevated glutathione peroxidase (GSH-Px) activity and adenosine 5'-triphosphate (ATP) levels, and ameliorated apoptosis in Aβ_25-35 (at a concentration of 50 μM for 24 h)-induced PC12 cells (P < 0.01). Both western blot and immunofluorescence analysis illustrated that the peptides regulated Akt/mTOR signaling through p-Akt (Ser473) and p-mTOR (S2481) and promoted autophagy by increasing the levels of LC3-II/LC3-I and Beclin-1 while lowering p62 expression (P < 0.01). The autophagy inhibitor (3-methyladenine, 3-MA) and inducer (rapamycin, RAPA) were combined used to confirm the contribution of peptide-regulated autophagy in antioxidative effects. Moreover, the peptides increased the levels of LAMP1, LAMP2, and Cathepsin D (P < 0.05) and promoted the fusion with lysosomes to form autolysosomes, accelerating ROS removal. These data suggested that walnut-derived peptides regulated oxidative stress by promoting autophagy in the Aβ_25-35-induced PC12 cells.

Bioactive Peptides from Walnut Residue Protein

Walnut residue is a kind of high-quality plant protein resource. The bioactive peptide prepared from walnut residue has excellent health care functions such as antioxidation and antihypertensive activity, but at present, walnut residue is often regarded as waste or low value feed, fertilizer and other materials. The uneconomical use of walnut residue has hindered the development of the walnut industry to some extent. Effective utilization of walnut residue protein to develop bioactive peptides and other products is of great significance to realize the comprehensive utilization of walnut residue, improve the added value of by-products, and change the current low utilization rate of walnut residue. In this paper, the preparation, purification and structure identification of walnut protein bioactive peptides are reviewed, and different functional walnut active peptides (WBPs) are introduced. The potential effects of these bioactivities on human health and their different uses in food, medicine and other industries are discussed. The purpose is to provide reference information for the effective utilization of walnut residue resources and the development of walnut industry.

Evaluation and structure-activity relationship analysis of antioxidant shrimp peptides

The effects of amino acids Gln and Lys on the antioxidant ability of peptides were investigated in this study. The identified peptides Lys-Met-Asp-Asp-Lys (KMDDK), Lys-Met-Asp-Asp-Gln (KMDDQ), Gln-Met-Asp-Asp-Lys (QMDDK), and Gln-Met-Asp-Asp-Gln (QMDDQ) were used to investigate their antioxidant activity and the structure-activity relationship by using UPLC-Q-TOF-MS, flow cytometry, laser scanning confocal microscopy and ¹H NMR spectroscopy. The results indicated that the four pentapeptides significantly increased the viability of PC12 cells and inhibited cell apoptosis and that QMDDQ possessed a stronger survival activity than the others in cell apoptosis. Moreover, the four peptides significantly decreased the scopolamine-induced ROS and LDH content in PC12 cells, and upregulated the SOD activity to the level of the scopolamine group. The DPPH and hydroxyl radical scavenging of QMDDQ were higher than those of the other peptides at 0.5 mg mL^-1 and 1.0 mg mL^-1 (P < 0.05). ¹H NMR spectra revealed that the prominent antioxidant ability of QMDDQ might be attributed to more active hydrogen sites and functional groups. The carboxyl active hydrogen atoms and amino active hydrogen atoms as active sites play a critical role in the antioxidant capacity.

Potential mechanisms mediating the protective effects of a peptide from walnut (Juglans mandshuricaMaxim.) against hydrogen peroxide induced neurotoxicity in PC12 cells

A novel neuroprotective peptide EVSGPGLSPN, which was identified from walnut protein hydrolysates, protected PC12 cells by blocking the NF-κB/caspase pathways.

Walnut protein isolates attenuate particulate matter-induced lung and cardiac injury in mice and zebra fish

Air pollution is an increasingly serious problem, and the fine particles of air pollution can cause diseases of the respiratory, cardiovascular, and immune systems. Walnut protein isolates (WPIs) are peptides purified from walnut protein hydrolysates that have very high antioxidant and 1,1-diphenyl-2-picrylhydrazyl radical 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH) scavenging activities. In this study, mice and zebra fish were used to test the effect of WPIs on the acute lung injury (ALI) and heart injury induced by particulate matter (PM). The WPIs protected against ALI in the PM-induced ALI mouse model by inhibiting myeloperoxidase (MPO), nitric oxide (NO), interleukin 1β(IL-1β), and interleukin 6(IL-6) in ALI mouse bronchoalveolar lavage fluid (BALF) and pro-inflammatory cytokine production and acyl carrier protein (ACP) level. In the zebra fish model, the WPIs promoted the secretion of PM into the intestinal tract, protected against the heart injury caused by PM, and promoted the phagocytosis of zebra fish macrophages. Therefore, WPIs are potential candidates to be a health-promoting product with no toxicity.

This study supports new prospects for WPI development and shows WPIs may be potential candidates for healthy products.

Walnut ( Juglans regia) Peptides Reverse Sleep Deprivation-Induced Memory Impairment in Rat via Alleviating Oxidative Stress

The aim of this study was to determine the neuroprotective effects of walnut protein hydrolysates (WPH) against memory deficits induced by sleep deprivation (SD) in rat and further to identify and characterize the potent neuroprotective peptides against glutamate-induced apoptosis in PC12 cells. Results showed that a remarkable amelioration effect on behavioral performance in Morris water maze test was observed for WPH and its low molecular weight fraction WPHL, especially for WPHL. Additionally, a reduction of antioxidant defense (catalase, glutathione peroxidase (GSH-px), and superoxide dismutase (SOD)) and an increase of malondialdehyde content induced by SD were normalized in brain of rat after oral administration of WPH and WPHL. Then three neuroprotective peptides including GGW, VYY, and LLPF were identified from WPHL, which could protect PC12 cells against glutamate-induced apoptosis with relative cell viability of 78.29 ± 3.09%, 80.65 ± 1.74%, and 83.97 ± 3.06%, respectively, versus glutamate group 48.61 ± 3.99%. The possible mechanism underlying their protective effects of GGW and VYY could be related to their strong radical scavenging activity as well as their ability to reduce reactive oxygen species production and the depletion of SOD and GSH-px in PC12 cells. Notably, the marked neuroprotective effects of LLPF, which did not show obvious free-radical scavenging activity in vitro, could be attributed to its strong effects on inhibiting Ca²⁺ influx and mitochondrial membrane potential collapse. Additionally, all these peptides could regulate the expression of apoptosis-related proteins (Bax and Bcl-2). Therefore, walnut peptides might be regarded as the potential nutraceuticals against neurodegenerative disorders associated with memory deficits.