Identification of antioxidant peptides released from defatted walnut (Juglans Sigillata Dode) meal proteins with pancreatin

Protective role of hazelnut peptides on oxidative stress injury in human umbilical vein endothelial cells

The crude protein hydrolysates of wild hazel have good immunoregulation and antioxidation effects. However, the components responsible for their antioxidation effect remain unknown. In this study, six antioxidative peptides (EW, DWDPK, ADGF, SGAF, ETTL, and AGGF) were tested for their protective effects on oxidative stress injury in human umbilical vein endothelial cells (HUVECs). The results demonstrated that the six peptides are nontoxic and have a protective effect on oxidative stress injury induced by Ang II. Three peptides (EW, ADGF, and DWDPK) inhibited the morphological changes, downregulated the content of lactate dehydrogenase and malondialdehyde, upregulated the activity of antioxidant enzymes catalase, total superoxide dismutase and glutathione peroxidase, and scavenged reactive oxygen species (ROS) in HUVECs. Quantitative reverse transcriptive polymerase chain reaction and western blot assays indicated that these three peptides regulated NADPH oxidase activity and ROS production by reducing NOX4 and p22phox levels. Overall, they have a significant protective effect against oxidative stress injury and have potential application in developing new functional foods. PRACTICAL APPLICATIONS: Corylus heterophylla Fisch is a good quality wild hazel distributed in Northeast China. Wild hazelnut of the species C. heterophylla Fisch was selected as experimental object and has high nutritive values and have abundant proteins (20%-30%), fats (40%-50%), carbohydrates (13%-24%), dietary fibers (8.2%-9.6%), vitamins, and micronutrients. Our results indicate that hazelnut peptides (EW, ADGF, and DWDPK) can ensure normal growth of cells by protecting important antioxidant enzyme systems, by enhancing antioxidant defense, by directly affecting nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, and by reducing intracellular reactive oxygen species (ROS) production in HUVECs, indicating that the three antioxidative peptides have a protective effect against Ang II-induced oxidative stress injury. Therefore, the antioxidative peptides from C. heterophylla Fisch may be a promising candidate for functional food ingredients and/or pharmaceuticals.

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

BACKGROUND

Walnut protein, which is obtained as a by-product of oil expression, has not been used efficiently. Although walnuts are beneficial for cognitive functioning, the potential of their protein composition in strengthening learning and memory functions remains unknown. In this study, the inhibition of memory impairment by the Manchurian walnut hydrolyzed peptide (MWHP) was evaluated.

RESULTS

Small-molecular-weight MWHP (<3 kDa) achieved the optimal antioxidative activity. Therefore, MWHP (<3 kDa) was subjected to the following mice trials to evaluate its attenuation effect on memory impairment. In the Morris water maze test, MWHP shortened the total path for searching the platform, reduced the escape latency, and increased the dwelling distance and time in the coverage zone. MWHP also prolonged the latency and diminished errors in the passive avoidance response tests. These behavioral tests demonstrated that MWHP could inhibit scopolamine-induced memory impairment. MWHP improved memory by reducing oxidative stress, inhibiting apoptosis, regulating neurotransmitter functions, maintaining hippocampal CA3 pyramidal neurons, and increasing calmodulin-dependent protein kinase II levels in brain tissues.

CONCLUSION

Experimental results proved that MWHP exhibits potential in improving memory and should be used to develop novel functional food. © 2018 Society of Chemical Industry.

Walnut Protein Hydrolysates Play a Protective Role on Neurotoxicity Induced by d-Galactose and Aluminum Chloride in Mice

In recent years, with an increase in the aging population, neurodegenerative diseases have attracted more and more attention. This study aimed to investigate the potential neuroprotective effect of defatted walnut meal protein hydrolysates (DWMPH) on neurotoxicity induced by d-galactose (d-gal) and aluminum chloride (AlCl₃) in mice. The animal models were established by combining treatments with d-gal (200 mg/kg/day, subcutaneously) and AlCl₃ (100 mg/kg in drinking water) for 90 days. During the 90 days, 1 g/kg of DWMPH was administrated orally every day. The results indicated that DWMPH treatment alleviated oxidative stress, reversed cholinergic dysfunction, and suppressed the release of proinflammatory cytokines in the brains of d-gal + AlCl₃-treated mice, and thus improving the learning and memory functions of these mice, which was closely correlated with the strong antioxidant activity of DWMPH. This finding suggests that DWMPH might be a promising dietary supplement in improving neuronal dysfunctions of the brain.

Almond, hazelnut and walnut, three nuts for neuroprotection in Alzheimer's disease: A neuropharmacological review of their bioactive constituents

An increase in the prevalence of Alzheimer's disease (AD) as a multifactorial neurodegenerative disorder is an almost obvious issue in the world. Researches on natural products for finding effective drugs to prevent the disease are in progress. There is special attention to the three types of nuts including almond, hazelnut and walnut in manuscripts of traditional Persian medicine (PM) as the preventive agents against brainatrophy and memory loss. The purpose of this study is a pharmacological review of their bioactive constituents and introducing the value of these nuts as the effective supplements and natural medicinal foods in AD patients. Databases including PubMed and ScienceDirect were searched in title, abstract and keywords from year 2000 to present for AD-related researches on these tree nuts, their major phytochemicals and their mechanisms of action. As result, almond, hazelnut and walnut provide macronutrients, micronutrients, and phytochemicals which affect several pathways in AD pathogenesis such as amyloidogenesis, tau phosphorylation, oxidative stress, cholinergic pathways, and some non-target mechanisms including cholesterol lowering and anti-inflammatory properties, as well as effect on neurogenesis. These nuts are recommended in PM for their brain-protective activity and particularly reversing brain atrophy in case of hazelnut. The therapeutical statements of PM scholars mentioned in their books are based on their clinical observations with support of a long history of experiences. Beyond the molecular activities attributed to the phytochemicals, the use of these tree nuts could be more considered in scientific researches as the effective nutrients for prevention or even management of AD.

Antiproliferative Activity of Walnut (Juglans regia L.) Proteins and Walnut Protein Hydrolysates

Proteins from Juglans regia L. were isolated. Then, proteins were hydrolyzed with different enzymes. Antiproliferative activity of proteins and of the protein hydrolysates of J. regia L. were evaluated using the sulforhodamine B method. Glutelin and prolamin proteins presented a high antiproliferative activity against cancer cells PC-3 (prostate) and K-562 (leukemia) with values of 43.9 and 84.4 μg/mL, respectively. The highest inhibitory effect observed was 50% at 0.25 μg/mL concentration in gastrointestinal digestion with pepsin and corolase pp in a dose-dependent manner against cancer cell UACC62 (melanoma). Pepsin hydrolysate showed inhibitory effects against cancer cell UACC62 (melanoma) with a concentration of 71.0 μg/mL. The effects were studied in a dose-dependent manner. The hydrolysate obtained with neutrase enzyme presented inhibitory effects against cancer cell UACC62 (melanoma) at a concentration of 25 μg/mL. Neither proteins nor protein hydrolysates presented cytotoxicity against normal cell assay VERO (epithelial).

Antioxidant and Anticancer Activities of Walnut (Juglans regia L.) Protein Hydrolysates Using Different Proteases

Walnut (Juglans regia L.) contains approximately 20-25 % protein with abundant essential amino acids. The enzymatic hydrolysate of Persian walnut (Chandler) seed proteins was prepared by incubation with three different proteases, including pancreatic chymotrypsin and trypsin, and a microbial enzyme proteinase K. The hydrolysates were found to possess excellent antioxidant capacities. The peptide fractions scavenged the 2, 2'-anizo-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radicals and inhibited the activity of reactive oxygen species. Walnut protein hydrolysates were also tested, for the first time, against the viability of human breast (MDA-MB231) and colon (HT-29) cancer cell lines. MTT, [3-(4, 5dimethylthiazolyl)-2,5-diphenyl-tetrazolium bromide], assay was used to assess in vitro cancer cell viability upon treatment with the peptide fractions. The peptide fractions showed cell growth inhibition of 63 ± 1.73 % for breast cancer and 51 ± 1.45 % for colon cancer cells. Thus, a direct correlation between antioxidant and anticancer activities of walnut peptide fractions exists and supports their potential therapeutic benefit.

Physico-chemical properties, antioxidant activities and antihypertensive effects of walnut protein and its hydrolysate

BACKGROUND

Some food proteins hydrolysates are found to possess multiple health effects. In this study, walnut protein (WP) was enzymatically hydrolysed by alcalase and trypsin under optimal conditions. The physico-chemical properties, antioxidant and angiotensin-converting enzyme (ACE) inhibitory activities of WP, alcalase-generated walnut protein hydrolysate (AWPH) and trypsin-generated walnut protein hydrolysate (TWPH) were comparatively studied. Stability properties of the walnut protein hydrolysate (WPH) and the antihypertensive activity in spontaneously hypertensive rats (SHRs) were also investigated.

RESULTS

The WPH showed higher physico-chemical properties, antioxidant activities, ACE inhibitory activity and stability against thermal treatment and gastrointestinal digestion than WP. The results of antihypertensive effects in SHRs showed that the most potent decrease of AWPH and TWPH in the systolic blood pressure occurred at 4 h (-26 mmHg) and 6 h (-30 mmHg) after administration. The study indicated that the WPH could significantly decrease the systolic blood pressure (P < 0.05).

CONCLUSION

The WPH exhibited high physico-chemical properties, potent inhibitory activities and high stability. TWPH was more effective than AWPH in the detected properties. The results would be helpful for the comprehensive utilisation of the walnut resources. © 2015 Society of Chemical Industry.

Neuroprotective effect of peptides extracted from walnut (Juglans Sigilata Dode) proteins on Aβ25-35-induced memory impairment in mice

Alzheimer's disease (AD) is one of the major neurodegenerative disorders of the elderly, which is characterized by the accumulation and deposition of amyloid-beta (Aβ) peptide in human brains. Oxidative stress and neuroinflammation induced by Aβ in brain are increasingly considered to be responsible for the pathogenesis of AD. The present study aimed to determine the protective effects of walnut peptides against the neurotoxicity induced by Aβ25-35 in vivo. Briefly, the AD model was induced by injecting Aβ25-35 into bilateral hippocampi of mice. The animals were treated with distilled water or walnut peptides (200, 400 and 800 mg/kg, p.o.) for five consecutive weeks. Spatial learning and memory abilities of mice were investigated by Morris water maze test and step-down avoidance test. To further explore the underlying mechanisms of the neuroprotectivity of walnut peptides, the activities of superoxide dismutase (SOD), glutathione (GSH), acetylcholine esterase (AChE), and the content of malondialdehyde (MDA) as well as the level of nitric oxide (NO) in the hippocampus of mice were measured by spectrophotometric method. In addition, the levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β) and IL-6 in the samples were determined using ELISA. The hippocampal expressions of inducible nitric oxide synthase (iNOS) and nuclear factor κB (NF-κB) were evaluated by Western blot analysis. The results showed that walnut peptides supplementation effectively ameliorated the cognitive deficits and memory impairment of mice. Meanwhile, our study also revealed effective restoration of levels of antioxidant enzymes as well as inflammatory mediators with supplementation of walnut peptides (400 or 800 mg/kg). All the above findings suggested that walnut peptides may have a protective effect on AD by reducing inflammatory responses and modulating antioxidant system.

Isolation of a novel bio-peptide from walnut residual protein inducing apoptosis and autophagy on cancer cells

Background

Walnut is unique because they have a perfect balance of n-6 and n-3 polyunsaturated fatty acids. The increasing market demand of walnut lipids results in the large amount of the oil extraction residue. The walnut residue is rich in nutritional proteins, and the uneconomic use of the by-product discouraged the development of walnut industry. Anticancer peptides have recently received attention as alternative chemotherapeutic agents that overcome the limits of current drugs. The aim of this study was to investigate whether anticancer bioactive peptide is contained in walnut.

Methods

Walnut residual protein was hydrolyzed separately by five different proteases. The sequential purification of the hydrolysates was carried out by ultra-filtration, gel filtration chromatography and RP-HPLC to obtain a cancer cell growth inhibitory peptide. Cell cycle distribution, Annexin V-FITC/PI double staining, TUNEL assay, western blot and immunofluorescence for LC3-II assay were used to detect apoptosis and autophagy on cells. Cytokine production was measured by ELISA kits, macrophage phagocytosis was measured by neutral red uptake assay, nitric oxide production was measured by Griess reagent.

Results

The hydrolysates of walnut residual protein produced by papain under the optimal conditions (5 % substrate concentration and an enzyme-substrate ratio of 10 % at temperature 60 C for 3 h), showed significant growth inhibitory activity on MCF-7. The amino acid sequence of the purified peptide was identified as CTLEW with a molecular weight of 651.2795 Da. It is a novel bio-peptide with an amphiphilic structure. CTLEW induced both apoptosis and autophagy on MCF-7 cells, inhibited the cancer cells growth of Caco-2 and HeLa significantly, but did not show any cytotoxic activity against non-cancerous IEC-6 cells. Moreover, the bio-peptide enhanced proliferation and IL-2 secretion of spleen lymphocytes, promoted phagocytosis and NO production of macrophages.

Conclusion

These results suggested that a novel bio-peptide, CTLEW inducing apoptosis and autophagy on MCF-7 cells can be released from walnut residual protein through papain hydrolyzing under the certain condition. The bio-peptide shows selective inhibition towards cancer cells growth and immunomodulatory activity.

Biologically active peptides: Processes for their generation, purification and identification and applications as natural additives in the food and pharmaceutical industries

Recent technological advances have created great interest in the use of biologically active peptides. Bioactive peptides can be defined as specific portions of proteins with 2 to 20 amino acids that have desirable biological activities, including antioxidant, anti-hypertensive, antithrombotic, anti-adipogenic, antimicrobial and anti-inflammatory effects. Specific characteristics, including low toxicity and high specificity, make these molecules of particular interest to the food and pharmaceutical industries. This review focuses on the production of bioactive peptides, with special emphasis on fermentation and enzymatic hydrolysis. The combination of different technologies and the use of auxiliary processes are also addressed. A survey of isolation, purification and peptide characterization methods was conducted to identify the major techniques used to determine the structures of bioactive peptides. Finally, the antioxidant, antimicrobial, anti-hypertensive, anti-adipogenic activities and probiotic-bacterial growth-promoting aspects of various peptides are discussed.