Antioxidant activities of the synthesized thiol-contained peptides derived from computer-aided pepsin hydrolysis of yam tuber storage protein, dioscorin

Preparation, bioactivities, and food industry applications of tuber and tuberous roots peptides: A review

Tuber and tuberous roots proteins are important sources for producing bioactive peptides. The objective of this review is to present the current research status of tubers and tuberous roots bioactive peptides (TTRBP), including its preparation methods, purification techniques, structure identification approaches, biological functions, and applications in the food industry. Moreover, the current challenges and future development trends of TTRBP are elucidated. Currently, TTRBP are mainly produced by enzymatic hydrolysis and fermentation. Pretreatment like high static pressure, ultrasound and microwave can assist enzymatic hydrolysis and facilitate TTRBP production. In addition, TTRBP are structurally diverse, which is related to the molecular weight, amino acids composition, and linkage mode. Accordingly, they have various biological activities (such as antioxidant, antihypertensive, hypoglycemic) and have been utilized in the food industry as functional ingredients and food additives. This review will provide valuable insights for the optimal utilization of tuber and tuberous roots.

Extracts and Scirpusin B from Recycled Seeds and Rinds of Passion Fruits (Passiflora edulis var. Tainung No. 1) Exhibit Improved Functions in Scopolamine-Induced Impaired-Memory ICR Mice

In this paper, the seeds and rinds of passion fruit, which are the agricultural waste of juice processing, were recycled to investigate their biological activities for sustainable use. De-oiled seed powders (S) were successively extracted by refluxing 95% ethanol (95E), 50E, and hot water (HW), respectively, to obtain S-95EE, S-50EE, and S-HWE. Dried rind powders were successively extracted by refluxing HW and 95E to obtain rind-HWE and rind-95EE, respectively. S-50EE and S-95EE showed the most potent extracts, such as anti-amyloid-β1-42 aggregations and anti-acetylcholinesterase inhibitors, and they exhibited neuroprotective activities against amyloid-β25-35-treated or H2O2-treated SH-SY5Y cells. Scirpusin B and piceatannol were identified in S-95EE, S-50EE, and rind-HWE, and they showed anti-acetylcholinesterase activity at 50% inhibitory concentrations of 62.9 and 258.9 μM, respectively. Daily pretreatments of de-oiled seed powders and rind-HWE (600 mg/kg), S-95EE, and S-50EE (250 mg/kg) or scirpusin B (40 mg/kg) for 7 days resulted in improved learning behavior in passive avoidance tests and had significant differences (p < 0.05) compared with those of the control in scopolamine-induced ICR mice. The seeds and rinds of passion fruit will be recycled as materials for the development of functional foods, promoting neuroprotection and delaying the onset of cognitive dysfunctions.

Vitisin A, a Resveratrol Tetramer, Improves Scopolamine-Induced Impaired Learning and Memory Functions in Amnesiac ICR Mice

Resveratrol has been reported to exhibit neuroprotective activities in vitro and in vivo. However, little is known about resveratrol tetramers of hopeaphenol, vitisin A, and vitisin B with the same molecular mass in the improvement of degenerative disorders. In this study, two 95% ethanol extracts (95EE) from stem parts of Vitis thunbergii Sieb. & Zucc. (VT-95EE) and from the root (R) parts of Vitis thunbergii var. taiwaniana (VTT-R-95EE) showed comparable acetylcholinesterase (AChE) inhibitory activities. It was found that VT-95EE and VTT-R-95EE showed different distribution patterns of identified resveratrol and resveratrol tetramers of hopeaphenol, vitisin A, and vitisin B based on the analyses of HPLC chromatographic profiles. The hopeaphenol, vitisin A, and vitisin B, showed AChE and monoamine oxidase-B inhibitions in a dose-dependent manner, among which vitisin B and vitisin A exhibited much better activities than those of resveratrol, and had neuroprotective activities against methylglyoxal-induced SH-SY5Y cell deaths. The scopolamine-induced amnesiac ICR mice treated with VT-95EE and its ethyl acetate-partitioned fraction (VT-95EE-EA) at doses of 200 and 400 mg/kg, or vitisin A at a dose of 40 mg/kg, but not vitisin B (40 mg/kg), were shown significantly to improve the impaired learning behaviors by passive avoidance tests compared to those in the control without drug treatments (p < 0.05). Compared to mice in the control group, the brain extracts in the vitisin A-treated mice or donepezil-treated mice showed significant reductions in AChE activities and malondialdehyde levels (p < 0.05), and elevated the reduced protein expressions of brain-derived neurotrophic factor (BDNF) and BDNF receptor, tropomyosin receptor kinase B (TrkB). These results revealed that vitisin A was the active constituent in the VT-95EE and VTT-95EE, and the VT medicinal plant and that the endemic variety of VTT has potential in developing functional foods for an unmet medical need for neurodegenerative disorders.

TL15 of Arthrospira platensis sulfite reductase scavenges free radicals demonstrated in oxidant induced larval zebrafish (Danio rerio) model

The antioxidant role of sulfite reductase (SiR) derived from Arthrospira platensis (Ap) was identified through a short peptide, TL15. The study showed that the expression of ApSiR was highly expressed on day ten due to sulfur deprived stress in Ap culture. TL15 peptide exhibited strong antioxidant activity when evaluated using antioxidant assays in a concentration ranging from 7.8 and 125 μM. Further, the cytotoxicity of TL15 peptide was investigated, even at the higher concentration (250 μM), TL15 did not exhibit any toxicity, when tested in vitro using human leucocytes. Moreover, a potential reduction in reactive oxygen species (ROS) production was observed due to the treatment of TL15 peptide (>15.6 μM) to H₂O₂ exposed leucocytes. For the in vivo assessment of TL15 toxicity and antioxidant ability, experiments were performed in zebrafish (Danio rerio) larvae to analyse the developmental toxicity of TL15 peptide. Results showed that, exposure to TL15 peptide in tested concentrations ranging from 10, 20, 40, and 80 μM, did not affect the development and physiological parameters of the zebrafish embryo/larvae such as morphology, survival, hatching and heart rate. Fluorescent assay was performed using DCFH-DA (2,7-dichlorodihydrofluorescein diacetate) to examine the production of intracellular reactive oxygen species (ROS) in zebrafish treated with TL15 peptide during the embryo-larval stages. Fluorescent images showed that pre-treatment with TL15 peptide to attenuate the H₂O₂ induced ROS levels in the zebrafish larvae in a dose-dependent manner. Further to uncover the underlying biochemical and antioxidant mechanism, the enzyme activity of superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation (LPO) levels were studied in zebrafish larvae. TL15 pre-treated groups showed enhanced antioxidant enzyme activity, while the hydrogen peroxide (H₂O₂) exposed larvae showed significantly diminished activity. Overall results from the study revealed that, TL15 act as a potential antioxidant molecule with dose-specific antioxidant property. Thus, TL15 peptide could be an effective and promising source for biopharmaceutical applications.

Recovery and identification bioactive peptides from protein isolate of Spirulina platensis and their in vitro effectiveness against oxidative stress-induced erythrocyte hemolysis

BACKGROUND

Spirulina platensis is recognized as one of the most nutritious foods, containing a high protein content of up to 70%. Meanwhile, he interest in using natural protein resources to develop bioactive peptides is steadily increasing. Therefore, this study released the bioactive peptides from S. platensis by enzymatic hydrolysis using pepsin (1:3000 U g^-1 ), and their amino acid sequences were determined by de novo sequencing. On this basis, the antioxidant activities of synthesized bioactive peptides were comprehensively evaluated by 2,2'-azinobis-3-ethylbenzothiazolin-6-sulfonic acid assay, 1,1-diphenyl-2-picryhydrazyl assay, and cell hemolysis assay induced by 2,2'-azobis-(2-amidino-propane) dihydrochloride (AAPH).

RESULTS

The degree of hydrolysis and recovery percentage of pepsin hydrolysis were 172 and 825 g kg^-1 respectively, and FFEFF (P1: m/z 736.4, 8%), EYFDALA (P2: m/z 828.4, relative intensity 18.5%), and VTAPAASVAL (P3: m/z 899.5, relative intensity 17.3%) were purified and identified. P2 possessed an excellent radical scavenging activity compared with P1, P3, and vitamin C, which was contributed to by its high β-sheet conformation and specific amino acid compositions. Moreover, P2 significantly attenuated AAPH-induced oxidative hemolysis of erythrocytes and protected the erythrocytes, because it reduced the formation of malondialdehyde and increased the enzyme activities of superoxide dismutase, catalase, and glutathione peroxidase in erythrocytes.

CONCLUSION

This study provided insights into the potential antioxidant function of the synthesized peptides originated from the bioactive peptides of S. platensis proteins, which would contribute to the development of natural antioxidant from new protein resources. © 2020 Society of Chemical Industry.

Grown to be Blue-Antioxidant Properties and Health Effects of Colored Vegetables. Part I: Root Vegetables

During the last few decades, the food and beverage industry faced increasing demand for the design of new functional food products free of synthetic compounds and artificial additives. Anthocyanins are widely used as natural colorants in various food products to replenish blue color losses during processing and to add blue color to colorless products, while other compounds such as carotenoids and betalains are considered as good sources of other shades. Root vegetables are well known for their broad palette of colors, and some species, such as black carrot and beet root, are already widely used as sources of natural colorants in the food and drug industry. Ongoing research aims at identifying alternative vegetable sources with diverse functional and structural features imparting beneficial effects onto human health. The current review provides a systematic description of colored root vegetables based on their belowground edible parts, and it highlights species and/or cultivars that present atypical colors, especially those containing pigment compounds responsible for hues of blue color. Finally, the main health effects and antioxidant properties associated with the presence of coloring compounds are presented, as well as the effects that processing treatments may have on chemical composition and coloring compounds in particular.

Research and Development of Proteins and Peptides with Therapeutic Potential from Yam Tubers

We discuss the diverse biological activities, therapeutic potential, and clinical applications of peptides and proteins isolated from various yams species including Dioscorea opposita Thunb (Chinese yam), D alata, D japonica (Japanese yam), D pseudojaponica, D batatas (Korea yam), and D cayenensis. Yam peptides and proteins have many pharmacological activities including immunomodulatory, antioxidant, estrogen-stimulating, osteogenic, angiotensin I-converting enzyme inhibiting, carbonic anhydrase and trypsin inhibiting, chitinase, anti-insect, anti-dust mite, lectin, and anti-proliferative activities. Yam peptides and proteins have therapeutic potential for treating cardiovascular diseases, inflammatory diseases, cancers, aging disorders, menopause, and osteoporosis.

Anti-glycation, anti-hemolysis, and ORAC activities of demethylcurcumin and tetrahydroxycurcumin in vitro and reductions of oxidative stress in D-galactose-induced BALB/c mice in vivo

BACKGROUND

There were few report concerning anti-glycation and antioxidant activities of the minor amounts of components in curcuminoids, demethylcurcumin and tetrahydroxycurcumin, in vitro and in vivo.

RESULTS

The bovine serum albumin/galactose of non-enzymatic glycation models, radical-induced hemolysis, and oxygen radical absorbance capacity (ORAC) were studied in vitro, and the D-galactose-induced oxidative stress in BALB/c mice and then demethylcurcumin or tetrahydroxycurcumin interventions in vivo. The parameters of oxidative stress in plasma and brain extracts were determined among animal groups with or without both curcuminoids interventions. The demethylcurcumin and tetrahydroxycurcumin exhibited anti-glycation, anti-hemolysis, and ORAC activities, and showed much better and significant difference (P < 0.05) compared to those of curcumin in vitro. In animal experiments, the intervened two curcuminoids at both concentrations showed to lower serum malondialdehyde (MDA), brain MDA levels and iNOS protein expressions, and elevate serum ORAC activities, and showed difference (P < 0.05) compared to the galactose-induced control.

CONCLUSION

The demethylcurcumin and tetrahydroxycurcumin showed potentials in developing functional foods for antioxidant-related purposes.

Design and characterization of a novel Arthrospira platensis glutathione oxido-reductase-derived antioxidant peptide GM15 and its potent anti-cancer activity via caspase-9 mediated apoptosis in oral cancer cells

Glutathione oxido-reductase (GR) is a primary antioxidant enzyme of most living forms which protects the cells from oxidative metabolism by reducing glutathione (GSH) from its oxidized form (GSSG). Although the antioxidant role of the enzyme is well characterized, the specific role of conserved N' peptide sequence in antioxidant mechanism remains unclear. In this study, we have identified an RNA sequence encoding GR enzyme from spirulina, Arthrospira platensis (Ap) and the changes in its gene expression profile was analysed during H₂O₂ stress. Results showed that H₂O₂ (10 mM) stimulated the expression of ApGR throughout the timeline of study (0, 5, 10, 15 and 20 days) with highest expression at 5^th day post-exposure which confirmed the antioxidant role of ApGR in spirulina during H₂O₂ induced oxidative stress. A dithiol containing short antioxidant peptide, ³⁹GGTCVIRGCVPKKLM⁵³ (GM15) from ApGR was predicted and its radicals (superoxide and hydroxyl radical) scavenging potential was confirmed by in vitro cell-free assays. GM15 (12.5 μM) reduced the intracellular generalized oxidative stress level, as measured using DCFDA assay in H₂O₂ exposed leucocytes without affecting any of the cellular population. Further, the biomedical application of the radical scavenging property of GM15 was validated in oral carcinoma (KB) cells where GM15 exhibited significant cytotoxicity. Also, GM15 exhibited heterogenous effects on intracellular oxidative stress level in KB cells: at lower concentration (6.25 μM), the peptide reduced oxidative stress whereas, at higher concentration (25 μM) it increased the intensity of oxidative stress. GM15 (25 μM) induced caspase-9 mediated apoptosis in KB cells along with membrane disruption and DNA degradation which are confirmed by propidium iodide (PI) internalization and comet assays, respectively. Overall, the study shows that GM15 peptide i) scavenges superoxide, hydroxyl radicals, and influences intracellular oxidative stress, and ii) has anti-cancer effect in oral cancer cells.

Selective Extraction and Antioxidant Properties of Thiol-Containing Peptides in Soy Glycinine Hydrolysates

A highly selective procedure to extract thiol-containing peptides (TCPs) from complicated soy glycinin hydrolysates (SGHs) was described. This procedure included the reduction of disulfide bonds by 1,4-dithiothreitol (DTT) and enrichment of TCPs through Thiopropyl-Sephrose 6B covalent chromatography. TCPs were confirmed using a strategy based on mass shift after differential alkylation of sulfhydryl groups with iodoacetamide and N-ethylmaleimide by matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS). The antioxidant activities of TCPs were evaluated using chemical assays. DTT reduction increased the concentration of sulfhydryl groups from 1.8 μmol/g to 113.8 μmol/g. The efficiency of the extraction was improved by optimizing the loading of sample, extraction and desorption time and the content of desorption reagent. Both of the adsorption and desorption process were found to fit a pseudo-second order model. MALDI-TOF-MS showed that 36 of the 45 extracted peptides were TCPs. The EC50 of TCPs for DPPH, hydroxyl radical, and superoxide anion radical was 0.1, 1.49 and 0.084 mg/mL, respectively. The reducing power of TCPs (0.2 mg/mL) was of 0.375. These results suggest that the combination of DTT reduction and Thiopropyl-Sepharose 6B covalent chromatograph was a successful pathway to extract TCPs from SGHs and the TCPs could be used as potential antioxidants.

135-Day Interventions of Yam Dioscorin and the Dipeptide Asn-Trp (NW) To Reduce Weight Gains and Improve Impaired Glucose Tolerances in High-Fat Diet-Induced C57BL/6 Mice

The C57BL/6J mice were fed a 135-day normal diet or a high-fat diet (HFD) without, or concurrent with, a single yam dioscorin (80 mg/kg) or dipeptide NW (40 mg/kg) intervention every day. The final body weights (g) of mice were 26.1 ± 1.4, 34.97 ± 2.1, 31.75 ± 2.6, and 31.66 ± 3.1, respectively, for normal diet-fed, HFD-fed, dioscorin-intervened, and NW-intervened group. The mice in both intervened groups showed similar less weight gains and had significant differences (P < 0.05) compared to those in the HFD group under the same cumulative HFD intakes. The blood biochemical index of mice with dioscorin interventions showed significantly lower contents in total cholesterol and low-density lipoprotein, and NW interventions showed significantly lower total triglyceride contents compared to those of the HFD group (P < 0.05). Both intervened mice exhibited similar reductions in total visceral lipid contents and have significant differences compared to those of the HFD group (P < 0.05). The dioscorin intervention was better than NW interventions in lowering blood glucose levels by oral glucose tolerance tests and both showed significant differences (P < 0.05) compared to those in the HFD group. Yam dioscorin or dipeptide NW will potentially be used for preventive functional foods of less body weight gains and impaired glucose tolerance controls, which require further clinical trial investigations.

Synthesized Peptides from Yam Dioscorin Hydrolysis in Silico Exhibit Dipeptidyl Peptidase-IV Inhibitory Activities and Oral Glucose Tolerance Improvements in Normal Mice

RRDY, RL, and DPF were the top 3 of 21 peptides for inhibitions against dipeptidyl peptidase-IV (DPP-IV) from the pepsin hydrolysis of yam dioscorin in silico and were further investigated in a proof-of-concept study in normal ICR mice for regulating glucose metabolism by the oral glucose tolerance test (OGTT). The sample or sitagliptin (positive control) was orally administered by a feeding gauge; 30 min later, the glucose loads (2.5 g/kg) were performed. RRDY, yam dioscorin, or sitagliptin preload, but not DPF, lowered the area under the curve (AUC0-120) of blood glucose and DPP-IV activity and elevated the AUC0-120 of blood insulin, which showed significant differences compared to control (P < 0.05 or 0.001). These results suggested that RRDY and yam dioscorin might be beneficial in glycemic control in normal mice and need further investigations in diabetic animal models.

Analysis of the quantitative structure–activity relationship of glutathione-derived peptides based on different free radical scavenging systems

In the present study, eleven glutathione-derived peptides, including Glu-Cys-His, Pro-Leu-Gly, Pro-Cys-Gly, Phe-Lys-Leu, Leu-His-Gly, Lys-Leu-Glu, Lys-Val-His, Tyr-Glu-Gly, Tyr-His-Leu, Gly-Glu-Leu and Gly-Pro-Glu, were designed.

Effects of yam dioscorin interventions on improvements of the metabolic syndrome in high-fat diet-induced obese rats

BACKGROUND

The metabolic syndrome (MS) is termed a cluster of multiple metabolic risk criteria which is positively correlated with cardiovascular disease and type 2 diabetes mellitus (DM). Yam dioscorins have been reported to exhibit biological activities, however, little is known their preventive effects on the MS. Therefore, a high-fat (HF) diet was used to induce Wistar rat obesity and then yam dioscorin (50 mg/kg, dio50) was intervened daily concurrent HF diet (HF diet + dio50) for five weeks to check the changes of weights of body and tissues, blood pressures, and impaired glucose tolerances. The in vitro peptic hydrolysates of dioscorin with molecular mass between 3 kDa and 10 kDa and less than 3 kDa were used to determine dipeptidyl peptidase IV (DPP IV) inhibitory activities which DPP IV inhibitor has been reported to prevent and treat type 2 DM.

RESULTS

There were no significant difference in body weights, feed intakes, feed conversion, and weights of adipose tissues of obese rats in groups of HF and (HF diet + dio50). However, the systolic blood pressures in obese rats of 2-, 3- and 4-week dioscorin interventions were showed significantly lower (P < 0.05) compared to the HF group. The dioscorin intervention (HF+ dio50) was showed significantly different (P < 0.05) and improved the impaired glucose tolerances compared to HF group in obese rats by the oral glucose tolerance tests. It was also found that the fraction with different molecular mass of dioscorin peptic hydrolysates (5 mg/ml) showed inhibitory activities against DPP IV using sitagliptin phosphate as positive controls.

CONCLUSIONS

Yam dioscorins exhibit improved MS activities in obese rats which the related mechanisms may need further investigations.

Vasorelaxing and antihypertensive activities of synthesized peptides derived from computer-aided simulation of pepsin hydrolysis of yam dioscorin

BACKGROUND

We reported that yam dioscorin and its peptic hydrolysates exhibited ACE inhibition and antihypertensive effects on SHRs, however, the active peptides are not really isolated until now. Using ACE inhibitory screenings, two penta-peptides, KTCGY and KRIHF, were selected for ex vivo and in vivo experiments.

RESULTS

KTCGY, KRIHF, and captopril were shown to have similar vasodilating effects against phenylephrine (PE)-induced tensions in rat endothelium-dependent thoracic aortic rings, however, KTCGYKTCGY (two-repeated KTCGY) and TCGYTCGY (two-repeated TCGY) were showed endothelium-independent vasodilating effects against PE-induced tensions. KTCGY, KRIHF (10 or 20 mg/kg), and captopril (10 mg/kg) were used to evaluate antihypertensive activity during 24-h after a single oral administration to spontaneously hypertensive rats (SHRs). The KTCGY and KRIHF showed significantly different and reduced the systolic blood pressure of SHRs compared to the blank.

CONCLUSIONS

These results suggest that KTCGY and KRIHF may contribute important roles in yam dioscorin for regulating blood pressure in vivo.

Dipeptide Phe-Cys derived from in silico thermolysin-hydrolysed RuBisCO large subunit suppresses oxidative stress in cultured human hepatocytes

A dipeptide (Phe-Cys) was predicted to be bioactive following bioinformatics analysis of the large subunit of plant and microalgae ribulose-1,5-bisphosphate carboxylase (RuBisCO), which was hydrolysed in silico with thermolysin. The peptide was synthesised and found to possess in vitro reducing potential and inhibitory activity against lipid peroxidation, comparable to the activity of glutathione. In cultured Chang human hepatocytes, 2.5-10 μM Phe-Cys was found to induce the suppression of reactive oxygen species formation and membrane lipid peroxidation in oxidative stressed cells. Intracellular glutathione levels were found to increase in the peptide-treated cells under normal condition, which can potentially contribute in protecting the cells from oxidative damage. Furthermore, Western blot analysis showed that the levels of antioxidant enzymes, catalase and superoxide dismutase-1, increased in the hepatic cells when treated with Phe-Cys in the presence of the oxidant. The results show that this peptide has great potential to be used against oxidative stress-induced health conditions.

Effect of ultrasound on the activity and conformation of α-amylase, papain and pepsin

The effect of ultrasound on the activity of α-amylase, papain and pepsin was investigated and the mechanism of the effect was explored by determining their conformational changes. With the irradiation of power ultrasound, the activity of α-amylase and papain was inhibited, while the activity of pepsin was activated. According to the analysis of circular dichroism, Fourier transform infrared and fluorescence spectroscopy, the πo → π(∗) amide transitions and secondary structural components, especially β-sheet, of these three enzymes were significantly influenced by ultrasound. The tryptophan fluorescence intensity of the three enzymes was also observed to be affected by sonication. Furthermore, it was found that the pepsin molecule might gradually be resistant to prolonged ultrasonic treatment and recover from the ultrasound-induced damage to its original structure. The results suggested that the activity of α-amylase, papain and pepsin could be modified by ultrasonic treatment mainly due to the variation of their secondary and tertiary structures.

Asn-Trp dipeptides improve the oxidative stress and learning dysfunctions ind-galactose-induced BALB/c mice

Asn-Trp (NW) interventions for 4 weeks can attenuate the oxidative stress and learning dysfunctions induced by dailyd-galactose subcutaneous injection for 8 weeks.