A novel application of pulsed electric field (PEF) processing for improving glutathione (GSH) antioxidant activity

Pulsed electric fields disaggregating chlorophyll aggregates and boosting its biological activity

Chlorophyll molecules in solution spontaneously form chlorophyll aggregates due to intermolecular interactions such as hydrophobic bonding and π-π stacking, which reduce the biological activity of the chlorophyll solution. In this study, it was explored the mechanism of pulsed electric fields (PEF) parameters on the structure and biological activity of chlorophyll aggregates. The results showed that the microstructure of chlorophyll aggregates can be changed, leading to the formation of smaller particles by adjusting parameters during PEF treatment. Moreover, the smaller chlorophylls aggregates exhibited the stronger antioxidant and anti-inflammatory activities in vitro compared to control (without PEF treatment). Moreover, PEF treatment also induced changes in the microscopic state of chlorophylls confirmed by SEM. Molecular dynamics (MD) simulations indicated that PEF treatment increased the radius of gyration and solvent-accessible surface area (SASA) of chlorophyll aggregates while decreasing their density compared to untreated sample. These results suggested that PEF treatment can disrupt the interaction between chlorophyll molecules, leading to the disaggregation of chlorophyll aggregates and enhancing its bioactivity.

Production of bioactive peptides by high-voltage pulsed electric field: Protein extraction, mechanism, research status and collaborative application

Bioactive peptides exhibit a variety of potential applications in the fields of medicine, food and cosmetics. However, studies have shown that the traditional preparation is characterized by low efficiency, substantial pollution, limited activities and poor purity, which constrains their further application. High-voltage pulsed electric field (HPEF) technology, as a physical non-thermal processing method, shows unique advantages in bioactive peptide preparation. Through comprehensive analysis, this paper reveals the main principle of HPEF technology, the extraction of proteins (break up cellular tissue), the structural changes of proteins, enzymes and bioactive peptides after treatment, the improvement of bioactive peptides' functional properties and the potential in promoting bioactive peptides' large-scale production. Besides, this paper introduces the application of other non-thermal processing technologies, artificial intelligence and nanotechnology, providing new ways of thinking for the efficient preparation and application of bioactive peptides and establishes a theoretical foundation for the application and promotion of HPEF technology.

Potential Application of Egg White Peptides for Antioxidant Properties: Perspectives from Batch Stability and Network Pharmacology

This study investigated the batch stability of egg white peptides (EWPs) during the enzymatic hydrolysis process, and confirmed the potential application of four crucial four peptides inoxidative damage repair. The results revealed that different batches of EWPs had good stability relating to antioxidant activity. With a similar sequence to confirmed antioxidant peptides, four EWPs (QMDDFE, WDDDPTD, DEPDPL, and FKDEDTQ) were identified withhigh repetition rates, and their potential to repair oxidative damage was investigated. Network pharmacology results showed that these four peptides could regulate the targets related to oxidative damage. Enrichment results demonstrated that these four peptides could influence the targets and pathways related to glutathione transferase activity (enrichment score: 148.0) and glutathione metabolism (p value: 9.22 × 10-10). This study could provide evidence for the batch stability of hydrolyzed prepared EWPs, and offer theoretical support for the development of antioxidant damage ingredients derived from foods.

Saccharomyces cerevisiae-incorporated and sucrose-rich sodium alginate film: An effective antioxidant packaging film for longan preservation

A sodium alginate (SA) film incorporated with Saccharomyces cerevisiae (SE) and sucrose (SU) was fabricated to control the quality and pericarp browning of longan. The SE with satisfactory glutathione production was selected as the antioxidant agent. The scanning electron microscopy (SEM) results revealed that the SU-rich SA film could be used as an effective carrier to protect the cell integrity of SE. The FTIR and mechanical property results indicated that the SA-SE film with the incorporation of SU has good flexibility due to the existence of hydrogen bonds. Notably, the cell viability of the SE was significantly improved with the addition of SU, which positively affects the antioxidant property of the film during the storage period. Finally, the SA-SE-3.0%SU films obviously improved the quality and pericarp browning of longan. The SA-based film incorporated with SU and SE may be established as a novel antioxidant fruit packaging material.

Synergistic In Vitro Anticancer Toxicity of Pulsed Electric Fields and Glutathione

Despite continuous advancement in skin cancer therapy, the disease is still fatal in many patients, demonstrating the need to improve existing therapies, such as electrochemotherapy (ECT). ECT can be applied in the palliative or curative setting and is based on the application of pulsed electric fields (PEF), which by themselves exerts none to low cancer toxicity but become potently toxic when combined with low-dosed chemotherapeutics such as bleomycin and cisplatin. Albeit their favorable side-effect profiles, not all patients respond to standard ECT, and some responders experience tumor recurrence. To identify potential adjuvant or alternative agents to standard electrochemotherapy, we explored the possibility of combining PEF with a physiological compound, glutathione (GSH), to amplify anticancer toxicity. GSH is an endogenous antioxidant and is available as a dietary supplement. Surprisingly, neither GSH nor PEF mono treatment but GSH + PEF combination treatment exerted strong cytotoxic effects and declined metabolic activity in four skin cancer cell lines in vitro. The potential applicability to other tumor cells was verified by corroborating results in two leukemia cell lines. Strikingly, GSH + PEF treatment did not immediately increase intracellular GSH levels, while levels 24 h following treatment were enhanced. Similar tendencies were made for intracellular reactive oxygen species (ROS) levels, while extracellular ROS increased following combination treatment. ROS levels and the degree of cytotoxicity could be partially reversed by pre-incubating cells with the NADPH-oxidase (NOX) inhibitor diphenyleneiodonium (DPI) and the H₂O₂-degrading enzyme catalase. Collectively, our findings suggest a promising new "endogenous" drug to be combined with PEF for future anticancer research approaches.

Effect of Chitosan Nanoemulsion on Enhancing the Phytochemical Contents, Health-Promoting Components, and Shelf Life of Raspberry (Rubus sanctus Schreber)

Due to high water content and perishability, the raspberry fruit is sensitive to postharvest fungal contamination and postharvest losses. In this study, chitosan was used as an edible coating to increase the storage of raspberries, and nanotechnology was used to increase chitosan efficiency. The fruit was treated with an emulsion containing nanoparticles of chitosan (ECNPC) at 0, 2.5, and 5 g L−1, and stored for 9 d. Decay extension rate, fruit phytochemical contents, including total phenolics, flavonoids, and anthocyanin content, phenylalanine ammonia-lyase (PAL), and guaiacol-peroxidase enzymes and antioxidant activity, and other qualitative properties were evaluated during and at the end of storage. After 9 d of storage, the highest amounts of phenolics compounds, PAL enzyme activity, and antioxidant activity were observed in fruit treated with ECNPC at 5 g L−1. The highest levels of total phenol, PAL enzyme activity, and antioxidant activity were 57.53 g L−1, 118.88 μmol/min trans-cinnamic acid, and 85.16%, respectively. ECNPC can be considered as an effective, safe, and environmentally friendly method for enhancing fruit phytochemical contents, postharvest life, and health-promoting capacity.

Immunomodulatory Activity Improvement of Pine Nut Peptides by a Pulsed Electric Field and Their Structure-Activity Relationships

In this study, Alg-Gly-Ala-Val-Leu-His (RGAVLH) obtained from pine nut ( Pinus koraiensis Sieb. et Zucc.) protein was chosen to investigate the phenomenon of immunomodulatory activity improvement upon pulsed electric field (PEF) processing. The influence of electric field intensity on immunomodulatory activity of RGAVLH was evaluated using RAW 264.7 cells. It was found that RGAVLH can not only significantly ( p < 0.05) improve the capability of macrophage phagocytosis but also promote the production of nitric oxide. RGAVLH treated under an electric field intensity of 40 kV/cm exhibited the best immunomodulatory activity. The primary and secondary structures of PEF-treated peptides were analyzed by mid-infrared (MIR) spectroscopy, Raman spectroscopy, circular dichroism spectroscopy, and one-dimensional/two-dimensional nuclear magnetic resonance spectroscopy. After PEF treatment, the primary structure of RGAVLH was not influenced, as evaluated by MIR and Raman spectra. In addition, the content of β-sheet was decreased and active hydrogen was changed in PEF-treated RGAVLH solution. Moreover, the long-range connectivity between C_αH (3.39 ppm) and N_αH (8.24 ppm) was enhanced by PEF. Therefore, the improvement of the immunomodulatory activity of RGAVLH might result from the changes of the spatial state and spatial force in the peptide solution system.

Intracellular antioxidant activity and apoptosis inhibition capacity of PEF-treated KDHCH in HepG2 cells

The effect of pulsed electric field (PEF) treatment on the intracellular antioxidant and apoptotic activity of the peptide Lys-Asp-His-Cys-His (KDHCH) was examined using model HepG2 cells. First, PEF treatment conditions specific for the antioxidant peptide were optimized, and it was found that PEF treatment could enhance DPPH, ABTS and hydroxyl radical scavenging capacity of KDHCH. Second, KDHCH subjected to PEF treatment at 1800 Hz and 15 kV/cm was investigated using various intracellular antioxidant assays. PEF treatment decreased the EC50 value and increased the protective ability of oxidative stress inhibition and reactive oxygen species (ROS) scavenging activity of KDHCH. Furthermore, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and glutathione reductase (GR) activities of KDHCH-pre-treated HepG2 cells increased significantly compared with those of the H₂O₂ damaged group, whereas lactate dehydrogenase (LDH) and malonaldehyde (MDA) content were decreased. PEF-treated KDHCH exhibited an increased capacity to maintain the stability of mitochondrial membrane potential (MMP) and reduced the level of caspase-3. These results indicate that PEF treatment can enhance the intracellular antioxidant activity of KDHCH, which can inhibit the effect of H₂O₂ oxidation on HepG2 cells by inhibiting the accumulation of intracellular ROS, regulating antioxidant related enzymes, and blocking the apoptotic mitochondrial pathways activated by ROS.

Analysis of α-helix unfolding in the pine nut peptide Lys-Cys-His-Lys-Pro induced by pulsed electric field

BACKGROUND

A variety of analytical techniques were applied to explore the effects of pulsed electric field (PEF) on α-helix structural changes in the novel antioxidant peptide Lys-Cys-His-Lys-Pro (KCHKP, 611.76 Da).

RESULTS

The relative α-helix content of the KCHKP peptide was significantly altered from 100% to 89.91 ± 0.97% when the electric pulse frequency was 1800 Hz and the field intensity was 10 kV cm^-1 . Moreover, the 1,1-diphenyl-2-pycryl-hydrazyl (DPPH) and 2,2-azinobis diammonium salt (ABTS) radical-scavenging activities of PEF-treated KCHKP were increased from 56.31% ± 0.74% to 84.33% ± 1.23% and from 40.56% ± 0.78% to 51.33% ± 0.27%, respectively.

CONCLUSION

PEF treatment increased peptide linkage stretch vibration and altered hydrogen bonding of KCHKP. The stability of the α-helix structure was influenced by hydrogen bonds within the peptide linkage of KCHKP induced by PEF and was related to changes in antioxidant activity. © 2017 Society of Chemical Industry.

Effects of pulsed electric field on intracellular antioxidant activity and antioxidant enzyme regulating capacities of pine nut (Pinus koraiensis) peptide QDHCH in HepG2 cells

Effects of pulse electric field (PEF) on antioxidant activity of pine nut (Pinus koraiensis) peptide were discussed using H₂O₂-induced HepG2 cells and changes of peptide structures were measured by MIR, NMR and CD spectra. Using HPLC-MS/MS, a novel peptide was identified as QDHCH. After PEF treatment the DPPH and ABTS radical inhibition, and CAA values of QDHCH were increased to 85.13%±0.17%, 95.45%±0.12%, and 4670.10μmol of quercetin equivalents/100g. The PEF-treated QDHCH has better protective oxidative stress inhibitory of 74.22±3.70%, and the T-SOD, CAT, GSH-Px and GSH-Rx activities in cells were significantly increased by 91.92, 7.98, 18.5 and 18.79U/mg prot, while the MDA content was decreased to 8.45±0.71U/mg prot compared with H₂O₂ damaged group. In addition, the hydroxyl radical scavenging activity of QDHCH was increased by 10.53%; the basic structure was not changed by PEF, while the influenced secondary structures may induce the antioxidant activity improvement in HepG2 cells.

Antioxidant Activity Improvement and Evaluation of Structure Changes of SHECN Treated by Pulsed Electric Field (PEF) Technology

The purpose of the study was to evaluate the relationship between antioxidant activity improvement and structure changes of peptide (Ser-His-Glu-Cys-Asn (SHECN) isolated from soybean treated by pulsed electric field (PEF). The two-factor-at-a–time (TFAT) was performed to investigate interaction of electric field intensity (5, 10, 15 and 20 kV/cm) and pulse frequency (1,800 and 2,400 Hz) on antioxidant activity improvement and structure changes. Compared with untreated peptide, DPPH radical inhibition of SHECN was significantly increased to 95.54 ± 0.16 % at optimal conditions (electric field intensity 15 kV/cm, pulse frequency 1,800 Hz and a retention time of 2 h). Results showed that the primary structure of SHECN had not been changed based on the nuclear magnetic resonance analysis. However, the secondary structure of peptide, especially α-helix can be changed. These results suggested that mechanism of antioxidant activity improvement is related to secondary structure changes.

Effects on functional groups and zeta potential of SAP1<MW<3kDa treated by pulsed electric field technology

BACKGROUND

SAP_1<MW<3kDa was chosen to investigate the improvement of antioxidant activity of peptides treated with pulsed electric field (PEF) technology. The effects of electric field intensity and pulse frequency on SAP_1<MW<3kDa were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical inhibition, as well as the zeta potential and functional groups.

RESULTS

One-factor-at-a-time tests indicated that the PEF-treated sample had the strongest antioxidant activity (P < 0.05) and the lowest zeta potential value. The increase of antioxidant activity of SAP_1<MW<3kDa may be attributed to a loss of C = C and the amide band. Using a response surface methodology (RSM) experiment, it was shown that DPPH radical inhibition of SAP_1<MW<3kDa increased to 90.22 ± 0.90% at the optimal conditions (electric field intensity 15 kV cm^-1 , pulse frequency 1600 Hz and flow velocity 2.93 mL min^-1 ). Furthermore, the PEF-treated SAP_1<MW<3kDa under optimal conditions lacked the characteristic absorbance of N-H, C = C and the amide band and the zeta potential was reduced to -18.0 mV.

CONCLUSION

Overall, the results of the present study suggest that the improvement of antioxidant activity of SAP_1<MW<3kDa is a result of the contribution of the functional groups and the change in zeta potential when treated with PEF. © 2016 Society of Chemical Industry.

Effect of pulsed electric field (PEF) on structures and antioxidant activity of soybean source peptides-SHCMN

Recently, high-intensity pulsed electric field (PEF) has successfully used in improvement of antioxidant activity. Ser-His-Cys-Met-Asn (SHCMN) obtained from soybean protein was chosen to investigate the phenomenon of antioxidant activity improvement. Effects of PEF treatment on antioxidant activity of SHCMN were evaluated by DPPH radical inhibition. Nuclear magnetic resonance (NMR), mid-infrared (MIR), circular dichroism (CD) were used to analyze structures of SHCMN. Two-factor-at-a-time results show that DPPH radical inhibition of SHCMN is significantly (P<0.05) increased to 94.35±0.03% at conditions of electric field intensity of 5kV/cm, pulse frequency of 2400Hz, and retention time of 2h. In addition, MIR and NMR spectra show that the basic structure of peptides SHCMN is stable by PEF treatment. But the secondary structures (α-helix, β-turn, and random coil) can be affected and zeta potential of PEF-treated SHCNM was reduced to 0.59±0.03mV. The antioxidant activity improvement of SHCMN might result from the changes of secondary structures and zeta potential.

Effects of Pulsed Electric Fields (PEF) on Vitamin C and Its Antioxidant Properties

In this study, pulsed electric fields (PEF) treatments and their effects on the structure of vitamin C (VIT-C) were estimated by fluorescence and Fourier transform infrared (FT-IR) spectroscopy, the relative content of VIT-C was measured by HPLC and the antioxidant properties of treated VIT-C by DPPH radical scavenging as well as reducing power tests. The fluorescence intensity of treated VIT-C increased slightly compared to the untreated VIT-C. Moreover, the effect of PEF on the structure of VIT-C was observed using the FT-IR spectra. These phenomena indicated that the PEF affected the conformation of VIT-C, which promoted the VIT-C isomer transformed enol-form into keto-form. In addition, the PEF treatments did not suffer the damage to VIT-C and could slow down the oxidation process in involving of experimental conditions by HPLC. The antioxidant properties of the treated VIT-C were enhanced, which was proved by radical scavenging and also the reducing power tests.

Effects of nonthermal preservation technologies on antioxidant activity of fruits and vegetables: A review

Consumer demand for safe and nutritious fruits and vegetables has given rise to the development of a number of nonthermal food preservation techniques. Recent studies have highlighted that antioxidant activity of fruits and vegetables plays an important role in human health. In this paper, the influences of nonthermal preservation technologies, including pulsed electric field, radiation processing, dense phase carbon dioxide, ozone processing, and edible coatings, on the antioxidant capacity and related compounds in fruits and vegetables are reviewed. The proposed mechanisms and future trends are also discussed to accelerate the further commercialization and exploration of these novel technologies, which will, in turn, help to promote human health.

Geraniin exerts cytoprotective effect against cellular oxidative stress by upregulation of Nrf2-mediated antioxidant enzyme expression via PI3K/AKT and ERK1/2 pathway

BACKGROUND

Geraniin, an active compound with remarkable antioxidant activity, was isolated from Geranium sibiricum. The present study aimed to investigate whether geraniin has the ability to activate Nrf2, induce antioxidant enzyme expression and protect cells from oxidative damage.

METHODS

The cells were pretreated with geraniin for 24h and exposed to hydrogen peroxide (H₂O₂) for 4h. Intracellular reactive oxygen species (ROS) levels, mitochondrial membrane potential and apoptosis were measured. We also investigated intracellular glutathione (GSH) levels and changes in nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated signaling cascade in cells treated with geraniin.

RESULTS

We investigated the protective effects of geraniin against H₂O₂-induced apoptosis in HepG2 cells. Geraniin significantly reduced H₂O₂-induced oxidative damage in a dose dependent manner. Further, geraniin induced the expression of heme oxygenase-1 (HO-1), NAD(P)H quinone oxidoreductase-1 (NQO1) and level of glutathione (GSH) in a concentration- and time-dependent manner, and increased Nrf2 nuclear translocation. The Nrf2-related cytoprotective effects of geraniin were PI3K/AKT and extracellular signal-regulated protein kinase1/2 (ERK1/2) pathway-dependent. However, inhibitors of PI3K/AKT and ERK1/2 (LY294002 or U0126) not only suppressed geraniin-induced nuclear translocation of Nrf2 but also abolished the expression of HO-1, NQO1 and GSH.

CONCLUSIONS

These results demonstrated that geraniin induced Nrf2-mediated expression of antioxidant enzymes HO-1 and NQO1, presumably via PI3K/AKT and ERK1/2 signaling pathways, thereby protecting cells from H₂O₂-induced oxidative cell death.

GENERAL SIGNIFICANCE

Geraniin, at least in part, offers an antioxidant defense capacity to protect cells from the oxidative stress-related diseases.

Antioxidative effect of ginseng stem-leaf saponins on oxidative stress induced by cyclophosphamide in chickens

Previous investigation demonstrated that oral administration of ginseng stem-leaf saponins in chickens could enhance the immune response. The present study was designed to evaluate the effects of ginseng stem-leaf saponins on oxidative stress induced by cyclophosphamide in chickens. One hundred and twenty chickens were randomly divided into 5 groups. Groups 1 to 4 received intramuscular injection of cyclophosphamide to induce oxidative stress while group 5 was injected with saline solution and served as control. Following administration of cyclophosphamide, groups 1 to 3 were orally administered ginseng stem-leaf saponins at 2.5, 5, and 10 mg/kg BW in drinking water for 7 d, respectively. After that, the spleen, thymus, bursa, and serum were collected to measure the indices of the organs and oxidative parameters. The results showed that ginseng stem-leaf saponins significantly inhibited cyclophosphamide-induced oxidative stress by increasing the organ indices, total antioxidant capacity, and the levels of glutathione, ascorbic acid, and α-tocopherol, while elevating the activity of total superoxide dismutase, catalase, and glutathione peroxidase, as well as decreasing the protein carbonyl content and malondialdehyde. Therefore, ginseng stem-leaf saponins could be a promising agent against oxidative stress in the poultry industry.

Antioxidant properties can be tuned in the presence of an external electric field: accurate computation of O–H BDE with range-separated density functionals

The effect of external electric field on the antioxidant properties of gallic and caffeic acids is studied. The performance of range-separated functionals in reproducing the O–H BDE is tested in the presence of an external electric field.