Azobis 2-amidinopropane Dihydrochloride Research Articles

Novel C3-Methylene-Bridged Indole Derivatives with and without Substituents at N1: The Influence of Substituents on Their Hemolytic, Cytoprotective, and Antimicrobial Activity.

Alkaloids are natural compounds useful as scaffolds for discovering new bioactive molecules. This study utilized alkaloid gramine to synthesize two groups of C3-substituted indole derivatives, which were either functionalized at N1 or not. The compounds were characterized by spectroscopic methods. The protective effects of the new compounds against in vitro oxidative hemolysis induced by standard oxidant 2,2'-azobis(2-amidinopropane dihydro chloride (AAPH) on human erythrocytes as a cell model were investigated. Additionally, the compounds were screened for antimicrobial activity. The results indicated that most of the indole derivatives devoid of the N1 substitution exhibited strong cytoprotective properties. The docking studies supported the affinities of selected indole-based ligands as potential antioxidants. Furthermore, the derivatives obtained exhibited potent fungicidal properties. The structures of the eight derivatives possessing indole moiety bridged to the imidazole-, benzimidazole-, thiazole-, benzothiazole-, and 5-methylbenzothiazoline-2-thiones were determined by X-ray diffraction. The C=S bond lengths in the thioamide fragment pointed to the involvement of zwitterionic structures of varying contribution. The predominance of zwitterionic mesomers may explain the lack of cytoprotective properties, while steric effects, which limit multiple the hydrogen-bond acceptor properties of a thione sulfur, seem to be responsible for the high hemolytic activity.

AAPH-oxidised whey protein isolate forms a weak interfacial layer and promotes lipid oxidation in oil-in-water emulsions

The objective of this work was to investigate the interfacial adsorption properties and lipid oxidation of oil-in-water (O/W) emulsions prepared by 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) oxidised whey protein isolate (WPI) with different oxidation degrees. The results indicated that as the AAPH concentration increased, the degree of oxidation of WPI also increased significantly, as confirmed by the higher protein carbonyl and N'-formyl-L-kynurenine levels. AAPH interacted with WPI mainly through hydrogen bonding and hydrophobic interactions. Higher AAPH concentration changed the structure of WPI, which verified by the results of intrinsic tryptophan fluorescence, circular dichroism spectra and SDS-PAGE. Moreover, the ζ-potential and adsorbed proteins of O/W emulsions prepared by oxidised-WPI decreased with increasing degree of protein oxidation, but the droplet size of O/W emulsions increased. In addition, higher oxidation degrees of oxidised-WPI promoted lipid oxidation of O/W emulsions, reflected by an increase in lipid hydroperoxide and malondialdehyde levels. These findings indicated that oxidised WPI could lead to quality deterioration of O/W emulsions, especially for those with a higher degree of oxidation.

Insights into Gastrointestinal Redox Dysregulation in a Rat Model of Alzheimer's Disease and the Assessment of the Protective Potential of D-Galactose.

Recent evidence suggests that the gut plays a vital role in the development and progression of Alzheimer's disease (AD) by triggering systemic inflammation and oxidative stress. The well-established rat model of AD, induced by intracerebroventricular administration of streptozotocin (STZ-icv), provides valuable insights into the GI implications of neurodegeneration. Notably, this model leads to pathophysiological changes in the gut, including redox dyshomeostasis, resulting from central neuropathology. Our study aimed to investigate the mechanisms underlying gut redox dyshomeostasis and assess the effects of D-galactose, which is known to benefit gut redox homeostasis and alleviate cognitive deficits in this model. Duodenal rings isolated from STZ-icv animals and control groups were subjected to a prooxidative environment using 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) or H2O2 with or without D-galactose in oxygenated Krebs buffer ex vivo. Redox homeostasis was analyzed through protein microarrays and functional biochemical assays alongside cell survival assessment. Structural equation modeling and univariate and multivariate models were employed to evaluate the differential response of STZ-icv and control samples to the controlled prooxidative challenge. STZ-icv samples showed suppressed expression of catalase and glutathione peroxidase 4 (GPX4) and increased baseline activity of enzymes involved in H2O2 and superoxide homeostasis. The altered redox homeostasis status was associated with an inability to respond to oxidative challenges and D-galactose. Conversely, the presence of D-galactose increased the antioxidant capacity, enhanced catalase and peroxidase activity, and upregulated superoxide dismutases in the control samples. STZ-icv-induced gut dysfunction is characterized by a diminished ability of the redox regulatory system to maintain long-term protection through the transcription of antioxidant response genes as well as compromised activation of enzymes responsible for immediate antioxidant defense. D-galactose can exert beneficial effects on gut redox homeostasis under physiological conditions.

Free radical scavenging and anti-isolated human LDL oxidation activities of Butea superba Roxb. extract

BackgroundButea superba Roxb. (B. superba), is an herbal plant traditionally used for rejuvenation. Additionally, there have been reports on its antioxidant properties. Low-density lipoproteins (LDL) oxidation is the leading cause of cardiovascular diseases (CVDs). Natural products with antioxidant properties have the potential to inhibit LDL oxidation. However, no work has been done about the anti-isolated human LDL oxidation of B. superba extract (BSE). This study aimed to investigate the antioxidant potential of BSE and its ability to prevent isolated human (LDL) oxidation induced by free radical agents.MethodsThe antioxidant properties were investigated by antioxidant assays, including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS), ferric reducing ability power (FRAP), nitric oxide (NO) and peroxynitrite scavenging assay. More so, anti-isolated human LDL oxidation activities were evaluated by 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) and 3-morpholinosydnonimine hydrochloride (SIN-1) induced LDL oxidation assay.ResultsBSE exhibited a significant (p < 0.05) antioxidant activity in all the test systems, demonstrating its potential as a potent free radical scavenger. It displayed scavenging effects on DPPH (p < 0.05; IC50 = 487.67 ± 21.94 µg/ml), ABTS (p < 0.05; IC50 = 30.83 ± 1.29 µg/ml). Furthermore, it generated significantly (p < 0.05) increased antioxidant capacity in a dose-dependent manner in FRAP assay and exhibited significantly (p < 0.01) higher percent NO scavenging activity than gallic acid. Besides, BSE at 62.5 µg/ml exhibited a considerable percent peroxynitrite scavenging of 71.40 ± 6.59% after a 2 h period. Moreover, BSE demonstrated anti-isolated human LDL oxidation activity induced by AAPH and SIN-1 (p < 0.05) and revealed scavenging activity similar to ascorbic acid (p > 0.05). Identifying the main constituents of BSE revealed the presence of genistein, daidzein, and biochanin A through Liquid Chromatography-Mass Spectrometer/Mass Spectrometer (LC–MS/MS) analysis.ConclusionThis is the first report that the presence of isoflavones in BSE could play an important role in its antioxidation and isolated human LDL oxidation scavenging properties. These findings suggest the potential for developing antioxidant herbal supplements. However, further studies must be investigated, including efficacious and safe human dosages.

A newly synthesized flavone avoids COMT-catalyzed methylation and mitigates myocardial ischemia/reperfusion injury in H9C2 cells via JNK and P38 pathways.

Luteolin is a flavone that provides defense against myocardial ischemia/reperfusion (I/R) injury. However, this compound is subjected to methylation mediated by catechol-O-methyltransferase (COMT), thus influencing its pharmacological effect. To synthesize a new flavone from luteolin that avoids COMT-catalyzed methylation and find out the protective mechanism of LUA in myocardial I/R injury. Luteolin and 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) were used to synthesize the new flavone known as LUAAPH-1 (LUA). Then, the myocardial ischemia/reperfusion injury cell model was established using H9c2 cells to detect the effect in myocardial ischemia/reperfusion regulation and to identify the underlying mechanism. Pretreatment with LUA (20 μmol/l) substantially increased cell viability while reducing cell apoptosis rate and caspase-3 expression induced by I/R, and the protective effect of LUA on cell viability was stronger than diosmetin, which is the major methylated metabolite of luteolin. In addition, intracellular reactive oxygen species (ROS) production and calcium accumulation were both inhibited by LUA. Furthermore, we identified that LUA markedly relieved the promotive effects of I/R stimulation upon JNK and p38 phosphorylation. LUT pretreatment conveys significant cardioprotective effects after myocardial I/R injury, and JNK and p38 MAPK signaling pathway may be involved.

Analgesic and antiinflammatory activities of the aqueous root extract of Algerian Bunium incrassatum

The present study was designed to evaluate the antioxidant, analgesic, and antiinflammatory activities of Bunium incrassatum aqueous extract (BIAE) from roots. Tests of radical scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and induced erythrocyte hemolysis using 2,2'-azo bis (2-amidinopropane) dihydrochloride (AAPH) were used for antioxidant activity evaluation. The antiinflammatory activity was tested in Croton oil- and xylene-induced ear edema and carrageenaninduced paw edema. The antinociceptive effect was tested with the pain model induced by formalin and acetic acid-induced writhing response. The results revealed that BIAE exhibited a strong protective effect against AAPH-induced hemolysis of erythrocytes. In contrast, in the DPPH test, BIAE showed moderate activity (IC50: 1.07?}0.078 mg/mL) compared to BHT. In the antiinflammatory test, oral administration of BIAE (100, 300, and 600 mg/kg) significantly reduced the edema in the three models used. In antinociceptive experiments, the pretreatment with BIAE produced important analgesic activity. Additionally, the pretreatment of mice with BIAE significantly reduced the paw-licking time in the second phase. The results of this study revealed the antioxidant, analgesic, and antiinflammatory potential of BIAE, and demonstrated the importance of B. incrassatum as a source of compounds for therapeutic uses.

Protective Effects of Mulberry (Morus atropurpurea Roxb.) Leaf Protein Hydrolysates and Their In Vitro Gastrointestinal Digests on AAPH-Induced Oxidative Stress in Human Erythrocytes.

Mulberry leaf protein hydrolysates (HMP), and their in vitro gastrointestinal digests (GHMP), have shown favorable chemical antioxidant activities. The aim of this study is to investigate the potential protective effects of HMP and GHMP against 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative stress in human erythrocytes. The inhibition rate of hemolysis, the reactive oxygen species (ROS) level, the concentration of malondialdehyde (MDA), the reduced glutathione (GSH) and oxidized glutathione (GSSH), and the enzymatic activities of total superoxide dismutase (SOD), catalase (CAT), and cellular glutathione peroxidase (GSH-Px) were evaluated as the biomarkers of oxidative status in human erythrocytes. The results showed that HMP and GHMP effectively inhibit the occurrence of erythrocyte hemolysis in the range of 0.025-1.0 mg/mL, and the inhibition rates of HMP and GHMP reached 92% and 90% at concentrations of 0.4 mg/mL and 1.0 mg/mL, respectively. HMP and GHMP reduced the AAPH-induced oxidative hemolysis damage via suppressing the generation of ROS by inhibiting the formation of MDA, maintaining the balance of GSH/GSSG, and preserving the activities of the antioxidant enzymes, including SOD, GSH-Px, and CAT. Our findings revealed that both HMP and GHMP could be used as natural antioxidants, and have the potential for further application in the development of functional foods.

Effects of AAPH on structure, allergenicity and physicochemical properties of shrimp myofibrillar protein

Lipid peroxidation has been shown to associate with meat quality by affecting physicochemical properties of myofibrillar proteins. In this work, shrimp myofibrillar protein (MP) was oxidized using 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH), which could generate peroxyl radicals in lipid peroxidation. Results showed that increasing AAPH concentration led to an increase in carbonyl groups and a decrease in free amino and sulfhydryl thiol groups in MP. Secondary structural analysis of MP revealed a conversion of α-helix to β-sheet content after AAPH treatment. SDS-PAGE showed the band intensity of tropomyosin was reduced after AAPH treatment, indicating a reduced allergenicity of tropomyosin. Moderate oxidation (1–10 mmol/L AAPH) promoted the formation of a dense network of MP gel, resulting in enhanced textural and rheological properties. However, excessive oxidation (10–20 mmol/L AAPH) weakened the MP gel strength and decreased its water-holding capacity. These findings provide theoretical guidance for developing shrimp surimi products with desirable textures.

The Impact of AAPH-Induced Oxidation on the Functional and Structural Properties, and Proteomics of Arachin.

The aim of this study was to investigate the effect of 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidation on the functional, structural properties and proteomic information of arachin. The results showed that moderate oxidation improved the water/oil holding capacity of proteins and increased the emulsifying stability, while excessive oxidation increased the carbonyl content, reduced the thiol content, altered the structure and thermal stability, and reduced most of the physicochemical properties. Through LC-QE-MS analysis, it was observed that oxidation leads to various modifications in arachin, including carbamylation, oxidation, and reduction, among others. In addition, 15 differentially expressed proteins were identified. Through gene ontology (GO) analysis, these proteins primarily affected the cellular and metabolic processes in the biological process category. Further Kyoto encyclopedia of genes and genomes (KEGG) analysis revealed that the "proteasome; protein processing in the endoplasmic reticulum (PPER)" pathway was the most significantly enriched signaling pathway during the oxidation process of arachin. In conclusion, this study demonstrated that AAPH-induced oxidation can alter the conformation and proteome of arachin, thereby affecting its corresponding functional properties. The findings of this study can potentially serve as a theoretical basis and foundational reference for the management of peanut processing and storage.

The effects of free radicals and metal ion on milk protein β‐lactoglobulin (BLG) glyco‐oxidation

SummaryIn this study, the effects of H2O2, 2,2′‐Azobis(2‐amidinopropane) dihydrochloride (AAPH) and metal ion Fe3+ on β‐lactoglobulin (BLG) glyco‐oxidation were investigated. The results demonstrated all the three inducers caused BLG morphology change and higher molecular weight BLG‐glucose (BLG‐Glu) adducts formation. H2O2 and AAPH significantly accelerated BLG oxidation by increasing carbonyl content and decreasing freesulphydryls (P &lt; 0.05). However, Fe3+ showed little influence on carbonyl and free sulphydryls contents. All the three inducers promoted fluorescent‐advanced glycation end products (fl‐AGEs) and carboxymethyl‐lysine (CML) formation. Fe3+ and H2O2 (0.5% and 1%) could increase methylglyoxal (MGO) level and caused less time to reach its peak concentration than control group. Compared with the control group, new glycation sites were determined in H2O2, AAPH and Fe3+ treatments, indicating the inductive effect of those free radicals or metal ion on BLG glycation. The results will provide important information for the control of protein‐based products glyco‐oxidation during food processing and storage.

In vitro investigations of biological activities of Thymus willdenowii and Thymus atlanticus polyphenol-rich extracts

Thyme species produce a wide variety of phenolic compounds including tannins, phenolic acids, and flavonoids. Thymus atlanticus (T. atlanticus) and Thymus willdenowii (T. willdenowii) are important thyme species in the southeast of Morocco, with numerous biological properties. The polyphenolic extracts of these two thyme species were obtained using ethanol through Soxhlet apparatus. Antioxidant (DPPH, FRAP, and TAC methods), antihemolytic (2,2'-Azobis(2-amidinopropane) dihydrochloride (AAPH) induced hemolysis test), hypolipidemic (3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity inhibition test), and anti-inflammatory (protein denaturation inhibition) effects of extracts were carried out using in vitro methods. The results showed that the polyphenolic extracts of these two species revealed important amounts of phenolic compounds. The contents of flavonoids were significant in the two species, while the contents of tannins and anthocyanin were very low. T. atlanticus showed an important antioxidant activity and a considerable antihemolytic effect in AAPH-induced hemolysis test (IC50 = 0.29 mg/mL), while T. willdenowii showed an important anti-inflammatory activity in heat-induced protein denaturation test (IC50 = 1.61 mg/mL). Moreover, both extracts at a dose of 20 µg/mL showed an important in vitro hypolipidemic activity by inhibiting HMG-CoA reductase activity (T. willdenowii: 51.16 %; T. atlanticus: 62.83 %). In conclusion, T. willdenowii and T. atlanticus extracts have considerable antioxidant, antihemolytic, hypolipidemic, and anti-inflammatory effects. The richness of these species in polyphenols gives them a large specter of biological properties, making them a valuable source of natural bioactive compounds that could prevent or treat various diseases.

Protection of C2C12 skeletal muscle cells toward oxidation by a polyphenol-rich plant extract

Graphical abstract Abstract Sarcopenia is a very disabling age-related disease which affects the mass and strength of skeletal muscles. This syndrome has no efficient treatment and is associated with important oxidative stress which could play important role in skeletal muscle degeneration. In this context, the cytoprotective activity and the antioxidant properties of a polyphenol-rich plant extract (PRPE) were evaluated in undifferentiated C2C12 murine skeletal muscle cells (myoblasts). PRPE is a potent antioxidant mixture as shown by its reactive oxygen species (ROS) scavenging properties by using the Kit Radicaux Libres method and the dihydroethidium (DHE) scavenging assay. In addition, PRPE has significant protecting properties in C2C12 cells toward oxidative stress triggered by 2, 2′-azobis (2-amidinopropane) dihydrochloride (AAPH) which is an ROS generator, as measured by different complementary approaches. PRPE counteracts several AAPH-induced cytotoxic effects. PRPE prevents morphological changes evaluated by phase contrast microscopy and decreases the number of dying cells determined by counting in the presence of trypan blue and the intracellular ROS overproduction evaluated by flow cytometry after staining with DHE. In addition, PRPE tends to normalize the expression of genes (peroxiredoxin 1 (Pdrx1), nuclear factor erythroid 2-related factor 2 (Nrf2), and peroxisome proliferator-activator receptor gamma coactivator 1-alpha (Pgc1α)) involved in the oxidant stress defense under ROS exposure. Altogether; our data show that PRPE has potent antioxidant properties and protects C2C12 skeletal muscle cells toward AAPH-induced oxidative stress. These cytoprotective properties of PRPE in skeletal muscle cells submitted to a pro-oxidant environment deserve further investigation in the context of sarcopenia.

Screening and Evaluation of Active Compounds in Polyphenol Mixtures by a Novel AAPH Offline HPLC Method and Its Application.

In this study, we developed a novel offline high-performance liquid chromatography (HPLC) method based on 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) radicals for antioxidant screening in 20 polyphenolic compounds and used the Trolox equivalent antioxidant capacity assay to evaluate their antioxidant activity. Compared to the existing offline HPLC methods based on 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH), the offline HPLC method based on the AAPH radical is more sensitive. Additionally, we applied this method to Lepechinia meyenii (Walp.) Epling extract and screened out seven antioxidants, caffeic acid, hesperidin, rosmarinic acid, diosmin, methyl rosmarinate, diosmetin, and n-butyl rosmarinate, which are known antioxidants. Therefore, this study provides new insights into the screening of antioxidants in natural extracts.

Anthocyanins Prevent AAPH-Induced Steroidogenesis Disorder in Leydig Cells by Counteracting Oxidative Stress and StAR Abnormal Expression in a Structure-Dependent Manner

Testosterone deficiency may increase the risk of sexual dysfunction and the failure of spermatogenesis. Oxidative stress that is derived from the destruction of homeostasis, disease, and exposure to contaminants can damage the steroidogenicity process in Leydig cells, resulting in a reduction in testosterone synthesis. Anthocyanins are a group of innoxious antioxidants widely recognized in food sources, and are an ideal candidate to relieve oxidative stress-related steroidogenesis disorder. However, there is still a major gap in our knowledge of the structure-function relationship of anthocyanin on the activity mentioned above. In the present study, four anthocyanins including cyanidin-3-glucoside (Cy-3-glu), delphinidin-3-glucoside (Dp-3-glu), pelargonidin-3-glucoside (Pg-3-glu), and cyanidin-3,5-diglucoside (Cy-3,5-diglu) were applied to reverse testosterone generation after employing 2,2'-Azobis(2-amidinopropane)-dihydrochloride (AAPH) as the inducer of oxidative stress in R2C cells. The results demonstrated that all four kinds of anthocyanins can inhibit ROS generation, alleviate mitochondrial membrane potential damage, and contribute to increased testosterone. Among them, Cy-3,5-diglu with diglycoside performed best on antioxidative ability and improved cell dysfunction and upregulated the expression of the steroidogenic acute regulatory protein (StAR). The molecular docking further revealed the direct combination between anthocyanins and StAR, suggesting that anthocyanins with monosaccharide were more likely to interact with StAR than with diglycoside. Taken together, these data indicate that recipient R2C cells under oxidative stress submitted to anthocyanins exhibited improved steroidogenesis in a structure-dependent manner. Anthocyanins could be considered the ideal ingredients against oxidative stress-induced testosterone deficiency.

Amentoflavone-Enriched Selaginella rossii Protects against Ultraviolet- and Oxidative Stress-Induced Aging in Skin Cells.

Selaginellaceae plants are used in cosmetics to limit skin aging. This study is the first to investigate the anti-aging effects of Selaginella rossii (SR) on ultraviolet B (UVB)- and oxidative stress-induced skin cells. The 95% ethanol extract of Selaginella rossii (SR95E) contained much higher amounts of amentoflavone (AMF), an active compound, than other Selaginellaceae plants and was more effective in inhibiting matrix metalloproteinase (MMP)-1 expression in CCD-986sk fibroblasts. SR95E significantly decreased UVB-induced MMP-1, MMP-2, MMP-3 and MMP-9 expression and enhanced procollagen type I C-peptide content and mRNA expression of collagen type I alpha (COL1A)1 and COL1A2 in CCD-986sk fibroblasts. In HaCaT keratinocytes, SR95E treatment also dose-dependently decreased UVB-induced MMP-1 concentration and MMP-1, MMP-2, MMP-3 and MMP-9 mRNA expression. Moreover, SR95E treatment markedly inhibited UVB-induced c-Jun N-terminal kinase and p38 mitogen-activated protein kinase signaling and nuclear factor kappa-B signaling in HaCaT cells. Furthermore, SR95E and AMF markedly regulated the 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced expression of cellular senescence-related markers, including p16, p21 and LMNB1, in HaCaT cells. Overall, this study indicates that SR may have potential as a functional material on preventing UVB- and AAPH-induced skin aging and wrinkles.

Kinetics of lipid radical formation in lipoproteins from β-thalassemia: Implication of cholesteryl esters and α-tocopherol

Vascular complications in β-thalassemia are associated with oxidative modification of lipoproteins under high oxidative stress. The lipid components of lipoproteins are oxidized via lipid peroxidation and produce lipid radicals (L•) as the key initial intermediates. Modification of lipid components, therefore, might result in alterations in the rate and products of lipid peroxidation. In this study, the kinetics of L• formation during the 2,2'-Azobis(2-amidinopropane) dihydrochloride (AAPH)- and hemin-induced oxidation of low-density and high-density lipoproteins (LDL and HDL) from β-thalassemia patients and healthy volunteers were investigated using a specific and sensitive fluorescence probe for L•. Kinetic parameters, including initial lag time, propagation rate and total L• production, were calculated by monitoring a fluorescence-active NBD-Pen-L• adduct. Oxidation of thalassemia lipoproteins exhibited a significantly shorter lag time but a slower propagation rate of L• formation when compared with healthy lipoproteins. LDL showed higher resistance to oxidation during the initiation phase but higher L• formation than HDL. Our results indicated that the levels of α-tocopherol determined the initial lag time, whereas the levels of core lipids and cholesteryl esters, especially cholesteryl linoleate (CL), determined the propagation rate and total L• production. The difference in potency of AAPH and hemin supported that hemin preferentially targeted core lipids. Moreover, analysis of 13-hydroxyoctadecadienoic acid cholesteryl ester (13-HODE-CE)/CE ratio indicated that thalassemia lipoproteins have higher susceptibility to oxidation than healthy lipoproteins. In conclusion, our findings suggested that CL and α-tocopherol were implicated in the susceptibility of lipoproteins to lipid peroxidation in physiological and pathological conditions of β-thalassemia.

Raman Spectroscopy investigate structural change of rice bran protein induced by three oxidants

ABSTRACT The effects of lipid peroxidation on rice bran protein (RBP) structure was examined through Raman Spectroscopy. 2,2’-azobis (2-amidinopropane) dihydrochloride (AAPH), acrolein, and malondialdehyde (MDA) are chosen for lipid peroxidation. Incubation of RBP with the increasing concentration of three oxidants resulted in a gradual generation of protein carbonyl derivatives. It can be deduced from the Raman spectra that a low concentration of AAPH and acrolein both decreased the percentage of α-helix and β-sheet, which increased with MDA concentration. The Raman intensities of tryptophan residues of oxidized RBP by AAPH and acrolein, both initially increased and then decreased with oxidation concentration. After MDA treatment, the Raman intensities corresponding to Trp residues and Tyr doublet ratio of RBP were increased and then decreased, and decreased and then increased with oxidation concentration, respectively. The structural change induced by RBP oxidation with the Raman Spectroscopy can aid in refining the function of RBP characteristics and control the adjustment of the storage condition.

Functional and Allergenic Properties Assessment of Conalbumin (Ovotransferrin) after Oxidation.

Conalbumin (CA) is an iron-binding egg protein that has various bioactivities and causes major allergenicity in humans. This study investigated how oxidation affects the multiple functional properties of CA. The lipid peroxidation method was used to prepare treated CA [2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH)-CA and acrolein-CA] complexes. CA induced structural changes through oxidation. These changes enhanced the digestibility, rate of endocytosis in dendritic cells, and emulsifying and foaming properties of CA. ELISA and immunoblot analysis showed that the complexes reduced the IgE-binding ability of CA through lipid oxidation. KU812 cell assays showed that modification by AAPH and acrolein caused the release of IL-4 and histamine to decline. In conclusion, oxidation treatment modified the functional and structural properties of CA, reducing allergenicity during processing and preservation.

Pomegranate (Punica granatum) By-Product Extract Influences the Oxylipids Profile in Primary Bovine Aortic Endothelial Cells in a Model of Oxidative Stress

Aerobic metabolism produces reactive oxygen species (ROS) as a natural by-product that can play a significant role in cell signaling and homeostasis. Excessive and uncontrolled production of ROS, however, can lead to oxidative stress that causes damage to immune cells and is related to several diseases in dairy cattle. Endothelial cells are essential for optimal immune and inflammatory responses but are especially sensitive to the damaging effects of ROS. Accordingly, investigating antioxidant strategies that can mitigate the detrimental impact of ROS on endothelial functions could impact compromised host defenses that lead to increased disease susceptibility. The objective of this study was to test the antioxidant effect of different concentrations (20, 40, 60, 80 μg/ml) of pomegranate by-product extract (PBE) on bovine aortic endothelial cells (BAECs). A model of oxidative stress was developed using in vitro exposure of BAEC to 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) to induce the formation of ROS. The BAEC were then analyzed for cell viability, ROS production, fatty acids profile, and oxylipids formation. The BAECs viability did not change after different concentrations of PBE and remained up to 80% over control; whereas, intracellular ROS showed a reduction passing from 20 to 50% with increasing PBE concentration from 20 to 80 μg/ml, respectively. The PBE extract clearly demonstrated efficacy in reducing the concentrations of pro-inflammatory oxylipids with a concomitant enhancement of anti-inflammatory oxylipids. In particular, the pro-inflammatory 13-hydroxyoctadecadienoic acid and its derived anti-inflammatory 13-hydroperoxoctadecaienoic acid were found lower and higher, respectively, in PBE+AAPH treated cells than AAPH treatment. Data from the present study support in vivo future experimental use of pomegranate by-product extract to study its potential beneficial effect against oxidative stress conditions in dairy cattle.

Effects of Peroxyl Radicals on the Structural Characteristics and Fatty Acid Composition of High-Density Lipoprotein from Duck Egg Yolk

In this study, high-density lipoprotein (HDL) from duck egg yolk was subjected to oxidation with a system based on 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH)-derived peroxyl radicals. The effects of peroxyl radicals on the protein carbonyl, free sulfhydryl, secondary/tertiary structure, surface hydrophobicity, solubility, particle size distribution, zeta potential and fatty acid composition of HDL were investigated by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Fourier-transform infrared spectroscopy (FTIR), circular dichroism (CD), fluorescence spectroscopy, dynamic light scattering and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The results indicated that the content of protein carbonyl was significantly increased, that of free sulfhydryl was obviously reduced, and the ordered secondary structure was also decreased with increasing AAPH concentration. In addition, the surface hydrophobicity and solubility of HDL showed apparent increases due to the exposure of hydrophobic groups and aggregation of protein caused by oxidation. The fatty acid composition of HDL exhibited pronounced changes due to the disrupted protein–lipid interaction and lipid oxidation by AAPH-derived peroxyl radicals. These results may help to elucidate the molecular mechanism for the effect of lipid oxidation products on the oxidation of duck yolk proteins.