Peroxyl Radical Scavenging Activity Research Articles

Enzyme-Digested Edible Bird's Nest (EBND) Prevents UV and Arid Environment-Induced Cellular Oxidative Stress, Cell Death and DNA Damage in Human Skin Keratinocytes and Three-Dimensional Epithelium Equivalents.

The aim of this study is to investigate the repressive effects of enzyme-digested edible bird's nest (EBND) on the combination of arid environment and UV-induced intracellular oxidative stress, cell death, DNA double-strand breaks (DSBs) and inflammatory responses in human HaCaT keratinocytes and three-dimensional (3D) epithelium equivalents. An oxygen radical antioxidant capacity assay showed that EBND exhibited excellent peroxyl radical scavenging activity and significantly increased cellular antioxidant capacity in HaCaT cells. When EBND was administered to HaCaT cells and 3D epitheliums, it exhibited significant preventive effects on air-drying and UVA (Dry-UVA)-induced cell death and apoptosis. Dry-UVA markedly induced intracellular reactive oxygen species (ROS) generation in HaCaT cells and 3D epitheliums as quantified by CellROX® Green/Orange reagents. Once HaCaT cells and 3D epitheliums were pretreated with EBND, Dry-UVA-induced intracellular ROS were significantly reduced. The results from anti-γ-H2A.X antibody-based immunostaining showed that EBND significantly inhibited Dry-UVA-induced DSBs in HaCaT keratinocytes. Compared with sialic acid, EBND showed significantly better protection for both keratinocytes and 3D epitheliums against Dry-UVA-induced injuries. ELISA showed that EBND significantly suppressed UVB-induced IL-6 and TNF-α secretion. In conclusion, EBND could decrease arid environments and UV-induced harmful effects and inflammatory responses in human keratinocytes and 3D epithelium equivalents partially through its antioxidant capacity.

Peroxyl radical scavenging activity measurement of antioxidants using histidine-stabilized and glutathione-capped fluorescent gold nanoclusters

A fluorescent gold nanocluster was used for determining peroxyl radical scavenging activity of antioxidants. Histidine was used as a green reducing and protective agent, and glutathione (GSH) enhanced the fluorescence intensity of histidine-stabilized gold nanoclusters (AuNCs) by ligand exchange process. When AAPH-induced oxidation of GSH occurred, the initial fluorescence intensity of GSH-capped AuNCs (λex = 450 nm λem = 502 nm) was decreased with static quenching. The decline of fluorescence intensity of the GSH-capped AuNCs upon peroxyl radical attack is diminished with the addition of antioxidants to the reaction medium, the difference in fluorescence intensity being related to peroxyl radical scavenging activity of antioxidants. The 50 % inhibitive concentration of related antioxidant compounds were determined and compared to those of crocin bleaching assay. Inhibition % of sage (Salvia officinalis L.) and green tea (Camellia sinensis) infusions against peroxyl radicals were investigated. The proposed assay can be used for simple and selective estimation of the peroxyl radical scavenging activity in complex matrices, as histidine-stabilized GSH-capped AuNCs were selective toward peroxyl radicals, not affected by other ROS at the studied concentrations.

Computational analysis of peroxyl radical scavenging capacity of coumestrol: insights into kinetics and reaction mechanisms

AbstractCoumestrol (COM) is a phytoestrogen from the coumestan family that occurs naturally in various foods such as clover, soybeans, alfalfa sprouts, and legumes. Besides its antiestrogenic activity, COM exerts various biological activities, including anticancer, antioxidant, and α‐glucosidase inhibitory. In terms of antioxidant activity, COM has shown an excellent profile according to experimental studies; however, its mechanism of action has not been successfully determined thus far. In this contribution, we evaluated the kinetics and mechanism of the peroxyl radical (ROO•) scavenging activity of COM using quantum chemistry methods. It has been shown that the environment and the nature of the ROO• radical play a determining role in the antioxidant activity of COM. In lipid media, COM exhibits moderate ROO• scavenging activity via the formal hydrogen transfer (FHT) mechanism regardless of the nature of the ROO• radical. However, in polar environments, its activity becomes more important as the reactivity of the ROO• radical increases. Under these conditions, the single electron transfer (SET) mechanism becomes dominant or even exclusive.

Efficacy of Propyl Selenoethers Against Peroxyl Radical Induced Protein Damage: Effect of Functional Group Substitution

Background: Proteins are the critical bio-molecules for cellular function and are also considered to be highly susceptible to reactive oxygen species (ROS)-induced oxidative damages. Methods: The present study aimed to evaluate some simple water-soluble aliphatic organoselenium compounds bearing different functional groups but of similar carbon chain (propyl) length for a protective effect against 2,2’-azobis-(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative damage using mitochondria as an in vitro model. Results: The results indicated that APPH (20 mM) treatment of mitochondrial fraction induced protein carbonylation, leading to inactivation of redox enzymes and electron transport chain (ETC) and, ultimately the mitochondrial dysfunction. On the other hand, treatment with 0.5 mM of monoselenobutyric acid (SeBA) and monoselenopropyl alcohol (SePOH) significantly prevented APPH-induced protein carbonylation in mitochondrial fraction and restored activities of mitochondrial proteins. On the contrary, monoselenopropyl amine (SePAm) treatment at identical concentrations did not show significant protection to mitochondrial activity from AAPH-induced oxidative damages. The above results concur with the reported peroxyl radical scavenging activities of the above molecules. Conclusion: In conclusion, SeBA and SePOH are potential candidate molecules to protect proteins from oxidative damage and, therefore, can be useful for managing oxidative stress in cellular models.

Effect of immersion time of dried scallop on amino acids, antioxidant and ACE inhibitory activities in Japanese traditional Dashi

The dried adductor muscle of scallop (Mizuhopecten yessoensis) has been used as a material for “dashi.” To prepare dashi, the dried scallop must be soaked in water before boiling. Although dashi recipes using dried scallops have been passed down for many generations as a local food, the optimum immersion time prior to cooking has not been elucidated. Thus, the objective of the present study was to determine the optimum immersion time of dried scallops for the preparation of dashi from the viewpoint of components and biological activities.Immersion of dried scallops changed the L * (lightness), a* (redness), and b* (yellowness) of dashi, and subsequent heat treatment led to evident changes in these values. Glycine (Gly), taurine (Tau), and arginine (Arg) are the major components of dashi, accounting for approximately 62%, 15%, and 11% of the total free amino acids, respectively. When the immersion time was 8 h and more, these major amino acids were significantly increased in dashi with or without heating compared to that after 1 h of immersion without heating.Heat treatment significantly decreased maltose in dashi prepared after 8 h of immersion. Dashi prepared following 4 h or more of immersion had significantly enhanced peroxyl radical scavenging and angiotensin converting enzyme (ACE) inhibitory activities compared to those prepared following 1 h of immersion.A minimum of 8 h of immersion appears to be necessary for preparing dashi rich in umami, sweetness, and antioxidant and ACE inhibitory activities. An extended immersion time (12 h) caused evident progress in the Maillard reaction. The soluble and aromatic compounds of the reaction products may affect the taste and functionality of dashi.

Protein hydrolysate from duck egg white by Flavourzyme® digestion: Process optimisation by model design approach and evaluation of antioxidant capacity and characteristic properties

Studies on duck egg white (DEW) hydrolysate with potential health benefits are limited despite the fact that duck egg is an excellent source of protein to develop hydrolysate similar to that of a chicken egg. The present communication deals with the optimisation of antioxidant capacity of hydrolyzed protein using Flavourzyme® assisted digestion of DEW, adopting Response surface methodology, for the development of hydrolysate from DEW (R2 = 0.9868). Antioxidant capacity was measured by %ABTS•+ scavenging activity. Hydrolysis for 19.24 h and enzyme/substrate ratio of 320.8 μL (164.4 unit) enzyme/20 mL of DEW were recorded as optimum. The DEW hydrolysate (DEWH) exhibited a maximum %ABTS•+ scavenging activity of 56.9, at a concentration of 10 μL at 52.28 μg mL−1 proteins (15.4 μmol L−1 Trolox equivalent). The DEWH also showed strong peroxyl and DPPH radical scavenging activities. Powder of DEWH was prepared by spray and freeze-drying. The DEWH were analysed by RP-HPLC, SDS-PAGE, SEM and FTIR. The results suggest that hydrolysis of DEW proteins by Flavourzyme® could be exploited for effective utilization of duck eggs to produce natural antioxidant-rich hydrolysate, which could significantly contribute to the socio-economic development of the poultry farmers and supplement human nutrition in future.

Modeling the peroxyl radical scavenging behavior of Carnosic acid: Mechanism, kinetics, and effects of physiological environments

Carnosic acid (CA), a phenolic diterpene and abietane-type compound, is a potent natural antioxidant with medical benefits. The present paper elucidates, for the first time, the kinetics and the exact mechanism of the peroxyl radical scavenging activity of CA in the gas phase and under physiological conditions. According to the obtained results, the reaction of CA with HOO• is significantly faster in aqueous solution than in the gas phase and nonpolar environments. The abstraction of the hydrogen atom from 2-OH is the decisive mechanism in the gas phase and nonpolar media, while both hydrogen abstraction (15%) and electron transfer (85%) mechanisms can take place in aqueous solution. The overall rate coefficient in water (4.73 × 106 M−1 s−1) is about 36 times higher than that of the reference antioxidant Trolox (1.30 × 105 M−1 s−1), suggesting that CA is a potent scavenger of peroxyl radicals in polar media.

Characterization of antioxidant efficacy of peptide extracts as affected by peptide interactions during the ripening of Spanish dry-cured ham

Microenvironmental factors may influence the antioxidant efficacy of food-derived peptides. This study evaluated the in vitro antioxidant properties of peptides released during the ripening (9 to 24 months of processing) of Spanish dry-cured ham (Biceps femoris muscle) assisted by spectral-chromatographic methodologies. Results indicated that 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical-cation (ABTS●+) quenching capacity of peptide extracts significantly increased (P < 0.05) until 24 months whereas peroxyl radical (ROO●) scavenging activity increased slowly and remained with non-significant change (P > 0.05) between 15 and 24 months. However, both ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH●) scavenging ability significantly decreased (P < 0.05) at 24 months. Additionally, morphological traits of peptide extracts suggested that a prolonged ripening enabled the formation/reconstruction of intra-/inter-molecular interactions in dispersion medium. Meta-analysis of chromatographic and spectral fingerprinting proved that the non-conjugated/π-conjugated oligomers mediated by aromatic moieties probably differentiated DPPH● and ABTS●+ antioxidant performance of peptides, showing a potentially altered solvent polarization process.

Hydrogen-Generating Silica Material Prevents UVA-ray-Induced Cellular Oxidative Stress, Cell Death, Collagen Loss and Melanogenesis in Human Cells and 3D Skin Equivalents.

Ultraviolet-A (UVA) irradiation induces harmful effects on skin cells and accelerates skin aging through oxidative stress. In this study, the effects of a hydrogen-generating silica material named ULH-002 against UVA injuries in human cells and 3D skin equivalents were investigated. The oxygen radical absorption capacity (ORAC) assay showed that both freshly prepared ULH-002 solutions and 7-day-old solutions exhibited equal peroxyl radical (ROO·) scavenging activities concentration-dependently. CellROX® green/orange staining showed that ULH-002 could reduce UVA-induced oxidative stress in human keratinocytes HaCaT and human gingival fibroblasts (HGFs). ULH-002 significantly prevented UVA-induced apoptotic/necrotic cell death and cell-viability decline in HGFs and keratinocytes, as shown by Annexin V/PI apoptosis assay and PrestoBlue assay, respectively. Immunostaining showed that ULH-002 prevented the UVA-induced deterioration of expression of both type IV and I collagens in the 3D skin equivalents, and similarly in monolayer HGFs. UVA-enhanced melanogenesis was observed in human melanocytes HMV-II and HMV-II cell-containing 3D skin equivalents, but markedly prevented by ULH-002 as demonstrated by Fontana–Masson’s staining. In conclusion, our data suggested that ULH-002 could protect human keratinocytes and fibroblasts from UVA-induced injuries, prevent the loss of type IV and I collagens, as well as reduce melanogenesis. ULH-002 might be developed as a skin care reagent in the cosmetic industry.

Effects of Nitrogen Availability on the Antioxidant Activity and Carotenoid Content of the Microalgae Nephroselmis sp.

Nephroselmis sp. was previously identified as a species of interest for its antioxidant properties owing to its high carotenoid content. In addition, nitrogen availability can impact biomass and specific metabolites’ production of microalgae. To optimize parameters of antioxidant production, Nephroselmis sp. was cultivated in batch and continuous culture conditions in stirred closed photobioreactors under different nitrogen conditions (N-repletion, N-limitation, and N-starvation). The aim was to determine the influence of nitrogen availability on the peroxyl radical scavenging activity (oxygen radical absorbance capacity (ORAC) assay) and carotenoid content of Nephroselmis sp. Pigment analysis revealed a specific and unusual photosynthetic system with siphonaxanthin-type light harvesting complexes found in primitive green algae, but also high lutein content and xanthophyll cycle pigments (i.e., violaxanthin, antheraxanthin, and zeaxanthin), as observed in most advanced chlorophytes. The results indicated that N-replete conditions enhance carotenoid biosynthesis, which would correspond to a higher antioxidant capacity measured in Nephroselmis sp. Indeed, peroxyl radical scavenging activity and total carotenoids were higher under N-replete conditions and decreased sharply under N-limitation or starvation conditions. Considering individual carotenoids, siphonaxanthin, neoxanthin, xanthophyll cycle pigments, and lycopene followed the same trend as total carotenoids, while β-carotene and lutein stayed stable regardless of the nitrogen availability. Carotenoid productivities were also higher under N-replete treatment. The peroxyl radical scavenging activity measured with ORAC assay (63.6 to 154.9 µmol TE g−1 DW) and the lutein content (5.22 to 7.97 mg g−1 DW) were within the upper ranges of values reported previously for other microalgae. Furthermore, contents of siphonaxanthin ere 6 to 20% higher than in previous identified sources (siphonous green algae). These results highlight the potential of Nephroselmis sp. as a source of natural antioxidant and as a pigment of interest.

On the peroxyl radical scavenging ability of β‐sitosterol in lipid media: A theoretical study

AbstractVegetable consumption was considered healthy, mainly because a large number and variety of antioxidants were identified from them. However, the main component in all vegetables is β‐sitosterol, and although its antioxidant capacity was reported, little is known about the reaction mechanism involved. In this study, thermodynamic and kinetic studies of the peroxyl radical scavenging activity of β‐sitosterol in lipid media were carried out, employing the density functional theory (DFT). The results showed that the hydrogen transfer (HT) reaction mechanism is the most important in the peroxyl radical scavenging activity of β‐sitosterol when peroxyl radicals with a medium reactivity such as •OOH and •OOCH3 were considered. However, when the peroxyl radical has significant reactivity, it could react through the radical adduct formation (RAF) mechanism. The calculated overall reaction rate constants of the peroxyl radical scavenging of β‐sitosterol were 8.76 × 103 and 1.54 × 102 M−1 s−1 for the peroxyl radicals •OOH and •OOCH3, respectively. According to the previous results, β‐sitosterol might be considered a modest antioxidant, which prevents oxidative damage to biological molecules such as cell membrane lipids. These results support the idea that vegetables could be considered antioxidants in the organism, and therefore, considering the consumption of vegetables in the daily diet could prevent cell aging by inhibiting oxidative damage.

Insights into the Discovery of Novel Neuroprotective Agents: A Comparative Study between Sulfanylcinnamic Acid Derivatives and Related Phenolic Analogues.

Exogenous antioxidants may be beneficial therapeutic tools to tackle the oxidative damage in neurodegenerative diseases by regulation of the redox state that is critical for cell viability and organ function. Inspired by natural plant polyphenols, a series of cinnamic acid-based thiophenolic and phenolic compounds were synthesized and their antioxidant and neuroprotective properties were studied. In general, our results showed that the replacement of the hydroxyl group (OH) by a sulfhydryl group (SH) increased the radical scavenging activity and enhanced the reaction rate with 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•) and galvinoxyl radical (GO•). These results correlated well with the lower oxidation potential (Ep) values of thiophenols. However, a lower peroxyl radical (ROO•) scavenging activity was observed for thiophenols in oxygen radical absorbance capacity (ORAC-FL) assay. Furthermore, the introduction of 5-methoxy and 5-phenyl groups in the aromatic ring of 4-thioferulic acid (TFA) 2 and ferulic acid (FA) 1 did not significantly improve their antioxidant activity, despite the slight decrease of Ep observed for compounds 5, 6, and 9. Concerning cinnamic acid amides, the antioxidant profile was similar to the parent compounds. None of the compounds under study presented significant cytotoxic effects in human differentiated neuroblastoma cells. Thiophenolic amide 3 stands out as the most promising thiophenol-based antioxidant, showing cellular neuroprotective effects against oxidative stress inducers (hydrogen peroxide and iron).

Protective Effects of Novel Antioxidant Peptide Purified from Alcalase Hydrolysate of Velvet Antler Against Oxidative Stress in Chang Liver Cells in Vitro and in a Zebrafish Model In Vivo.

Velvet antler has a long history in traditional medicine. It is also an important healthy ingredient in food as it is rich in protein. However, there has been no report about antioxidant peptides extracted from velvet antler by enzymatic hydrolysis. Thus, the objective of this study was to hydrolyze velvet antler using different commercial proteases (Acalase, Neutrase, trypsin, pepsin, and α-chymotrypsin). Antioxidant activities of different hydrolysates were investigated using peroxyl radical scavenging assay by electron spin resonance spectrometry. Among all enzymatic hydrolysates, Alcalase hydrolysate exhibited the highest peroxyl radical scavenging activity. Alcalase hydrolysate was then purified using ultrafiltration, gel filtration, and reverse-phase high performance liquid chromatography. The purified peptide was identified to be Trp-Asp-Val-Lys (tetrapeptide) with molecular weight of 547.29 Da by Q-TOF ESI mass spectroscopy. This purified peptide exhibited strong scavenging activity against peroxyl radical (IC50 value, 0.028 mg/mL). In addition, this tetrapeptide showed significant protection ability against AAPH-induced oxidative stress by inhibiting of reactive oxygen species (ROS) generation in Chang liver cells in vitro and in a zebrafish model in vivo. This research suggests that the tetrapeptide derived from Alcalase-proteolytic hydrolysate of velvet antler are excellent antioxidants and could be effectively applied as functional food ingredients and pharmaceuticals.

Ionic liquid associated with ultrasonic-assisted extraction: A new approach to obtain carotenoids from orange peel.

The aim of this study was to develop a new method for carotenoid extraction from orange peel, using ionic liquid (IL) to replace conventional organic solvents, assisted by ultrasound. Four different IL were tested: 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]), 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), and 1-hexyl-3-methylimidazolium chloride ([HMIM][Cl]). Response surface methodology was applied in order to optimize the carotenoid extraction conditions, and Amberlite XAD-7HP resin was used to separate the carotenoids from the IL, allowing their recovery. Determination of carotenoids was carried out by high-performance liquid chromatography coupled to photodiode array and mass spectrometry detectors (HPLC-DAD-MSn). Thermal stability at different temperatures (60 °C and 90 °C) and peroxyl radical scavenging activity of the carotenoid extracts obtained with acetone and IL were evaluated. [BMIM][Cl] was the most effective IL, leading to a total carotenoid content of 32.08 ± 2.05 μg/g, while 7.88 ± 0.59 μg/g of dry matter was obtained by acetone extraction. IL and carotenoid recoveries using XAD-7HP resin were in the range of 59.5-63.8% and 52.2-58.7%, respectively. A carotenoid extract was successfully obtained with IL, finally isolated just by using ethanol, besides being more stable and presenting higher antioxidant activity than that obtained with acetone.

Detailed Investigation of the Outstanding Peroxyl Radical Scavenging Activity of Two Novel Amino-Pyridinol-Based Compounds.

The ability of two novel amino-pyridinol based compounds (NPyr6 and NPyr7) as peroxyl radical scavengers was investigated in silico. The gathered data indicate that they are exceptionally efficient in that role. However, solvent polarity influences their relative efficiency for that purpose. NPyr6 was identified as the best peroxyl radical scavenger in lipid solution, while NPyr7 takes that place in aqueous solution. Both compounds present two acid-base equilibria, which influence their reactivity in aqueous solution. The associated pKa values were estimated. Several reaction mechanisms were explored. Hydrogen transfer from the phenolic group was identified as the chemical route with the highest contribution to the antioxidant behavior of the investigated compounds in both, nonpolar medium and aqueous solution (at 2 ≤ pH ≤ 10). At higher pH other reaction pathways become the most relevant ones. In addition, their bioavailability, cell permeability, safety, and manufacturability were evaluated. According to these, particularly toxicity, NPyr7 seems to be a better candidate for use as an oral drug to fight oxidative stress than NPyr6.

Free radical scavenging activity of the peptide from the Alcalase hydrolysate of the edible aquacultural seahorse ( Hippocampus abdominalis )

Seahorses, Hippocampus abdominalis, have a long history in traditional Chinese medicine as an important healthy ingredient in foods. This study evaluated the antioxidant activity of an enzymatic hydrolysate prepared from a seahorse bred in Jeju, South Korea. Experiments were performed in vitro using electron spin resonance spectrometry (ESR) to determine the free radical scavenging activity and in vivo using a zebrafish model to determine the protective effects against 2,2-azobis hydrochloride (AAPH)-induced oxidative damage. H. abdominalis protein hydrolysate (HPH) exhibited peroxyl radical scavenging activity (IC50 =0.58mg/ml) generated by the water-soluble AAPH (azo initiator of peroxyl radicals). HPH reduced dose-dependently both intracellular reactive oxygen species (ROS) levels in AAPH-induced cells and cell death in AAPH-induced zebrafish embryos. The antioxidant peptide purified from HPH was identified as a tripeptide (alanine-glycine-aspartic acid) using Q-TOF ESI mass spectroscopy. Thus, this study demonstrated that HPH contains antioxidant peptides that exhibit a strong antioxidant activity. PRACTICAL APPLICATIONS: Hippocampus abdominalis is one of the largest seahorse species and cultivated in many countries. Because of its large body size compared to other seahorse species, H. abdominalis has acquired considerable consumer attraction in the global market. Owing to its biologically useful properties, it recently gained attention as the natural products obtained from H. abdominalis have varied applications in the field of medicine, health care products, and functional foods. Thus, commercial products of this particular seahorse species are popular among customers, especially in China. The purpose of this study was to evaluate the antioxidant property of H. abdominalism, cultured in a commercial seahorse farm in Jeju Island. Owing to its prominent antioxidant activity, it could be used as an ingredient in medicinal preparations, nutraceuticals, and functional foods.

Naturally occurring rare sugars are free radical scavengers and can ameliorate endoplasmic reticulum stress.

Because of potential use of naturally occurring rare sugars as sweeteners, their effect on superoxide (SO), hydroxyl and peroxyl radicals and endoplasmic reticulum (ER) stress was examined in human coronary artery endothelial cells. SO generation was measured using the superoxide-reactive probe 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2-A]pyrazin-3-one hydrochloride chemiluminescence. Phycoerythrin fluorescence based assay was used to monitor scavenging activity of sugars in the presence of hydroxyl or peroxyl radical generators [CuSO4 and azobis (2 amidinopropane) hydrochloride respectively]. Measurements were made in relative light units (RLU). ER stress was measured with an ER stress-sensitive secreted alkaline phosphatase (SAP) assay and by Western blot analysis of the expression and phosphorylation of key proteins in the unfolded protein response, namely CHOP47, eIF2α and JNK1. D-Glucose (27.5mM) increased SO generation (5536±283vs.2963±205RLU in controls; p<0.0007) and decreased SAP secretion (73411±3971vs.101749±7652RLU in controls; p<0.005) indicating ER stress. Treatment of cells with 5.5 or 27.5mM of D-allulose, D-allose, D-sorbose and D-tagatose reduced SO generation (all p<0.05). This could not be attributed to inhibition of cellular uptake of dextrose by the rare sugars tested. In a cell free system, all four rare sugars had significantly more SO, hydroxyl and peroxyl radical scavenging activity compared to dextrose (all p<0.01). Treatment of cells with rare sugars reduced ER stress. However, unlike other three rare sugars, D-sorbose did not inhibit tunicamycin-induced eIF2α phosphorylation. Naturally occurring rare sugars are free radical scavengers and can reduce ER stress.

Comparison of Lipid Peroxyl Radical Scavenging Activity and total Phenolic content of four selected Citrus species leaves Extract

Comparison of Lipid Peroxyl Radical Scavenging Activity and total Phenolic content of four selected Citrus species leaves Extract

Novel antioxidant peptides obtained by alcalase hydrolysis of Erythrina edulis (pajuro) protein.

Oxidative reactions are responsible for the changes in quality during food processing and storage. Oxidative stress is also involved in multiple chronic diseases, such as cardiovascular and neurodegenerative disorders, diabetes, cancer, and aging. The consumption of dietary antioxidants has been demonstrated to help to reduce the oxidative damage in both the human body and food systems. In this study, the potential of Erythrina edulis (pajuro) protein as source of antioxidant peptides was evaluated. Pajuro protein concentrate hydrolyzed by alcalase for 120 min showed potent ABTS·+ and peroxyl radical scavenging activity with Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) values of 1.37 ± 0.09 µmol TE mg-1 peptide and 2.83 ± 0.07 µmol TE mg-1 peptide, respectively. Fractionation of the hydrolyzate to small peptides resulted in increased antioxidant activity. De novo sequencing of most active fractions collected by chromatographic analysis enabled 30 novel peptides to be identified. Of these, ten were synthesized and their radical activity evaluated, demonstrating their relevant contribution to the antioxidant effects observed for pajuro protein hydrolyzate. The sequences identified represent an important advance in the molecular characterization of the pajuro protein, demonstrating its potential as a source of antioxidant peptides for food and nutraceutical applications. © 2018 Society of Chemical Industry.

A novel colorimetric sensor for measuring hydroperoxide content and peroxyl radical scavenging activity using starch-stabilized gold nanoparticles

A novel colorimetric nanosensor was developed for evaluating peroxyl radical scavenging activity of phenolic antioxidants and for the detection of hydroperoxides formed during AAPH-induced oxidation of linoleic acid emulsions. Starch was used as a green reduction/stabilization agent for gold nanoparticles (AuNPs) synthesis in alkaline medium. When tert-butyl hydroperoxide (tert-BHP) was incubated with an excess of iodide ions in a 37 °C water bath for 90 min, triodide (I3–) was formed in an amount equivalent to tert-BHP concentration. Upon the addition of starch-stabilized gold nanoparticles (ss-AuNPs) solution to the incubation mixture, triiodide ions were rapidly adsorbed on the surface of AuNPs and caused their aggregation. A concomitant red shift (from 525 nm to 563 nm) of surface plasmon resonance (SPR) absorption of the nanoparticles was observed, absorbance linearly increasing with aqueous tert-BHP concentration. The method provided an LOD of 39 µM for tert-BHP, and was validated through linearity, precision and accuracy. The concentration of hydroperoxides estimated in linoleic acid peroxidation correlated well with those found by the reference ferric thiocyanate assay. Peroxyl radical scavenger antioxidants decreased the red-shifted SPR absorption of aggregated ss-AuNPs, thereby enabling an indirect estimation of antioxidant activity. This AuNPs-based colorimetric sensor is the first of its kind to directly determine peroxyl radical scavenging activity of polyphenols. The half-maximal inhibitive concentrations (IC50) of selected antioxidant compounds were calculated by utilizing the decrease in absorbance with increasing concentration of scavengers, and compared to those of classical oxygen radical absorbance capacity (ORAC) assay. The proposed nanosensor was superior over FL-based ORAC in determining the peroxyl radical scavenging activity of the lipophilic antioxidant α-tocopherol. The percentage scavenging of real samples such as green tea infusion and synthetic serum were determined. The proposed assay can be used for estimating the peroxyl scavenging of various food and biological samples in terms of its low cost, ease of use and compatibility.