Peroxyl Radicals Research Articles

Theoretical Insights into the Oxidative Stress-Relieving Properties of Pinocembrin─An Isolated Flavonoid from Honey and Propolis.

Bee products are a valuable group of substances that have a wide range of applications for humans. They contain a high level of polyphenolic compounds, which have been shown to combat radicals and effectively reduce oxidative stress. In this study, density functional theory was utilized to determine the anti-OOH activity, sequestration of free Cu(II) and Fe(III) ions, the potential pro-oxidative activity of the formed complexes, and the repairing capabilities toward essential biomolecules. The kinetic constants for scavenging of hydroperoxide radical were found to be low, with an order of magnitude not exceeding 10-3 M-1 s-1. Chelating properties showed slightly more satisfactory outcomes, although most complexes exhibited pro-oxidant activity. Pinocembrin, however, proved effective in repairing oxidatively damaged biological compounds and restoring their original functionality. The study found that whilst the system displays limited type I and type II antioxidant activity, it may support the role of physiological reductants already present in the biological matrix.

In Vitro Antioxidant and In Vivo Antigenotoxic Features of a Series of 61 Essential Oils and Quantitative Composition-Activity Relationships Modeled through Machine Learning Algorithms.

The antioxidant activity of essential oils (EOs) is an important and frequently studied property, yet it is not sufficiently understood in terms of the contribution of EOs mixtures' constituents and biological properties. In this study, a series of 61 commercial EOs were first evaluated as antioxidants in vitro, following as closely as possible the cellular pathways of reactive oxygen species (ROS) generation. Hence, EOs were assessed for the ability either to chelate metal ions, thus interfering with ROS generation within the respiratory chain, or to neutralize 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and lipid peroxide radicals (LOO•), thereby halting lipid peroxidation, as well as to neutralize 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid cation radicals (ABTS•+) and hydroxyl radicals (OH•), thereby preventing the ROS species from damaging DNA nucleotides. Showing noteworthy potencies to neutralize all of the radicals at the ng/mL level, the active EOs were also characterized as protectors of DNA double strands from damage induced by peroxyl radicals (ROO•), emerging from 2,2'-azobis-2-methyl-propanimidamide (AAPH) as a source, and OH•, indicating some genome protectivity and antigenotoxicity effectiveness in vitro. The chemical compositions of the EOs associated with the obtained activities were then analyzed by means of machine learning (ML) classification algorithms to generate quantitative composition-activity relationships (QCARs) models (models published in the AI4EssOil database available online). The QCARs models enabled us to highlight the key features (EOSs' chemical compounds) for exerting the redox potencies and to define the partial dependencies of the features, viz. percentages in the mixture required to exert a given potency. The ML-based models explained either the positive or negative contribution of the most important chemical components: limonene, linalool, carvacrol, eucalyptol, α-pinene, thymol, caryophyllene, p-cymene, eugenol, and chrysanthone. Finally, the most potent EOs in vitro, Ylang-ylang (Cananga odorata (Lam.)) and Ceylon cinnamon peel (Cinnamomum verum J. Presl), were promptly administered in vivo to evaluate the rescue ability against redox damage caused by CCl4, thereby verifying their antioxidant and antigenotoxic properties either in the liver or in the kidney.

A Conjugated Microporous Polymer/Wood Aerogel with Physical Adsorption, Chemical Degradation and Antibacterial Self-Cleaning Triple Sewage Treatment Functions.

Conjugated microporous polymers (CMPs) have important applications in the fields of optoelectronics and sewage treatment due to their high specific surface area, broad visible absorption, processability and simple synthesis process. Biocompatibility, recycling, mass production and solar photodegradation are particularly important in wastewater treatment. Here, A CMP with a high specific surface area and a hierarchical pore structure (CPOP) was constructed based on 4,4',4″-Tris(carbazol-9-yl)-triphenylamine (3CZ-TPA). Furthermore, a CMP-loaded wood aerogel (CPOP/wood aerogel) with physical adsorption, chemical degradation, bacterial inhibition and self-cleaning properties was prepared by in situ polymerization and used for wastewater treatment. The obtained CPOP/wood aerogel is highly biocompatible and easy to recycle. In addition, the inherent broad visible light absorption property of CPOP endows it with promising photocatalytic properties. Subsequently, we investigated the photocatalytic mechanism of CPOP, and the results showed that it was mainly affected by peroxyl radicals, which implied and confirmed its microbial self-cleaning for secondary cleaning of water pollutants. The reported studies on CPOP/wood aerogel provide a new direction for water purification materials with excellent adsorption, degradation and antibacterial properties.

Emodin derivatives as promising multi-aspect intervention agents for amyloid aggregation: molecular docking/dynamics simulation, bioactivities evaluation, and cytoprotection.

Alzheimer's disease (AD) is a progressive neurodegenerative disease with complex pathogenesis. Despite the pathogenesis is unknown, the misfolding and accumulation of β-amyloid (Aβ) peptide play the important role in the occurrence and development of AD. Hence, multi-aspect intervention of the misfolded Aβ peptides aggregation is a promising therapy for AD. In previous work, we obtained the emodin derivatives (a-d) with multifunctional anti-AD activities, including metal ions chelation, cholinesterase inhibition, and hydroxyl/superoxide anion radical elimination. In this work, we predicted the interaction of emodin derivatives (a-d) with Aβ by combining molecular docking simulation and molecular dynamics simulation, and evaluated the ability to intervene with the self-, Cu2+- and AChE-induced Aβ aggregation via in vitro methods. The results indicated that a-d could act as the potent multi-aspect intervention agents for Aβ aggregation. In addition, a-d could effectively eliminate peroxyl radical, had virtually no neurotoxicity, and protect cells from oxidative and Aβ-induced damage. The prediction results of ADMET properties showed that a-d had suitable pharmacokinetic characteristics. It suggested that a-d could act as the promising multi-targeted directed ligands (MTDLs) for AD. These results may provide meaningful information for the development of the potential MTDLs for AD which are modified from natural-origin scaffolds.

Current evidence of the role of vitamin E in prolonging a healthy life

This is a narrative review of the evidence of α-tocopherol importance in human health, especially with regards to its vitamin role. α-Tocopherol is a potent peroxyl radical scavenger, and this role is prominent in its efficacy in maintaining the metabolic health of tissues. Vitamin E deficiency is discussed as a tool to understand the impact of α-tocopherol’s absence promoting increased lipid peroxidation and polyunsaturated fatty acid depletion. Downstream deficiency consequences include impacts on choline and one-carbon metabolism, glucose and energy metabolism, and their interactions with critical thiols, such as glutathione. Importantly, human vitamin E deficiency, caused by genetic defects in the α-tocopherol transfer protein (α-TTP), provides important clues for the necessity of α-tocopherol for the peripheral nervous system. Moreover, α-TTP expression in the liver, brain, eyes, and placenta illustrates that these tissues are especially vulnerable and require this specific α-tocopherol delivery mechanism for their protection. Although clinical trial evidence is limited and equivocal about the health benefits of vitamin E supplements, there is epidemiologic evidence of the long-term benefits of increased α-tocopherol intakes in ’healthy’ diets (high in vegetables and fruits, fish, nuts, and seeds, as well as fiber). Significance statement The elaborate regulation of α-tocopherol concentrations by the human body suggests that the consistent consumption of the recommended amounts of dietary α-tocopherol (15 mg) over a lifetime are protective of the at-risk tissues, as well as providing protection from chronic diseases.

Peptidomics Analysis of Soy Protein Hydrolysates-Antioxidant Properties and Mechanism of their Inhibition of the Oxidation of Palm Olein during Frying Cycles.

This study determined for the first time the structure of the peptides (i.e., peptidomics) in soy protein hydrolysates and elucidated their effects on an oil's oxidative stability during frying cycles. The oil investigated was palm olein during 0, 4, 8, and 12 frying cycles of plantain banana chips. Proteins were extracted and hydrolyzed with two proteases. Trypsin hydrolysate (HTRY) exhibited higher anti-radical activity (DPPH, 70.2%) than the control (unhydrolyzed proteins, 33.49%) and pepsin hydrolysate (HPEP, 46.1%) at 200 µg/mL. HPEP however showed a 4.6-fold greater reduction of ferric ions (FRAP) while also possessing a higher peroxyl radical scavenging ability (716 ± 30 µM Trolox Eq/g) than HTRY (38.5 ± 35 µM Trolox Eq/g). During oil oxidative stability tests, HPEP improved the oxidative stability of the palm olein oil after 8 and 12 frying cycles, characterized by lower concentrations of hydroperoxides, and carbonyl and volatile compounds. HTRY however exerteda pro-oxidant activity. Structural data from SDS-PAGE and tandem mass spectrometry showed that the mechanism for the greater activity of the pepsin hydrolysate occurred due to unique structural features and a higher percentage of short-chain peptides. This was justified by a 25, 31, and 48% higher contents of tryptophan, histidine, and methionine, respectively (important amino acids with hydrogen atom transfer and electron-donating capacities) in the peptides identified in the pepsin hydrolysate.

Potential role of tocopherol in protecting crop plants against abiotic stresses.

The changing global climate have given rise to abiotic stresses that adversely affect the metabolic activities of plants, limit their growth, and agricultural output posing a serious threat to food production. The abiotic stresses commonly lead to production of reactive oxygen species (ROS) that results in cellular oxidation. Over the course of evolution, plants have devised efficient enzymatic and non-enzymatic anti-oxidative strategies to counteract harmful effects of ROS. Among the emerging non-enzymatic anti-oxidative technologies, the chloroplast lipophilic antioxidant vitamin A (Tocopherol) shows great promise. Working in coordination with the other cellular antioxidant machinery, it scavenges ROS, prevents lipid peroxidation, regulates stable cellular redox conditions, simulates signal cascades, improves membrane stability, confers photoprotection and enhances resistance against abiotic stresses. The amount of tocopherol production varies based on the severity of stress and its proposed mechanism of action involves arresting lipid peroxidation while quenching singlet oxygen species and lipid peroxyl radicals. Additionally, studies have demonstrated its coordination with other cellular antioxidants and phytohormones. Despite its significance, the precise mechanism of tocopherol action and signaling coordination are not yet fully understood. To bridge this knowledge gap, the present review aims to explore and understand the biosynthesis and antioxidant functions of Vitamin E, along with its signal transduction and stress regulation capacities and responses. Furthermore, the review delves into the light harvesting and photoprotection capabilities of tocopherol. By providing insights into these domains, this review offers new opportunities and avenues for using tocopherol in the management of abiotic stresses in agriculture.

T-BuOOH/TiO2 Photocatalytic System as a Convenient Peroxyl Radical Source at Room Temperature under Visible Light and Its Application for the CH-Peroxidation of Barbituric Acids

TiO2 is one of the most promising heterogeneous photoredox catalysts employed in oxidative pollutant destruction, CO2 reduction, water splitting, disinfection, solar cell design and organic synthesis. Due to the wide bandgap of TiO2, visible light energy is not sufficient for its activation, and electron/hole pairs generated upon UV irradiation demonstrate limited selectivity for application in organic synthesis. Thus, the development of TiO2-based catalytic systems activated by visible light is highly attractive. In the present work we demonstrate the generation of t-BuOO• radicals from tert-butylhydroperoxide catalyzed using commercially available unmodified TiO2 under visible light. This finding was used for the highly selective CH-peroxidation of barbituric acids, which contrasts with the behavior of the known TiO2/H2O2/UV photocatalytic system used for deep oxidation of organic pollutants.

Potent Antioxidant and Anti-Tyrosinase Activity of Butein and Homobutein Probed by Molecular Kinetic and Mechanistic Studies.

Butein (BU) and homobutein (HB) are bioactive polyhydroxylated chalcones widespread in dietary plants, whose antioxidant properties require mechanistic definition. They were investigated by inhibited autoxidation kinetic studies of methyl linoleate in Triton™ X-100 micelles at pH 7.4, 37 °C. Butein had kinh = (3.0 ± 0.9) × 104 M-1s-1 showing a chain-breaking mechanism with higher antioxidant activity than reference α-tocopherol (kinh = (2.2 ± 0.6) × 104 M-1s-1), particularly concerning the stoichiometry or peroxyl radical trapping n = 3.7 ± 1.1 vs. 2.0 for tocopherol. Homobutein had kinh = (2.8 ± 0.9) × 103 M-1s-1, pairing the relative BDEOH measured by radical equilibration EPR as 78.4 ± 0.2 kcal/mol for BU and estimated as 82.6 kcal/mol for HB. The inhibition of mushroom tyrosinase (mTYR) by HB and BU was also investigated. BU gives a reversible uncompetitive inhibition of monophenolase reaction with KI' = 9.95 ± 2.69 µM and mixed-type diphenolase inhibition with KI = 3.30 ± 0.75 µM and KI' = 18.75 ± 5.15 µM, while HB was nearly competitive toward both mono- and diphenolase with respective KI of 2.76 ± 0.70 µM and 2.50 ± 1.56 µM. IC50 values (monophenolase/diphenolase at 1 mM substrate) were 10.88 ± 2.19 µM/15.20 ± 1.25 µM, 14.78 ± 1.05 µM/12.36 ± 2.00 µM, and 33.14 ± 5.03 µM/18.27 ± 3.42 µM, respectively, for BU, HB, and reference kojic acid. Molecular docking studies confirmed the mechanism. Results indicate very potent antioxidant activity for BU and potent anti-tyrosinase activity for both chalcones, which is discussed in relation to bioactivity toward protection from skin disorders and food oxidative spoilage.

Genome wide analysis for the identification and characterization of Superoxide-dismutase gene family in Rosa chinensis ascertains the role of salinity-responsive RcMSD1 protein and its interaction with peroxyl radical

Abiotic stresses e.g., cold, heat, and salinity affect the quality and yield of Rosa chinensis, a well-known ornamental and medicinal plant. Previously, several attempts have been made to identify the genes that confer resistance to oxidative stressors. Superoxide-dismutase (SOD) is a crucial member of the class metalloenzyme that responds to abiotic stresses and protects plants by countering the reactive-oxygen species (ROS). In this genome-wide association study, the SOD gene family has been investigated in R. chinensis. Seven SOD genes, including three Cu/ZnSODs, two MnSODs, and two FeSODs were identified. Phylogenetic analysis revealed that RcSODs are divided into three clades; (i) CSDs (Cu/ZnSODs) (ii) FSDs (FeSODs) and MSDs (MnSODs). Most of the RcSODs exhibited different exons/introns distribution patterns. Motifs 3 and 5 are conserved in all RcSODs genes. The RNA-seq data analysis and qRT-PCR-based expression profiling indicated that RcSODs exhibit diverse responses under salt stress conditions. The RcCSD1, RcCSD3, and RcFSD3 are significantly up-regulated under salt stress conditions in roots and down-regulated in leaves. This data provides valuable information for further application and function of SODs in R. chinensis under abiotic stresses.

Phototransformation of Lignin-related Compounds in Chromophoric Dissolved Organic Matter Solutions

Lignin is a major terrestrial source of chromophoric dissolved organic matter (CDOM), and studying the phototransformation of lignin monomers and their related compounds can enhance our understanding of CDOM intramolecular interactions. Coniferyl aldehyde (Coni) and sinapaldehyde (Sina) form ground-state complexes with CDOM, with equilibrium constants of 7,800 (± 1,800) and 20,000 (± 2,000) M−1, respectively. In comparison, vanillin (Van) exhibits minimal affinity for CDOM complexation. The bimolecular reaction rate constants between singlet oxygen (1O2) and these phenolic carbonyl compounds ranged from 0.46 (± 0.02) to 1.8 (± 0.1) × 107 M−1s−1, which is approximately one order of magnitude lower than their reaction rate constants (0.51 (± 0.02)–1.25 (± 0.02) × 108 M−1s−1) with the triplet excited state of CDOM (3CDOM*). In acidic CDOM solutions (pH 5.0), 1O2, H2O2, and organic peroxyl radicals had negligible impact on the transformation. Comparing the initial transformation rate in the presence and in the absence of NaN3 or furfuryl alcohol led to an overestimation of the contribution of 1O2 to the transformation of Van, Coni, or Sina. 3CDOM* scavengers could not fully inhibit the transformation of Coni or Sina. The remaining transformation is considered to arise from either the unquenched intra-CDOM phase 3CDOM* or a fraction of Coni⊂CDOM or Sina⊂CDOM complex, which underwent intramolecular photoinduced chemical reactions.

Modelling of Deep Street Canyon Air Pollution Chemistry and Transport: A Wintertime Naples Case Study

The impact of urban morphology on air quality, particularly within deep canyons with longer residence times for complex chemical processes, remains insufficiently addressed. A flexible multi-box framework was used to simulate air quality at different canyon heights (3 m and 12 m). This approach incorporated essential parameters, including ventilation rates, background concentrations, photochemical schemes, and reaction coefficients. A field campaign within a deep canyon with an aspect ratio of 3.7, in Naples, Italy was conducted and used for the model evaluation. The model performance demonstrated good agreement, especially at the street level, when employing a realistic light intensity profile and incorporating volatile organic compound (VOC) chemistry. Our findings indicate that peroxyl radical production affects NO2 and O3 levels by up to 9.5% in deep canyons and underscore the significance of vertical distribution (approximately 5% variance) in health assessments and urban air quality strategy development. The model response was sensitive to changes in emissions as expected, but also, somewhat more surprisingly, to background conditions, emphasizing that policies to remove pollution hotspots must include local and broader citywide action. This work advances the understanding of air quality dynamics in deep urban canyons and presents a valuable tool for effective air quality management in intricate urban environments.

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.

Carotenoids composition, antioxidant and antimicrobial capacities of Crocus sativus L. stigma

Carotenoid compounds are effective free-radical scavengers because they display a singlet oxygen-quenching property and can trap peroxyl radicals. Many extracts derived from natural sources consist of unique bioactive compounds. For example, hydrophilic carotenoids, such as crocin, are present in saffron and possess antioxidant, anticancer, anti -inflammatory and antimicrobial properties. Crocin is responsible for preventing and curing many health issues. This study investigated the antioxidant and antimicrobial properties of hydrophilic carotenoid (C50) molecules extracted from Crocus sativus L. (saffron stigma) grown in different locations. These compounds were tested for their antioxidant properties through 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, while antimicrobial activity was determined using disc diffusion method. Four carotenoid compounds (i.e. crocin, crocetin, β-carotene and zeaxanthin) were detected from the three saffron samples collected from various localities. High-performance liquid chromatography (HPLC) analysis was carried out to determine the physical and chemical properties of the carotenoid samples. The HPLC results indicated the presence of a single crocin peak at 440 nm. The crocin concentration in Iranian saffron was higher (11414.67±516.34 µg/g DW with 99.9% purity) than those in Turkish and Kashmiri saffron. This finding suggested that location significantly affected crocin concentration as well as carotenoid composition and content in saffron. Crocin molecules (100 µg/mL) showed the highest antibacterial activity against Staphylococcus epidermidis, with a 6.0 mm inhibition zone. Hence, crocin molecules (500 µg/mL) were effective antioxidant compounds as they showed 68% inhibition, with an IC50 value of 283.918±3.934 µg/mL. In addition to being a biocolourant source, crocin may be used for its antioxidant and antibacterial properties.

Modern Applications of Porphyrin-Based MOFs in Agriculture

Nanosized metal-porphyrinic frameworks are an interesting class of porous electro- and photoactive materials finding applications in medicine (photodymanic therapy, photothermal therapy, drug delivery and chemotherapy, immunotherapy), [1], sanitary and antimicrobial devices [2], waste water purification [3], photocatalytic organic transformations [4], production of solar fuels [5], and more recently, in agriculture [6]. The fact that porphyrin derivatives are colored, they are prone for the photosensitization of singlet oxygen (1O2(g); a reactive oxygen species of type II) either at the solid state/air interfaces or in solution leading to applications listed above using visible light. In fact, they even do this efficiently. Reactive oxygen species of type I (for examples, H-O radical, HO-OH, superoxide radical, perhydroxyl radical, etc) are also photo-produced when given metals inside the porphyrins and metallic nodes in the frameworks are used, or when the metal-porphyrinic frameworks form a composite with another semiconductor. Moreover, the size of the nanoparticles can be tailored. All of these properties are cleverly exploited in the field of agriculture and include the following applications: controlled delivery of pesticides and agro-chemicals, detection of pesticides and pathogenic metals, elimination of pesticides and toxic metals, and photodynamic antimicrobial activity, and the nanosized metal-porphyrinic frameworks also have an important implication in food safety. This presentation will describe these features along with new experimental results.

The key phytochemistry of rosemary (Salvia rosmarinus) contributing to hair protection against UV.

The objective of this work was to correlate the phytochemistry of rosemary (Salvia rosmarinus), a botanical with known antioxidant properties, to a UV protection benefit in hair. These data will give insights into mechanisms of UV damage, the ROS formed and their reactivity. LC-MS was used to compare the compounds in 10 commercial extracts of rosemary. ORAC (oxygen radical antioxidant capacity) and FRAP (ferric reducing antioxidant power) were used to measure the antioxidant capacity of the rosemary extracts. The ORAC assay measures ability of an antioxidant to react with a peroxyl radical via hydrogen atom extraction and FRAP measures electron transfer through reduction of ferric iron (Fe3+ ) to ferrous iron (Fe2+ ) by antioxidants present in the samples. Correlation of extract composition with antioxidant measures was performed using principal component analysis. Selected extracts were assessed for their ability to protect hair from UV damage in a model peptide system and on hair. In addition, the same methods were used to test rosmarinic acid and carnosic acid, key phytochemistries in the rosemary extracts. The model system was a peptide and its decomposition on exposure to UV was monitored by LC-MS in the absence and presence of the rosemary extracts. Hair degradation in the presence of UV was measured by exposure of UV in an Atlas weatherometer followed by extraction of degraded protein in water. A fragment of the S100A3 protein was used as a marker of UV damage (m/z = 1278) and quantified via LC-MS. Ten rosemary extracts were assessed for antioxidant performance and correlated with their compositions. The phytochemistry in each extract varied widely with a total of 33 individual compounds identified. The differences were most likely driven by the solvent and extraction method used by the supplier with extracts varying in the proportion of polar or non-polar compounds. This did influence their reactivity in the ORAC and FRAP assays and their efficacy in preventing protein damage. Two of the key compounds identified were rosmarinic acid and carnosic acid, with rosmarinic acid dominating in extracts with mainly polar compounds and carnosic acid dominating in extracts with mainly nonpolar compounds. Extracts with higher rosmarinic acid correlated with ORAC and FRAP scores, with UV protection on hair and in the peptide model system. The extracts chosen for hair experiments showed hair protection. UV protection was also measured for rosmarinic and carnosic acid. Despite the variation in the profile of phytochemistries in the 10 rosemary extracts, likely driven by the chosen extraction method, all rosemary extracts had antioxidant activity measured. This study suggests that the polyphenols (e.g. rosmarinic acid, glycosides of selgin) and abietane diterpenes (e.g. carnosic acid) are the principal compounds which enables the extracts to protect hair from UV.

Complexation of AAPH (2,2′-azobis(2-methylpropionamidine) dihydrochloride) with cucurbit[7]uril enhances the yield of AAPH-derived radicals

AAPH (2,2′-azobis(2-methylpropionamidine) dihydrochloride), a water-soluble azo compound is widely employed to produce peroxyl radicals for chemical and biological studies. This compound is shown herein to form a stable inclusion complex with cucurbit[7]uril (CB7), a well-established supramolecular host. Competitive binding assays using berberine dye, isothermal titration calorimetry (ITC), and nuclear magnetic resonance (1H NMR) experiments, provided evidence for the inclusion of AAPH inside the CB7 cavity with a binding constant of 2.51 ± 0.76 × 105 M−1 (determined by ITC). Computational analysis at B3LYP-D3BJ/6-311G(d,p) of the complex (AAPH@CB7) showed interactions of the positively-charged amino groups of AAPH with carbonyl functions at the CB7 entrances. Photolysis of AAPH@CB7 by illumination at 365 nm, gave a higher yield of carbon-centered radicals when compared to the absence of CB7, as evidenced by electron paramagnetic resonance spin trapping using α-phenyl-N-t-butylnitrone. Enhanced radical formation was corroborated by increased consumption of pyrogallol red, free Trp and Trp-containing peptides when these were exposed to AAPH@CB7 in the presence of light. The increased yield of radicals generated by AAPH@CB7 is believed to arise from a pull effect of CB7 portals on initial AAPH-derived carbon-centered radicals generated by photolysis. It is proposed that these radicals are exposed and released to the bulk solution and react with O2 to give peroxyl radicals. These results suggest that the AAPH@CB7 complex can be used to generate high yields of peroxyl radicals for their use in studying these species in material, environmental and biomedical sciences amongst others.

Kinetic Potentiometry as a Method for Studying the Interactions of Antioxidants with Peroxyl Radicals.

This work presents a new method using kinetic potentiometry to study the thermodynamic and kinetic parameters of the reactions of antioxidants with peroxyl radicals. The rate constants of the reaction of antioxidants with radicals have been determined, and the groups of "fast" and "slow" antioxidants have been conventionally distinguished. Fast antioxidants include ascorbic, uric, gallic, chlorogenic, caffeic acids, glutathione, L-cysteine, and catechol with constant values from (1.05-9.25) × 103 M·s-1; "slow" antioxidants are α-tocopherol (in aqueous media), ionol, 2,6-ditretbutylphenol, and compounds of the azoloazine series, modified with polyphenolic fragments, with constant values from (4.00-8.50) × 102 M·s-1. It is shown that the value of the rate constant is directly related to the type of kinetic dependence of the potential recorded when an antioxidant is introduced into the solution of the radical initiator. It is shown that the method with the determination of the induction period is difficult in the study of "slow" antioxidants. It has been established that the area above the curve of the kinetic dependence Exp(∆E) is directly related to the amount of inhibited peroxyl radicals and can be used to assess the inhibitory properties of an antioxidant from a thermodynamic point of view. "Fixed time method" and "Initial rate method" were used. Positive correlations between the described method have been established. The utility of the parameter of the area above the curve of the kinetic dependence Exp(∆E) in the study of objects of complex composition is shown.

Integrating chemical and biological data by chemometrics to evaluate detoxification responses of a neotropical bivalve to metal and metalloid contamination

Mangroves represent a challenge in monitoring studies due to their physical and chemical conditions under constant marine and anthropogenic influences. This study investigated metals/metalloids whole-body bioaccumulation (soft tissues) and the risk associated with their uptake, biochemical and morphological detoxification processes in gills and metals/metalloids immobilisation in shells of the neotropical sentinel oyster Crassostrea rhizophorae from two Brazilian estuarine sites. Biochemical and morphological responses indicated three main mechanisms: (1) catalase, superoxide dismutase and glutathione played important roles as the first defence against reactive oxygen species; (2) antioxidant capacity against peroxyl radicals, glutathione S-transferase, metallothionein prevent protein damage and (3) metals/metalloids sequestration into oyster shells as a mechanism of oyster detoxification. However, the estimated daily intake, target hazard quotient, and hazard index showed that the human consumption of oysters would not represent a human health risk. Among 14 analysed metals/metalloids, chemometrics indicate that Mn, As, Pb, Zn and Fe overload the antioxidant system leading to morphological alterations in gills. Overall, results indicated cellular vacuolization and increases in mucous cell density as defence mechanisms to prevent metals/metalloids accumulation and the reduction in gill cilia; these have long-term implications in respiration and feeding and, consequently, for growth and development. The integration of data from different sites and environmental conditions using chemometrics highlights the main biological patterns of detoxification from a neotropical estuarine bivalve, indicating the way in which species can cope with metals/metalloids contamination and its ecological consequences.

Effects of simulated gastrointestinal digestion/epithelial transport on phenolics and bioactivities of particles of brewer’s spent yeasts loaded with Brazilian red propolis

Red propolis from northeast Brazil contains mainly isoflavonoids as bioactive compounds, and its consumption may counteract unregulated and exacerbated formation of reactive oxygen species and inflammatory cytokines/chemokines. Moreover, the production of particles using sustainable carriers have been studied to increase the use of propolis as a functional food ingredient. Hence, the objective of this work was to investigate the effects of simulated gastrointestinal digestion followed by a cell-based epithelial transport on phenolic profile, anti-inflammatory and antioxidant activities of particles of brewer’s spent yeasts (BSY) loaded with ethanolic extract of Brazilian red propolis (EEP). As a result, the EEP phenolic diversity decreased throughout the simulated gastrointestinal system, and was modulated by the particle production, as detected by high-performance liquid chromatography – electrospray ionization – quadrupole-time-of-flight-mass spectrometry (HPLC-ESI-QTOF-MS). Concomitantly, the antioxidant activity, as assessed by the ability to scavenge peroxyl and superoxide radicals, hydrogen peroxide, and hypochlorous acid, generally decreased at a higher extent for the particles of EEP with BSY (EEP-BSY) throughout the experiments. Nonetheless, after epithelial transport through the Caco-2 cell monolayer, the basolateral fraction of both EEP-BSY and EEP decreased the activation of pro-inflammatory transcription factor NF-κB by 83% and 65%, respectively, as well as the release of TNF-α (up to 51% and 38%, respectively), and CXCL2/MIP-2 (up to 33% and 25%, respectively). Therefore, BSY may be an interesting carrier for EEP bioencapsulation, since it preserves its anti-inflammatory activity. Further studies should be encouraged to investigate the feasibility of adding it in formulations of functional foods, considering its effect on sensory attributes.