A peroxyoxalate chemiluminescence-based assay for the evaluation of hydrogen peroxide scavenging activity employing 9,10-diphenylanthracene as the fluorophore

Recent Advances in Electrochemical Sensing of Hydrogen Peroxide (H2O2) Released from Cancer Cells

Cancer is by far the most common cause of death worldwide. There are more than 200 types of cancer known hitherto depending upon the origin and type. Early diagnosis of cancer provides better disease prognosis and the best chance for a cure. This fact prompts world-leading scientists and clinicians to develop techniques for the early detection of cancer. Thus, less morbidity and lower mortality rates are envisioned. The latest advancements in the diagnosis of cancer utilizing nanotechnology have manifested encouraging results. Cancerous cells are well known for their substantial amounts of hydrogen peroxide (H₂O₂). The common methods for the detection of H₂O₂ include colorimetry, titration, chromatography, spectrophotometry, fluorimetry, and chemiluminescence. These methods commonly lack selectivity, sensitivity, and reproducibility and have prolonged analytical time. New biosensors are reported to circumvent these obstacles. The production of detectable amounts of H₂O₂ by cancerous cells has promoted the use of bio- and electrochemical sensors because of their high sensitivity, selectivity, robustness, and miniaturized point-of-care cancer diagnostics. Thus, this review will emphasize the principles, analytical parameters, advantages, and disadvantages of the latest electrochemical biosensors in the detection of H₂O₂. It will provide a summary of the latest technological advancements of biosensors based on potentiometric, impedimetric, amperometric, and voltammetric H₂O₂ detection. Moreover, it will critically describe the classification of biosensors based on the material, nature, conjugation, and carbon-nanocomposite electrodes for rapid and effective detection of H₂O₂, which can be useful in the early detection of cancerous cells.

Methods to evaluate the scavenging activity of antioxidants toward reactive oxygen and nitrogen species (IUPAC Technical Report)

This project was aimed to identify the quenching chemistry of biologically important reactive oxygen and nitrogen species (ROS/RNS, including radicals), to show antioxidant action against reactive species through H‐atom and electron transfer reactions, and to evaluate the ROS/RNS scavenging activity of antioxidants with existing analytical methods while emphasizing the underlying chemical principles and advantages/disadvantages of these methods. In this report, we focused on the applications and impact of existing assays on potentiating future research and innovations to evolve better methods enabling a more comprehensive study of different aspects of antioxidants and to provide a vocabulary of terms related to antioxidants and scavengers for ROS/RNS. The main methods comprise the scavenging activity measurement of the hydroxyl radical (•OH), dioxide(•1–) (O2 •–: commonly known as the superoxide radical), dihydrogen dioxide (H2O2: commonly known as hydrogen peroxide), hydroxidochlorine (HOCl: commonly known as hypochlorous acid), dioxidooxidonitrate(1–) (ONOO−: commonly known as the peroxynitrite anion), and the peroxyl radical (ROO•). In spite of the diversity of methods, there is currently a great need to evaluate the scavenging activity of antioxidant compounds in vivo and in vitro. In addition, there are unsatisfactory methods frequently used, such as non-selective UV measurement of H2O2 scavenging, producing negative errors due to incomplete reaction of peroxide with flavonoids in the absence of transition metal ion catalysts. We also discussed the basic mechanisms of spectroscopic and electrochemical nanosensors for measuring ROS/RNS scavenging activity of antioxidants, together with leading trends and challenges and a wide range of applications. This project aids in the identification of reactive species and quantification of scavenging extents of antioxidants through various assays, makes the results comparable and more understandable, and brings a more rational basis to the evaluation of these assays and provides a critical evaluation of existing ROS/RNS scavenging assays to analytical, food chemical, and biomedical/clinical communities by emphasizing the need for developing more refined, rapid, simple, and low‐cost assays and thus opening the market for a wide range of analytical instruments, including reagent kits and sensors.

Antioxidant Potential of Pine Needles: A Systematic Study on the Essential Oils and Extracts of 46 Species of the Genus Pinus

The antioxidant activity of the essential oils, as well as of the organic and hydroethanolic extracts, of the fresh needles of 54 pine taxa was evaluated using the peroxy-oxalate and luminol chemiluminescence assays. Among all evaluated essential oils, P. canariensis and P. attenuata displayed the highest levels of activity. P. contorta var. murrayana, followed by P. nigra var. caramanica, exhibited the highest antioxidant capacity among the organic extracts, while the most active hydroethanolic extract was that of P. nigra subsp. nigra. Based on the overall levels of activity, the latter taxon was selected for phytochemical analysis targeting the isolation of the bioactive constituents. As such, the organic extract of P. nigra subsp. nigra was subjected to chromatographic separations to yield 11 secondary metabolites (1-11) that were evaluated for their antioxidant activity. Nonetheless, the isolated compounds were found to be less active than the crude extract, thus suggesting the potential role of synergism.

Antioxidant capacity of teas and herbal infusions: polarographic assessment

Hydrogen peroxide scavenging (HPS) activity of unfermented (green, yellow, and white), partially fermented (oolong), and completely fermented (black) tea ( Camellia sinensis ), maté ( Ilex paraguariensis ), and various herbal infusions, as well as individual compounds (flavan-3-ols, flavonols, cinnamic and benzoic acids, and methylxanthines), was assessed by recently developed direct current (DC) polarographic assay. Correlations of tea and herbal infusion HPS activity with total phenolic content determined using the Folin-Ciocalteu assay (FC-GAE) (0.81 and 0.93), ferric reducing/antioxidant power (FRAP) (0.97 and 0.92), 1,1-diphenyl-2-picrylhydrazyl (DPPH) (0.77 and 0.80), and 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) scavenging (0.86 and 0.86) were statistically significant. Correlations between relative antioxidant capacity index (RACI), calculated by assigning all applied assays equal weight, and HPS (0.98), FRAP (0.97), ABTS (0.89), and DPPH (0.89) confirmed DC polarographic assay reliability when applied individually. Correlation analysis, ANOVA, and Levene and Tukey's HSD tests unequivocally confirmed this reliable, rapid, and low-cost assay validity, clearly demonstrating its advantages over spectrophotometric assays applied.

Raman spectroscopy for scavenging activity assay using nanoshell precursor nanocomposites as SERSprobes

In this work, we have developed a novel SERS-based approach to detect hydrogen peroxide (H2O2) scavenging activity by using gold nanoshell precursor nanocomposites (SiO2/GNPs) as nanoprobes. H2O2 can reduce AuCl4- to Au0 and enlarge the gold nanoparticles (GNPs) that attached on the surface of SiO2. As the concentration of H2O2 increases, the surface coverage of resultant gold on silica cores increases accordingly until continuous gold nanoshells (GNSs) are formed. During the growth process, there is a strong correlation between the SERS-activity of the GNSs and the amount of H2O2 that is used as reductant. When H2O2 reaches 250 μM, the resultant GNSs show the highest SERS-activity. H2O2 can be scavenged by antioxidants such as tannic acid and L-apple acid. Their H2O2 scavenging activities were determined by restraining the H2O2-mediated (250 μM) growth of SiO2/GNPs. The decrease of the SERS-activity was proportional to the H2O2 scavenging activity of the antioxidant. The results showed that tannic acid had a much higher H2O2 scavenging activity than that of L-apple acid.

Natural and synthetic 2'-hydroxy-chalcones and aurones: synthesis, characterization and evaluation of the antioxidant and soybean lipoxygenase inhibitory activity

A series of 2'-hydroxy-chalcones and their oxidative cyclization products, aurones, have been synthesized and tested for their antioxidant and lipoxygenase inhibitory activity. The natural product aureusidin (31) was synthesized in high yield by a new approach. An extensive structure-relationship study was performed and revealed that several chalcones and aurones possess an appealing pharmacological profile combining high antioxidant and lipid peroxidation activity with potent soybean LOX inhibition.

In vivo imaging of hydrogen peroxide with chemiluminescent nanoparticles

The overproduction of hydrogen peroxide is implicated in the development of numerous diseases and there is currently great interest in developing contrast agents that can image hydrogen peroxide in vivo. In this report, we demonstrate that nanoparticles formulated from peroxalate esters and fluorescent dyes can image hydrogen peroxide in vivo with high specificity and sensitivity. The peroxalate nanoparticles image hydrogen peroxide by undergoing a three-component chemiluminescent reaction between hydrogen peroxide, peroxalate esters and fluorescent dyes. The peroxalate nanoparticles have several attractive properties for in vivo imaging, such as tunable wavelength emission (460-630 nm), nanomolar sensitivity for hydrogen peroxide and excellent specificity for hydrogen peroxide over other reactive oxygen species. The peroxalate nanoparticles were capable of imaging hydrogen peroxide in the peritoneal cavity of mice during a lipopolysaccharide-induced inflammatory response. We anticipate numerous applications of peroxalate nanoparticles for in vivo imaging of hydrogen peroxide, given their high specificity and sensitivity and deep-tissue-imaging capability.

Novel chemiluminescent detection of chemical warfare simulant

A glow assay technology for the detection of a chemical warfare simulant is presented, which is based on modulating the peroxyoxalate chemiluminescence pathway by way of utilising an oximate super nucleophile that gives an "off-on" glow response.

A microfluidic system for evaluation of antioxidant capacity based on a peroxyoxalate chemiluminescence assay

A microfluidic system incorporating chemiluminescence detection is reported as a new tool for measuring antioxidant capacity. The detection is based on a peroxyoxalate chemiluminescence (PO-CL) assay with 9,10-bis-(phenylethynyl)anthracene (BPEA) as the fluorescent probe and hydrogen peroxide as the oxidant. Antioxidant plugs injected into the hydrogen peroxide stream result in inhibition of the CL emission which can be quantified and correlated with antioxidant capacity. The PO-CL assay is performed in 800-microm-wide and 800-microm-deep microchannels on a poly(dimethylsiloxane) (PDMS) microchip. Controlled injection of the antioxidant plugs is performed through an injection valve. Of the plant-food based antioxidants tested, beta-carotene was found to be the most efficient hydrogen peroxide scavenger (SAHP of 3.27x10(-3) micromol-1 L), followed by alpha-tocopherol (SAHP of 2.36x10(-3) micromol-1 L) and quercetin (SAHP of 0.31x10(-3) micromol-1 L). Although the method is inherently simple and rapid, excellent analytical performance is afforded in terms of sensitivity, dynamic range, and precision, with RSD values typically below 1.5%. We expect our microfluidic devices to be used for in-the-field antioxidant capacity screening of plant-sourced food and pharmaceutical supplements.

Determination of hydrogen peroxide scavenging activity of cinnamic and benzoic acids employing a highly sensitive peroxyoxalate chemiluminescence-based assay: Structure–activity relationships

A series of cinnamic acids along with their corresponding benzoate analogues were tested for their ability to scavenge hydrogen peroxide (H(2)O(2)), by using a highly sensitive, peroxyoxalate chemiluminescence assay. Among benzoic acid derivatives, vanillic acid (3-hydroxy-4-methoxybenzoic acid) was found to be the most efficient H(2)O(2) scavenger with its hydrogen peroxide scavenging activity (SA(HP)) being 170.20 microM(-1), whereas protocatechuic acid (3,4-dihydroxybenzoic acid) exhibited the weakest activity (5.90 microM(-1)). Caffeic acid (3,4-dihydroxycinnamic acid) was the strongest antioxidant amongst cinnamate derivatives with a SA(HP) = 8.2 microM(-1), as opposed to m-coumaric acid (2-hydroxycinnamic acid), which was found to be a poor hydrogen peroxide scavenger (SA(HP) = 0.18 microM(-1)). Comparison between the two groups revealed that benzoate derivatives are much stronger hydrogen peroxide quenchers in relation with their cinnamate analogues, and this finding was discussed on a basis of structure-activity relationships and comparative assessment of other antioxidant characteristics.

Synthesis, immunological activities, and scavenging ability toward superoxide anion of (1→3)-β-d-pentaglucoside and its epoxyalkyl derivatives

The epoxyalkyl (1-->3)-beta-D-pentaglucosides 2 and 3 were synthesized in order by acetylation, glycosidation, oxidation, and deacetylation of 1. The immunological activities (superoxide anion production activity, phagocytic activity, and lymphocyte proliferation) and scavenging ability toward superoxide anion of (1-->3)-beta-D-pentaglucoside (1) and its epoxyalkyl derivatives (2 and 3) were investigated. Superoxide anion released from human blood monocytes was measured by the reduction of ferricytochrome c. Phagocytosis by peritoneal macrophages was detected through a teal ingesting that measured the chicken red blood cells (CRBC). Lymphocyte proliferation was determined by the MTT method. The scavenging ability of 1, 2, and 3 toward superoxide anions was evaluated by means of chemiluminescence (CL). The results showed that 2 and 3 had a little higher immunological activity and scavenging ability toward superoxide anion than 1, which indicated that the reducing end of the oligoglucosides was quite important for maximum biological activity.