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Aalt Bast - One of the best experts on this subject based on the ideXlab platform.
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applicability of an improved trolox equivalent antioxidant capacity teac assay for evaluation of antioxidant capacity measurements of mixtures
Food Chemistry, 1999Co-Authors: R Van Den Berg, Guido R M M Haenen, H Van Den Berg, Aalt BastAbstract:The TEAC (Trolox equivalent antioxidant capacity) assay is based on scavenging of 2,2'-azinobis-(3- ethylbenzothiAzoline-6-sulfonate) radical anions (ABTS(.-)). In this report we describe a modification based on pre-generation of the ABTS radical anions with a thermolabile Azo Compound, 2,2'-Azobis- (2-amidinopropane)HCl (ABAP). This modification makes the assay less susceptible to artefacts, e.g. influence on the radical generation process. For most antioxidants tested, a biphasic reaction pattern was seen, i.e. a fast and slow scavenging rate. We evaluated application of the assay with both lipophilic and hydrophilic Compounds with antioxidant capacity. Several organic solvents, compatible with water, were tested with α-tocopherol, quercetin and β-carotene. It was found that the TEACs differed in various solvents. Under standardized conditions additivity of TEACs obtained from individual antioxidants could be demonstrated. This might enable application of the assay for the identification of 'unknown' antioxidants. Copyright (C) 1999 Elsevier Science Ltd. Chemicals/CAS: 2,2' Azobis(2 amidinopropane), 13217-66-8; alpha tocopherol, 1406-18-4, 1406-70-8, 52225-20-4, 58-95-7, 59-02-9; ascorbic acid, 134-03-2, 15421-15-5, 50-81-7; aurantiin, 10236-47-2, 12619-61-3, 29658-83-1, 82350-96-7; beta carotene, 7235-40-7; cryptoxanthin, 472-70-8; dehydroascorbic acid, 33124-69-5, 490-83-5; hesperidin, 520-26-3; lycopene, 502-65-8; quercetin, 117-39-5; trolox C, 56305-04-5; zeaxanthin, 144-68-3
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applicability of an improved trolox equivalent antioxidant capacity teac assay for evaluation of antioxidant capacity measurements of mixtures
Food Chemistry, 1999Co-Authors: R Van Den Berg, Guido R M M Haenen, H Van Den Berg, Aalt BastAbstract:The TEAC (Trolox equivalent antioxidant capacity) assay is based on scavenging of 2,2'-azinobis-(3- ethylbenzothiAzoline-6-sulfonate) radical anions (ABTS(.-)). In this report we describe a modification based on pre-generation of the ABTS radical anions with a thermolabile Azo Compound, 2,2'-Azobis- (2-amidinopropane)HCl (ABAP). This modification makes the assay less susceptible to artefacts, e.g. influence on the radical generation process. For most antioxidants tested, a biphasic reaction pattern was seen, i.e. a fast and slow scavenging rate. We evaluated application of the assay with both lipophilic and hydrophilic Compounds with antioxidant capacity. Several organic solvents, compatible with water, were tested with α-tocopherol, quercetin and β-carotene. It was found that the TEACs differed in various solvents. Under standardized conditions additivity of TEACs obtained from individual antioxidants could be demonstrated. This might enable application of the assay for the identification of 'unknown' antioxidants. Copyright (C) 1999 Elsevier Science Ltd. Chemicals/CAS: 2,2' Azobis(2 amidinopropane), 13217-66-8; alpha tocopherol, 1406-18-4, 1406-70-8, 52225-20-4, 58-95-7, 59-02-9; ascorbic acid, 134-03-2, 15421-15-5, 50-81-7; aurantiin, 10236-47-2, 12619-61-3, 29658-83-1, 82350-96-7; beta carotene, 7235-40-7; cryptoxanthin, 472-70-8; dehydroascorbic acid, 33124-69-5, 490-83-5; hesperidin, 520-26-3; lycopene, 502-65-8; quercetin, 117-39-5; trolox C, 56305-04-5; zeaxanthin, 144-68-3
Y. Ozaki - One of the best experts on this subject based on the ideXlab platform.
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Enzyme immunoassay utilizing surface-enhanced Raman scattering of the enzyme reaction product
Analytical Chemistry, 1997Co-Authors: Takuro Takama, And Yoshinori Yamaguchi, H. Yamamoto, Y. OzakiAbstract:We propose here a new enzyme immunoassay based on surface-enhanced Raman scattering (SERS). In the proposed system, antibody immobilized on a solid substrate reacts with antigen, which binds with another antibody labeled with peroxidase. If this immunocomplex is subjected to reaction with o-phenylenediamine and hydrogen peroxide at 37 °C, Azoaniline is generated. This Azo Compound is adsorbed on a silver colloid. In this system, only the Azo Compound gives a strong surface-enhanced resonance Raman (SERRS) spectrum. The spectrum shows intense bands at 1582 and 1442 cm-1 due to the CC and NN stretching modes, respectively. A linear relationship was observed between the peak intensity of the NN stretching band and the concentration of antigen, revealing that one can determine the concentration of antigen by the SERRS measurement of the reaction product. The correlation coefficient between the peak intensity and the concentration was calculated to be 0.999 for the concentration range from 0.158 to 2.5 ng/mL. ...
Guido R M M Haenen - One of the best experts on this subject based on the ideXlab platform.
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applicability of an improved trolox equivalent antioxidant capacity teac assay for evaluation of antioxidant capacity measurements of mixtures
Food Chemistry, 1999Co-Authors: R Van Den Berg, Guido R M M Haenen, H Van Den Berg, Aalt BastAbstract:The TEAC (Trolox equivalent antioxidant capacity) assay is based on scavenging of 2,2'-azinobis-(3- ethylbenzothiAzoline-6-sulfonate) radical anions (ABTS(.-)). In this report we describe a modification based on pre-generation of the ABTS radical anions with a thermolabile Azo Compound, 2,2'-Azobis- (2-amidinopropane)HCl (ABAP). This modification makes the assay less susceptible to artefacts, e.g. influence on the radical generation process. For most antioxidants tested, a biphasic reaction pattern was seen, i.e. a fast and slow scavenging rate. We evaluated application of the assay with both lipophilic and hydrophilic Compounds with antioxidant capacity. Several organic solvents, compatible with water, were tested with α-tocopherol, quercetin and β-carotene. It was found that the TEACs differed in various solvents. Under standardized conditions additivity of TEACs obtained from individual antioxidants could be demonstrated. This might enable application of the assay for the identification of 'unknown' antioxidants. Copyright (C) 1999 Elsevier Science Ltd. Chemicals/CAS: 2,2' Azobis(2 amidinopropane), 13217-66-8; alpha tocopherol, 1406-18-4, 1406-70-8, 52225-20-4, 58-95-7, 59-02-9; ascorbic acid, 134-03-2, 15421-15-5, 50-81-7; aurantiin, 10236-47-2, 12619-61-3, 29658-83-1, 82350-96-7; beta carotene, 7235-40-7; cryptoxanthin, 472-70-8; dehydroascorbic acid, 33124-69-5, 490-83-5; hesperidin, 520-26-3; lycopene, 502-65-8; quercetin, 117-39-5; trolox C, 56305-04-5; zeaxanthin, 144-68-3
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applicability of an improved trolox equivalent antioxidant capacity teac assay for evaluation of antioxidant capacity measurements of mixtures
Food Chemistry, 1999Co-Authors: R Van Den Berg, Guido R M M Haenen, H Van Den Berg, Aalt BastAbstract:The TEAC (Trolox equivalent antioxidant capacity) assay is based on scavenging of 2,2'-azinobis-(3- ethylbenzothiAzoline-6-sulfonate) radical anions (ABTS(.-)). In this report we describe a modification based on pre-generation of the ABTS radical anions with a thermolabile Azo Compound, 2,2'-Azobis- (2-amidinopropane)HCl (ABAP). This modification makes the assay less susceptible to artefacts, e.g. influence on the radical generation process. For most antioxidants tested, a biphasic reaction pattern was seen, i.e. a fast and slow scavenging rate. We evaluated application of the assay with both lipophilic and hydrophilic Compounds with antioxidant capacity. Several organic solvents, compatible with water, were tested with α-tocopherol, quercetin and β-carotene. It was found that the TEACs differed in various solvents. Under standardized conditions additivity of TEACs obtained from individual antioxidants could be demonstrated. This might enable application of the assay for the identification of 'unknown' antioxidants. Copyright (C) 1999 Elsevier Science Ltd. Chemicals/CAS: 2,2' Azobis(2 amidinopropane), 13217-66-8; alpha tocopherol, 1406-18-4, 1406-70-8, 52225-20-4, 58-95-7, 59-02-9; ascorbic acid, 134-03-2, 15421-15-5, 50-81-7; aurantiin, 10236-47-2, 12619-61-3, 29658-83-1, 82350-96-7; beta carotene, 7235-40-7; cryptoxanthin, 472-70-8; dehydroascorbic acid, 33124-69-5, 490-83-5; hesperidin, 520-26-3; lycopene, 502-65-8; quercetin, 117-39-5; trolox C, 56305-04-5; zeaxanthin, 144-68-3
Paul D. White - One of the best experts on this subject based on the ideXlab platform.
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The mutagenic activity of select Azo Compounds in MutaMouse target tissues in vivo and primary hepatocytes in vitro
Mutation Research Genetic Toxicology and Environmental Mutagenesis, 2019Co-Authors: Julie Cox, Paul D. WhiteAbstract:Abstract The mutagenicity of Direct Black 38, Sudan I, and Para Red were evaluated in the in vivo MutaMouse assay and the in vitro MutaMouse primary hepatocyte (PH) assay. Direct Black 38 is an International Agency for Research on Cancer (IARC) Group 1 carcinogen and a prototypical benzidine-based Azo Compound that requires Azo-reduction to yield a DNA-reactive metabolite. Sudan I and Para Red are structurally related Azo Compounds that have been detected as illegal contaminants in foods. Sudan I is an in vivo mutagen, and both it and Para Red are known to be mutagenic in vitro. Sudan I is oxidized by hepatic and/or bladder enzymes to yield a mutagenic metabolite, but little is known about Para Red. In the present study, Direct Black 38 elicited a significant mutagenic response in the bone marrow, glandular stomach, small intestine and colon in vivo, and in PHs in vitro. Sudan I elicited a weak positive response in the bone marrow and a marginally significant treatment effect in the bladder (p = 0.059); it did not elicit a significant response in PHs in vitro. Para Red elicited a positive response in the colon, as well as in PHs in vitro, albeit at a cytotoxic concentration. The findings are well aligned with the known mechanisms of action of Direct Black 38 and Sudan I; they suggest that intestinal Azo-reduction plays an important role in the activation of Para Red. The MutaMouse pH results illustrate the ability of this assay to detect chemicals requiring Azo-reduction; however, they also demonstrate a gap in applicability domain, as MutaMouse PHs elicit a negative response following exposure to Sudan I. Elucidation of the mechanisms underlying this gap will require further study.
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Empirical analysis of BMD metrics in genetic toxicology part I: in vitro analyses to provide robust potency rankings and support MOA determinations
Mutagenesis, 2015Co-Authors: John W Wills, George E. Johnson, Shareen H Doak, Wout Slob, Lya G. Soeteman-hernández, Paul D. WhiteAbstract:Genetic toxicity testing has traditionally been used for hazard identification, with dichotomous classification of test results serving to identify genotoxic agents. However, the utility of genotoxicity data can be augmented by employing dose-response analysis and point of departure determination. Via interpolation from a fitted dose-response model, the benchmark dose (BMD) approach estimates the dose that elicits a specified (small) effect size. BMD metrics and their confidence intervals can be used for Compound potency ranking within an endpoint, as well as potency comparisons across other factors such as cell line or exposure duration. A recently developed computational method, the BMD covariate approach, permits combined analysis of multiple dose-response data sets that are differentiated by covariates such as Compound, cell type or exposure regime. The approach provides increased BMD precision for effective potency rankings across Compounds and other covariates that pertain to a hypothesised mode of action (MOA). To illustrate these applications, the covariate approach was applied to the analysis of published in vitro micronucleus frequency dose-response data for ionising radiations, a set of aneugens, two mutagenic Azo Compounds and a topoisomerase II inhibitor. The ionising radiation results show that the precision of BMD estimates can be improved by employing the covariate method. The aneugen analysis provided potency groupings based on the BMD confidence intervals, and analyses of Azo Compound data from cells lines with differing metabolic capacity confirmed the influence of endogenous metabolism on genotoxic potency. This work, which is the first of a two-part series, shows that BMD-derived potency rankings can be employed to support MOA evaluations as well as facilitate read across to expedite chemical evaluations and regulatory decision-making. The follow-up (Part II) employs the combined covariate approach to analyse in vivo genetic toxicity dose-response data focussing on how improvements in BMD precision can impact the reduction and refinement of animal use in toxicological research.
Jun-ichi Anzai - One of the best experts on this subject based on the ideXlab platform.
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[3+3]Cycloalkyne dimers linked by an Azo group: a stable cis-Azo Compound forms polymeric aggregates by nonplanar pi-pi interactions.
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]cycloalkyne dimers linked by the Azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-Azo Compounds were synthesized by the oxidative coupling of a [3+3]cycloalkyne amine derivative, and the stereochemistry was determined by UV-vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl Azo Compounds, these Azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model Compound lacking the cyclic helicene structure isomerizes readily.
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3 3 cycloalkyne dimers linked by an Azo group a stable cis Azo Compound forms polymeric aggregates by nonplanar π π interactions
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]cycloalkyne dimers linked by the Azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-Azo Compounds were synthesized by the oxidative coupling of a [3+3]cycloalkyne amine derivative, and the stereochemistry was determined by UV−vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl Azo Compounds, these Azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model Compound lacking the cyclic helicene s...