Recent Advances in Antioxidant Capacity Assays

This work presents a survey of the important antioxidant capacity/activity assays applied for a diversity of samples including plant extracts, foods, biological material, etc. The published materials are critically discussed, emphasizing the recent findings in the field. New and emergent antioxidant capacity assays, such as nanoparticles-based assay, are also presented. The discussion includes chemical-based methods as well as biochemical and cellular assays. Chemical methods detailed are radical/ROS-based scavenging assays (the trolox equivalent antioxidant capacity (TEAC/ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC) assays, chemiluminescence methods, total radical-trapping antioxidant parameter (TRAP), total oxy radical scavenging capacity (TOSC), and β-carotene bleaching assays), non-radical redox potential-based assays (ferric reducing antioxidant power (FRAP), cupric reducing antioxidant capacity (CUPRAC), nanoparticle-based methods and electrochemical methods), metal chelation capacity and total phenolic content tests. The biochemical-based assays and in vivo assays discussed include the oxidation of low density lipoprotein (LDL), the thiobarbituric acid reactive substances (TBARS) and the cellular antioxidant activity (CAA) assays. While a direct link between the antioxidant capacity and health benefits is still a matter of debate, the antioxidant testing methodologies presented in this chapter remain valuable for the high efficiency and cost-effective evaluation of antioxidants, from compound discovery to quality control

Chemiluminescence Determination of the Total Antioxidant Capacity of Rosemary Extract

Total antioxidant capacity (TAC

Flow Injection System with Fluorimetric Detection for Hydrogen Peroxide Scavenging Activity Evaluation of Several Synthetic Antioxidants

A flow injection analysis (FIA

Capteurs et biocapteurs pour l'analyse par injection en flux

Ce travail a pour objet la mise au point de (bio)capteurs utilisables dans des systèmes d'analyse en flux. L'AChE a été choisie comme bio récepteur biologique pour la mise au point des méthodes sensibles pour la détection des insecticides neurotoxiques. Deux axes principaux de recherche ont été suivis : (i) la mise au point des nouvelles méthodes d'immobilisation de l'AChE basées sur des liaisons de bioaffinité (ii) l'utilisation des enzymes provenant de différentes origines ou modifiées génétiquement pour améliorer la sensibilité et la sélectivité des analyses. Les biocapteurs développés dans cette thèse ont été mis au point et optimisés dans des systèmes appelés " batch " ou utilisés couplés avec les techniques d'analyse en flux. L'immobilisation par affinité de l'AChE d'une manière originale a été réalisée en utilisant la Con A (une lectine) qui peut se lier avec les sucres se trouvant à la surface de l'enzyme. Les deux méthodes proposées permettent l'immobilisation orientée de l'AChE, l'élimination des barrières de diffusion, la réutilisation des transducteurs...L'utilisation des enzymes provenant des organismes différents permet la construction de biocapteurs avec des performances améliorées. Ce travail a permis la mise au point de biocapteurs très sensibles pour la détection des insecticides carbamates grâce à l'utilisation de trois mutants de Dm. En plus, il a été proposé un système d'analyse en flux capable de faire la différence entre les inhibitions produites par des insecticides et d'autres composés. Au vu les résultats obtenus, nous pouvons envisager des applications potentielles études dans le domaine du monitorage de l'environnement.This work was focused on the development of (bio)sensors for the flow injection analysis. The AChE was chosen as biocomponent for the realisation ofbiodevices, which are sensitive towards neurotoxic insecticides.Two main research directions were followed in this study: (i) the realisation of new methods for AChE immobilisation based on bioaffinity links (ii) the use of enzymes that are obtained from different sources or genetically modified toimprove the sensitivity and the selectivity of the determinations. The biosensors developed in this thesis were studied and optimised in " batch " systems or used coupled with flow analysis techniques. The bioaffinity AChE immobilisation in an original manner was carried out with Con A (a lectine) that interacts with the sugars present on the surface of the enzyme. The immobilisation is performed in several independent steps and produce a sandwich like structure in which the Con A makes a bridge between the AChE and the support activated by a sugar. The two proposed methods allowsthe oriented immobilisation of the AChE, the elimination of the diffusion barriers, the reuse of the transducers... The use of the enzymes from different organisms allows the construction of biosensors with improved performances. In this thesis, we constructed biosensors highly sensitive towards the carbamate insecticides by using three mutants of Dm. Also, it was proposed a flow analysis system able to differentiate between the inhibitions produced by the insecticides or by interfering compounds Considering the obtained results, the biosensors could be successfully used for environmental monitoring.PERPIGNAN-BU Sciences (661362101) / SudocSudocFranceF

Total Antioxidant Capacity of Some Commercial Fruit Juices: Electrochemical and Spectrophotometrical Approaches

The aim of this paper was to assess the total antioxidant capacity of some commercial fruit juices (namely citrus), spectrophotometrically and by the biamperometric method, using the redox couple DPPH· (2,2-diphenyl-1-picrylhydrazyl)/DPPH (2,2-diphenyl-1-picrylhydrazine). Trolox® was chosen as a standard antioxidant. In the case of the spectrophometric method, the absorbance decrease of the DPPH· solution was followed. For the biamperometric method, the influence of some parameters like the potential diference, ΔE, DPPH· concentration, and Trolox® concentration was investigated. The calibration graph obtained for Trolox® presents linearity between 5 and 30 µM, (y = 0.059 x + 0.0564, where y represents the value of current intensity, expressed as μA and x the value of Trolox® concentration, expressed as μM; r2 = 0.9944). The R.S.D. value for the biamperometric method was 1.29% (n = 10, c = 15 μM Trolox®). In the case of the spectrophotometric method, the calibration graph obtained for Trolox® presents linearity between 0.01 and 0.125 mM (y = -9.5789 x+1.4533, where y represents the value of absorbance and x, the value of Trolox® concentration, expressed as mM; r2 = 0.9963). The R.S.D. value for the spectrophotometric method was 2.05%. Both methods were applied to total antioxidant activity determination in real samples (natural juices and soft drinks) and the results were in good agreement

Heat shock, visible light or high calcium augment the cytotoxic effects of <i>Ailanthus altissima</i> (Swingle) leaf extracts against <i>Saccharomyces cerevisiae</i> cells

<div><p>To gain new insight into the antimicrobial potential of <i>Ailanthus altissima</i> Swingle, ethanol leaf extracts were evaluated for the antifungal effects against the model yeast <i>Saccharomyces cerevisae</i>. The extracts inhibited the yeast growth in a dose-dependent manner, and this effect could be augmented by heat shock, exposure to visible light or exposure to high concentrations of Ca²⁺. Using transgenic yeast cells expressing the Ca²⁺-dependent photoprotein, aequorin, it was found that the leaf extracts induced cytosolic Ca²⁺ elevation. Experiments on yeast mutants with defects in Ca²⁺ transport demonstrated that the cytotoxicity of the <i>A. altissima</i> leaf extracts (AaLEs) was mediated by transient pulses of Ca²⁺ ions which were released into the cytosol predominantly from the vacuole. The investigation of the antifungal synergies involving AaLEs may contribute to the development of optimal and safe combination therapies for the treatment of drug-resistant fungal infections.</p></div