Novel modified electrode with immobilized galvinoxyl radical for the voltammetric determination of antioxidant activity

Antiradical and Antioxidant Activity of Compounds Containing 1,3-Dicarbonyl Moiety: An Overview

Free radicals and oxidants may cause various damages both to the lifeworld and different products. A typical solution for the prophylaxis of oxidation-caused conditions is the usage of various antioxidants. Among them, various classes are found-polyphenols, conjugated polyalkenes, and some sulfur and nitrogen derivatives. Regarding the active site in the molecules, a widely discussed group of compounds are 1,3-dicarbonyl compounds. Among them are natural (e.g., curcumin and pulvinic acids) and synthetic (e.g., 4-hydroxy coumarins, substituted Meldrum's acids) compounds. Herein, information about various compounds containing the 1,3-dicarbonyl moiety is covered, and their antiradical and antioxidant activity, depending on the structure, is discussed.

Electrochemical Characterization of the Antioxidant Properties of Medicinal Plants and Products: A Review

Medicinal plants are an important source of bioactive compounds with a wide spectrum of practically useful properties. Various types of antioxidants synthesized in plants are the reasons for their application in medicine, phytotherapy, and aromatherapy. Therefore, reliable, simple, cost-effective, eco-friendly, and rapid methods for the evaluation of antioxidant properties of medicinal plants and products on their basis are required. Electrochemical methods based on electron transfer reactions are promising tools to solve this problem. Total antioxidant parameters and individual antioxidant quantification can be achieved using suitable electrochemical techniques. The analytical capabilities of constant-current coulometry, potentiometry, various types of voltammetry, and chrono methods in the evaluation of total antioxidant parameters of medicinal plants and plant-derived products are presented. The advantages and limitations of methods in comparison to each other and traditional spectroscopic methods are discussed. The possibility to use electrochemical detection of the antioxidants via reactions with oxidants or radicals (N- and O-centered) in solution, with stable radicals immobilized on the electrode surface, via oxidation of antioxidants on a suitable electrode, allows the study of various mechanisms of antioxidant actions occurring in living systems. Attention is also paid to the individual or simultaneous electrochemical determination of antioxidants in medicinal plants using chemically modified electrodes.

Constant-Current Coulometry with Electrogenerated Titrants as a Novel Tool for the Essential Oils Screening Using Total Antioxidant Parameters

Essential oils are widely used in aromatherapy, medicine, and food industries due to a wide spectrum of bioactivity. Their antioxidant properties can be considered as markers of therapeutic effect and quality. Constant–current coulometry with electrogenerated titrants has been successfully applied for these purposes for the first time. Fifteen types of essential oils from various plant materials have been studied. Their composition has been identified by gas chromatography with mass-spectrometric detection (GC-MS). The reactivity of individual antioxidants of essential oils towards electrogenerated titrants (bromine and ferricyanide ions) has been estimated. Total antioxidant parameters, in particular total antioxidant capacity (TAC) and ferric reducing power (FRP) based on the reactions of essential oil antioxidants with electrogenerated bromine and ferricyanide ions, respectively, have been evaluated. Positive correlations (r = 0.7051–0.9558) with common antioxidant tests (antioxidant activity by reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) and total phenolic content by the Folin–Ciocalteu method) have been obtained. Coulometric approaches overcome the limitations of spectrophotometry and are applicable to a wider range of essential oils.

Antioxidant assessment of agricultural produce using fluorescence techniques: a review

The study of bioactive compounds like food antioxidants is getting huge attention and curiosity by researchers and other relevant stakeholders (e.g., food and pharmaceutical industries) due to their health benefits. However, the currently available protocols to estimate the antioxidant activity of foods are time-consuming, destructive, require complex procedures for sample preparation, need technical persons, and not possible for real-time application, which are very important for large-scale or industrial applications. On the other hand, fluorescence spectroscopy and imaging techniques are relatively new, fast, mostly nondestructive, and possible to apply real-time to detect the antioxidants of foods. However, there is no review article on fluorescence techniques for estimating antioxidants in agricultural produces. Therefore, the present review comprehensively summarizes the overview of fluorescence phenomena, techniques (i.e., spectroscopy and computer vision), and their potential to monitor antioxidants in fruits and vegetables. Finally, opportunities and challenges of fluorescence techniques are described toward developing next-generation protocols for antioxidants measurement. Fluorescence techniques (both spectroscopy and imaging) are simpler and faster than available traditional methods of antioxidants measurement. Moreover, the fluorescence imaging technique has the potential to apply in real-time antioxidant identification in agricultural produce such as fruits and vegetables. Therefore, this technique might be used as a next-generation protocol for qualitative and quantitative antioxidants measurement after improvements like new material technologies for sensor (detector) and light sources for higher sensitivity and reduce the cost of implementing real-world applications.