Methods to Determine Chain-Breaking Antioxidant Activity of Nanomaterials beyond DPPH•. A Review

Abstract

This review highlights the progress made in recent years in understanding the mechanism of action of nanomaterials with antioxidant activity and in the chemical methods used to evaluate their activity. Nanomaterials represent one of the most recent frontiers in the research for improved antioxidants, but further development is hampered by a poor characterization of the ‘‘antioxidant activity’’ property and by using oversimplified chemical methods. Inhibited autoxidation experiments provide valuable information about the interaction with the most important radicals involved in the lipid oxidation, namely alkylperoxyl and hydroperoxyl radicals, and demonstrate unambiguously the ability to stop the oxidation of organic materials. It is proposed that autoxidation methods should always complement (and possibly replace) the use of assays based on the quenching of stable radicals (such as DPPH• and ABTS•+). The mechanisms leading to the inhibition of the autoxidation (sacrificial and catalytic radical trapping antioxidant activity) are described in the context of nanoantioxidants. Guidelines for the selection of the appropriate testing conditions and of meaningful kinetic analysis are also given.

Concentration-dependent HAT/ET mechanism of the reaction of phenols with 2,2-diphenyl-1-picrylhydrazyl (dpph˙) in methanol

“…There are many well-documented shortcomings of the dpph˙ assay, including poor or no correlation with the antioxidant activity of phenols measured under physiologically relevant conditions (reactivity toward peroxyl radicals). 5 Another problem with the dpph˙ assay is that IC 50 parameter reflects the position of redox equilibrium between dpph˙ and the tested compound, established after the incubation time, and gives no information about the kinetics and stoichiometry of the reaction. 5 b , d…”

“…This two-step mechanism is described as Sequential Proton-Loss Electron Transfer (SPLET), 3,4 with k ET >> k HAT , see Chart 1A , and even traces of ArO − causing an enormous increase of overall rate of reaction 1 . 2 Mixed mechanism in alcohols excludes dpph˙ as mimetic to peroxyl radicals but, regardless of this controversy, 5 reaction 1 is one of the most frequently used colorimetric assays employed for quick assessment of the antiradical abilities of natural and synthetic compounds, with more than 40 thousand papers published during the last decade (SCOPUS, keywords “dpph” and “antioxidant”).…”

A Review on Phytochemicals and Pharmacological Activities as Ethnomedicinal Uses of Duku (Lansium domesticum Corr.)

“…Beta-hydroxy acid, tert-butyl hydroquinone, propyl gallate, and butylated hydroxytoluene are examples of synthetic antioxidants that have been widely employed across the world [43], [44]. However, these synthetic antioxidants have negative side effects on the heart and lungs, including carcinogenic and cytotoxic consequences [45]. Natural items having antioxidant capabilities, such as L. domesticum, have been discovered (Table 3).…”

“…Uncontrolled cell proliferation and differentiation are hallmarks of cancer. It has the ability to infect organs and tissues, and it is a serious public health concern in both developed and developing countries [45]. The assessment of cytotoxic activity against cancer cell lines in vitro and animal cancer models in vivo was a major factor in the development of new anticancer drugs from natural sources such as plants, marine creatures, and microorganisms [51].…”

A Comprehensive Review of the Development of Carbohydrate Macromolecules and Copper Oxide Nanocomposite Films in Food Nanopackaging

“…Nanotechnology-arisen products are now used in numerous fields of life and have shown their potential from industry to basic sciences and medicine to develop new tools, systems, and drugs [13,14]. Metallic nanoparticles (MNPs) synthesized by multiple unique methods and properties, which help their exploitation in independent fields, such as nanodiagnostics [15,16], nanomedicine [17][18][19], antibacterial [19][20][21], antioxidant [19,20,22,23], luminescence [24,25], photocatalytic [24,26], painting, ceramic, glass production, and food packaging industry [27][28][29][30][31][32][33][34]. Nanoparticles such as titanium, silver, zinc, and copper have been applied worldwide to form nanocomposite packaging materials with antimicrobial and antioxidant activities [7,[35][36][37].…”