This review summarizes the multifaceted aspects of antioxidants and the basic kinetic models of inhibited autoxidation and analyzes the chemical principles of antioxidant capacity assays. Depending upon the reactions involved, these assays can roughly be classified into two types:  assays based on hydrogen atom transfer (HAT) reactions and assays based on electron transfer (ET). The majority of HAT-based assays apply a competitive reaction scheme, in which antioxidant and substrate compete for thermally generated peroxyl radicals through the decomposition of azo compounds. These assays include inhibition of induced low-density lipoprotein autoxidation, oxygen radical absorbance capacity (ORAC), total radical trapping antioxidant parameter (TRAP), and crocin bleaching assays. ET-based assays measure the capacity of an antioxidant in the reduction of an oxidant, which changes color when reduced. The degree of color change is correlated with the sample's antioxidant concentrations. ET-based assays include th...

The Chemistry behind Antioxidant Capacity Assays

Methods available for the measurement of antioxidant capacity are reviewed, presenting the general chemistry underlying the assays, the types of molecules detected, and the most important advantages and shortcomings of each method. This overview provides a basis and rationale for developing standardized antioxidant capacity methods for the food, nutraceutical, and dietary supplement industries. From evaluation of data presented at the First International Congress on Antioxidant Methods in 2004 and in the literature, as well as consideration of potential end uses of antioxidants, it is proposed that procedures and applications for three assays be considered for standardization: the oxygen radical absorbance capacity (ORAC) assay, the Folin-Ciocalteu method, and possibly the Trolox equivalent antioxidant capacity (TEAC) assay. ORAC represent a hydrogen atom transfer (HAT) reaction mechanism, which is most relevant to human biology. The Folin-Ciocalteu method is an electron transfer (ET) based assay and gives reducing capacity, which has normally been expressed as phenolic contents. The TEAC assay represents a second ET-based method. Other assays may need to be considered in the future as more is learned about some of the other radical sources and their importance to human biology.

https://faculty.missouri.edu/~glaserr/3700s14/Antioxidant-Capacity_jf0502698.pdf

Standardized Methods for the Determination of Antioxidant Capacity and Phenolics in Foods and Dietary Supplements

Phenolics are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants. Plant polyphenols have drawn increasing attention due to their potent antioxidant properties and their marked effects in the prevention of various oxidative stress associated diseases such as cancer. In the last few years, the identification and development of phenolic compounds or extracts from different plants has become a major area of health- and medical-related research. This review provides an updated and comprehensive overview on phenolic extraction, purification, analysis and quantification as well as their antioxidant properties. Furthermore, the anticancer effects of phenolics in-vitro and in-vivo animal models are viewed, including recent human intervention studies. Finally, possible mechanisms of action involving antioxidant and pro-oxidant activity as well as interference with cellular functions are discussed.

/pdf/plant-phenolics-extraction-analysis-and-their-antioxidant-2ee2ft7zgl.pdf

Plant phenolics: extraction, analysis and their antioxidant and anticancer properties.

https://aggie-horticulture.tamu.edu/faculty/cisneros/Papers/Thaipong_2006.pdf

Comparison of ABTS, DPPH, FRAP, and ORAC assays for estimating antioxidant activity from guava fruit extracts

Phenolic compounds in plants and agri-industrial by-products: Antioxidant activity, occurrence, and potential uses

A method for assaying the antioxidant capacity of a skin care product, the method including preparing an emulsion base, dissolving a sample of a skin care product into the emulsion base to form a homogeneous emulsion mixture, adding a detection probe to the homogeneous emulsion mixture, adding reactive oxygen species generator and/or reactive nitrogen species generator to the homogeneous emulsion mixture, measuring the fluorescence intensity change of the detection probe in the presence of the sample over time, in the presence of the standard over time, and in the presence of a blank over time, and calculating the initial rate of oxidation of the detection probe to determine the antioxidant capacity of the sample of the skin care product.

Method for assaying the antioxidant capacity of a skin care product

Bioavailability and Antioxidant Effects of A Xanthone‐rich Dietary Supplement in Humans

Incorporation of blueberries in food products has increased rapidly in last decade. The purposes of this study were to evaluate the blueberry in commercial food products presence by measuring signature compounds, and to further assess their anti-inflammatory effects. Anthocyanins (ACNs) and chlorogenic acid (CGA) were selected as candidate signature compounds. In ten selected blueberry-containing commercial food products, only four contained ACNs, while eight contained CGA. Because CGA was more stable, it was considered as a better indicator of blueberry presence. Blueberry contents in these commercial food products were then estimated based on their CGA contents. Polyphenol-enriched fractions from these food products were prepared and subjected to NF-κB inhibition assay to evaluate their anti-inflammatory effects. All fractions inhibited NF-κB activation dose-dependently. There was a weak correlation between anti-inflammatory effects and blueberry contents. The data also pointed out that ACNs in their native forms were probably the most active anti-inflammatory components in blueberries. Journal of Nature and Science, 1(4):e65, 2015

Evaluating commercial food products for presence of blueberries and for their anti-inflammatory effects

Verfahren zum austesten der antioxidanskapazität einer probe

The invention provides novel and improved methods that allow effective capture of valuable active ingredients in biomass (e.g., DDGS) at cost-effective commercial scale. The invention also provides novel compositions of active ingredients with unique properties (e.g., nutritional values and enhanced bioavailability).

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Papers

Method for assaying the antioxidant capacity of a skin care product

Bioavailability and Antioxidant Effects of A Xanthone‐rich Dietary Supplement in Humans

Evaluating commercial food products for presence of blueberries and for their anti-inflammatory effects

Verfahren zum austesten der antioxidanskapazität einer probe

Biomass extracts and methods thereof