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

There has been increasing interest in the research on flavonoids from plant sources because of their versatile health benefits reported in various epidemiological studies. Since flavonoids are directly associated with human dietary ingredients and health, there is need to evaluate structure and function relationship. The bioavailability, metabolism, and biological activity of flavonoids depend upon the configuration, total number of hydroxyl groups, and substitution of functional groups about their nuclear structure. Fruits and vegetables are the main dietary sources of flavonoids for humans, along with tea and wine. Most recent researches have focused on the health aspects of flavonoids for humans. Many flavonoids are shown to have antioxidative activity, free radical scavenging capacity, coronary heart disease prevention, hepatoprotective, anti-inflammatory, and anticancer activities, while some flavonoids exhibit potential antiviral activities. In plant systems, flavonoids help in combating oxidative stress and act as growth regulators. For pharmaceutical purposes cost-effective bulk production of different types of flavonoids has been made possible with the help of microbial biotechnology. This review highlights the structural features of flavonoids, their beneficial roles in human health, and significance in plants as well as their microbial production.

/pdf/chemistry-and-biological-activities-of-flavonoids-an-483pb5vgo0.pdf

Chemistry and Biological Activities of Flavonoids: An Overview

Publisher Summary This chapter discusses ferric reducing/antioxidant power (FRAP) assay. The ferric reducing/antioxidant power (FRAP) assay is a recently developed, direct test of “total antioxidant power.” The FRAP assay is robust, sensitive, simple, and speedy and facilitates experimental and clinical studies investigating the relationship among antioxidant status, dietary habits, and risk of disease. Measurement of the total antioxidant power of fresh biological fluids—such as blood plasma—can be measured directly; the antioxidant content of various dietary agents can be measured objectively and reproducibly and their potential for improving the antioxidant status of the body investigated and compared. The FRAP assay is also sensitive and analytically precise enough to be used in assessing the bioavailability of antioxidants in dietary agents to help monitor longitudinal changes in antioxidant status associated with an increased intake of dietary antioxidants and to investigate the effects of disease on antioxidant status.

Ferric reducing/antioxidant power assay: direct measure of total antioxidant activity of biological fluids and modified version for simultaneous measurement of total antioxidant power and ascorbic acid concentration

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

Drinking green tea leads to a rapid increase in plasma antioxidant potential

Panax pseudoginseng (Shachi) are well known for their antioxidant properties. The aim of this study was to explore Sanchi extracts, potential protection of human cellular DNA from oxidative challenge induced by hydrogen peroxide in vitro. Aqueous and alcoholic extracts of Shachi were incubated with human lymphocytes from 1×10−2% to 1×10−7% (w/v) for 30 mins. Pre-treated cells were then stressed with 50 µM hydrogen peroxide. Washed cells were subjected to the standard and the lysed cell comet assays. Results showed that water extracts of Sanchi at specific concentrations were able to diminish human DNA damage induced by hydrogen peroxide in both standard and lysed cell comet assays. No effect was observed in ethanolic extract. More pronounced protective effect in lysed cell comet assay model implied cell membrane limited the availability of active ingredients of Sanchi to nucleus.

An in vitro study of Sanchi (Panax pseudoginseng) for its DNA protective effect

Oxidative stress can damage cells, protein and DNA and is known to be involved in the development and progression of many diseases. Diets rich in plant-based foods are associated with improved health. Ganoderma lucidum (Lingzhi or Reishi) medicinal mushroom has been used for centuries in Asia for health promotion and has a wide range of reputed health benefits. This study investigated the antioxidant properties of G. lucidum and its effects on DNA damage and repair in lymphocytes in a cross-over human intervention study. Blood samples were collected from 7 healthy volunteers at 0 (fasting), 90 and 180 min post-ingestion of a single dose (3.3 g) of G. lucidum or water (control). Plasma total antioxidant power and the effect on lymphocyte DNA damage and repair were assessed before and after each treatment. Lymphocytes were harvested immediately after blood collection at 0 and 180 min, oxidatively challenged, then incubated in complete culture medium for DNA damage repair. Results show that intake of G. lucidum caused an acute increase in plasma antioxidant power, but did not significantly affect the level or rate of repair in lymphocytic DNA. These results show that the bioavailable antioxidants absorbed from G. lucidum have no effect on DNA resistance to oxidative stress or repair in vivo.

Antioxidant power and DNA repair effects of Lingzhi or Reishi medicinal mushroom, Ganoderma lucidum (W.Curt.:Fr.) P. Karst. (Aphyllophoromycetideae), in human acute post-ingestion study.

Iris F.F. Benzie

Papers

Drinking green tea leads to a rapid increase in plasma antioxidant potential

An in vitro study of Sanchi (Panax pseudoginseng) for its DNA protective effect

Antioxidant power and DNA repair effects of Lingzhi or Reishi medicinal mushroom, Ganoderma lucidum (W.Curt.:Fr.) P. Karst. (Aphyllophoromycetideae), in human acute post-ingestion study.

Personal perspective of a group of nursing students in Hong Kong on diet and health : implication for nurse education

Lingzhi polyphorous fungus (Ganoderma lucidum)