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

It is desirable to use lower doses of antibiotics in treating bacterial infections, as antibiotics are expensive and may come with undesirable side effects including kidney and/or liver damage. Moreover, using a high dose of antibiotics may lead to development of resistance in bacteria to the antibiotics themselves. More importantly, increasing the dosage may not be able to increase the amount of antibiotics entering the body. Therefore, it may be desirable to devise methods to lower the minimal inhibitory concentration of antibiotics. This invention provides a method to reduce the minimal inhibitory concentration of antibiotics by adding Ganoderma lucidum , or commonly know as Lingzhi, extracts, and therefore, lower does of antibiotics may be required.

Methods of reducing minimal inhibitory concentration of antibiotics and compositions resulting therefrom

P114 In vitro antioxidant activities of various types of chinese tea

Atorvastatin treatment-related changes to in vivo oxidant:antioxidant balance as assessed by plasma allantoin and lipid standardised vitamin E levels

/pdf/metabolic-abnormalities-associated-with-microalbuminuria-in-1gj3dlvgwk.pdf

Metabolic abnormalities associated with microalbuminuria in systemic lupus erythematosus

Atherosclerosis results from inflammatory processes involving biomarkers, such as lipid profile, haemoglobin A1C, oxidative stress, coronary artery calcium score and flow-mediated endothelial response through nitric oxide. This paper proposes a health status coefficient, which comprehends molecular and clinical measurements concerning atherosclerosis to provide a measure of arterial health. An arterial health status map is produced to map the multi-dimensional measurements to the health status coefficient. The mapping is modeled by a fuzzy system embedded with the health domain expert knowledge. The measurements obtained from the pilot study are used to tune the fuzzy system. The inferred arterial health coefficients are stored into the data cubes of a multi-dimensional database. Due to this adaptability and transparency of fuzzy system, the health status map can be easily updated when the refinement of fuzzy rule base is needed or new measurements are obtained.

Iris F.F. Benzie

Papers

Methods of reducing minimal inhibitory concentration of antibiotics and compositions resulting therefrom

P114 In vitro antioxidant activities of various types of chinese tea

Atorvastatin treatment-related changes to in vivo oxidant:antioxidant balance as assessed by plasma allantoin and lipid standardised vitamin E levels

Metabolic abnormalities associated with microalbuminuria in systemic lupus erythematosus

Construction of Multi-dimensional Arterial Health Status Map based on Molecular and Clinical Measurements, Fuzzy System and Data Cubes.