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

The antioxidant activities and total phenolics of 28 plant products, including sunflower seeds, flaxseeds, wheat germ, buckwheat, and several fruits, vegetables, and medicinal plants were determined. The total phenolic content, determined according to the Folin−Ciocalteu method, varied from 169 to 10548 mg/100 g of dry product. Antioxidant activity of methanolic extract evaluated according to the β-carotene bleaching method expressed as AOX (Δ log A470/min), AA (percent inhibition relative to control), ORR (oxidation rate ratio), and AAC (antioxidant activity coefficient) ranged from 0.05, 53.7, 0.009, and 51.7 to 0.26, 99.1, 0.46, and 969.3, respectively. The correlation coefficient between total phenolics and antioxidative activities was statistically significant. Keywords: Antioxidant activity; phenolics; medicinal plants; oilseeds; buckwheat; vegetables; fruits; wheat products

Antioxidant Activity and Total Phenolics in Selected Fruits, Vegetables, and Grain Products

The antioxidative activity of a total of 92 phenolic extracts from edible and nonedible plant materials (berries, fruits, vegetables, herbs, cereals, tree materials, plant sprouts, and seeds) was examined by autoxidation of methyl linoleate. The content of total phenolics in the extracts was determined spectrometrically according to the Folin-Ciocalteu procedure and calculated as gallic acid equivalents (GAE). Among edible plant materials, remarkable high antioxidant activity and high total phenolic content (GAE > 20 mg/g) were found in berries, especially aronia and crowberry. Apple extracts (two varieties) showed also strong antioxidant activity even though the total phenolic contents were low (GAE < 12.1 mg/g). Among nonedible plant materials, high activities were found in tree materials, especially in willow bark, spruce needles, pine bark and cork, and birch phloem, and in some medicinal plants including heather, bog-rosemary, willow herb, and meadowsweet. In addition, potato peel and beetroot peel extracts showed strong antioxidant effects. To utilize these significant sources of natural antioxidants, further characterization of the phenolic composition is needed.

Antioxidant activity of plant extracts containing phenolic compounds

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

Free radicals are common outcome of normal aerobic cellular metabolism. In-built antioxidant system of body plays its decisive role in prevention of any loss due to free radicals. However, imbalanced defense mechanism of antioxidants, overproduction or incorporation of free radicals from environment to living system leads to serious penalty leading to neuro-degeneration. Neural cells suffer functional or sensory loss in neurodegenerative diseases. Apart from several other environmental or genetic factors, oxidative stress (OS) leading to free radical attack on neural cells contributes calamitous role to neuro-degeneration. Though, oxygen is imperative for life, imbalanced metabolism and excess reactive oxygen species (ROS) generation end into a range of disorders such as Alzheimer's disease, Parkinson's disease, aging and many other neural disorders. Toxicity of free radicals contributes to proteins and DNA injury, inflammation, tissue damage and subsequent cellular apoptosis. Antioxidants are now being looked upon as persuasive therapeutic against solemn neuronal loss, as they have capability to combat by neutralizing free radicals. Diet is major source of antioxidants, as well as medicinal herbs are catching attention to be commercial source of antioxidants at present. Recognition of upstream and downstream antioxidant therapy to oxidative stress has been proved an effective tool in alteration of any neuronal damage as well as free radical scavenging. Antioxidants have a wide scope to sequester metal ions involved in neuronal plaque formation to prevent oxidative stress. In addition, antioxidant therapy is vital in scavenging free radicals and ROS preventing neuronal degeneration in post-oxidative stress scenario.

Oxidative stress and neurodegenerative diseases: a review of upstream and downstream antioxidant therapeutic options.

Sea buckthorn (Hippophae rhamnoides) is a unique plant currently being domesticated. The fruit is the main component of value, although the leaves are occasionally made into sea buckthorn tea. The two main sources of valuable products are derived from the berries, juice from the fleshy tissue and seed as a single seed from each berry. The juice provides a nutritious beverage, high in suspended solids and very high in vitamin C and carotenes. The juice may contain an oil phase trapped within the suspended solids, or the oil may be removed as pulp oil and provided separately. The pulp remaining after juice removal provides for extraction of "sea buckthorn yellow", a pigment that has potential use as a food coloring material. The seed is a source of seed oil, which is very unsaturated and shows promise, because of its light absorption and emollient properties, as an ingredient in cosmetics, phytopharmaceuticals, or UV skin protectant preparations. It may be prepared by conventional extraction techniques or by supercritical carbon dioxide extraction. The manufacture of the main products derived from sea buckthorn is described, including several examples from the patent literature. The available compositional data for the main products are tabulated to form a comprehensive source of information on the manufacture and composition of sea buckthorn products.

/pdf/sea-buckthorn-products-manufacture-and-composition-gb0byqxwkl.pdf

Sea buckthorn products: manufacture and composition.

Samples of buckwheat from four cultivars grown at three locations in western Canada for 4 years were used to study the effect of cultivar, location, and growing season on the flavonoid content and antioxidative activities of the seed. Buckwheat contained an average of 387 and 1314 mg/100 g of flavonoid and 47 and 77 mg/100 g of rutin in the seed and hull, respectively. Location was the main source of variation for flavonoid and rutin contents of the seed, while growing season had significant influence on the flavonoid content of the hulls. Variation in antioxidative activities was mainly due to a cultivar × environment effect. Antioxidative activities expressed as AOX (Δ log A470/min), AA (% inhibition relative to control), and ORR (oxidation rate ratio) ranged from 0.42, 114, and 0.16 to 1.63, 48, and 0.59, respectively. Flavonoid content in buckwheat was strongly correlated with rutin content and weakly associated with antioxidative activities, while rutin content was not related to antioxidative activi...

Flavonoids and antioxidative activities in buckwheat.

Ninety-six samples of flaxseed from eight cultivars grown at four locations in western Canada for three years were used to study the effect of cultivar, location, and growing season on the phenolic acid contents of the seed. Flaxseed contained 8-10 g/kg of total phenolic acids, about 5 g/kg of esterified phenolic acids, and 3-5 g/kg of etherified phenolic acids. The esterified phenolic acids represented 48-66% of the total phenolic acids and were not dependent on cultivar. Variation in phenolic acids was mainly due to seasonal effect. While growing location had significant effects on phenolic acid contents of individual cultivars, no overall significant location effect was observed. The yellow-seeded flaxseed cultivar Linola 947 had lower levels of total and esterified phenolic acids compared to the traditional brown-seeded type. Phenolic acid contents of flaxseed were independent of protein and oil contents. A strong positive correlation was found between the constitutive concentrations of total and etherified phenolic acids in flaxseed and resistance to fusarium wilt.

Phenolic acids in flaxseed

Phytic acid content of meal from eight flaxseed cultivars grown in 1991, 1992, and 1993 at four locations in western Canada was determined to examine the effect of cultivar, location, and growing season. Flaxseed contained 23-33 g of phytic acid per kilogram of meal, and averages for years and locations were significantly different among all cultivars. Yearly differences in phytic acid were significant at most locations. Variation in phytic acid was mainly due to cultivar and the interaction of cultivar with location and year. The stability of phytic acid concentration in various environments appears to be genetically controlled. In flaxseed, phytic acid was independent of oil content and was not related to seed yield. A negative correlation was found between phytic acid and iodine value and phenolic acids of flaxseed.

B. D. Oomah

Papers

Antioxidant Activity and Total Phenolics in Selected Fruits, Vegetables, and Grain Products

Sea buckthorn products: manufacture and composition.

Flavonoids and antioxidative activities in buckwheat.

Phenolic acids in flaxseed

Phytic Acid Content of Flaxseed As Influenced by Cultivar, Growing Season, and Location