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

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

Phenolics and polyphenolics in foods, beverages and spices: Antioxidant activity and health effects – A review

Both lipophilic and hydrophilic antioxidant capacities were determined using the oxygen radical absorbance capacity (ORACFL) assay with fluorescein as the fluorescent probe and 2,2‘-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator on over 100 different kinds of foods, including fruits, vegetables, nuts, dried fruits, spices, cereals, infant, and other foods. Most of the foods were collected from four different regions and during two different seasons in U.S. markets. Total phenolics of each sample were also measured using the Folin−Ciocalteu reagent. Hydrophilic ORACFL values (H-ORACFL) ranged from 0.87 to 2641 μmol of Trolox equivalents (TE)/g among all of the foods, whereas lipophilic ORACFL values (L-ORACFL) ranged from 0.07 to 1611 μmol of TE/g. Generally, L-ORACFL values were <10% of the H-ORACFL values except for a very few samples. Total antioxidant capacity was calculated by combining L-ORACFL and H-ORACFL. Differences of ORACFL values in fruits and vegetables from different...

https://faculty.missouri.edu/~glaserr/3700s14/Antioxidant_WuJAgFoodChem5240262004.pdf

Lipophilic and hydrophilic antioxidant capacities of common foods in the United States

Antioxidant activity of some algerian medicinal plants extracts containing phenolic compounds

Summary Some of the most exciting research in the last decade has been the discovery of a group of nutrients, which have protective eAects against cell oxidation. These naturally occurring compounds impart bright colour to fruits and vegetables and act as antioxidants in the body by scavenging harmful free radicals, which are implicated in most degenerative diseases. Epidemiological studies have established a positive correlation between the intake of fruits and vegetables and prevention of diseases like atheroscelerosis, cancer, diabetes, arthritis and also ageing. So pronounced has been their eAect on ageing that they have been called ‘fountains of youth’. Fruits and vegetables have thus had conferred on them the status of ‘functional foods’, capable of promoting good health and preventing or alleviating diseases. Phenolic flavonoids, lycopene, carotenoids and glucosinolates are among the most thoroughly studied antioxidants. The present review highlights the potential of fruits and vegetables rich in antioxidants, their health benefits and the eAect of processing on the bioavailability of these nutrients. The paper also reviews some of the important methods used to determine the antioxidant activity.

Antioxidants in fruits and vegetables – the millennium’s health

The anti-oxidant activity of extracts from 36 vegetables was evaluated by using a model system consisting of β-carotene and linoleic acid. The total phenolics of the extracts was determined spectrophotometrically according to the Folin–Ciocalteau procedure and ranged from 34 to 400 mg (100 g)−1 on a fresh weight basis. Mint, aonla, black carrots, chenopodium, fenugreek, kachnar and ginger had high phenolic contents. The anti-oxidant activity expressed as per percent inhibition of oxidation ranged from a high of 92% in turmeric extracts to a low of 12.8% in long melon. Other vegetables found to have high anti-oxidant activity (>70%) were kachnar, aonla, ginger, fenugreek, mint, beetroot, black carrots, Brussels sprouts, broccoli, lotus stem, yam, coriander and tomato. Anti-oxidant activity correlated significantly and positively with total phenolics (r2=0.6578, P < 0.05). The results indicate that vegetables containing high phenolics may provide a source of dietary anti-oxidants.

Anti‐oxidant activity and total phenolic content of some Asian vegetables

Antioxidants in tomato (Lycopersium esculentum) as a function of genotype

Changes in total phenolics, antioxidant activity (AOX), carotenoids, capsaicin and ascorbic acid were monitored during three maturity stages in 10 genotypes of sweet pepper. In an attempt to explain the variations during maturity stages (green, intermediate and red/yellow), the data was expressed both on fresh and dry weight basis. All the antioxidant constituents (phenolics, ascorbic acid and carotenoids) and AOX, when expressed on fresh weight basis in general, showed an overall increasing trend during maturity in all the genotypes studied. On dry weight basis, phenolic content declined in majority of the genotypes during maturity to red stage. This decline was significant ( P 0.05 ) in Parker, Torkel, HA-1038 and Flamingo. Genotype Flamingo and Golden Summer had the highest phenolic content of 852.0 mg 100 g−1 and 720.5 mg 100 g−1, at their final red and yellow maturity stages, respectively. With maturation, most of the cultivars showed a declining trend with regard to capsaicin content while total carotenoids and β-carotene content increased significantly. Anupam was a promising genotype in terms of both total carotenoids and β-carotene content. Ascorbic acid content declined progressively with advancing maturity. Genotype HA-1038 had the maximum content (3030 mg 100 g−1 dwb) at the green stage. AOX in general, increased with maturity and registered a 1.30–1.95fold increase from green to red stage. The study proposes the nutritional significance of consuming sweet peppers at the red maturity stage because of enhanced functional properties. Overall genotype Flamingo and Anupam represent superior genotypes for both nutrition and germplasm improvement.

H. C. Kapoor

Papers

Antioxidants in fruits and vegetables – the millennium’s health

Anti‐oxidant activity and total phenolic content of some Asian vegetables

Antioxidants in tomato (Lycopersium esculentum) as a function of genotype

Antioxidant constituents in some sweet pepper (Capsicum annuum L.) genotypes during maturity

Antioxidant activity in some red sweet pepper cultivars