Antioxidative effect measurement

The terminology describing the action of antioxidants is unfortunately not clear. Terms such as antioxidant power , antioxidant effectiveness , antioxidant ability , antioxidant activity , and antioxidant capacity are often used interchangeably and without discrimination. Here we use the term antioxidant activity as meaning a measure of the rate of antioxidant action, and the term antioxidant capacity as meaning a measure of the extent of antioxidant action, i.e. the amount of radicals or intermediates and products produced during oxidation that are quenched by a given antioxidant. Thus antioxidant activity is related to the kinetics of the antioxidant action and antioxidant capacity to the stoichiometry. 

This method is also used to measure ex vivo low-density lipoprotein (LDL) oxidation. LDL is isolated fresh from blood samples, oxidation is initiated by Cu(II) or AAPH, and peroxidation of the lipid components is followed at 234 nm for conjugated dienes (Prior and others 2005). In this specific case the procedure can be used to assess the interaction of certain antioxidant compounds, such as vitamin E, carotenoids, and retinyl stearate, exerting a protective effect on LDL (Esterbauer and others 1989). Hence, Viana and others (1996) studied the in vitro antioxidative effects of an extract rich in flavonoids. Similarly, Pearson and others (1999) assessed the ability of compounds in apple juices and extracts from fresh apple to protect LDL. Wang and Goodman (1999) examined the antioxidant properties of 26 common dietary phenolic agents in an ex vivo LDL oxidation model. Salleh and others (2002) screened 12 edible plant extracts rich in polyphenols for their potential to inhibit oxidation of LDL in vitro. Gongalves and others (2004) observed that phenolic extracts from cherry inhibited LDL oxidation in vitro in a dose-dependent manner. Yildirin and others (2007) demonstrated that grapes inhibited oxidation of human LDL at a level comparable to wine. Coinu and others (2007) studied the antioxidant properties of extracts obtained from artichoke leaves and outer bracts measured on human oxidized LDL. Milde and others (2007) showed that many phenolics, as well as carotenoids, enhance resistance to LDL oxidation. 

Figure 11.1. Effect of storage temperature (0, 5, 10°C) on (I) total anthocyanins (mg/100 g FW), (II) total phenols (mg/100 g FW), and (III) antioxidant capacity measured as ORAC (p.mol TE/g FW) of strawberry fruit (cv. Chandler). Bars show the final values after treatments. Different letters on top of the bars indicate statistical differences among treatments (p < 0.05).

Thus, antioxidant effects of nitrite in cured meats appear to be due to the formation of NO. Kanner et al. (1991) also demonstrated antioxidant effects of NO in systems where reactive hydroxyl radicals ( OH) are produced by the iron-catalyzed decomposition of hydrogen peroxide (Fenton reaction). Hydroxyl radical formation was measured as the rate of benzoate hydtoxylation to salicylic acid. Benzoate hydtoxylation catalyzed by cysteine-Fe +, ascorbate - EDTA-Fe, or Fe was significantly decreased by flushing of the reaction mixture with NO. They proposed that NO liganded to ferrous complexes reacted with H2O2 to form nitrous acid, hydroxyl ion, and ferric iron complexes, preventing generation of hydroxyl radicals. 

In vivo studies were also conducted by several researchers. Anraku et al. (2009) examined the antioxidant effects of water-soluble chitosan in normal subjects by measuring the reduction of indices of oxidative stress. Treatment with chitosan for 4weeks produced a significant decrease in levels of plasma glucose and the atherogenic index, and led to an increase in high-density lipoprotein cholesterol (HDL-C). Chitosan treatment also lowered the ratio of oxidized to reduced albumin and increased total plasma antioxidant activity. Further, Anraku et al. (2011) proved the antioxidant effects of high MW chitosan in normal volunteers, and the obtained results were consistent with previous results observed by Anraku et al. (2009). 

Determination of Antioxidant Effect The measurement was based on consumption of dissolved oxygen by a sunflower oil emulsion in a closed system with or without the presence of antioxidant material. 

PJ consumption exhibited antioxidative effects also when administered to E° mice.28 The basal oxidative state, measured as lipid peroxides in plasma of control E° mice (that did not consume PJ), increased gradually during aging from 260 nmol/mL of plasma at 6 weeks of age to 309 and 535 nmol/mL of plasma after 9 and 14 weeks of age, respectively. Following PJ consumption, plasma lipid peroxidation was markedly reduced, and this effect was PJ concentration dependent (Figure 8.3B). Similarly, serum total antioxidant status was higher in E° mice that consumed PJ in comparison to control mice, and this effect was again juice concentration dependent.28... 

The antioxidizing effect of amine on oxidative degradation of vulcanized rubber is evaluated from the following measurements ... 

The oils of ajowan show excellent antioxidant effects (better than those of the synthetic antioxidant and butylated hydroxytoluene Gurdip et al., 1998). Mehta et al. (1994) demonstrated ajowan as a source of natural lipid antioxidant. Soybean oil treated with meth-anolic extracts has been subjected to storage and heating tests, which showed a marked decrease in oxidation of the oil as measured using peroxide values, conjugated diene... 

The phenolic antioxidant activity in the corn oil emulsions of 17 selected Spanish wines and two Californian wines was examined for their preventive capability for lipid oxidation as dietary antioxidants. The inhibition of hydroperoxide formation [measured as percent of control for 10 iM gallic acid equivalents (GAE)] was increased from 8.4 to 40.2% in the presence of the red wines, from 20.9 to 45.8% with the rose wines, and from 6.5 to 47.0% with the white wines. The inhibition of hydroperoxide formation at 20 xM GAE was increased from 11.9 to 34.1% in the presence of red wines, from 0.1 to 34.5% with the rose wines, and from 3.3 to 37.2% with the white wines. The inhibition of the hexanal formation at 10 (jlM GAE was increased from 23.6 to 64.4% in the presence of red wines, from 42.7 to 68.5% with the rose wines, and from 28.4 to 68.8% with the white wines. Moreover, the inhibition of the hexanal formation at 20 xM GAE was increased from 33.0 to 46.3% in the presence of red wines, from 11.3 to 66.5% with the rose wines, and from - 16.7 to + 21.0% with the white wines. The antioxidant effect declined apparently with increasing concentration. The antioxidant activity might be ascribed to the five main groups of phenolics identified in the wines benzoic acids, anthocyanins, flavan-3-ols, flavonols, and hexanal [38]. 

Although the OSl method is useful for quality control of oils, it is not recommended for measurement of antioxidant activity for certain reasons. The high temperatures used do not allow reliable predictions of antioxidant effectiveness at lower temperatures. Volatile antioxidants may be swept out of the oil by the air flow under test conditions, and also the oils are severely deteriorated when endpoint is reached (12). 

In addition to measuring the antioxidant effects of prenylated flavonoids from Sophora flavescens by using in vitro l,l-diphenyl-2-picrylhydrazyl (DPPH), 2,2/-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), per-oxynitrite (ONOCT), and total reactive oxygen species (ROS) assays, the examination of the inhibition of tert-butylhydroperoxide (f-BIIP)-induced intracellular ROS generation and f-BHP-induced activation of nuclear factor-kB (NF-/cB) was also added as a further examination of kuraridinol (9),... 

More recently, studies on the absorption of flavonoid glycosides typical of berries and grapes are reported. Lapidot et al. (1998) traced anthocyanins in human urine after the intake of 300 ml red wine, corresponding to 218 mg of anthocyanins. Totals of 1.5-5.1% of the anthocyanins were recovered in the urine within 12 h after wine consumption, two compounds were unchanged, whereas other compounds seemed to have undergone molecular modifications. The anthocyanin levels of the urine reached a peak within 6 h of consumption. Serafini et al. (1998) tested the effects of the intake of the nonalcoholic fraction of red or white wine on plasma antioxidant capacity, measured as total radical-trapping parameter (TRAP), and on... 

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