Antioxidant potency

Table 7. Antioxidant Potency of Vitamins and Phenolics Based on LDL Oxidation In Vitrei...

Nielsen, I.L.F. et al., Quantification of anthocyanins in commercial black currant juices by simple high-performance liquid chromatography investigation of their pH stability and antioxidative potency, J. Agric. Food Chem., 51, 5861, 2003. 

The potency of a chain-breaking antioxidant, which scavenges peroxyl radicals, will decrease as the concentration of lipid peroxides in the LDL particle increases (Scheme 2.2). This is illustrated in the experiment shown in Fig. 2.3 in which the antioxidant potency of a peroxyl radical scavenger (BHT) decreases as a function of added exogenous hpid hydroperoxide. If the endogenous lipid peroxide content of LDL were to vary between individuals, this could explain the observed diferences in the effectiveness of a-tocopherol in suppressing lipid peroxidation promoted by copper. 

Bioactive compounds, such as carotenoids have strong antioxidative properties and are used as efficient radical scavengers. In some natural sources several carotenoid isomers can be found, which differ in their biochemical activities such as bioavailability or antioxidation potency. Knowing the structure and concentration of each stereoisomer is crucial for an understanding of the effectiveness... 

Ke, P.J., Nash. D.M., and Ackman, R.G. 1977. Mackerel skin lipids as an unsaturated fat model system for the determination of antioxidative potency of TBHQ and other antioxidant compounds. J. Am. Oil Chem. Soc. 54 417-420. 

The antioxidant activity of flavonoids in liposomes has also been extensively studied. Gordon and Roedig-Penman [93] used liposomes formed from egg PC to compare the antioxidant potencies of myricetin (31) and quercetin... 

Pomegranate Juice Polyphenols and Antioxidant Potency in Comparison to other Fruit Juices... 

Figure 8.2 Pomegranate juice polyphenols and antioxidant potency in comparison to other fruit juices. Total polyphenol concentration in the different juices was determined using quercetin as a standard. LDL (100 pg of protein/milliliter) was preincubated with increasing volume concentration (0-25 pL) of the juices. Then, 5 pmol/L of CuS04 was added, and the LDL was further incubated for 2 hours at 37°C. The extent of LDL oxidation was measured by the thiobar-bituric acid reactive substance (TBAR) assay, and the ICh, values (the concentration needed to get 50% inhibition) are given. Results are given as mean S.D. of three different experiments.

In addition to free fatly acids and their esters as previously described, compounds with antioxidant potency were also used as acyl donors. In order to investigate the synthesis of hybrid antioxidants, the enzymatic acylation of escuhn catalyzed by immobilized CALB in the ionic liquids [bmtm]BF4 and [bmim]PF6 was investigated using several phenolic acids as well as their corresponding vinyl esters. 

Anson, N.M. Berg, R.V.D. Flavenaar, R. Bast, A. Flaenen, G.R.M.M. 2008. Ferulic aeid from aleurone determines the antioxidant potency of wheat grain (Triticum aestivum L.). J. Agric. Food Chem. 56 5589-5594. 

A variant of the Hantzsch reaction catalyzed by molecular iodine (Scheme 20) provided Ai-Aryl dUiydrop3Tidine derivatives 86, which were evaluated for their antidyslipidemic and antioxidant potencies [52]. Several compounds exhibited promising antidyslipidemic and antioxidant activities (Table 7). 

Quercetin and other flavonoids are effective inhibitors of 02 -production by cells. Quercetin is a potent inhibitor of human neutrophil degranulation and 02 -production, and also inhibits the phosphorylation of neutrophil proteins accompanying neutrophil activation by phorbol myristate acetate. Quercetin can also suppress lipid peroxidation in several biological systems, such as mitochondria, microsomes, chloro-plasts, and erythrocytes. Silymarin, a 3-OH flavone present in Silybum marianum (the European milk thistle), protects rat liver mitochondria and microsomes from lipid peroxide formation induced by Fe " "-ascorbate and NADPH-Fe -ADP systems. Soybean isoflavonoids have shown antioxidative potency... 

The comparison of the antioxidant potency of hydroxytyrosol, tyrosol, oleuropein with respect to vitamin E and BHT and the synergistic effect with vitamin E were studied in thermal initiated oxidation of methyl linoleate in the presence of azo-compounds, in heptanol or propanohwater. The activity of the phenols was expressed as increase of induction period and extent of reaction inhibition [47]. The azo compounds initiated oxidation is a free radical chain process. Confirming the results from a previous study [43], this study showed that hydroxytyrosol and oleuropein were much more effective than BHT and vitamin E in extending the induction period. Tyrosol was devoid of activity and no synergistic effect on the preservation of methyl linoleate was foxmd when vitamin E was used together with tyrosol. 

When comparing the antioxidant potencies of both the traditional/fermented and green/unfermented rooibos and honeybush, evidence is difficult to select for the best one, since the activity is highly dependent on the assay used, the nature of the raw material, and type of samples (aqueous extracts, enriched-extracts or solvent extracts) used. 

Nickander KK, McPhee BR, Low PA. Tritshcler H. Alpha-lipoic acid antioxidant potency against lipid peroxidation of neural tissues in vitro and implications for diabetic neuropathy. Free Radical Biol Med 1996 21 631-639. 

Katsoura MH, Polydera AC, Tsironis L et al (2006) Use of ionic liquids as media for the biocatalytic preparation of flavonoid derivatives with antioxidant potency. J Biotechnol 123 491-503... 

Silkeberg, A. and Kochhar, S.P. (2000) Refining of edible oil retaining maximum antioxidative potency. US Patent number 6,033,706 and EPA no. 98102528.1-2109,13.02.98 and other worldwide patent applications pending. 

Sulfur-containing compounds such as alpha-lipoic acid, methylsulfonylmethane, glutathione, N-acetylcysteine and cysteine are effective against oxidative stress and cell damage caused by free radicals (Bray and Taylor 1993, Pollack et al. 1996). Alpha-lipoic acid increases the antioxidant potency of further antioxidants such as vitamins E and C (Kagan et al. 1992). The course of acute pancreatitis is dramatically impaired in cases of very low antioxidant status. Whereas the sulfur antagonist selenium reduced remarkably the death rate (Kulinski et al. 1995), methionine was also used successfully in the treatment of this disease (Uden et al. 1990). 

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