Antioxidant activity, contributions

Divalent Sulfur Derivatives. A diaLkyl ester of thiodipropionic acid (16) is capable of decomposing at least 20 moles of hydroperoxide (17). Some of the reactions contributing to the antioxidant activity of these compounds are shown in Figure 3. 

An interesting development is the combination of HPLC and on-line measurement of reducing capacity or antioxidative activity. This approach allows both direct identification of antioxidative species in complex foods and quantification of the contribution to the overall antioxidative capacity in the absence of synergistic and antagonistic effects. Major advantages are less sample handling and the ability to rim large series of samples in an automated process. 

Chirinos, R. et al., High-performance liquid chromatography with photodiode array detection (HPLC-DAD)/HPLC-mass spectrometry (MS) profiling of anthocyanins from Andean mashua tubers (Tropaeolum tuberosum Ruiz and Pavon) and their contribution to the overall antioxidant activity, J. Agric. Food Chem., 54, 7089, 2006. 

Wayner, D.D., Burton, G.W., Ingold, K.U., Barclay, L.R.C. and Locke, S.J. (1987). Antioxidants in human blood plasma. The relative contributions of vitamin E, urate, ascorbate and protein to the total radical trapping antioxidant activity. Biochim. Biophys. Acta 925, 408-413. 

Evidence that caffeine contributes antioxidative activity has been shown by the detection of the oxidized caffeine product, 8-oxocaffeine (1,3,7-trimethyluric acid) in roasted, ground and instant coffees, in the range 4 to 35 ppm.160... 

Miller NJ and Rice-Evans CA. 1997. The relative contributions of ascorbic acid and phenolic antioxidants to tiie total antioxidant activity of orange and apple fruit juices and blackcurrant drinks. Food Chem... 

Amao MB, Cano A and Acosta, M. 2001a. The hydrophilic and lipophilic contribution to total antioxidant activity. Food Chem 73(2) 239—244. 

Some steroid molecules (estrone, estradiol, and estriol) have phenolic hydroxyl in the ring A (Figure 29.12) and therefore, are able to react as free radical scavengers. In 1987, Japanese authors [264,265] showed that all these compounds inhibited iron adriamycin- or iron ADP-ascorbate-dependent phospholipid and liposomal lipid peroxidation. Later on, most attention was drawn to the study of antioxidative properties of estradiol-17(3 (estrogen E2) it has been proposed that E2 antioxidant activity may contribute to cardioprotection observed after estrogen therapy in postmenopausal women. The necessity for the phenolic hydroxyl has been shown by studying the effects of several estrogens on LDL oxidation. It was found [266]... 

Reddivari, L., Hale, A. L., Miller, J. C. Jr. (2007a). Determination of phenolic content, composition and their contribution to antioxidant activity in specialty potato selections. Am. J. Potato Res., 84, 275-282. 

Many studies have related the antioxidant activity with liver protection against free radicals [245-247], although other mechanisms also contribute to the hepatoprotective action of EOs and their components [248]. 

The electronic property of the amino acid on the C-terminus also has an effect on antioxidant activity (Li et al., 2011), that is, the larger the electronic property, the higher is the activity. The C-terminus is a polar position that is thus affected by its electrostatic potential, to some extent therefore, the amino acids Trp, Glu, Leu, lie, Met, Val, Tyr, etc. are suitable at the C-terminus. Some researchers have speculated that the identity of the amino acid on the C-terminus would play an important role in its activity. Suetsuna (2000) separated and identified a radical scavenging peptide, Tyr-Phe-Tyr-Pro-Glu-Leu, from casein hydrolysate, and it was confirmed that the Glu-Leu on the C-terminus mainly contributed to its antioxidant activity. Kim et al. (2009) speculated that the hydrophobic property of the amino acid on the C-terminus, for example, Val and Leu, had a distinct effect on the activity, as determined from the analysis of antioxidative peptides derived from venison hydrolysate. 

Olive fruit has long been used as a food and as a source of edible oil for frying and salad dressings. The phenolic content in olive fruits is known to contribute to the natural bitterness and the final color of fruits (66), and to provide natural antioxidant activity in olive oil... 

The olives themselves contain many phenolic compounds with antioxidant properties. Bouaziz et al. (2005) investigated the olive cultivar Chemlali from Tunisia. Oleuropein (7.14), a bitter glycoside esterified with a phenolic acid, was the major compound present. Phenolic monomers and twelve flavonoids were also identified. The antioxidant activity of the extract was evaluated. Acid hydrolysis of the extract enhanced its antioxidant activity. / -Hydroxyphenyl-cthanol (7.12) and quercetin (1.43) showed antioxidant activities similar to that of 2,6-di-fert-butyl-4-methyl phenol (7.15), a reference compound with known antioxidant properties. It was suggested that a hydroxyl group at the ortho-position on the flavonoid B ring could contribute to the antioxidant activity of the flavonoids. 

Wayner DD, Burton GW, Ingold KU Barclay LR Locke SJ. 1987. The relative contributions to the total peroxyl radical-trapping antioxidant activity of human blood plasma. Biochim Biophys Acta 924 408-419. 

---