Antioxidants interaction with additives

Metal-deactivating antioxidants. Transition metal compounds decompose hydroperoxides with the formation of free radicals, thereby increasing the rate of oxidation. Such an enhanced oxidation can be slowed down by the addition of a compound that interacts with metal ions to form complexes that are inactive with respect to hydroperoxides. Diamines, hydroxy acids, and other bifunctional compounds exemplify this type of antioxidants. 

Phenol-induced oxidative stress mediated by thiol oxidation, antioxidant depletion, and enhanced free radical production plays a key role in the deleterious activities of certain phenols. In this mode of DNA damage, the phenol does not interact with DNA directly and the observed genotoxicity is caused by an indirect mechanism of action induced by ROS. A direct mode of phenol-induced genotoxicity involves covalent DNA adduction derived from electrophilic species of phenols produced by metabolic activation. Oxidative metabolism of phenols can generate quinone intermediates that react covalently with N-1,N of dG to form benzetheno-type adducts. Our laboratory has also recently shown that phenoxyl radicals can participate in direct radical addition reactions with C-8 of dG to form oxygen (O)-adducts. Because the metabolism of phenols can also generate C-adducts at C-8 of dG, a case can be made that phenoxyl radicals display ambident (O vs. C) electrophilicity in DNA adduction. 

As discussed below, the biological effects of flavonoids include the interaction with many biochemical targets in addition to their effects on the antioxidant status. However, as the cardiovascular effects of flavonoids are commonly attributed to their antioxidant effects, it seems pertinent to address herein the... 

The mechanism of melatonin s interaction with reactive species probably involves donation of an electron to form the melatoninyl cation radical or through a radical addition at the site C3. Other possibilities include hydrogen donation from the nitrogen atom or substitution at position C2, C4, and C7 and nitrosation [169]. The mechanisms by which melatonin protects against LP most likely involve direct or indirect antioxidant and free-radical scavenging activities of this indoleamine [169,171]. 2-Phenyl indole derivatives have redox properties because of the presence of an electron-rich aromatic ring system that allows the indoleamine to easily function as an electron donor. For these derivatives, the possible antioxidant mechanism might be most probably toward carbon-centered radicals described by Antosiewicz et al. [172]. 

Tomboulian et al. (2002) has reported that butylated hydroxytoluene (BHT) can impart a "burnt plastic" odor and is an additive in HDPE pipes. Quinone may be derived from BHT due to interactions with residual chlorine in pipes (Anselme et al., 1985). Yam et al. (1996) reported that antioxidants, such as vitamin E, Irganox 1010, and BHT, contributed to off-flavors in water. Vitamin E yielded less off-flavor, possibly due to lower aldehyde and ketone concentrations. Extrusion temperatures over 280 °C and exposure time for melt contributed to more oxidation of LDPE films and higher intensities of off-flavors in water in contact with LDPE with different antioxidants (Andersson et al., 2005). 

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