Antioxidant definition

Type of antioxidant Definition Most commonly used... 

Classification Polymeric antioxidant Definition 1,4-Benzenediol, 2-(1,1-dimethylethyl) polymer with diethenylbenzene, 4-(1,1-dimethylethyl) phenol, 4-methoxyphenol, 4,4 -(1-methylethylidene) bis (phenol), 4-methylphenol Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and fumes Uses Preservative, antioxidant in foods Regulatory FDA 21CFR 172.105... 

In their review some years ago, Reddy and Rao (1986) cited several lines of evidence for peroxisome-proliferation-mediated oxidative stress being associated with hepatocarcinogenesis. They mentioned the sustained increase in hydrogen peroxide production, the detectable increased levels of hydrogen peroxide in the livers of treated animals, increased lipid peroxidation associated with treatment and marked inhibition of hepatocarcinogenesis by antioxidant compounds. However, definitive studies remain to be carried out. 

Aroma value, definition, 193 Ascoibic acid, natural antioxidant, 58 Ascoibyl palmitate, natural antioxidant, 58... 

Further studies are required to unravel this mystery of how the methoxy substitutions and the a, p-unsaturated p-diketone moiety actually influence conformational changes, lipophillicity, electron density distribution, and redox properties of curcuminoids. Correlating these physicochemical properties with the unique pleiotropic effects of curcuminoids is a rewarding exercise. Such studies would definitely provide proper reasoning in understanding these markedly different antioxidant, antitumor, and anti-inflammatory activities of natural curcuminoids from turmeric. 

Given a NO/3NO- couple potential of 0.39 V, the effecter molecule of NOS would thus be expected to be ONOO, not NO. However, the direct detection of NO in living systems by a number of techniques (17,18,26) as well as the observation that activation of NOS results in antioxidant chemistry [briefly reviewed in (160-162)] suggest otherwise. The definitive mediation of vascular tone by NO (18, 31) and the discrete effects of HNO and NO donors observed in vitro, in vivo, and ex vivo corroborate the implications that NO cannot be readily reduced to NO- under physiological conditions (147). Additionally, the oxidation of methyl viologen by O2 was determined to be two orders of magnitude... 

The definition of an antioxidant suggests a functional assay of antioxidants by measuring inhibition of appropriate (easy to study) oxidation reactions. Such assays can be called inhibition assays for antioxidants (Fig. 2). Various oxidants are used in TAC assays. In many cases, thermal decomposition of 2,2 -azobis (2-amidopropane) (ABAP) is the source of oxidizing radicals. ABAP undergoes temperature-dependent homolysis. The primary radicals produced by thermal decomposition of the initiator react with oxygen to produce peroxyl and alkoxyl radicals, which are oxidizing species in the system (Fig. 3). The amount of free radicals formed in an aqueous medium by decomposition of ABAP at pH 7.4 and at 37°C equals 1.36 x 10-6 [ABAP] x t, where t is time in seconds and [ABAP] is in mol L-1 (N8). 

To better appreciate why reading the specification definitions is so important, let s consider the following example. Imagine a chemist has discovered a tris-phenolic compound (Figure 5.10) and is particularly excited about its antioxidant activity, which will be useful as a food additive due to the compound s apparent lack of toxicity. 

The only official definition of antioxidants is related to dietary antioxidants,"... 

The definition proposed by the Panel on Dietary Antioxidants and Related Compounds of the Food and Nutrition Board is that a dietary antioxidant is a substance... 

The evidence that a 24-hour fasting and tranquillity have both the ability for a strong antioxidant activity and may create some complexity in the definition of antioxidants. In many instances, subjects suffering from some diseases (hypertension, infection, inflammation) or under particular conditions such as menopause may also have OS, which can be considered as an epiphenomenon of that given condition. Once the disease (or the symptom and/or the condition) is controlled by a therapy, the OS may disappear. This means that a product can be considered as an antioxidant indirectly." These aspects may further complicate the definition of an antioxidant. 

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