Antioxidative activity definition

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 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. 

Most of the studies on the antioxidant activity of SF have been performed using y-oryzanol or the addition of rice bran oil (containing also other components with antioxidant activity), and from those studies it is not possible to evaluate the activities of single compounds. Further, the information obtained on the relative antioxidant activities of the different FSs varies from one study to another (Table 10.2). One reason for this may be that the range of antioxidant tests used in these studies is wide and the results, therefore, are not necessarily comparable. More studies are definitely needed to fully understand the possible differences in the antioxidant activity of different SFs in different oxidation systems. 

All aerobic organisms possess an antioxidant defense system to protect against ROS-mediated injury. A broad definition of an antioxidant is any substance that, when present at low concentrations compared to those of an oxidizable substrate, significantly delays or prevents oxidation of that substrate [37-38]. Oxidizable substrates include DNA, lipids, proteins, and carbohydrates. This definition emphasizes the importance of the damaged target studied and the source of ROS used when the in vitro antioxidant activity of a compound is studied [37]. The human antioxidant defense system consists of an enzymatic and a non-enzymatic system. 

As indicated in Table XIII, human exposure to soybean isoflavones, measured in DES equivalents, is considerably more likely than exposure to coumestrol in soybeans. Several fold Increases in Isoflavone content during germination is a definite possibility. The Importance of soybean estrogens, particularly in germinated soybeans, in the etiology of deleterious reactions in humans needs more study. Soybean isoflavones and phenolic acids probably account for the antioxidant activity of soybeans, defatted soy flour, protein concentrates, and Isolates (89). 

Telysheva, G., Dizhbite, T., Tirzite D., Juijane V. Applicability of a free radical (DPPH-) method for estimation of antioxidant activity of lignin and its derivatives. 5th International lignin institute, Forum, Commercial outlets for new lignins and definitions of new projects, Bordeaux, France, Proceedings, pp. 153-160. (2000)... 

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... 

Native Ap is unstructured and its function is still uncertain. Several possible roles have been suggested, including cholesterol transport, antioxidative protection and TGF-P activity (5-7). Similarly, a definite function for APP is still unidentified. APP is a putative Notch-like receptor for an unknown ligand (8) and has been suggested to play a role in intercellular adhesion (9). 

Promoters appear to have a relatively high tissue specificity. Thus, phenobarbital functions as a promoter for rodent liver neoplasia but not urinary bladder neoplasia. Saccharin, on the other hand, promotes urinary bladder neoplasia but not liver neoplasia in the rat. Similarly, 12-o-tetradecano-ylphorbol-13-acetate (phorbol ester) is a potent skin and forestomach neoplasm promoter in the laboratory rodent but has no appreciable activity in the liver. Other agents, such as the antioxidants 3-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-met-hoxyphenol, may act as promoters in one organ and antipromoters in another and have no effect in a third organ. Thus, the practical definition of a promoter must include the designation of the susceptible tissue. 

The occurrence of mitochondrial damage and oxidative stress has been repeatedly found in the chnical setting and in e q)erimental models of Parkinson s disease [52]. Treatment of Parkinson s disease patients with vitamin E has not provided definite positive results however, a combination of antioxidants [46, 53], including vitamins such as niacin and riboflavin, is strongly recommended [46,54]. Treatment of patients with Alzheimer s disease with vitamin E (2000 mg day ) has been reported to improve the patients event-free-sur-vival (cognitive activity) [55]. It has also been claimed that an increased intake of vitamin E lowers the risk of Alzheimer s disease [56,57]. 

The lifetime of reactive oxygen species (ROS) is extremely short, and if a physiological acceptor does not immediately neutralize them, ROS can damage biological systems. All aerobic organisms have developed more or less complex systems to neutralize them before their potentially harmful effect is activated. Nutritional elements are also extremely important. Foods that have potential or definite antioxidant capacities are mainly vegetables and fruits, as well as beverages like red wine, tea and beer. 

A native of the American Southwest, and a traditional medicine of Native Americans, a tea made from the leaves and twigs contains the lignan named nordihydoiguaiaretic acid (NDGA). Considered the active ingredient, it has powerful antioxidant properties. The leaf extract of a South American subspecies was in fact found to inhibit cancer growth. In any event, there are reports of liver damage from its use. Definitive human clinical trials await. 

Definition of the total phenol type antioxidant content and activity of compounds with respect to oxygen and its radicals in various alcohol drinks by two electrochemical methods. 

The activity of antioxidants reverses under certain conditions they become prooxidants. One way in which a-tocopherol can become perox-idatively active is shown in Formula 3.81. Another way is through the formation of the chro-manoxyl radical in concentrations high enough to overcome the inertness mentioned in 3.7.3.1 and abstract H-atoms from unsaturated acyl lipids to a definite extent, starting lipid peroxidation. This activity reversion, which is also undesirable from a nutritional and physiological point of... 

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