Prooxidants applications

Tocopherols are considered as natural antioxidants for lipid-containing foods and marketed as all natural. They are permitted in food application according to GMP regulations (21CFR 182.3890). Natural tocopherols are limited to 0.03% (300 ppm) in animal fats (9 CFR 318.7). As most vegetable oils naturally contain tocopherols, the addition of this antioxidant may pose prooxidant effects. 

In principle, ascorbic acid and its salts (sodinm or calcinm ascorbate) are water solnble antioxidants, not widely applicable for lipid systems but extensively nsed in beverages. In aqneons systems containing metals, ascorbic acid may also act as a prooxidant by reducing the metals that become active catalysts of oxidation in their lower valences. However, in the absence of added metals, ascorbic acid is an effective antioxidant at high concentrations. The action of ascorbic acid in lipid autoxidation is dependent on concentration, the presence of metal ions, and other antioxidants. It has been shown that ascorbates can protect plasma and LDL lipids from peroxidative damage, and it may inhibit the binding of copper ions to LDL. " In several countries, ascorbic pahnitate is used in fat containing foods due to its lipid solubility. However whether ascorbic palmitate exerts a better... 

Four main types of polymer are currently accepted as being environmentally degradable. They are the photolytic polymers, peroxidisable polymers, photo-biodegradable polymers and hydro-biodegradable polymers. Commercial products may be composite materials in which hydrolysable and peroxidisable polymers are combined (e.g. starch-polyethylene composites containing prooxidants). The application, advantages and limitations of each group will be briefly discussed. 

Transition metal prooxidants cause problems during both the manufacture and use of plastics products. Firstly they catalyse rheological changes in the polymer during processing and reduce shelf-life before use. Secondly it is difficult to control the induction time to photooxidation. It will be seen below that control of peroxidation is essential to the application of degradable plastics in agriculture. 

APPLICATION OF ELECTRON SPIN RESONANCE TO STUDY FOOD ANITOXIDATTVE AND PROOXIDATIVE ACTIVITIES... 

Ascorbic acid is known for its complex multi-functional effects, as an antioxidant, a prooxidant, and a metal chelator, reducing agent or as an oxygen scavenger. A combination of these effects may predominate in many food applications. In aqueous media, ascorbic acid is active as an antioxidant at relatively high concentrations (approximately 1 mM), but it can act as a prooxidant at lower concentrations (approximately 0.01 mM), especially in the presence of metal ions. At a given concentration, there is a crossover effect ... 

This book discusses these and other pitfalls inherent in basic studies that use artificial radical initiators with unrealistic models and homogeneous systems. The application of simple research models may lead to numerous problems in the ultimate interpretation of results, because lipid oxidation proceeds by a complex sequence of reactions influenced by many factors, all of which become extremely difficult to unravel in real food and biological systems. These systems are multi-phased and controlled by complex colloidal phenomena affecting different sites of oxidation and antioxidation. In interpreting the effects of prooxidant and antioxidant compounds their effective concentrations in different phases must be considered. A dimension of lipid oxidation that is important to better understand control methods deals with the relative partition of oxidants and antioxidants in multiphase systems. This topic has not received sufficient attention. 

In a biofortified experiment, the oxidant status (levels of lipid peroxidation and H2O2 concentrations), as well as Se and S accumulation in lettuce plants were investigated. It is found that, Se concentration was higher for selenate presence compared to selenite in the edible parts of lettuce. The application of 15 pM Se as selenite caused a decline in the biomass and an intensification of prooxidative processes in the plant s tissues and as toxic should be excluded from further biofortification experiments. These results also indicated that an application of either selenate or selenite to the nutrient solution at concentrations below 15 pM can be used for biofortification of lettuce with Se (Table 6.1 Hawrylak-Nowak 2013)... 

In addition to the use of alkyl gallates as food and cosmetic additives, the multifunctional action of these compounds and their potential application for other purposes has been widely investigated, as described below. Some of these applications, which are discussed below, involve their use as enzymatic inhibitors, as anticancer, antifungal and antimicrobial agents, and as additives in nonfood and noncosmetic industries (Figure 14.2). These applications are mainly based on the antioxidant and prooxidant properties of these compounds, which, together with their potential toxicity, are also discussed below. 

For instance, one of the most important directions in the prospective development of DNA biosensors successfully applicable in practice can be seen in the investigation of protective membranes, which prevent the biosensor surface from unwanted fouling and interferences. One such an example is shown in our paper [47] where novel electrochemical DNA-based biosensors with outer-sphere Nafion and chitosan protective membranes were prepared for the evaluation of antioxidant properties of beverages (beer, coffee, and black tea) against prooxidant hydroxyl radicals. 

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