Antioxidants combinations

Introducing long aliphatic chains into a stabilizer molecule decreases volatility and increases solubility in hydrocarbon polymers. This improves performance. However, it also increases the equivalent weight of the active moiety. Di- and polyphenoHc antioxidants combine relatively low equivalent... 

For in vitro treatment, the antioxidant combination leads to a PF of 10.0. With (3-carotene alone as the antioxidant the PF was only 3.5, while for a-tocopherol alone it was 3.6, and for ascorbic acid alone there was no significant protection. 

Hence, for both of the oxidants, N02 and ONOO-, a marked synergism in cell protection by the antioxidant combination of P-CAR with vitamins E and C was observed for both in vivo and in vitro experiments, although the synergistic effect was more pronounced in protection from N02 . 

Bohm, F, Edge, R, Lange, L, and Truscott, TG, 1998a. Enhanced protection of human cells against ultraviolet light by antioxidant combinations involving dietary carotenoids. J Photochem Photobiol B 44, 211-215. 

The possible involvement of free radicals in the development of hypertension has been suspected for a long time. In 1988, Salonen et al. [73] demonstrated the marked elevation of blood pressure for persons with the lowest levels of plasma ascorbic acid and serum selenium concentrations. In subsequent studies these authors confirmed their first observations and showed that the supplementation with antioxidant combination of ascorbic acid, selenium, vitamin E, and carotene resulted in a significant decrease in diastonic blood pressure [74] and enhanced the resistance of atherogenic lipoproteins in human plasma to oxidative stress [75]. Kristal et al. [76] demonstrated that hypertention is accompanied by priming of PMNs although the enhancement of superoxide release was not correlated with the levels of blood pressure. Russo et al. [77] showed that essential hypertension patients are characterized by higher MDA levels and decreased SOD activities. 

Since carbon black has many stable free radicals, it may be added to polymers such as polyolefins to retard free radical by attracting and absorbing other free radicals. It is customary to add small amounts of other antioxidants to enhance the stabilization by a synergistic effect whereby many antioxidant combinations are more stable than using only one antioxidant. 

Because the potential benefits outweigh the possibilities of harm, many experts recommend a daily multivitamin that does not exceed the RDA of it component vitamins. Multivitamins ensure an adequate intake for those vitamins—folic acid, vitamin B6, vitamin B12, and vitamin D—that are most likely to be deficient. However, the the evidence is insufficient to recommend for or against the use of supplements of vitamins A, C, or E multivitamins with folic acid or antioxidant combinations for the pre vention of cancer or cardiovascular disease. Most experts recommend against the use of p-carotene supplements, either alone or in combina Don, for the prevention of cancer or cardiovascular disease. 

Another approach to achieving an effective colour suppression in polymers containing tocopherol is through the use of small concentrations of non-phosphorous-containing compounds, such as polyhydric alcohols [33]. The effect of polyhydric alcohols on colour reduction shows that increasing the concentration of alcohols (e.g. trimethylolpropane, TMP) in the antioxidant combination leads to greater reduction in colour, concomitant with... 

Table 12 Some of the most important clinical/epidemiological studies related to antioxidant combinations in food ...

Greul, A.K. et al., Photoprotection of UV-irradiated human skin an antioxidative combination of vitamins E and C, carotenoids, selenium and proanthocyanidins, Skin Pharmacol. Appl. Skin Physiol., 15, 307, 2002. 

Figure 6. Inhibition of discoloration with benzophenone-antioxidant combination—Fade-ometer exposure...

Figures 6, 7, and 8 show the stabilizing efficiency of the combinations consisting of the above absorbers and the antioxidant 2,4,6-tri-fert-butyl-phenol, on Fade-ometer exposure. The total additive concentration in each polystyrene sample was 0.25%. The data show that the rate of discoloration of the polymer was inhibited to a greater extent with the ultraviolet absorber-antioxidant combinations than with the absorber alone. Only a small amount (0.075%) of the antioxidant was required for increased effectiveness of the combination.

Figure II. Inhibition of discoloration with benzylidene-antioxidant combination...

In view of this wavelength dependence on photooxidation further studies were carried out to determine the role of antioxidants and ultraviolet absorber-antioxidant combinations in photooxidation reactions. 

Besides heat stabilizers, commercial PET is doped with an antioxidant combination of hindered phenols with aliphatic or aromatic phosphites and, in some cases, by a dehydrating agent. 

In an antioxidant combination that contains compounds exhibiting different mechanisms of action and physical properties, inhibition of oxidation occurs in... 

Antioxidants with different degrees of potency are formulated in an antioxidant combination/mixture. 

Antioxidants Combined application of the antioxidants zinc, selenium and tocopherol yielded better treatment results and a reduced mortality rate in alcoholic hepatitis. (75, 139) Alcohol-induced liver diseases are considered to be diseases associated with free radicals oxidative stress is thought to be a contributory factor of disease. (51, 145)... 

McCarthy TJ, Zeelie JJ, Krause DJ. The antimicrobial action of zinc ion/antioxidant combinations. J Clin Pharm Ther 1992 17 51-54. 

It has been known that various antioxidants reduce VSCs in raw meats. Nam et al. 40) showed that addition of antioxidants such as tocopherols, gallic acid and sesamol reduced the production of some VSCs in raw pork homogenates and patties. Addition of ascobic acid at 0.1% (wt/wt) or sesamol + a-tocopherol each at 0.01% level to ground beef before irradiation effectively reduced lipid oxidation and VSCs 41). Patterson and Stevenson (25) found that dietary supplementation of a-tocopherol and ascorbic acid to hens reduced the yield of total volatiles. Dietary vitamin E added to turkey diets reduced production of MT, DMS, CS2 DMDS and some hydrocarbons and aldehydes of raw turkey meat 42). However, Lee et al. 43) found antioxidant combinations (sesamol+a-tocopherol and gallate+a-tocopherol) had very little effect on the development of off-odor and the formation of VSCs due to irradiation in raw turkey meat. 

Table 4.7 Oxidation stability of a lubricant stabilised with a synergistic antioxidant combination Test fluid...

Burton, G.W., Joyce, A., and Ingold, K.U., Is vitaminE the only hpid soluble, chain breaking, antioxidant combination in human blood plasma and erythrocyte membranes Arch. Biochem. Biophys., 221, 281-290,1983. 

Metal deactivators are used in situations where plastics come into contact with metals such as polyethylene cable covers. These antioxidants combine with metal ions to form a stable complex at the interface, thereby preventing metals from accelerating degradation of the polymer. 

Ascorbic acid is known to form powerful synergistic antioxidant combinations with tocopherols. Reduction of a transitory tocopherol semiquinone radical by ascorbate is likely reaction. The reduction of a phenolic antioxidant semiquinone by ascorbic acid is chosen by Uri (1961) as an excellent... 

Some secondary antioxidants combine sulfur and phosphorus in the same molecule, for example trilamyl trithiophosphite. 

The antioxidant systems for polyolefin hot water pipe traditionally rely on hindered phenol antioxidants combined with phosphites or phosphonates and sulfur based co-stabilisers. The last-mentioned substances can taint the water so, for potable water systems, HALS stabilisers have replaced the sulfur compoimds. 

Several companies now offer combinations of phenolic antioxidant with a phosphite in the same product. Cytec Industries markets a phenolic antioxidant combined with a hydrolysis-resistant phosphite, called Cyanox XS4. The components are both high molecular weight substances, so as to increase permanence and thermal stability. Cyanox XS4 was first targeted at polyolefins, where it was claimed to widen the processing window and reduce costs by allowing less stabiliser to be used, while still achieving minimal discoloration and melt flow. 

Antioxidant combinations containing a grafted (g) photoantioxidant Concentration in PP film (%) EMT (h) ... 

The methods by which antioxidants function were outlined in Section 9.2. Subsequent sections however amply demonstrated that the behaviour of an antioxidant in an accelerated-sulphur cured diene rubber vulcanizate can be very different from its behaviour in a simple hydrocarbon like petrol or polyethylene or even a peroxide-cured natural rubber. Antioxidant combinations which in some circumstances behave synergistically may in other cases be antagonistic to each other. As was demonstrated in Fig. 9.1 an increase in the antioxidant loading may decrease the degree of pro-... 

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