Antioxidants solubility

The solubility of antioxidants determines their phase distribution in foods. It has been observed that compared to lipid-soluble antioxidants water-soluble antioxidants like ascorbate yield better protection to strongly lipophilic food systems like pure oils. In contrast, antioxidants soluble in lipids like the tocopherols yield better protection to oil-in-water emulsions when compared to water-soluble antioxidants (Porter, 1993). The explanation offered for this... 

Tocophersolan PEG Antioxidant, solubility Attenuation of multi drug... 

Fig. 1 demonstrates a possibility to examine water-soluble analytes. Two different forms of the same phenolic antioxidant soluble in chlorobenzene (Fig. 1, curve 1) and in water (Fig. 1, curve 2) were injected in the same amount into the same probe organic solution. As it is seen from Fig. 1, in both cases results are very similar the chemiluminescence time profiles are nearly the same. Thus, antioxidant easily diffuses from water into the organic phase of the probe solution and inhibits oxidation reaction there, which is manifested by the CL quenching. 

Awareness of healthful constituents in foods that can exert a positive influence on health, by reducing risk from cancer, heart disease, arthritis, Alzheimer s disease, and others has also increased [6]. These include antioxidants, soluble fibers, trace elements, and anti-microbials. Much of the available information is anecdotal or from the non-peer reviewed literature, and awaits scientific research to catch up with observations from advocates of various types and sources of foods. Also, dietary supplements are expanding in the market place as the source of nutraceuticals in place of natural sources in foods, stimulating questions regarding their bioavailability and relative benefits. 

Here we have to distinguish between transparent and non-transparent polyamides. In the former, the known phenolic antioxidants soluble in polyamides may be used, and perhaps compatible UV-stabilizers based on benzotriazole. For the latter, all stabilizers or stabilizer systems suitable for polyamides can be used, such as phenolic antioxidants, phosphites, and inorganic systems [502]. 

It is difficult to see how an antioxidant can be effective if does not have some solubility in the polymer matrix. There have been various studies of antioxidant solubility reported. A key investigation was by Billingham et al. [ 15 ] who determined the solubility of five phenolic antioxidants in different aliphatic compounds, polyethylene and polypropylene as shown in Table 4.1. The levels of solubility reported were quite low, often being in the range of 0.1 to 0.4 wt% in these polymers. This is associated with their higher level of polarity compared to that of the polymers they are intended to protect. 

The equilibrium solubility of an additive in a polymer is the most important single physical property of the system since it determines how much additive can exist in the polymer as a homogeneous solution. Since polymers are normally processed some two hundred degrees above their service temperatures, a polymer-additive solution, which may be homogeneous at the elevated temperatures, may pass through the equilibrium solubility on cooling and the solid polymer becomes supersaturated with the additive which in turn may precipitate as a separate phase and exudes to the polymer surface (this is called blooming ). It is observed here that solubility characteristics of transformation products (see Section 19.3.3.l.iv) are also important in consideration of antioxidant solubility. 

The behaviour of an antioxidant in a closed system (in an oxygen absorption test) is dominated by different physical characteristics. Table 4 demonstrates a general relationship between antioxidant effectiveness and solubility in a hydrocarbon solvent suggesting that antioxidant solubility in the polymer can be critical in certain applications. In the case of low molecular weight antioxidants with low solubility and high mobility, the excess blooms to the surface where it is ineffective as a stabilizer and is aesthetically objectionable. The solubility of a series of antioxidants which contain the same... 

There are, indeed, many biological implications that have been triggered by the advent of fullerenes. They range from potential inhibition of HIV-1 protease, synthesis of dmgs for photodynamic therapy and free radical scavenging (antioxidants), to participation in photo-induced DNA scission processes [156, 157, 158, 159, 160, 161, 162 and 163]. These examples unequivocally demonstrate the particular importance of water-soluble fullerenes and are summarized in a few excellent reviews [141, 1751. 

More recendy, molecular molybdenum-sulfur complexes and clusters have been used as soluble precursors for M0S2 in the formulation of lubricating oils for a variety of appHcations (70). Presumably, the oil-soluble molybdenum—sulfur-containing precursors decompose under shear, pressure, or temperature stress at the wear surface to give beneficial coatings. In several cases it has been shown that the soluble precursors are trifunctional in that they not only display antifriction properties, but have antiwear and antioxidant characteristics as weU. In most cases, the ligands for the Mo are of the 1,1-dithiolate type, including dithiocarbamates, dithiophosphates, and xanthates (55,71). 

Alkylated phenol derivatives are used as raw materials for the production of resins, novolaks (alcohol-soluble resins of the phenol—formaldehyde type), herbicides, insecticides, antioxidants, and other chemicals. The synthesis of 2,6-xylenol [576-26-1] h.a.s become commercially important since PPO resin, poly(2,6-dimethyl phenylene oxide), an engineering thermoplastic, was developed (114,115). The demand for (9-cresol and 2,6-xylenol (2,6-dimethylphenol) increased further in the 1980s along with the growing use of epoxy cresol novolak (ECN) in the electronics industries and poly(phenylene ether) resin in the automobile industries. The ECN is derived from o-cresol, and poly(phenylene ether) resin is derived from 2,6-xylenol. 

Solubility. Another desirable property of a degradant is its high solubihty in mbber but poor solubihty in water and solvents that come in contact with mbber. Poor solubihty in the mbber means that only small quantities of antioxidants can be dissolved without producing a bloom. As an example, N,lSf-diphenyl- phenylenediamine (DPPD) has limited use because of its poor solubihty in mbber. On the other hand, phenohc and phosphite antioxidants have high solubihty and bloom is not a problem. 

The total antioxidant activity of teas and tea polyphenols in aqueous phase oxidation reactions has been deterrnined using an assay based on oxidation of 2,2 -azinobis-(3-ethylbenzothiazoline-sulfonate) (ABTS) by peroxyl radicals (114—117). Black and green tea extracts (2500 ppm) were found to be 8—12 times more effective antioxidants than a 1-mAf solution of the water-soluble form of vitamin E, Trolox. The most potent antioxidants of the tea flavonoids were found to be epicatechin gallate and epigallocatechin gallate. A 1-mAf solution of these flavanols were found respectively to be 4.9 and 4.8 times more potent than a 1-mAf solution of Trolox in scavenging an ABT radical cation. 

Ascorbic acid also forms soluble chelate complexes with iron (142—145). It seems ascorbic acid has no effect on high iron levels found in people with iron overload (146). It is well known, in fact, that ascorbic acid in the presence of iron can exhibit either prooxidant or antioxidant effects, depending on the concentration used (147). The combination of citric acid and ascorbic acid may enhance the iron load in aging populations. Iron overload may be the most important common etiologic factor in the development of heart disease, cancer, diabetes, osteoporosis, arthritis, and possibly other disorders. The synergistic combination of citric acid and ascorbic acid needs further study, particularly because the iron overload produced may be correctable (147). 

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... 

Butadiene reacts readily with oxygen to form polymeric peroxides, which are not very soluble in Hquid butadiene and tend to setde at the bottom of the container because of their higher density. The peroxides are shock sensitive therefore it is imperative to exclude any source of oxygen from butadiene. Addition of antioxidants like /-butylcatechol (TBC) or butylated hydroxy toluene (BHT) removes free radicals that can cause rapid exothermic polymerizations. Butadiene shipments now routinely contain about 100 ppm TBC. Before use, the inhibitor can easily be removed (247,248). Inert gas, such as nitrogen, can also be used to blanket contained butadiene (249). 

Catalyst residues, particularly vanadium and aluminum, have to be removed as soluble salts in a water-washing and decanting operation. Vanadium residues in the finished product are kept to a few ppm. If oil-extended EPDM is the product, a metered flow of oil is added at this point. In addition, antioxidant, typically of the hindered phenol type, is added at this point. 

Material dried Antioxidant Water-soluble polymer Antibiotic filter cake Petroleum coke... 

For hot melt adhesives there are other considerations as well in choosing an antioxidant. Primary among these are volatility and solubility. Low molecular weight antioxidants (MW <400) should be avoided, for example BHT, as these... 

Other metal salts of naphthenic acids have many varied uses. For example, calcium naphthenate is a lubricating oil additive, and zinc naphthenate is an antioxidant. Lead, zinc, and barium naphthenates are wetting agents used as dispersion agents for paints. Some oil soluble metal naphthenates, such as those of zinc, cobalt, and lead, are used as... 

Erythorbic acid and sodium erythorbate are very safe products, widely used in the food industry as antioxidants and alternatives to vitamin C. In the water treatment industry, they are strong reducing agents that reduce metal oxides and hydroxides to their more soluble ferrous forms and promote the passivation of boiler waterside surfaces (magnetite formation). 

Gliszczyhska-Swigl, A. (2006). Antioxidant activity of water soluble vitamins in the TEAC (trolox equivalent antioxidant capacity) and the FRAP (ferric reducing antioxidant power) assays. Food Chemistry, Vol.96, No.l, (May 2006), pp. 131-136, ISSN 0308-8146. 

No unequivocal unique function for vitamin E has been defined. However, it does act as a hpid-soluble antioxidant in cell membranes, where many of its functions can be provided by synthetic antioxidants. Vitamin E is the generic descriptor for two famihes of compounds, the tocopherols and the tocotrienols (Figure 45—5). The different vitamers (compounds having similar vitamin activity) have different biologic potencies the most active is D-a-tocopherol, and it is usual to express vitamin E intake in milhgrams of D-a-tocoph-erol equivalents. Synthetic DL-a-tocopherol does not have the same biologic potency as the namrally occurring compound. 

Vitamin E is the Major Lipid-Soluble Antioxidant in Cell Membranes Plasma Lipoproteins... 

Besides other functions, vitamin Bj2 and fohc acid take part in providing one-carbon residues for DNA synthesis, deficiency resulting in megaloblastic anemia. Vitamin C is a water-soluble antioxidant that maintains vitamin E and many metal cofactors in the reduced state. 

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