Synergistic protection

Ma J, Qiu J, Hirt L, Dalkara T, Moskowitz MA. Synergistic protective effect of caspase inhibitors and bfgf against brain injury induced by transient focal ischaemia. Br J Pharmacol 2001 133 345-350. 

Conte A, Pellegrini S, Tagliazucchi D. 2003. Synergistic protection of PC 12 cells from P-amyloid toxicity by resveratrol and catechin. Brain Res Bull 62 29-38. 

Specific combinations of low- and high-molecular-mass HALS as well as the combination of two kinds of polymeric HALS have given pronounced synergistic protection to polyolefins [91], However, the combination of two low-molecular-mass HALS usually does not have more than an additive effect and some specific compounds may have a strong antagonistic effect. Some combinations of low-and high-molecular-mass HALS may also be antagonistic to one another. The performance of the combinations of two HALS stabiUzers cannot be predicted but must be determined experimentally. 

The reduction of a-tocopheroxyl radical by polyphenols is dependent on their structure. This has been critically shown for hydroxycinnamates, caflfeic, and /t-coumaric acids, the latter missing one of the -OH groups of the catecholic moiety. Although caffeic acid efficiently reduces a-tocopheroxyl radical to a-TOH, />-coumaric acid increases the rate of a-TOH consumption, and a clear synergistic protection of LDL from oxidation is observed only with caffeic acid plus a-TOH (Laranjinha et al, 1995). This effect of j9-coumaric acid was interpreted in terms of the stability of hydroxycinnamates-derived phenoxyl radicals and is supported by the higher reduction potential of /t-coumaric radical as compared with that of caffeic radical (Foley et al, 1999). Thus, conversely to caffeic acid o-semiquinone radical, j7-coumaric acid phenoxyl radical was able to oxidize a-TOH. 

Mixtures of nitrites and phosphonates also show synergistic protection effects on carbon steel corrosion (Lazarides et al., 1979). Marshall suggests (1981) that ferric aminophosphonates are deposited at anodic areas, and that the oxidation of iron is supported by the reduction of nitrite. It is more likely that nitrite shifts the potential of the metal surface to more positive values by reduction or adsorption, which facilitates the adsorption of phosphonate. After a longer time, the adsorbed phosphonate forms a solid compound of ferric aminophosphonate. 

For high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and PP combinations of phenolic antioxidants and phosphites lead to a synergistic protection of the polymer. For HDPE and LLDPE an increased amount of phosphite provided increased processing stability at constant phenol concentration. A 4 1 ratio of phosphite to phenol exhibited the best performance, while the most efficient ratio for protecting melt flow of the PP was found when a 2 1 ratio of phosphite to phenol was added [167], According to Parrondo molecular weight changes can best be reduced with phenolic antioxidants, while phosphites prevent discoloration [168]. 

Antiozonants are a very large part of the rubber antidegradant market. Many times antiozonants are used together with antioxidants in rubber compounds to achieve the best synergistic protection from oxidative degradation while the rubber product is in use. Virtually all chemical antiozonants can act, at least to some extent, as antioxidants. 

Citric acid is used in carbonated beverages to provide tartness, modify and enhance flavors, and chelate trace metals. It is often added to jams and jellies to control pH and provide tartness. It is used in cured and freeze-dried meat products to protect the amino acids (qv) and improve water retention. Bakers use it to improve the flavor of fmit fillings in baked goods. Because citric acid is a good chelator for trace metals, it is used as an antioxidant synergist in fats and oils, and as a preservative in frozen fish and shellfish (7) (see Antioxidaisits). 

BHA and BHT, which are both fat soluble, are effective ia protecting animal fat from oxidation, and are often added duting the rendering process. Propyl gallate is also effective, but it has limited fat solubiUty, and turns bluish black ia the presence of iron. It is typically used as a synergist ia combination with BHA or BHT. TBHQ is most effective against oxidation ia polyunsaturated vegetable oils (qv), and is often used ia soybean oil (19). 

Basic FGF can also stimulate murine hemopoietic progenitors in vitro. It is synergistic with hemopoietic growth factors such as GM-CSF, EPO, and Meg-CSF and has radioprotective activity in vivo, increasing the number of day-9 and day-12 CFU-S from lethaUy irradiated animals (195). Furthermore, b-FGF combiaed with GM-CSF protects against the killing of murine and human CFU-GM exposed to radiation in vitro (195). 

The synergistic effect of a hydroperoxide decomposer, eg, dilauryl thiodipropionate [123-28-4] (34), and a radical scavenger, eg, tetrakis[methylene(3,5-di-/ f2 butyl-4-hydroxyhydrocinnamate)]methane (9), ia protecting polypropylene duting an oxygen-uptake test at 140°C is shown ia Table 3. 

N— compounds used as acid inhibitors include heterocyclic bases, such as pyridine, quinoline and various amines. Carassiti describes the inhibitive action of decylamine and quinoline, as well as phenylthiourea and dibenzyl-sulphoxides for the protection of stainless steels in hydrochloric acid pickling. Hudson e/a/. refer to coal tar base fractions for inhibition in sulphuric and hydrochloric acid solutions. Good results are reported with 0-25 vol. Vo of distilled quinoline bases with addition of 0 05m sodium chloride in 4n sulphuric acid at 93°C. The sodium chloride is acting synergistically, e.g. 0-05m NaCl raises the percentage inhibition given by 0-1% quinoline in 2n H2SO4 from 43 to 79%. Similarly, potassium iodide improves the action of phenylthiourea . 

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