Oxides gallates

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). 

Chemical Antioxidant Systems. The antioxidant activity of tea extracts and tea polyphenols have been determined using in vitro model systems which are based on hydroxyl-, peroxyl-, superoxide-, hydrogen peroxide-, and oxygen-induced oxidation reactions (109—113). The effectiveness of purified tea polyphenols and cmde tea extracts as antioxidants against the autoxidation of fats has been studied using the standard Rancimat system, an assay based on air oxidation of fats or oils. A direct correlation between the antioxidant index of a tea extract and the concentration of epigallocatechin gallate in the extract was found (107). 

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. 

Propyl gallate is an antioxidant. It protects against oxidation by hydrogen peroxide and oxygen free radicals in a catalytic manner similar to superoxide dismutase. 

Propyl gallate is used to protect oils and fats in products from oxidation. It is used in foods, cosmetics, hair products, adhesives, and lubricants. 

Antioxidants are not important only to the health conscious food manufacturers also rely on these chemicals to maintain the shelf life of their products. Synthetic antioxidants such as butylated hydroxyanisole, butylated hydroxytoluene, propyl gallate and tert-butyl hydroquinone were widely used in food processing to control oxidation and maintain food quality. However, as these synthetic antioxidants are suspected to be carcinogenic they now have restricted use in food (Madahavi and Salunkhe, 1995). Therefore, natural antioxidant sources, especially of plant origin, are of great interest to the food industry. 

The catechins are soluble in water, colorless, and possess an astringent taste. They are easily oxidized and form complexes with many other substances including the methylxanthines.44 Epigallocatechin gallate is the... 

Bisflavanols are the compounds formed by the coupling of the quino-nes produced by the oxidation of epigallocatechin and epigallocatechin gallate.50 The three predicted bisflavanols have been found and characterized in black tea. They are illustrated in Figure 5. They occur only in very small quantities in black tea, presumably because of high reactivity. Re-... 

The combination of caffeine with the oxidation products of gallated flavanols produces the characteristic described as tangy astringency , probably equivalent to the term briskness applied by professional tea-... 

Tobi SE, Gilbert M, Paul N and McMillan TJ. 2002. The green tea polyphenol, epigallocatechin-3-gallate, protects against the oxidative cellular and genotoxic damage of UVA radiation. Int J Cancer 102(5) 439-444. 

Lin, Y.L. and Lin, J.K., (-)-Epigallocatechin-3-gallate blocks the induction of nitric oxide synthase by down-regulating lipopolysaccharide-induced activity of transcription factor nuclear factor-kappaB, Mol Pharmacol, 52, 465, 1997. 

Katiyar, S.K. and Mukhtar, H., Green tea polyphenol (-)-epigallocatechin-3-gallate treatment to mouse skin prevents UVB-induced infiltration of leukocytes, depletion of antigen-presenting cells, and oxidative stress, J Leukoc Biol, 69, 719, 2001. 

Lorenz, M., Wessler, S., Follmann, E., Michaelis, W., Dusterhoft, T., Baumann, G., Stangl, K, and Stangl, V., A constituent of green tea, epigallocatechin-3-gallate, activates rndothelial nitric oxide synthase by a phosphatidylinositol-3-OH-kinase-, cAMP-dependent protein kinase-, and Akt-dependent pathway and leads to endothelial-dependent vasorelaxation, J. Biol Chem., 279, 6190, 2004. 

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