Gallates

FLUORINECOMPOUNDS,ORGANIC - FLUORINATED ALIPHATIC COMPOUNDS] (Vol 11) n-Propyl gallate [129-79-9]... 

Antioxidants (qv) have a positive effect on oils when present in the proper concentration. Sterols and tocopherols, which are natural antioxidants, may be analy2ed by gas-Hquid chromatography (glc), high performance Hquid chromatography (hplc), or thin-layer chromatography (tic). Synthetic antioxidants maybe added by processors to improve the performance or shelf life of products. These compounds include butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), / fZ-butyUiydroquinone (TBHQ), and propyl gallate. These materials may likewise be analy2ed by glc, hplc, or tic. Citric acid (qv), which functions as a metal chelator, may also be deterrnined by glc. 

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). 

Electrolysis. GalHum can be extracted by direct electrolysis of the aluminate solution at a strongly agitated mercury cathode. The recovery from a sodium gallate solution resulting from the carbonation process is another possibiHty. This process is probably no longer operative because of the environmental problems associated with the mercury. 

Purification. Extraction from aluminum or 2inc ores produces cmde galHum metal or concentrates. These concentrates are transformed to sodium gallate, galHum chloride, or galHum sulfate solutions which are purified, then electroly2ed. GalHum is deposited as a Hquid. 

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. 

Niai) Dimethylbis(pyrazol-l-yl)gallate [GaMe2(Pz)2] Ni[GaMe2(Pz)2]2 75JCS(D)176 ... 

Niai) Dimethylbis(3,5 -dimethylpyrazol-1 -yl)gallate [GaMe2(DMPz)2] Complicated structure 80CJC1091 s... 

Cu(H) Dimethylbis(3-methylpyrazol-l -yl)gallate [GaMe2(MPz)2] CuO[GaMe2(MPz)2](3MPz) 2 76CJC343 G... 

The amphoteric behaviour of Ga" salts parallels that of Al indeed, Gai03 is slightly more acidic than AI2O3 and solutions of gallates tend to be more stable than aluminales. Consistent with this, pKa for the equilibrium... 

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