gallic acid


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gallic acid

or

3,4,5-trihydroxybenzoic acid

(trī'hīdrŏk`sēbĕnzō`ĭk), C6H2(OH)3CO2H, colorless crystalline organic acid found in gallnuts, sumach, tea leaves, oak bark, and many other plants, both in its free state and as part of the tannin molecule (see tannintannin,
 tannic acid,
or gallotannic acid,
astringent vegetable product found in a wide variety of plants. Sources include the bark of oak, hemlock, chestnut, and mangrove; the leaves of certain sumacs; and plant galls.
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). Since gallic acid has hydroxyl groups and a carboxylic acid group in the same molecule, two molecules of it can react with one another to form an ester, digallic acid. Gallic acid is obtained by the hydrolysis of tannic acid with sulfuric acid. When heated above 220°C;, gallic acid loses carbon dioxide to form pyrogallol, or 1,2,3-trihydroxybenzene, C6H3(OH)3, which is used in the production of azo dyes and photographic developers and in laboratories for absorbing oxygen.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Gallic Acid

 

(also called 3,4,5-trihydroxybenzoic acid), an organic compound; forms a crystal hydrate with the first molecule of water (C7H6O5- H2O). Colorless crystals that darken on exposure to light. Readily soluble in boiling water and in alcohol but less soluble in ether and only slightly soluble in cold water. Dissociation constant K = 3.9 × 10-5 (25° C). When heated to 100°-120° C, gallic acid loses water; the melting point of the anhydrous acid is 240° C (with decomposition). With ferric chloride it gives a bluish black color.

Free gallic acid is present in tea, tanbark, and tannin extracts;

it is produced by the hydrolysis of tannin. Gallic acid is used in chemical analysis, in the synthesis of dyes (anthragallol and others), in microscopy, and as a depolarizer in electrochemical analysis. Dry distillation of gallic acid yields pyrogallol.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

gallic acid

[′gal·ik ′as·əd]
(organic chemistry)
C7H6O5 A crystalline compound that forms needles from solutions of absolute methanol or chloroform, dissolves in water, alcohol, ether, and glycerol; obtained from nutgall tannins or from Penicillium notatum fermentation; used to make antioxidants and ink dyes and in photography.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Dynamic changes in amino acids, catechins, caffeine and gallic acid in green tea during withering.
Total phenol contents (TPC) are reported in mg/g of DW as gallic acid equivalents by reference to standard curve (y = 2.327, [r.sup.2] = 0.9849) and total flavonoid contents (TFC) as rutin equivalent in mg/g by reference to standard curve (y = 8.250x, [r.sup.2] = 0.998).
Nalini, "Chemopreventive efficacy of gallic acid, an antioxidant and anticarcinogenic polyphenol, against 1,2-dimethyl hydrazine induced rat colon carcinogenesis," Investigational New Drugs, vol.
In order to optimize the CPE of gallic acid, bergenin, quercitrin, and embelin from the herbal sample, a series of experiments including the type of surfactant, surfactant concentration, ultrasonic extracting time, ultrasonic extraction power, solid-liquid rate, ionic strength, pH of sample solution, bath temperature, and time under different conditions were studied.
The HPLC elution profile recorded at 280 nm showed 5 phenolic acids: gallic acid, epicatechin, coumaric acid, apigenin, and naringenin (Figure 1(a)) with concentrations of 1111.41 [micro]g/mL, 198.52 [micro]g/mL, 147.73 [micro]g/mL, 7.89 [micro]g/mL, and 6.13 [micro]g/mL, respectively (Table 2), while the HPLC elution profile of flavonoids (Figure 1(b); Table 2) recorded at 360 nm identified 3 compounds: rutin, quercetin, and kaempferol, with concentrations of 50.74 [micro]g/mL, 6.78 [micro]g/mL, and 14.42 [micro]g/mL.
The results of present study indicated that the interactions between thrombin and phenolic acids were weak except for gallic acids. On the other hand, in docking results, phenolic acids could only interact with residues other than activity centre due to lack of space matching.
Twelve gallotannins, monomers and oligomers of gallic acid with a hexoside moiety, were characterized in the analyzed extracts.
The groups were normal control (NC, water), radiation control (RC, water+EBR), gallic acid control (GC, 100 mg/kg b.wt of gallic acid), gallic acid pretreatment (GR, 100 mg/kg b.wt of gallic acid+EBR), DMSO control (DC, 10% DMSO), DMSO pretreatment (DR, 10% DMSO+EBR), lutein control (LC, optimized dose-250 mg/kg b.wt), and lutein pretreatment (LR, 250 mg/kg b.wt of lutein+EBR).
The negative control (DPPH + ethanol p.a.] and the positive control (DPPH + gallic acid) were made in various concentrations.
Total phenolics of quince (Cydonia oblonga Miller) leaves extracts were determined with Folin-Ciocalteu reagent according to the method of Slinkard & Singleton (1977), with some modifications by using gallic acid as standard (S.
An active ingredient in the serum, called Diglucosyl Gallic Acid (DGA), stops the spread of melanin throughout the skin.