Gallic acid hợp chất kháng L1210
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| Names | |||
|---|---|---|---|
| Preferred IUPAC name
3,4,5-Trihydroxybenzoic acid
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| Other names
Gallic acid
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| Identifiers | |||
3D model (JSmol)
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| ChEBI | |||
| ChemSpider | |||
| ECHA InfoCard | 100.005.228 | ||
| EC Number | 205-749-9 | ||
| KEGG | |||
PubChem CID
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| RTECS number | LW7525000 | ||
| UNII | |||
| Properties | |||
| C7H6O5 | |||
| Molar mass | 170.12 g/mol | ||
| Appearance | White, yellowish-white, or pale fawn-colored crystals. | ||
| Density | 1.694 g/cm3 (anhydrous) | ||
| Melting point | 260 °C (500 °F; 533 K) | ||
| 1.19 g/100 mL, 20°C (anhydrous) 1.5 g/100 mL, 20 °C (monohydrate) | |||
| Solubility | soluble in alcohol, ether, glycerol, acetone negligible in benzene, chloroform, petroleum ether | ||
| log P | 0.70 | ||
| Acidity (pKa) | COOH: 4.5, OH: 10. | ||
| -90.0·10−6 cm3/mol | |||
| Hazards | |||
| Main hazards | Irritant | ||
| Safety data sheet | External MSDS | ||
| NFPA 704 | |||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
| 5000 mg/kg (rabbit, oral) | ||
| Related compounds | |||
Related
| phenols, carboxylic acids | ||
Related compounds
| Benzoic acid, Phenol, Pyrogallol | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Infobox references | |||
Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid, a type of phenolic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants.[1] The chemical formula of gallic acid is C6H2(OH)3COOH. It is found both free and as part of hydrolyzable tannins. The gallic acid groups are usually bonded to form dimers such as ellagic acid. Hydrolyzable tannins break down on hydrolysis to give gallic acid and glucose or ellagic acid and glucose, known as gallotannins and ellagitannins, respectively.[2]
Gallic acid forms intermolecular esters (depsides) such as digallic and trigallic acids, and cyclic ether-esters (depsidones).[3]
Gallic acid is commonly used in the pharmaceutical industry[4] as a standard for determining the phenol content of various analytes by the Folin-Ciocalteau assay; results are reported in gallic acid equivalents.[5] Gallic acid can also be used as a starting material in the synthesis of the psychedelic alkaloid mescaline.[6]
The name is derived from oak galls, which were historically used to prepare tannic acid. Despite the name, gallic acid does not contain gallium. Salts and esters of gallic acid are termed "gallates".
Contents
[hide]Historical context and uses[edit]
Gallic acid is an important component of iron gall ink, the standard European writing and drawing ink from the 12th to 19th centuries, with a history extending to the Roman empire and the Dead Sea Scrolls. Pliny the Elder (23-79 AD) describes his experiments with it and writes that it was used to produce dyes. Galls (also known as oak apples) from oak trees were crushed and mixed with water, producing tannic acid. It could then be mixed with green vitriol (ferrous sulfate) — obtained by allowing sulfate-saturated water from a spring or mine drainage to evaporate — and gum arabic from acacia trees; this combination of ingredients produced the ink.[7]
Gallic acid was one of the substances used by Angelo Mai (1782–1854), among other early investigators of palimpsests, to clear the top layer of text off and reveal hidden manuscripts underneath. Mai was the first to employ it, but did so "with a heavy hand", often rendering manuscripts too damaged for subsequent study by other researchers.[citation needed]
Gallic acid was first studied by the Swedish chemist Carl Wilhelm Scheele in 1786.[8] In 1818, French chemist and pharmacist Henri Braconnot (1780–1855) devised a simpler method of purifying gallic acid from galls;[9] gallic acid was also studied by the French chemist Théophile-Jules Pelouze (1807–1867),[10] among others.
Metabolism[edit]
Biosynthesis[edit]
Gallic acid is formed from 3-dehydroshikimate by the action of the enzyme shikimate dehydrogenase to produce 3,5-didehydroshikimate. This latter compound tautomerizes to form the redox equivalent gallic acid, where the equilibrium lies essentially entirely toward gallic acid because of the coincidentally occurring aromatization.[11][12]
Degradation[edit]
Gallate dioxygenase is an enzyme found in Pseudomonas putida that catalyses the reaction
- gallate + O2 → (1E)-4-oxobut-1-ene-1,2,4-tricarboxylate.
Gallate decarboxylase is another enzyme in the degradation of gallic acid.
Conjugation[edit]
Gallate 1-beta-glucosyltransferase is an enzyme that uses UDP-glucose and gallate, whereas its two products are UDP and 1-galloyl-beta-D-glucose.
Health effects[edit]
It is a weak carbonic anhydrase inhibitor.[13] In basic research, gallic acid extracted from grape seeds has been shown to inhibit the formation of amyloid fibrils, one of the potential causes of Alzheimer's disease and Parkinson's disease.[14][15][16] One study indicated that gallic acid has this effect on amyloid protein formation by modifying the properties of alpha-synuclein, a protein associated with the onset of neurodegenerative diseases.[16]
Natural occurrence[edit]
Gallic acid is found in a number of land plants, such as the parasitic plant Cynomorium coccineum,[17] the aquatic plant Myriophyllum spicatum, and the blue-green algaMicrocystis aeruginosa.[18] Gallic acid is also found in various oak species,[19] Caesalpinia mimosoides,[20] and in the stem bark of Boswellia dalzielii,[21] among others. Many foodstuffs contain various amounts of gallic acid, especially fruits (including strawberries, grapes, bananas),[22][23] as well as teas,[22][24] cloves,[25] and vinegars.[26][clarification needed]
Production[edit]
Gallic acid is easily freed from gallotannins by acidic or alkaline hydrolysis. When gallic acid is heated with concentrated sulfuric acid, rufigallol is produced by condensation. Oxidation with arsenic acid, permanganate, persulfate, or iodine yields ellagic acid, as does reaction of methyl gallate with iron(III) chloride.[3]
Spectral data[edit]
| UV-Vis | |
|---|---|
| Lambda-max: | 220, 271 nm (ethanol) |
| Extinction coefficient (log ε) | |
| IR | |
| Major absorption bands | ν : 3491, 3377, 1703, 1617, 1539, 1453, 1254 cm−1 (KBr) |
| NMR | |
| Proton NMR (acetone-d6): d : doublet, dd : doublet of doublets, m : multiplet, s : singlet | δ :
7.15 (2H, s, H-3 and H-7)
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| Carbon-13 NMR (acetone-d6): | δ :
167.39 (C-1),
144.94 (C-4 and C-6), 137.77 (C-5), 120.81 (C-2), 109.14 (C-3 and C-7) |
| Other NMR data | |
| MS | |
| Masses of main fragments | ESI-MS [M-H]- m/z : 169.0137 ms/ms (iontrap)@35 CE m/z product 125(100), 81(<1) |
Reference[20]
Esters[edit]
Also known as galloylated esters:
- Methyl gallate
- Ethyl gallate, a food additive with E number E313
- Propyl gallate, or propyl 3,4,5-trihydroxybenzoate, an ester formed by the condensation of gallic acid and propanol
- Octyl gallate, the ester of octanol and gallic acid
- Dodecyl gallate, or lauryl gallate, the ester of dodecanol and gallic acid
- Epicatechin gallate, a flavan-3-ol, a type of flavonoid, present in green tea
- Epigallocatechin gallate (EGCG), also known as epigallocatechin 3-gallate, the ester of epigallocatechin and gallic acid, and a type of catechin
- Gallocatechin gallate (GCG), the ester of gallocatechin and gallic acid and a type of flavan-3ol
- Theaflavin-3-gallate, a theaflavin derivative
