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The following 12 pages are in this category, out of 12 total. This list may not reflect recent changes (learn more).
1. Gallic acid – Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula of gallic acid is C6H23COOH and it is found both free and as part of hydrolyzable tannins. The gallic acid groups are 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, gallic acid forms intermolecular esters such as digallic and trigallic acids, and cyclic ether-esters. Gallic acid can also be used as a material in the synthesis of the psychedelic alkaloid mescaline. The name is derived from oak galls, which were used to prepare tannic acid. Despite the name, gallic acid does not contain gallium, salts and esters of gallic acid are termed gallates. Pliny the Elder describes his experiments with it and writes that it was used to produce dyes, galls from oak trees were crushed and mixed with water, producing tannic acid. Gallic acid was one of the used by Angelo Mai, among other early investigators of palimpsests, to clear the top layer of text off. Mai was the first to employ it, but did so with a heavy hand, gallic acid was first studied by the Swedish chemist Carl Wilhelm Scheele in 1786. Gallic acid is a component of some pyrotechnic whistle mixtures, 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, gallate dioxygenase is an enzyme found in Pseudomonas putida that catalyses the reaction gallate + O2 → -4-oxobut-1-ene-1,2, 4-tricarboxylate. Gallate decarboxylase is another enzyme in the degradation of gallic acid, 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. It is a carbonic anhydrase inhibitor. In basic research, gallic acid extracted from seeds has been shown to inhibit the formation of amyloid fibrils, one of the potential causes of Alzheimers disease. One study indicated that gallic acid has this effect on amyloid protein formation by modifying the properties of alpha-synuclein, gallic acid is classified as a mutagen and a teratogen. Gallic acid is found in a number of plants, such as the parasitic plant Cynomorium coccineum, the aquatic plant Myriophyllum spicatum. Gallic acid is found in various oak species, Caesalpinia mimosoides
2. Sanguisorbic acid – Sanguisorbic acid is a constituent of some ellagitannins. It is constituted by a hexahydroxydiphenic acid unit linked by an O-C bond to a gallic acid and it is found in 2, 3-O-hexahydroxydiphenoyl-4, 6-O-sanguisorboyl--glucose, an ellagitannin found in Rubus sanctus. It is also found in lambertianin A, B, C and D, sanguisorbic acid dilactone Valoneic acid Plant polyphenols, vegetable tannins revisited by Edwin Haslam, page 136
3. Syringic acid – Syringic acid is a naturally occurring O-methylated trihydroxybenzoic acid, a type of chemical compound. Syringic acid can be found in Ardisia elliptica, syringic acid can be prepared by selectively hydrolyzing eudesmic acid with 20% sulfuric acid. Syringic acid can be found in the palm and its oil. It is also present in wine and its presence in the ancient Egyptian drink shedeh could confirm it was made out of grape, as syringic acid is released by the breakdown of the compound malvidin, also found in red wine. It is also found in vinegar, syringic acid can be enzymatically polymerised. Laccase and peroxidase induced the polymerization of syringic acid to give a bearing a carboxylic acid at one end
4. Valoneic acid – Valoneic acid is a hydrolysable tannin. It is a component of some hydrolysable tannins such as mallojaponin, the difference with its isomer sanguisorbic acid is that the hydroxyl that links the hexahydroxydiphenoyl group to the galloyl group belongs to the HHDP group. Valoneic acid dilactone Valonea Sanguisorbic acid Plant polyphenols, vegetable tannins revisited, page 136 by Edwin Haslam
5. Digallic acid – Digallic acid is a polyphenolic compound found in Pistacia lentiscus. Digallic acid is present in the molecule of tannic acid. Digalloyl esters involve either -meta or -para depside bonds, tannase is an enzyme that uses digallate to produce gallic acid. This enzyme can also be used to produce acid from gallotannins
6. 1,2,3,4,6-Pentagalloyl glucose – 1,2,3,4, 6-Pentagalloylglucose is the pentagallic acid ester of glucose. It is a gallotannin and the precursor of ellagitannins, pentagalloyl glucose can precipitate proteins including human salivary α-amylase. It may also be used in radioprotection,1,2,3,4, 6-Pentagalloyl glucose can be found in Punica granatum, Elaeocarpus sylvestris, Rhus typhina, and Paeonia suffruticosa. The enzyme beta-glucogallin-tetrakisgalloylglucose O-galloyltransferase uses 1-O-galloyl-beta-D-glucose and 1,2,3, 6-tetrakis-O-galloyl-beta-D-glucose to produce D-glucose, tellimagrandin II is formed from pentagalloyl glucose by oxidative dehydrogenation and coupling of 2 galloyl groups. Pentagalloyl glucose can undergo oxidation reactions which are depending on the pH