Gentisic acid

Gentisic acid

Skeletal formula of gentisic acid
Space-filling model of the gentisic acid molecule
Names
Preferred IUPAC name 2,5-Dihydroxybenzoic acid
Other names DHB 5-Hydroxysalicylic acid Gentianic acid Carboxyhydroquinone 2,5-Dioxybenzoic Acid Hydroquinonecarboxylic acid
Identifiers
CAS Number	490-79-9 checkY
3D model (JSmol)	Interactive image
ChEBI	CHEBI:17189 checkY
ChEMBL	ChEMBL1461 checkY
ChemSpider	3350 checkY
ECHA InfoCard
E number
KEGG	C00628 checkY
PubChem CID	3469
UNII	VP36V95O3T checkY
CompTox Dashboard (EPA)	{{#property:P3117}}
InChI InChI=1S/C7H6O4/c8-4-1-2-6(9)5(3-4)7(10)11/h1-3,8-9H,(H,10,11) checkY Key: WXTMDXOMEHJXQO-UHFFFAOYSA-N checkY InChI=1/C7H6O4/c8-4-1-2-6(9)5(3-4)7(10)11/h1-3,8-9H,(H,10,11) Key: WXTMDXOMEHJXQO-UHFFFAOYAO
SMILES O=C(O)c1cc(O)ccc1O
Properties
Chemical formula	C7H6O4
Molar mass	154.121 g·mol−1
Appearance	white to yellow powder
Melting point	204 °C (399 °F; 477 K)
Solubility in water	very soluble
Solubility in ethanol	very soluble
Solubility in diethyl ether	very soluble
Solubility in acetone	soluble
Acidity (pKa)	2.97
Related compounds
Related compounds	2,3-Dihydroxybenzoic acid 2,4-Dihydroxybenzoic acid 2,6-Dihydroxybenzoic acid 3,4-Dihydroxybenzoic acid 3,5-Dihydroxybenzoic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). checkY verify (what is checkY☒N ?) Infobox references

Gentisic acid is a dihydroxybenzoic acid. It is a derivative of benzoic acid and a minor (1%) product of the metabolic break down of aspirin, excreted by the kidneys.

It is also found in the African tree Alchornea cordifolia and in wine.

Production

Gentisic acid is produced by carboxylation of hydroquinone.

C₆H₄(OH)₂ + CO₂ → C₆H₃(CO₂H)(OH)₂

This conversion is an example of a Kolbe–Schmitt reaction.

Alternatively the compound can be synthesized from salicylic acid via Elbs persulfate oxidation.

Reactions

In the presence of the enzyme gentisate 1,2-dioxygenase and oxygen, gentisic acid undergoes a ring-opening reaction to give maleylpyruvate:

C₇H₆O₄ + O₂ ⇌ C₇H₆O₆

Applications

As a hydroquinone, gentisic acid is readily oxidised and is used as an antioxidant excipient in some pharmaceutical preparations.

In the laboratory, it is used as a sample matrix in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, and has been shown to conveniently detect peptides incorporating the boronic acid moiety by MALDI.

For detection of gentisic acid, the whole-cell biosensor has been developed by using maleylpyruvic acid-inducible gene expression system and gentisate 1,2-dioxygenase gene from chemolithoautotrophic bacterium Cupriavidus necator.