Gentisic acid

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Gentisic acid[1]
Skeletal formula of gentisic acid
Space-filling model of the gentisic acid molecule
IUPAC name
2,5-dihydroxybenzoic acid
Other names
2,5-dihydroxybenzoic acid
5-Hydroxysalicylic acid
Gentianic acid
2,5-Dioxybenzoic Acid
Hydroquinonecarboxylic acid
3D model (JSmol)
ECHA InfoCard 100.007.017
Molar mass 154.12 g/mol
Appearance white to yellow powder
Melting point 200 to 205 °C (392 to 401 °F; 473 to 478 K) (Sublimes)
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

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.[2]

It is also found in the African tree Alchornea cordifolia and in wine.[3]


Gentisic acid is produced by carboxylation of hydroquinone.[4]

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.[5][6]


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,[7] and has been shown to conveniently detect peptides incorporating the boronic acid moiety by MALDI.[8]


  1. ^ Gentisic acid - Compound Summary, PubChem.
  2. ^ Levy, G; Tsuchiya, T (1972-09-31). "Salicylate accumulation kinetics in man". New England Journal of Medicine. 287 (9): 430–2. doi:10.1056/NEJM197208312870903. PMID 5044917. Check date values in: |date= (help)
  3. ^ Comparison of Phenolic Acids and Flavan-3-ols During Wine Fermentation of Grapes with Different Harvest Times. Rong-Rong Tian, Qiu-Hong Pan, Ji-Cheng Zhan, Jing-Ming Li, Si-Bao Wan, Qing-Hua Zhang and Wei-Dong Huang, Molecules, 2009, 14, pages 827-838, doi:10.3390/molecules14020827
  4. ^ Phillip M. Hudnall "Hydroquinone" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. 2005 Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_499.
  5. ^ Behrman, E.J. (1988). Organic Reactions, Volume 35. New York: John Wiley & Sons Inc. p. 440. ISBN 0471832537.
  6. ^ R. U. Schock Jr.; D. L. Tabern (1951). "The Persulfate Oxidation of Salicylic Acid. 2,3,5-Trihydroxybenzoic Acid". The Journal of Organic Chemistry. 16 (11): 1772–1775. doi:10.1021/jo50005a018.
  7. ^ Strupat K, Karas M, Hillenkamp F (1991). "2,5-Dihidroxybenzoic acid: a new matrix for laser desorption-ionization mass spectrometry". Int. J. Mass Spectrom. Ion Process. 72 (111): 89–102. Bibcode:1991IJMSI.111...89S. doi:10.1016/0168-1176(91)85050-V.
  8. ^ Crumpton, J.; Zhang, W.; Santos, W. L. (2011). "Facile Analysis and Sequencing of Linear and Branched Peptide Boronic Acids by MALDI Mass Spectrometry". Analytical Chemistry. 83 (9): 3548–3554. doi:10.1021/ac2002565. PMC 3090651. PMID 21449540.