Gentisic acid explained

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.^[1]

It is also found in the African tree Alchornea cordifolia and in wine.^[2]

Production

Gentisic acid is produced by carboxylation of hydroquinone.^[3]

C₆H₄(OH)₂ + CO₂ → C₆H₃(CO₂H)(OH)₂This conversion is an example of a Kolbe–Schmitt reaction.

Alternatively the compound can be synthesized from salicylic acid via Elbs persulfate oxidation.^{[4] [5]}

Reactions

In the presence of the enzyme gentisate 1,2-dioxygenase, gentisic acid reacts with oxygen to give maleylpyruvate:

2,5-dihydroxybenzoate + O₂

\rightleftharpoons maleylpyruvate

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,^[6] and has been shown to conveniently detect peptides incorporating the boronic acid moiety by MALDI.^[7]

Cited sources

• Book: Haynes. Haynes, William M. . 2016. . 97th . . 9781498754293.

Notes and References

1. 10.1056/NEJM197208312870903. Salicylate accumulation kinetics in man. New England Journal of Medicine. 1972-08-31. G. Levy. Tsuchiya, T. 287. 9. 430–2. 5044917 .
2. 10.3390/molecules14020827 . free . Comparison of Phenolic Acids and Flavan-3-ols During Wine Fermentation of Grapes with Different Harvest Times . 2009 . Tian . Rong-Rong . Pan . Qiu-Hong . Zhan . Ji-Cheng . Li . Jing-Ming . Wan . Si-Bao . Zhang . Qing-Hua . Huang . Wei-Dong . Molecules . 14 . 2 . 827–838 . 6253884 .
3. Hudnall, Phillip M. (2005) "Hydroquinone" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. Wiley-VCH, Weinheim. .
4. Book: Behrman, E.J.. Organic Reactions, Volume 35. 1988. John Wiley & Sons Inc.. New York. 978-0471832539. 440.
5. Schock, R. U. Jr. . Tabern, D. L. . The Persulfate Oxidation of Salicylic Acid. 2,3,5-Trihydroxybenzoic Acid. The Journal of Organic Chemistry. 1951. 16. 11. 1772–1775. 10.1021/jo50005a018.
6. Strupat K, Karas M, Hillenkamp F . 2,5-Dihidroxybenzoic acid: a new matrix for laser desorption-ionization mass spectrometry . Int. J. Mass Spectrom. Ion Process. . 72 . 111 . 89–102 . 1991 . 10.1016/0168-1176(91)85050-V . 1991IJMSI.111...89S.
7. Crumpton. J.. Zhang, W. . Santos, W. L. . Facile Analysis and Sequencing of Linear and Branched Peptide Boronic Acids by MALDI Mass Spectrometry. Analytical Chemistry. 2011. 83. 9. 3548–3554. 10.1021/ac2002565. 21449540. 3090651.