Chemistry:Homogentisic acid

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Homogentisic acid
Homogentisic acid.svg
Homogentisic Acid 3D balls.png
Preferred IUPAC name
(2,5-Dihydroxyphenyl)acetic acid
Other names
Melanic acid
3D model (JSmol)
MeSH Homogentisic+acid
Molar mass 168.148 g·mol−1
Melting point 150 to 152 °C (302 to 306 °F; 423 to 425 K)
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

Homogentisic acid (2,5-dihydroxyphenylacetic acid) is a phenolic acid usually found in Arbutus unedo (strawberry-tree) honey.[1] It is also present in the bacterial plant pathogen Xanthomonas campestris pv. phaseoli[2] as well as in the yeast Yarrowia lipolytica[3] where it is associated with the production of brown pigments. It is oxidatively dimerised to form hipposudoric acid, one of the main constituents of the 'blood sweat' of hippopotamuses.

It is less commonly known as melanic acid, the name chosen by William Prout.

Human pathology

Accumulation of excess homogentisic acid and its oxide, named alkapton, is a result of the failure of the enzyme homogentisic acid 1,2-dioxygenase (typically due to a mutation) in the degradative pathway of tyrosine, consequently associated with alkaptonuria.[4]


It is an intermediate in the catabolism of aromatic amino acids such as phenylalanine and tyrosine.

4-Hydroxyphenylpyruvate (produced by transamination of tyrosine) is acted upon by the enzyme 4-Hydroxyphenylpyruvate dioxygenase to yield homogentisate.[5] If active and present, the enzyme homogentisate 1,2-dioxygenase further degrades homogentisic acid to yield 4-Maleylacetoacetic acid.[6]


  1. Paolo Cabras; Alberto Angioni; Carlo Tuberoso; Ignazio Floris; Fabiano Reniero; Claude Guillou; Stefano Ghelli (1999). "Homogentisic Acid: A Phenolic Acid as a Marker of Strawberry-Tree (Arbutus unedo) Honey". J. Agric. Food Chem. 47 (10): 4064–4067. doi:10.1021/jf990141o. PMID 10552766. 
  2. "Brown pigmentation of Xanthomonas campestris pv. phaseoli associated with homogentisic acid". Canadian Journal of Microbiology 40 (1): 28–34. 1994. doi:10.1139/m94-005. 
  3. Alexandra Carreira; Luísa M. Ferreira; Virgílio Loureiro (2001). "Brown Pigments Produced by Yarrowia lipolytica Result from Extracellular Accumulation of Homogentisic Acid". Appl Environ Microbiol 67 (8): 3463–3468. doi:10.1128/AEM.67.8.3463-3468.2001. PMID 11472920. 
  4. "Natural history of alkaptonuria". New England Journal of Medicine 347 (26): 2111–21. 2002. doi:10.1056/NEJMoa021736. PMID 12501223. 
  5. Lindstedt, Sven; Odelhog, Birgit; Rundgren, Marianne (1977). "Purification and Some Properties of 4-Hydroxyphenylpyruvate Dioxygenase from Pseudomonas sp. P.J. 814". Biochemistry 16 (15): 3369–3377. doi:10.1021/bi00634a013. 
  6. "The oxidation in liver of l-tyrosine to acetoacetate through p-hydroxyphenylpyruvate and homogentisic acid". The Biochemical Journal 49 (5): 686–93. October 1951. doi:10.1042/bj0490686. PMID 14886367.