Aesculin

Aesculin, also called æsculin or esculin, is a coumarin glucoside that naturally occurs in the trees horse chestnut (Aesculus hippocastanum),[1] California buckeye (Aesculus californica),[2] prickly box (Bursaria spinosa), and daphnin (the dark green resin of Daphne mezereum). It is also found in dandelion coffee.

Not to be confused with aescin, a saponin also found in horse chestnut.
Aesculin
Names
IUPAC name
7-hydroxy-6-{[(2S,3R,4S,5S,6R)-3,4,5-trihydroxy- 6-(hydroxymethyl)-2-tetrahydropyranyl]oxy}-2-chromenone
Other names
  • Æsculin
  • Esculin
  • Esculetin 6-β-D-glucoside
  • 6,7-Dihydroxycoumarin 6-β-D-glucoside
  • 6,7-Dihydroxychromen-2-one 6-β-D-glucoside
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.007.744
UNII
Properties
C15H16O9
Molar mass 340.282 g/mol
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

Medical uses

As medication, aesculin is sometimes used as a vasoprotective agent.[3]

Aesculin is also used in a microbiology laboratory to aid in the identification of bacterial species (especially Enterococci and Listeria). In fact, all strains of Group D Streptococci hydrolyze æsculin in 40% bile.

Aesculin hydrolysis test

Aesculin is incorporated into agar with ferric citrate and bile salts (bile aesculin agar).[4] Hydrolysis of aesculin forms aesculetin (6,7-dihydroxycoumarin) and glucose. Aesculetin forms dark brown or black complexes with ferric citrate, allowing the test to be read.

The bile aesculin agar is streaked and incubated at 37 °C (99 °F) for 24 hours. The presence of a dark brown or black halo indicates that the test is positive. A positive test can occur with Enterococcus, Aerococcus, and Leuconostoc. Aesculin will fluoresce under long wave ultraviolet light (360 nm) and hydrolysis of aesculin results in loss of this fluorescence.

Enterococcus will often flag positive within four hours of the agar being inoculated.

UV visible spectrum of aesculin with a maximum of absorbance at 346 nm

Warnings

Aesculin ingestion can produce stomachache, spasms, diarrhea, disorientation and even death at high doses.

References
  1. "Plant poisons: Aesculin". University of Bristol. Retrieved July 17, 2018.
  2. C. Michael Hogan (2008) California Buckeye: Aesculus californica, GlobalTwitcher.com, N. Stromberg ed.
  3. Esculin. Drugs.com. Retrieved 11 June 2016.
  4. National Standard Methods MSOP 48 (Bile aesculin agar) and BSOPTP 2 (Aesculin hydrolysis test (UK))
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