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Esculin

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Esculin

Not to be confused with aescin, a saponin also found in horse chestnut.
Aesculin
Identifiers
CAS number 531-75-9 YesY
PubChem 5281417
ChemSpider 4444765 YesY
UNII 1Y1L18LQAF YesY
Jmol-3D images Image 1
Properties
Molecular formula C15H16O9
Molar mass 340.282 g/mol
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Aesculin, also rendered Æsculin or Esculin, is a coumarin glucoside that naturally occurs in the horse chestnut (Aesculus hippocastanum),[1] California Buckeye (Aesculus californica),[2] Prickly Box (Bursaria spinosa) and in daphnin (the dark green resin of Daphne mezereum). It is also found in dandelion coffee.

Medical uses

Aesculin is 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).[3] Hydrolysis of the aesculin forms aesculetin (6,7-dihydroxycoumarin) and glucose. The 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 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): hydrolysis of aesculin results in loss of this fluorescence.

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


Line notes

References

  • National Standard Methods MSOP 48 (Bile aesculin agar) and BSOPTP 2 (Aesculin hydrolysis test (UK)).
  • , GlobalTwitcher.com, N. Stromberg ed.
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