Aesculin

Not to be confused with aescin, a saponin also found in horse chestnut.

Aesculin
IUPAC name 7-hydroxy-6-{[(2S,3R,4S,5S,6R)-3,4,5-trihydroxy- 6-(hydroxymethyl)-2-tetrahydropyranyl]oxy}-2-chromenone
Other names Esculetin 6-β-D-glucoside
Identifiers
CAS number	531-75-9 Y
PubChem	5281417
ChemSpider	4444765 Y
UNII	1Y1L18LQAF Y
ChEMBL	CHEMBL482581 Y
Jmol-3D images	Image 1
SMILES O=C/3Oc2c(cc(O[C@@H]1O[C@@H]([C@@H](O)[C@H](O)[C@H]1O)CO)c(O)c2)\C=C\3
InChI InChI=1S/C15H16O9/c16-5-10-12(19)13(20)14(21)15(24-10)23-9-3-6-1-2-11(18)22-8(6)4-7(9)17/h1-4,10,12-17,19-21H,5H2/t10-,12-,13+,14-,15-/m1/s1 Y Key: XHCADAYNFIFUHF-TVKJYDDYSA-N Y InChI=1/C15H16O9/c16-5-10-12(19)13(20)14(21)15(24-10)23-9-3-6-1-2-11(18)22-8(6)4-7(9)17/h1-4,10,12-17,19-21H,5H2/t10-,12-,13+,14-,15-/m1/s1 Key: XHCADAYNFIFUHF-TVKJYDDYBL
Properties
Molecular formula	C15H16O9
Molar mass	340.282 g/mol
Exact mass	340.079432
Y (verify) (what is: Y/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 glucoside that naturally occurs in the horse chestnut (Aesculus hippocastanum),^[1] California Buckeye (Aesculus californica)^[2] and in daphnin (the dark green resin of Daphne mezereum).

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

1. ^ Plant poisons: Aesculin]
2. ^ C. Michael Hogan, 2008
3. ^ National Standard Methods (UK)

References

• Plant poisons: Aesculin
• National Standard Methods MSOP 48 (Bile aesculin agar) and BSOPTP 2 (Aesculin hydrolysis test (UK)).
• C. Michael Hogan (2008) California Buckeye: Aesculus californica, GlobalTwitcher.com, N. Stromberg ed.