Aesculin

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

Aesculin

File:Aesculin.svg
Names
IUPAC name 6-(β-D-Glucopyranosyloxy)-7-hydroxy-2H-1-benzopyran-2-one
Systematic IUPAC name 7-Hydroxy-6-{[(2S,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy}-2H-1-benzopyran-2-one
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
CAS Number	531-75-9 checkY
3D model (JSmol)	Interactive image
ChEBI	CHEBI:4853
ChEMBL	ChEMBL482581 checkY
ChemSpider	4444765 checkY
DrugBank	DB13155
ECHA InfoCard
EC Number	208-517-5
E number
KEGG	C09264
PubChem CID	5281417
UNII	1Y1L18LQAF checkY
CompTox Dashboard (EPA)	{{#property:P3117}}
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 checkY Key: XHCADAYNFIFUHF-TVKJYDDYSA-N checkY 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
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
Properties
Chemical formula	C15H16O9
Molar mass	340.284 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). checkY verify (what is checkY☒N ?) Infobox references

Aesculin, also called æsculin or esculin, is a coumarin glucoside that naturally occurs in the trees horse chestnut (Aesculus hippocastanum), California buckeye (Aesculus californica), and prickly box (Bursaria spinosa). It is also found in daphnin (the dark green resin of Daphne mezereum), dandelion coffee, and olive bark. It is reported to be present in olive bark, but not in olive leaf; therefore, identification of aesculin in abundance in an olive extract indicates that the extract has been derived from olive bark.

Uses

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 aesculin in 40% bile.

Aesculin hydrolysis test

Aesculin is incorporated into agar with ferric citrate and bile salts (bile aesculin agar). 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.

File:Esculine UV vis spectrum.png

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

File:Esculin-chestnut-bark-fluorescence.jpg

Fluorescence of esculin, disolving in water from chestnut tree bark, at 403 nm.