2.3.2.2 Esculetin
Synonyms Aesculetin; Chicorigenin; 6, 7-Dihydroxy-coumarin.
Biological Source It is the aglucon of esculin and cichorlin: Esculin is derived from two different plant sources, namely: (a) the barks of Crataegus oxycantha L. (Rosaceae)-Hawthorn; and (b) the flowers of Centarea cyanus Linn., (Compositae). It is a glucoside which upon hydrolysis gives the aglucon esculetin.
Esculetin is also obtained from cichorlin, which is a glucoside and found to be isomeric with esculin. Cichorlin is present in the flowers of the chicory plant (Chichorium intybus L., family: Compositae).
Preparation It is obtained by the hydrolysis of the following two glucosides, namely:
(a) From Esculin:
(b) From Cichorlin:
Characteristic Features It is obtained as prisms from glacial acetic acid and as leaflets by vacuum sublimation. Its mp is 268-270°C. It is soluble in dilute alkalies (2M solution) with the emission of blue fluorescence. It is almost insoluble in ether and in boiling water, but moderately soluble in hot ethanol and in glacial acetic acid.
Uses It is mostly in filters for absorption of uv-light
