2.3.2.1 Umbelliferone
Synonyms Hydrangin; Skimmetin.
Biological Sources Umbelliferone is present in a variety of medicinal plants, for instance: Apium graveolens L. (Apiaceae) Celery; Artemisia abrotanum L. (Asteraceae)-Southernwood, Old Man; Daphne mezereum L. (Thymelaeaceae)-Mezereon; Dipteryx odorata (Aubl.) Willd. (Fabaceae)-Tonka Bean, Tonga, Cumaru; Ferula sumbul Hook. (Apiaceae)-Sumbul, Mask Root; Hydrangea paniculata Seib. (Saxifragaceae)-Peegee; Lavandule angustifolia Mill. (Lamiaceae)-Lavender; Matricaria chamomilla L. (Asteraceae)-Hungarian Camomile, German Camomile, Manzanilla; and Pimpinella anisum L. (Apiaceae)-Anise.
Preparation Asafoetida contains resin (40-65%) which consits of chiefly a resin-alcohol asaresinotannol both in the free or combined form with ferulic acid, and of course, free umbelliferone is totally absent in the drug. Thus, umbelliferone is prepared by treating ferulic acid with HCl which gets converted to umbellic acid and the latter loses a molecule of water to give rise to umbelliferone as given below:
Umbelliferone may also be obtained by distillation of resin from Umbelliferae.*
Characteristic Features It is obtained as needles from water. It develops the characteristic odour of coumarin on heating. Its mp is 225-228°C. It usually sublimes. Its solubility in water is very poor i.e., it dissolves 1 g in nearly 100 ml of boiling water. It is freely soluble in ethanol, chloroform, acetic acid and dilute alkaline solution. It is sparingly soluble in ether and the solutions exhibit a distinct blue fluorescence.
Identification Test When 0.5 g of umbelliferone is triturated with pure sand (SiO2) and 5 ml of HCl, added 5 ml of water, filtered and to the filtrate added an equal volume of ammonia solution, it gives a beautiful blue fluorescence.
Uses
1. It is an important ingredient in most sunscreen lotions and creams.
2. It is most importantly used as an intracellular and pH sensitive fluorescent indicator and bloodbrain-barrier (BBB) probe.
---------------------------
* Z wenger, Ann., 115, 1, 15 (1860).
