2.1.3 Cascara Sagrada
Interestingly, the very name ‘cascara sagrada’ is Spanish for the sacred bark; Rhamnus is the ancient classical name for buckthorn, and Purshianus was attributed as a mark of honour and respect to the great German botanist Friedrich Pursch.
Synonyms Sacred bark; Chitten bark; Chittin bark; Purshiana bark; Persian bark; Bearberry bark; Bearwood; Cascara bark; Cortex Rhamni purshianae.
Biological Source Cascara sagrada is the dried bark of Rhamanus purshiana DC., belonging to
family Rhamnaceae, from which a naturally occurring cathartic is extracted. It is usually collected at least one year prior to its use.
Geograhical Source It is invariably obtained from cultivated as well as wild shrubs and small trees grown in Northern Idaho, West to Northern California, North Carolina, Oregon, in Kenya and Western Canada.
Preparation The bark is collected, during the dry season (April to August) from the 8 to 9 years old trees that have gained a height of 16-18 meters with their stems having a diameter of 8 to 10 cm, by inflicting longitudinal incisions on the fully developed stems. In usual practice, the coppicing technique is employed for the collection of bark. The bark is carefully stripped off from the branches and the stems. They are subsequently allowed to dry in shade by putting their inner-surface facing the ground so as to permit the completion in the enzymatic conversion of the anthranol derivative i.e., glycosides (an emetic principle) to its anthraquinone derivative usually present in the fresh drug, thereby exerting a milder cathartic activity. During this span of one year the drug must be duly protected from rain or humid environment so as to check the growth of mould.
Description
Colour : Outside-purplish brown; Inside reddish brown.
Odour : A typically nauseatic odour.
Taste : Persistently bitter.
Size : Occurs in varying sizes of thickness between 1 to 4 mm.
Shape : Mostly occurs in quills or channels. Also available in small, flat and broken segments.
However, internally the bark exhibits longitudinal striations; whereas externally the bark appears to be quite smooth and usually displays the presence of seattered lenticles, lichens and cork. Besides, mostly insects and liveworts are found on the exterior surface of the bark.
Chemical Constituents The cascara sagrada bark is found to contain two major types of anthracene compounds, namely:
(a) Normal O-Glycosides These are based on emodin like structures and constitute about 10 to 20% of the total glycosides, and
(b) Aloin-like C-Glycosides These comprise of about 80 to 90% of the total glycosides.
The two C-glycosides are known as barbaloin and deoxybarbaloin (or chrysaloin) as given below:
The main active constituents are four glycosides usually designed as Cascarosides A, B, C and D. From extensive and intensive studies of these cascarosides by optical rotary dispersion (ORD) technique it has been established that the cascarosides A and B are solely based on optical isomers of barbaloin ; whereas cascarosides C and D on optical isomers of deoxybarbaloin. However, from a close inspection of all the four basically primary glycosides of barbaloin and deoxybarbaloin it may be revealed that they possess the characteristic features of O-glycosides as well as C-glycosides.
Salient Features The sailent features of the various glycosides are as follows:
(i) About six anthracene derivatives isolated and identified in the drug belong to the category of O-glycosides which are solely based on emodin,
(ii) Dried cascara bark normally produces not less than 7% of the total hydroxyanthracene derivatives, calculated as cascaroside A, and
(iii) The remaining cascarosides must make up at least 60% of this total quantum.
Perhaps the presence of a ‘lactone’ in the drug attributes a bitter taste to it.
Casanthranol is the purified version of a mixture of anthranol glycosides highly water-soluble and duly extracted from cascara sagrada. It has been reported that each gramme of casanthanol contains not less than 200 mg of the entire hydroxyanthracene derivative, calculated as cascaroside A, out of which not less than 80% of the respective derivatives mainly consists of cascarosides.
Chemical Test It gives a positive indication with Modified Borntrager’s test because of the presence of C-glycosides.
Substituents/Adulterants The barks of Rhamanus californica and R. fallax are generally used as a substitute for cascara sagrada bark. Sometimes the frangula bark is also used as a substitute for this drug. However, the former types of barks (Rhamnus species) exhibit a more uniform coat of lichens along with broader medullary rays when compared to the original drug species.
