The official cascara sagrada is the dried bark of Rhamnus pushiana collected from small to medium-sized wild deciduous trees. They usually range from 20 to 40 feet high and possess thin, elliptic to ovate-oblong, acutely pointed leaves. The greenish flowers are ar-ranged in umbellate cymes and the fruit is purplish-black and broadly obovoid (8 mm long). The commercial bark is flattened or transversely curved, longitudinally ridged with a brownish to red-brown color. It has gray or white lichen patches and occasional moss attachments. Cascara trees are found in North America in California, Oregon, Washington, Idaho, Montana and as far north as South-east British Columbia.
The American cascara is a folkloric medicine of relatively recent origin, having been introduced as a tree bark laxative by early Mexican and Spanish priests of California (probably Rhamnus Califomica). R. purshiana itself was not described officially until 1805 and the bark was not brought into regular medicinal use until 1877. The European counterpart (European buckthorn, Rhamnus frangula) was described much earlier by the Anglo-Saxons. In fact, the berries were official in the 1650 London Pharmacopoeia.
The active laxative principles of cascara include at least 6% to 9% anthracene derivatives which exist as normal O-glycosides and C-glycosides. The four primary glycosides or cascaroside A, B, C and D, contain both 0- and C-glycosidin linkages. Chemically these are designated as the C-10 isomers of the 8-0-[3-D-glucopy-ranosides of aloin and chrysophanol. The probable break-down products of the C-glycosides are the two aloins: Barbaloin which is derived from aloe-emodin anthrone and chrysaloin which is derived from chrysophanol an-throne. Other glycosides isolated include a number of O-glycosides derived from emodin, emodin oxanthrone, aloe-emodin and chrysophanol. A number of dianthrones are also present including emodin, aloe-emodin, chrysophanol and the heterodianthrones, palmidin A, B and C. Compounds found in the free state include aloe-emodin, emodin and chrysophanol.
The free anthraquinones are likely formed in the leaves and stored in the bark largely as C-glycosides. The older bark contains the most C-glycosides. Although uneco-
nomical for commercial exploitation, R. purshiana ce suspension cultures produce anthracene derivatives,23
Cascara juice also contains other non-laxative COI pounds eg, rhamnol (cinchol, cupreol, quebrachol);
noleic, myristic and syringic-acids; resins, fat, starch ani glucose; malic and tannic acid. The dried seeds contail 6.7% to 25.4% protein, 13.4% to 56.9% oil and 1,3%11 2.3% ash.4 The presence in the bark of bitter substar and methylhydrocotoin is disputed.
A variety of extraction methods have been examined cascara. Boiling water prevents the losses and chang to the compound that occur in cold water extraction, Active fractions of anthraquinone glucosides have is olated from R. pushiana and R. frangula by high pressure liquid chromatography? Hydrophilic anthraquinonel glycosides have been separated from lesser hydrophili anthraquinone aglycones by XAD-2 column chromat raphy.
The quantitative analysis of anthraquinones a anthranol in 16 species of Rhamnus from South and Ea
Anatolia have been examined.9 Likewise, a new naphtha..: lene compound, nakahalene and known anthraquinonesj including physcion and frangulin B, have been isolated from Rhamnus species.
As in other laxatives (aloe, senna, etc), the anthraglycosides are responsible for the cathar. tic properties in cascara. Cascarosides A and B are the major active principles which act on the large intestine tinduce peristalsis and evacuation. More specifically, the anthraglycosides produce an active secretion of water and electrolytes within the lumen of the small intestine and inhibit the absorption of these from the large intestine, This causes an increase in the volume of the bowel contents and strengthens the dilatation pressure in the intestine to stimulate peristalsis. They exert with a minimum of side effects.s In general, the cascaro: sides are more active than their hydrolyzed by-products,2 Furthermore, these cascarosides possess a sweet and more pleasant taste than the aloins and hence should be extracted separately, if possible. Cascara is largely used in the form of a liquid extract or elixir or as tablets made from a standardized dry extract.
The daily dose ranges from 20 to 160 mg of the cascara derivatives for the treatment of constipations The aver.