Cascara Bark

CASCARA BARK

Synonyms

Californian Buckthorn, Cascara Buckthorn, Cascara Sagrada, Kaskara Sakrada, Kasukarasakurada, Pursh’s Buckthorn, Sacred Bark, Chittem Bark.

Biological Source

Cascara is the dried bark of Rhamnus purshiana DC., belong-ing to family Rhamnaceae. It is collected at least one year before use.

Geographical Source

It is indigenous to North America, British Columbia, Canada and Kenya.

Cultivation and Collection

It is an evergreen tree growing to 6–12 m in height. The plant prefers sandy, loamy and clay soils. The plant prefers acid, neutral and basic soils. It can grow in semishade or no shade. It requires moist soil. It is cultivated using different techniques like sowing seeds, cuttings and layering. Seeds are sown in the autumn in a cold frame. Stored seed will require 1–2 months cold stratification at about 5°C and should be sown as early in the year as possible in a cold frame or outdoor seed bed. Seedlings are transferred to the pots and then they are transplanted in late spring or early summer of the following year. Cuttings are carried out using half-ripe wood, July/August. Layering can be done in early spring.

Earlier the barks were collected by felling technique and then by making longitudinal incisions on the trees. To save the destruction of this species nowadays it is collected by coppicing method. So the stump remaining above the soil produces new shoots, which bear leaves, flowers and fruits and seed dispersal takes place and new plants grow. Bark is collected from 9 to 15 years old trees having minimum 10 cm diameter in dry weather after rains in May to August by making suitable transverse and longitudinal incisions. During drying the outer bark is protected from moisture and rains and inner bark is protected from direct sunlight. Moisture leads to mould due to the sunlight bark becomes black colour. After complete drying the bark is made in to small pieces that form squill. It should be harvested in the autumn or spring at least 12 months before it is used medicinally, in order to allow the more violent purgative effect to be modified with age.

Characteristics

The drug mostly occurs in quilled, channelled or incurved of varying lengths and sizes, usually 20 cm long and 1–4 mm thick, smooth or nearly so externally, covered with a greyish-white layer, which is usually easily removed, and frequently marked with spots or patches of adherent lichens. Beneath the surface it is violet-brown, reddish-brown or brownish, and internally a pale yellowish-brown and nearly smooth. Fracture is short and granular in the outer part and fibrous in the phloem. It has no marked odour, but a nauseous, bitter taste. It is frequently also imported in flattened packets, consisting of small pieces of the bark compressed into a more or less compact mass.

                                         Rhamnus purshiana

Microscopy

The cork consists of numerous layers of small, thin walled flattened, polygonal prisms, arranged in radial rows and having yellowish brown contents. Next to cork few layers of collenchyma cells are present. Groups of irregular thick walled lignified stone cells are in the cortex and 1–5 celled wide phloem rays and tangentially elongated lignified fibres in the phloem. The fibres are crystal fibres and surrounded by parenchyma containing calcium oxalate prisms. Crystal fibres are of diagnostic importance in identification of the powdered drug.

           Transverse section of Cascara bark

Chemical Constituents

Cascara bark contains 80–90% of C-glycosides and 10–20% O-glycosides. The C-glycosides present in cascara are aloin or barbaloin and 11-deoxyaloin or chrysaloin. Cascarosides A and B are the primary glycosides of aloin and cascarosides C and D are primary glycosides of chrysaloin. Cascara also contains chrysaloin and barbaloins, dianthrones of emodin, aloe-emodin, chrysophanol; heterodianthrones like Palmidins A, B and C, free emodin, aloe-emodin and a bitter lactone. Apart from glycosides it also contains fat, starch, glucose, volatile odorous oil, malic and tannic acids.

Fresh cascara bark contains anthranol derivatives which have griping; and emetic properties and after storage for one year, anthranol derivatives are oxidized to anthraquinone derivatives and bark loses irritant properties.

Chemical Test

It gives red colour with 5% potassium hydroxide solution.

Uses

Cascara sagrada is widely used as a gentle laxative that restores tone to the bowel muscles and thus makes repeated doses unnecessary. It is considered suitable for delicate and elderly persons and is very useful in cases of chronic constipation. The bark also has tonic properties, promot-ing gastric digestion and appetite. As well as its uses as a laxative, it is taken internally in the treatment of digestive complaints, haemorrhoids, liver problems and jaundice.

Substitutes

These include R. alnifolia, which is too rare to be a likely substitute; R. crocea, whose bark bears little resemblance to the official drug. R. californica is very closely related to R. purshiana. It has a more uniform coat of lichens and wider medullary rays than the official species, but resembles the latter in having sclerenchymatous cells. The bark of R.fallax has been recorded as a cascara substitute.

Marketed Products

It is one of the ingredients of the preparations known as Herbal Laxative (Trophic Canada Ltd.).