Source, Etc

The colocynth plant, Citrullus Colocynthis, Schrader (N.O. Cucurbitaceoe), is, like many other members of the same natural order, a scabrous, prostrate plant with a perennial root. It enjoys an extensive distribution throughout northern Africa, Syria, and northwestern India. In the African and Egyptian deserts it frequently occurs in enormous quantities; it is cultivated in Syria, Spain, Cyprus, and the north-western provinces of India.

The remarkable properties of this fruit must necessarily have attracted attention very early. Dioscorides and Pliny were both acquainted with it, and so also were the Arabian physicians, by whom probably its use was introduced into Europe.

The fruit, which is about the size of an apple, is collected when ripe, dried and then freed from the thin rind by peeling with a sharp knife, the peeled fruits being often termed ' apples.' Persian colocynth is peeled before drying and consequently shrinks considerably. Mogadore colocynth is imported unpeeled and commonly used for filling the show-jars in the pharmacist's window.

Description

The fruit of the colocynth plant is, when young, three-celled and bears numerous ovules attached to axile placentas. The placentas, however, grow from the centre towards the circumference of the fruit, and when they have nearly reached the pericarp divide in two, each half curving inwards and bearing numerous seeds on its margins. During these changes the carpellary walls disappear, and the fruit, originally three-celled, becomes spuriously one-celled. The pulp consists largely of the fleshy placentas; they usually split in a radial direction throughout the greater part of their length, and in the dried fruit they are deeply fissured.

As seen in commerce, colocynth fruits form more or less broken white balls, 5 cm. in diameter and light in weight. The rind has generally been carefully peeled off, and the outer surface is formed by part of the thin, whitish mesocarp, which, however, has in places itself been removed, disclosing the yellowish or nearly brown seeds, or the fleshy placentas. If a fruit is cut transversely the placentas will generally exhibit radiating fissures dividing the fruit into three portions, in each of which, near the periphery, a half of each placenta curves inwards and bears on its inner margin several vertical rows of seeds. These number from 200 to 300, and constitute about three-quarters of the weight of the fruit; they vary in colour from yellowish white to dark brown according to the degree of ripeness. They have a flattened ovoid shape, possess a hard seed-coat, and contain a small oily kernel which, however, strange as it may seem, forms, when properly prepared, a valuable addition to the scanty diet of certain tribes of Arabs.

Description 86Fig. 58.   Colocynth fruit. A, transverse section of young fruit, showing the placentas dividing near the margin and curving inwards; B, ripe fruit, showing each placenta fissured. (Moeller.)

Fig. 58. - Colocynth fruit. A, transverse section of young fruit, showing the placentas dividing near the margin and curving inwards; B, ripe fruit, showing each placenta fissured. (Moeller).

For medicinal use the light, whitish, spongy, pith-like pulp, the bulk of which is furnished by the placentas, should be freed from the seeds, as the pulp alone is official. It possesses a slight odour, but an intensely bitter taste, the seeds when quite free from pulp being almost tasteless.

Much of the colocynth at present imported consists of the pulp free from the seeds; for the latter some use, possibly the production of fixed oil, has apparently been found.

Constituents

The chief constituents of colocynth pulp appear to be an alkaloid producing very drastic purgation even in small doses, and amorphous resins soluble in ether and chloroform which also are powerful purgatives. Other constituents are a crystalline alcohol, citrullol, and a-elaterin; neither of these are purgative; a-elaterin is also present in elaterium (see ' Elaterium'). The presence of a crystallin glucoside, colocynthin, formerly reported, has not been confirmed. The pulp also contains from 1.0 to 1.3 per cent, of fixed oil and yields from 7 to 13 per cent, of ash; it contains no starch.

The small amount of fixed oil and the large amount of ash have been utilised to distinguish the powdered fruit from the powdered pulp. The seeds contain from 15 to 17 per cent, of oil, and yield only 25 to 3.O per cent, of ash. Powdered fruits yield from 4 to 6 per cent, of ash and about 10 per cent, fixed oil. Microscopical examination of the powder yields more definite results. Colocynth pulp consists of very large thin-walled parenchymatous cells with occasional fibro-vascular bundles, accompanied by tubular cells but no sclerenchy-matous cells are present in it, whereas the seed-coats abound in sclerenchymatous tissue which can be readily detected and identified.

Varieties

Turkey colocynth, which is the most esteemed, is imported from Syria, Cyprus, etc.; the fruits are carefully peeled, nearly white, and contain a larger proportion of pulp. During and since the war large quantities of very similar Sudan colocynth have been imported.

Spanish colocynth is less sightly, often discoloured, and contains less pulp.

Persian colocynth occurs in small, shrunken balls with little pulp; it is now seldom imported.

Mogadore colocynth is occasionally imported; it is unpeeled.

Uses

Colocynth is a gastro-intestinal stimulant or irritant and one of the most powerful of the official purgatives, acting as a hydra-gogue cathartic. It is employed as an occasional purgative to produce free evacuation of the bowels in bilious derangements or chronic constipation, but as it causes griping is seldom prescribed alone.