This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
The tree yielding this drug, Brayera an-thelmintica, Kunth (N.O. Rosaceoe), is a native of northeastern Africa. It is cultivated in Abyssinia, being commonly planted by the natives near their villages, and is in general use as a remedy for intestinal worms, from which they suffer severely. Bruce became acquainted with it in the course of his travels through Africa (about 1770).
The panicles of pistillate flowers are collected after fertilisation and dried. They are usually packed into cylindrical rolls (hanks) about 30 to 60 cm. in length and 5 to 8 cm. in diameter, bound round with a flexible monocotyledonous stem. The staminate inflorescences, which are sometimes borne on the same, sometimes on different trees, are also collected and the flowers stripped from them, but they are comparatively valueless and are not official.
The panicles attain as much as 60 cm. in length, and are of a decided, though dull, reddish or mauve colour (red kousso). The main axis is stout, covered with shaggy brown hairs, and branches repeatedly, forming a sympodial branch system. The branches spring from the axils of large bracts, and are more or less thickly covered with similar hairs and also with minute glands, the latter appearing under the lens as a brownish powder adhering to the surface. The flowers are very numerous and shortly stalked. Each bears on its pedicel two rounded bracts, and consists originally of two whorls of greenish sepals, a caducous white corolla, abortive stamens, and two monocarpellary ovaries enclosed in the tube of the calyx. After fertilisation the inner sepals bend over the young fruit and shrivel; the outer grow larger and become deeply veined with purple. Only one of the two ovaries arrives at matuiity. In the drug the most conspicuous part of the flower is the outer whorl of reddish, veined sepals; in its centre may be found the inner sepals bending over the immature fruit; of corolla and abortive stamens no trace is to be found.
Kousso has no marked odour, but possesses a bitter, acrid taste.
The student should soak a little kousso in water and, when thoroughly softened, examine it with the help of lens and dissecting needles. The two whorls of sepals and the young fruit can then be distinguished without difficulty.
The drug is easily identified, but the student should particularly observe
(a) The inner whorl of sepals bending over the young fruit,
(b) The enlarged, veined, outer whorl of sepals,
(c) The reddish colour of the drug, as these characters serve to distinguish the pistillate flowers, which alone are official, from the staminate.
The most important constituent of kousso is koso-toxin (Leichsenring, 1894), a highly active, amorphous, yellowish substance, of which 0.004 gm. is sufficient to kill a frog. Protokosin and kosidin are inactive, colourless, crystalline substances; a- and β-kosin are inactive, yellowish, crystalline substances and appear to be decomposition products, it being uncertain whether they occur preformed in the drug. Kousso also contains tannin and resin, and yields about 5 per cent, of ash.
Kosotoxin is insoluble in water but easily soluble in alcohol, ether, acetone, chloroform, etc, as well as in solutions of alkaline carbonates. Caustic alkalies convert it into kosin. By the action of zinc dust and caustic soda kosin and trimethylphloroglucin are obtained; this reaction indicates a close relationship with the vermifuge constituents of male fern and kamala, which under similar conditions yield trimethylphloroglucin and dimethylphloroglucin respectively.
Protokosin occurs in colourless needles melting at 176°, a-kosin, in yellowish needles melting at 161°, and β-kosin, in dark yellow prisms melting at 121°.
Under the name of ' loose kousso ' the flowers stripped from the panicles and dried are sometimes imported. They arrive usually in more or less fragmentary condition, and frequently contain a considerable admixture of staminate flowers. These may be easily distinguished by their greenish colour, small outer sepals densely covered with short hairs, and fertile stamens; they are often unexpanded. They are said to possess emetic properties, and to be a much less active anthelmintic than the pistillate flowers; the Pharmacopoeia, by describing the drug in panicles, properly excludes the use of loose kousso.
Fig. 37. - Brayera anthelmintica. A, flowering branch, three-fourths natural size (after Berg and Schmidt). B and C, staminate flower closed and open, magnified. D, pistillate flower, magnified. E, the same, cut longitudinally, magnified: b, outer, k, inner whorl of sepals; c, corolla. (Luerssen).
Kousso is used as an anthelmintic, tapeworms being readily killed by it. In large doses it produces nausea, vomiting, and colic. It is commonly administered in the form of an infusion, the dregs being swallowed, but probably an ethereal or ether-alcohol extract would be preferable.