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SENNA (Arab. sand) , a popular purgative, consisting of the leaves of two species of Cassia (natural order Leguminosae), viz. C. acutifolia and C. angustifolia. These are small shrubs about 2 ft. high, with numerous lanceolate or narrowly lanceolate leaflets arranged pinnately do a main stalk with no terminal leaflet; the yellow flowers are borne in long-stalked racemes in the leaf-axils, and are succeeded by broad flattish pods about 2 in. long. C. acutifolia is a native of many districts of Nubia , e.g. Dongola, Berber, Kordofan and Senaar, but is grown also in Timbuctoo and Sokoto. The leaflets are collected twice a year by the natives, the principal crop being gathered in September after the rainy season and a smaller quantity in April. The leaves are dried in the simplest manner by cutting down the shrubs and exposing them on the rocks to the burning sun until quite dry. The leaflets then readily fall off and are packed in large bags made of palm leaves, and holding about a quintal each. These packages are conveyed by camels to Assouan and Darao and thence to Cairo and Alexandria, or by ship by way of Massowah and Suakim. The leaflets form the Alexandrian senna of commerce. Formerly this variety of senna was much adulterated with the leaves of Solenostemma Argel, which, however, are readily distinguishableby their minutely wrinkled surface. Of late years Alexandrian senna has been shipped of much better quality. Occasionally a few leaves of a similar species with broader obovate leaves, C. obovata, may be found mixed with it. C. angustifolia affords the Bombay, East Indian, Arabian or Mecca senna of commerce. This plant grows wild in the neighbourhood of Yemen and Hadramaut in the south of Arabia, in Somaliland, and in Sind and the Punjab in India. The leaves are chiefly shipped from Mocha, Aden, Jeddah and other Red Sea ports to Bombay and thence to Europe, the average imports into Bombay amounting to about 250 tons annually, of which one-half is re-exported. Bombay senna is very inferior in appearance to the Alexandrian, as it frequently contains many brown and decayed leaflets and is mixed with leaf-stalks, &c. C. angustifolia is also cultivated in the extreme south of India, and there affords larger leaves, which are known in commerce as Tinnevelly senna. This variety is carefully collected, and consists almost exclusively of leaves of a fine green colour, without any admixture of stalks. It is exported from Tuticorin . American senna is Cassia marilandica.
The British Pharmacopoeia recognizes both Senna Alexandrina and Senna Indica. The composition of the leaves is the same in either case. The chief ingredient is cathartic acid, a sulphur containing glucoside of complex formula . It occurs combined with calcium and magnesium to form soluble salts. That this is the active principle of senna is shown by the fact that the cathartate of ammonia, when given separately, acts in precisely the same manner as senna itself. Cathartic acid can easily be decomposed into glucose and cathartogenic acid. The leaves contain at least two other glucosides, sennapicrin and sennacrol, but as these are insoluble in water, they are not contained in most of the preparations of senna. Senna also contains a little chrysophanic acid.
Of the numerous pharmacopoeial preparations three must be mentioned. The confectio sennae, an admirable laxative for children, contains senna, coriander fruit, figs, tamarind, cassia, pulp, prunes, extract of liquorice, sugar and water. When coated with chocolate it is known as Tamar Indien. The pulvis glycerhizae coin positus contains two parts of senna in twelve. the other ingredients being unimportant. A third preparation, rarely employed nowadays, is the nauseous " black draught," once in high favour. It is known as the mistura sennae composita, and contains sulphate of magnesium, liquorice, cardamoms, aromatic spirit of ammonia and infusion of senna. All the preparations are made indifferently from either kind of leaflet.
When taken internally, senna stimulates the muscular coat of the bowel in its entire length, the colon being more particularly affected. As some congestion of the rectum is thereby produced, senna is contra-indicated whenever haemorrhoids are present. The secretions of the bowel are not markedly stimulated, and the flow of bile is only slightly accelerated. The drug has the advantage, for most cases, of not producing subsequent constipation. The chief purgative ingredients are the cathartates already described. Partial absorption occurs, so that the colour of the urine may be darkened, and as the drug is also excreted by the active mamma it may cause purgation in a baby to whose mother it has been given.
Senna should not be used alone, as its taste and the pain induced by its muscular stimulation are both objectionable. There are many ways of using it. A few of the leaflets may be put into a dish of prunes, when a convenient aperient for children is desired. It is especially valuable in cases of atony of the colon, and the compound liquorice powder is safe and useful in the treatment of the constipation of pregnancy.
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