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Chapter: Pharmacognosy and Phytochemistry : Drugs Containing Glycosides

Senega consists of dried roots and rootstocks of Polygala senega Linn., belonging to family Polygalaceae.






Snake Root, Senegae Radix, Seneca. Milkwort, Mountain Flax, Rattlesnake Root, Radix Senegae, Senega Root.


Biological Source


Senega consists of dried roots and rootstocks of Polygala senega Linn., belonging to family Polygalaceae.


Geographical Source


Grows throughout central and western North America and Canada.




The name of the genus, Polygala, means ‘much milk,’ alluding to its own profuse secretions and their effects. ‘Senega’ is derived from the Seneca tribe of North American Indians, among whom the plant was used as a remedy for snake bites.


Cultivation and Collection


It is a perennial growing to 0.3 m by 0.3 m. Prefers a moderately fertile moisture-retentive well-drained soil, succeeding in full sun if the soil remains moist throughout the growing season, otherwise it is best in semishade. It is propagated by seeds or cuttings. Seeds are sown in spring or autumn in a cold frame. When the seedlings are large enough to handle, they are kept in individual pots and grown them on in the green house for their first winter. They are transplanted in late spring or early summer, after the last expected frosts.


The roots should be gathered when the leaves are dead, and before the first frost. Roots are dug out and the aerial stems attached to them are removed. From carelessness in collection other roots are often found mixed with it, but not for intentional adulteration. However some stem bases persist in the drug. Roots are washed and dried.




The root, varying in colour from light yellowish grey to brownish grey, and in size from the thickness of a straw to that of the little finger, has as its distinguishing mark a projecting line, along its concave side. It is usually twisted, sometimes almost spiral, and has at its upper end a thick, irregular, knotty crown, showing traces of numerous, wiry stems. It breaks with a short fracture, the wood often showing an abnormal appearance, since one or two wedge-shaped portions may be replaced by parenchymatous tissue, as if a segment of wood had been cut out. The keels are due to the development of the bast, and not to any abnormality in the wood. It taste sweet first and then turns to acrid and have characteristic odour.


             Rootstocks of Polygala senega 

Chemical Constituents


The root contains triterpenoid saponins. The active principle, contained in the bark, is Senegin. It is a white powder easily soluble in hot water and alcohol, forming a soapy emulsion when mixed with boiling water.


Senega contains 8–10% of a mixture of at least eight different saponins. The main saponin is senegin, which on hydrolysis yields presenegenin, glucose, galactose, rhamnose and xylose. The root contains polygalic acid, virgineic acid, pectic and tannic acids, yellow, bitter, colouring matter, cerin, fixed oil, gum, albumen, woody fibre, salts, alumina, silica, magnesia and iron.





The root promotes the clearing of phlegm from the bronchial tubes. It is antidote, cathartic, diaphoretic, diuretic, emetic, expectorant, sialagogue and stimulant. It was used by the North American Indians in the treatment of snake bites and has been found used in the treatment of various respiratory problems including pleurisy and pneumonia.


Allied Drugs


Polygala senega var. latifolia. (Northern senega), collected in the northwestern States, is considerably larger than the usual variety (Western senega), and darker in colour; it shows the keel less distinctly, but it has a very acrid taste.


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