Viola. Violet.
Synonyms.—Sweet Violet; English Violet.
Violet leaves and petals from Viola odorata, Linn. (N.O. Violaceae), indigenous to Europe and Northern Asia. The plant has an oblique rhizome, and produces long filiform runners. The leaves are reniform or heart-shaped, obtuse and crenate. The flowers are dark blue, and have a sweet agreeable odour; the odour is destroyed by desiccation, and the degree to which they retain their colour depends on the method of collecting and drying them. They should be gathered before full blown, deprived of the calyx, rapidly dried either in a heated room or in a current of very dry air, and kept in air-tight containers.
Constituents.—Violet flowers yield their odour and slightly bitter taste to boiling water. The plant, especially the rhizome, contains the alkaloid violine, which is combined with malic acid and may be isolated by removing the chlorophyll and fat from the alcoholic extract by ether, boiling the residue with diluted sulphuric acid, adding to the filtrate lead oxide, evaporating, and exhausting the residue with strong alcohol. It occurs as a yellowish, bitter, fusible powder, soluble in water, less so in alcohol, insoluble in ether. The blue colouring matter, which may be extracted from the petals by infusion with water, turns green and afterwards yellow with alkalies, and red with acids. A glucoside, viola-quercitrin, is also a constituent; it may be isolated by exhausting the fresh plant with warm alcohol, removing the alcohol by distillation, and treating the residue with warm distilled water from which it crystallises in fine yellow needles. On boiling with diluted mineral acids the glucoside is split up into quercetin and a fermentable sugar. The activity of the plant is probably due to this glucoside, its products of decomposition, or a ferment associated with it. Salicylic acid has also been obtained from the plant.
Action and Uses.—Preparations of violet have been used, internally and externally, in the treatment of cancer; for this purpose an infusion of the leaves in boiling water (1 in 5) has been administered in doses of 30 to 60 mils (1 to 2 fluid ounces). A syrup of the petals (see Syrupus Violae) and a liquid extract of the fresh leaves (2 in 1) are also used; the latter may be taken in teaspoonful doses or rubbed in locally. The fresh leaves are also prepared as a compress for local application. There is no trustworthy evidence that the preparations have any effect. The root acts as an emetic and cathartic in doses of 30 to 60 grains (2 to 4 grammes).
PREPARATION.
(Violet Powder is made from Orris root, not Violet. -Henriette)
- Syrupus Violae, B.P.C.—SYRUP OF VIOLET. 23 in 100.
- Used as a colouring agent in neutral or acid mixtures; it is also mixed with m equal volume of almond oil to form a demulcent mixture for children. Dose.—1 to 4 mils (½ to 1 fluid drachm).
