Viola. Violet.—The genus Viola (Fam. Violaceae) includes numerous species, many, perhaps all of which are possessed of analogous medicinal properties. Viola tricolor L., the Heart's-ease, Pansy, or Johnny-jump-up of the gardens, was formerly recognized by the U. S. Pharmacopoeia; while V. odorata L., and V. pedata L., have held places in both the British and the United States Pharmacopoeias.
V. odorata L. (Violette, Violette odorante, Fr.; Wohlriechendes Veilchen, Veilchen, G.; Violetta, It.; Violeta, Sp.), the common violet of Europe, resembles very closely the American blue violet, V. cucullata Ait., from which, however, it is at once distinguished by its delicious fragrance. It is the sweet violet of our gardens. V. pedata L., is an indigenous, stemless violet, characterized by its large blue or variegated beardless flowers, and its deeply three- to five-divided, pointed pedate leaves.
The flowers of V. odorata yield their odor and their slightly bitter taste to boiling water. Their infusion affords a delicate test for acids and alkalies, being reddened by the former and rendered green by the latter. Their odor is destroyed by desiccation, and the degree to which they retain their fine color depends upon the care used in collecting and drying them. They should be gathered before being fully blown, deprived of their calyx, and rapidly dried, either in a heated room or by exposing them to a current of very dry air. The flowers of other species are often mingled with them, and, if of the same color, are equally useful as a chemical test.
In the root, leaves, flowers, and seeds of Viola odorata, Boullay discovered an alkaloid, violine, allied to emetine, but possessing distinct properties. It exists in the plant combined with malic acid. Orfila asserts that it is exceedingly active and even poisonous. It is probably found in other species of viola. Mandolin (Jahresb., 1883) obtained a glucoside analogous to quercitrin, which he names viola- quercitrin. It crystallizes out of hot water in fine yellow needles. When boiled with diluted acids, it is decomposed into quercetin, isodulcite and a fermentable glucose, C27H30O16 + 3H2O = C6H14O6 + C6H12O6 + C15H10O7 - he also obtained salicylic acid from several species of viola. (A. J. P., 1882, 10.) Kraemer (Marking, 1896) detected methyl salicylate and this was later confirmed by Schimmel & Co. See also Gadd's article, Y. B. P., 1905, 466.
The herbaceous parts of various species of violets are mucilaginous, emollient, and slightly laxative, and have been used in pectoral, nephritic, and cutaneous diseases. In Europe a syrup prepared from the fresh flowers of Viola odorata is employed as an addition to demulcent drinks, and as a laxative for infants. The root, which has a bitter, nauseous, slightly acrid taste, acts in the dose of from thirty grains to a drachm (2.0-3.9 Gm.) as an emetic and cathartic. It is probable that the same property is possessed by the roots of all the violets, as it is known to be by several species of Ionidium, which belongs to the same family. The existence in small proportion of the emetic principle in the leaves and flowers accounts for their expectorant properties.
The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.