Oleum Menthae Viridis (U. S. P.)—Oil of Spearmint.
Preparations: Spearmint Water - Spirit of Spearmint
Related entries: Menthol (U. S. P.)—Menthol- Mentha Piperita (U. S. P.)—Peppermint - Oleum Menthae Piperitae (U. S. P.)—Oil of Peppermint - Mentha Viridis (U. S. P.)—Spearmint
"A volatile oil distilled from Mentha viridis, Linné (Nat. Ord.—Labiatae). It should be kept in well-stoppered bottles, in a cool place, protected from light"—(U. S. P.).
Preparation and Description.—The oil is obtained by distillation of spearmint herb with water; the yield from American fresh herb, gathered at the beginning of flowering, was 0.3 per cent (Schimmel & Co.). It is extensively distilled in this country, and in smaller quantities in Germany and Russia. The U. S. P. describes it as "a colorless, yellowish, or greenish-yellow liquid, becoming darker and thicker by age and exposure to the air, having the characteristic, strong odor of spearmint, and a hot, aromatic taste; Specific gravity, 0.930 to 0.940 at 15° C. (59° F.). With an equal volume of alcohol it forms a clear solution, which is neutral or slightly acid to litmus paper. When somewhat further diluted with alcohol, it becomes turbid. It also yields a clear solution with an equal volume of glacial acetic acid, and with half its volume of carbon disulphide; but with an equal volume of the latter it forms a turbid mixture"—(U.S.P.). The oil is optically laevo-rotatory (as high as -43°). An exceptionally high specific gravity (0.980) is reported by Schimmel & Co. for the oil above mentioned.
Chemical Composition.—This oil consists of two, and probably three, laevo-gyrate bodies. One is laevo-carvone (C10H14O), a ketone of a pure caraway odor, found also in the oils of caraway and dill (in the latter two as dextro-carvone). The quantity of carvone in spearmint oil was found by Kremers and Schreiner (Pharm. Review, 1896, p. 244) to be 66 per cent. The second body is laevo-limonene, once known as carvene (C10H16). The third constituent is probably pinene.
Action, Medical Uses, and Dosage.—Oil of spearmint is carminative, antispasmodic, and diuretic. It is used very frequently as a substitute for the oil of peppermint, and is more often prescribed on account of its diuretic properties. The tincture of the oil combined with potassium acetate renders the latter more efficient as a diuretic, besides imparting a pleasant flavor to it. The dose of the oil is 5 or 10 drops on sugar.