Related entry: Hedeoma (U. S. P.)—Hedeoma
A volatile oil distilled from the leaves and tops of Hedeoma pulegioides (Linné), Persoon. "It should be kept in well-stoppered bottles, in a cool place, protected from light"—(U. S. P.).
SYNONYMS: Oil of pennyroyal, Oil of American pennyroyal.
Preparation.—The oil of pennyroyal is distilled from the wild herb mainly in North Carolina, and eastern and southern Ohio, by means of rather crude apparatus, in the same manner as oil of sassafras (see T. C. Harris, Pharm. Jour. Trans., Vol. XVII, 1887, p. 672; and J. P. Patton, Proc. Amer. Pharm. Assoc., 1891, p. 548). The yield from the fresh herb in the districts named, is 10 to 25 pounds of oil from 1 ton of herb, gathered while in bloom and partially dried; Schimmel & Co. (Report, Oct., 1893) obtained 3 per cent from dried leaves, and 1.3 per cent from dried leaves and herb.
Description.—"A pale-yellowish, limpid liquid, having a characteristic, pungent, mint-like odor and taste. Specific gravity, 0.930 to 0.940 at 15° C. (59° F.). The oil should form a perfectly clear solution with twice its volume of a mixture of 3 volumes of alcohol and 1 volume of water, this solution being neutral or slightly acid to litmus paper. It is also readily soluble in carbon disulphide, or in glacial acetic acid"—(U. S. P.). By means of this test, adulteration with petroleum, oil of turpentine, etc., may be recognized. The oil is optically dextrogyrate (+18° to +22°).
Chemical Composition.—The principal constituent of oil of pennyroyal is pulegone, identified by Habhegger (Amer. Jour. Pharm., 1893, p. 417). Besides there are present two ketones (C10H18O), one hedeomol, the other probably menthone; further more, small quantities of formic, acetic, and isoheptylic acids (C7H14O2) (E. Kremers, Proc. Amer. Pharm. Assoc., 1887, pp. 546-561; and Pharm. Rundschau, 1891, p. 130).
Action, Medical Uses, and Dosage.—Oil of pennyroyal is a stimulant, carminative, antispasmodic, and emmenagogue. It has been used with benefit in cramp of the stomach, flatulent colic, nausea, amenorrhoea, and to diminish the harshness of griping, as well as nauseating, medicines. It is frequently employed for the purpose of occasioning abortion, but as with all agents of this sort, it is very dangerous. It is sometimes applied externally as a mild rubefacient. The dose is from 2 to 10 drops on sugar, or in emulsion. (For further uses, see Hedeoma.)
Related Oils.—OIL OF EUROPEAN PENNYROYAL. Distilled from Mentha Pulegium, Linné (Pulegium vulgare, Miller). A strongly aromatic, mint-like, yellowish or greenish-yellow oil, whose purity is to be tested for in the same manner as the American oil; it appears to possess like therapeutic properties. Specific gravity, 0.935 to 0.955. Contains about 80 per cent of the ketone pulegone (C10H18O), a colorless fluid having an agreeable, peppermint-like odor. Optical rotation of the oil +18° to +23°; of pulegone, +21° 16'. The boiling point of the latter, at reduced pressure (60 Mm.), is 130° to 131° C. (266° to 267.8° F.). The major portion of the oil distills at 212° to 216° C. (413.6° to 420.8° F.), pure pulegone at 221° to 222° C. (430.8° to 431.6° F.) (see Power, Essential Oils).
OIL OF PULEGIUM MICRANTHUM, Claus, resembles the preceding, but its boiling point is higher, and its specific gravity greater. This plant grows in southern Russia.