[Oil of Wintergreen]
Related entry: Gaultheria
"Oil of Gaultheria is the oil distilled from the leaves of Gaultheria procumbens, Linn., or from the bark of Betula lenta, Linn." Br.
Oil of Teaberry, Oil of Partridge-berry; Huile volatile (Essence) de Winter-green, Fr. Cod.; Essence de Gaultherie, Fr.; Wintergrünöl, Bergtheeöl, G.
Oil of gaultheria is no longer official in the U. S. P. IX. Under Methylis Salicylas the Pharmacopoeia directs that oil of gaultheria and oil of betula or sweet birch may be used.
The volatile oil of gaultheria is largely obtained in the United States by distillation of the plant. It probably does not exist in the plant, but is formed by a reaction between water and a neutral principle analogous to amygdalin, to which Procter has given the name of gaultherin. (A. J. P., xv.) This substance, which was called by Schneegans betulase, probably exists in all the numerous plants which yield methyl salicylate on distillation. The oil occurs in various of our native plants, and has been detected in Polygala paucifolia, Spiraea Ulmaria, Spiraea lobata, and Gaultheria chiogenes (?). T. E. de Vrij found it in considerable proportion in the Gaultheria leucocarpa and G. punctata, plants which are abundant in the volcanic regions of Java (A. J. P., 1879); while Bourquelot (C. R. S. B., iii, 1896) detected it in Monotropa Hypopitys, in Polygala Senega, and in other species of Polygala. (See also A. J. P., 1898, 412.) Much of the so-called oil of wintergreen is obtained from Betula lenta, which yields a product physically indistinguishable and difficult to differentiate chemically from methyl salicylate.
The still in which oil of wintergreen is distilled is generally a wooden box, about eight feet long, four feet wide, four feet high, with a copper bottom and stayed with bolts. The head of the still is copper, and connecting with this is a circular worm of the same material or of tin, placed in a barrel. The still being filled with wintergreen to within about twelve inches of the top, a sufficient quantity of water is added, and this is allowed to macerate from ten to twelve hours. The fire being started, the distillation commences, and continues for about eight hours; but during the first two or three hours ninety per cent. of the oil has passed over. For collecting the distillate, most of the distillers use a wide-mouthed bottle, fitted with a large cork having two holes. A small funnel is put into one of the holes, so that the beak is below the shoulder of the receiving vessel, and connected with the other hole is a suitable pipe forming an outlet. The oil and the water separate, the oil going to the bottom, and the water passes into a larger receptacle, where it is reserved for a subsequent operation (cohobation).
Occasionally the oil is very highly colored, and the wholesale dealers have three ways of "cleaning" it—redistillation, filtration, and de-colorization. In the last method the oil to be decolorized is put into a bottle, crystals of citric acid are added, and the whole is allowed to stand, agitating occasionally, until the oil is colorless, or nearly so.
Oil of gaultheria when freshly redistilled is nearly colorless, but as found in commerce has a brownish-yellow or reddish color. The U. S. P. VIII described it as "a colorless or almost colorless liquid, having a characteristic, strongly aromatic odor, and a sweetish, warm, and aromatic taste. Specific gravity: 1.172 to 1.180 at 25° C. (77° F.). Boiling point: 218° to 221° C. (424.4°-429.8° F.). It is slightly laevogyrate, up to -1° in a 100 Mm. tube, at 25° C. (77° F.). In other respects it has the same properties as, and conforms to the reactions and tests given under, Methylis Salicylas."
"Colorless or nearly colorless. Strong, characteristic odor; taste pungent. Specific gravity 1.180 to 1.187; optical rotation at 25° C. (77° F.) 0° to -1°; refractive index 1.537 to 1.539. Soluble in 6 parts of alcohol (70 per cent.) at 25° C. (77° F.). Contains not less than 99 per cent. of esters, calculated as methyl salicylate, CH3C7H5O3." Br.
It is stated to have been largely adulterated with chloroform. This and other impurities are to be detected by a comparison of the specific gravities and boiling points, or by fractional distillation. It is readily soluble in alcohol. When heated to about 80° C. (176° F.), the oil should not yield a colorless distillate having the characteristics of chloroform or of alcohol. (A. J. P., 1873, p. 521.) Another distinguishing property is that in aqueous solution it gives a purple color with ferric salts. Oil of sassafras may be detected by the separation of a deep-red resinous mass on treatment with nitric acid in the cold. Japanese oil of camphor and other light volatile oils used as adulterants can be detected by simply dropping the suspected oil in water; if pure, it sinks in a few seconds; if adulterated, some minutes are required. Cahours states that one-tenth of the oil consists of a peculiar hydrocarbon, which he called gaultherilene, and the remaining nine-tenths of methyl salicylate. (A. J. P., xiv, 211, xv, 241.) Trimble and Schroeter (A. J. P., 1889, 398) found that the amount of the hydrocarbon gaultherilene was much less than that stated by Cahours—in fact, only 0.3 per cent. By analysis and vapor density, determination they fixed its formula as C15H24, but they state that it may consist of a solid and a liquid portion. Power and Kleber (Fritzsche Bros. Circ., No. 7) assert that this hydrocarbon belongs to the paraffin series, and state that it is probably triacontane, C30H62. They also find in the oil an aldehyde or ketone, with an odor like oenanthic aldehyde, an apparently secondary alcohol, C6H16O, and an ester, C14H24O2. To the alcohol and the ester are attributed the characteristic odor of the oil. True oil of gaultheria contains about 99 per cent. of methyl salicylate. Synthetic oil of wintergreen is now extensively manufactured and used instead of the natural oil. For a process by H. T. Thayer, see A. J. P., 1895, 244.
Uses.—The therapeutic properties of this oil are precisely the same as those of Methyl Salicylate.
Dose, ten to twenty minims (0.6-1.3 mils).
The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.