Oleum Asari europaei. - Haselwurzol. - Essence d'Asaret.
Origin and Properties. The root of Asarum europseum, L. (family Aristolochiaceae), which grows in the shady hardwood forests of Europe, Siberia and the Caucasus, yields upon distillation about 1 p.c. of a viscid, heavy oil that sinks in water. It is brown in color, of a strong aromatic odor and a pepper-like, burning taste. Frequently the oil congeals shortly after distillation, often, however, crystals of asarone separate only after long standing. The specific gravity of the oil lies between 1,018 and 1,068. On account of its dark color, the angle of rotation has not yet been determined.
1) Report of Schimmel & Co. April 1891, 62.
2) J. C. Sawer, Odorographia. London 1892. Vol. 1, p. 325.
Composition. The separation of a solid body from this oil was first observed by Gorz1) in 1814. J. L. Lassaigne and H. Feneulle2) seem to have regarded as camphor the stearoptene obtained by the distillation of the root with water. Additional communications concerning this substance were made by Grager5) and by Blanchet and Sell4) who made the first elementary analysis of asarum camphor. C. Schmidt3) ascertained the crystallographic properties of the substance and gave to it the name asarone which is still in use.
B. Rizza and A. Butlerow6) recognized the presence of three methoxyl groups in asarone and proposed the formula C12H16O3 which later proved to be correct. T. Poleck and F. Staats7), however, first favored the formula C8H10O2, later C13H17O3 and finally C13H18O3.
The relative position in the molecule of the three methoxyl groups was ascertained by W. Will8) who showed that asarone is a hydroxyhydroquinone derivative. The synthesis of asarone, as accomplished later by L. Gattermann and F. Eggers9), revealed the following formula.
Concerning the internal arrangement of the C3H5 group J. F. Eykman10) made observations and derived from the index of refraction as well as the capacity for dispersion the conviction that asarone is a propenyl and not an allyl compound.
1) Pfaff, System der Materia Medica III. (1814), 230.
2) Journ. de Pharm. 6 (1820), 561 ff. - Trommsdorff's Neues Journ. der Pharm. 5, II (1821), 71.
3) J. N. Grager, Dissertatio de Asaro Europeeo. Gotting. 1830.
4) Liebig's Annalen (5 (1833), 296.
5) Ibidem 53 (1845), 156.
6) Berl. Berichte 17 (1884), 1159. - Journ. russ. phys. chem. Ges. 19 (1887), I. 1; Berl. Berichte 20 (1887), 222, Abstracts.
7) Berl. Berichte 17 (1884), 1415. - Chem. Ztg. 9 (1885), 1465; Jahresb. f. Pharm. 1885, 331. - Tagebl. der 59. Versammlung deutscher Natur-forscher 1886, 127; Jahresb. f. Pharm. 1886, 233.
8) Berl. Berichte 21 (1888), 614.
9) Ibidem 32 (1899), 289.
10) Ibidem 22 (1889), 3172.
The properties and derivatives of asarone are described in vol. I, p. 487.
Upon distillation of the constituents of the asarum oil that accompany the asarone, A. S. F. Petersenl) obtained a laevogyrate fraction boiling between 162 and 165° containing \-pinene. Upon direct bromination it yielded a liquid monobromide and, after heating to 250°, dipentene tetrabromide melting at 122°.
The higher boiling constituents of the oil distilled principally in the neighborhood of 250° and had the composition C11H1402. With sodium nitrite and glacial acetic acid a nitrite melting at 118° was obtained. When heated with hydrogen iodide, methyl iodide was split off. When oxidized with potassium permanganate, veratric acid was formed. On the strength of these results, Petersen regarded the substance boiling at about 250° as methyleugenol.
Mittmann2), however, is of opinion that not methyleugenol but methylisoeugeno/ is present. He bases his conclusion on a comparison with synthetic methyleugenol produced from bay oil eugenol and with the natural methyleugenol found in this oil. Inasmuch, however, as the phenol of the oil of bay, from which Mittmann prepared his methyl ether, was a mixture of eugenol and chavicol, as was shown later, his methyl ether could not have been a pure body. Hence the conclusions based thereon are valueless. For the present, it must, therefore, remain undecided as to whether asarum oil contains eugenol methyl ether or /soeugenol methyl ether.
The highest boiling fraction of the oil is colored green by a substance not further investigated.