Oleum Cubebarum. Cubebenol. - Essence de Cubebe.
Origin. The berry-like fruits of Piper Cubeba, L. (Cubeba officinalis, Miq., family Piperaceae), a climbing shrub, mostly enter commerce from Batavia and Singapore. This shrub is indigenous to the larger Sunda archipelago and is cultivated there as well as in Ceylon and other tropical islands.
As several investigations have shown1), commercial cubebs are frequently adulterated with similar fruits. Frequently also the fruits of closely related species are exported, and not infrequently, stems are admixed in considerable amounts. As a means of distinguishing false cubebs from the genuine ones, the sulphuric acid test is recommended. If to the crushed berry, contained in a porcelain dish, some concentrated sulphuric acid be added, the genuine berry shows a beautiful pink color, the false a yellowish-brown color. The difference is still better revealed by the amount of the ether extract obtained, genuine cubebs yielding 20 to 25 p. c, the false article but 15 p. c.
According to Holmes the following varieties yield genuine cubebs: Piper Cubeba var. Rinoe katoentjar and P. C. var. Rinoe tjaroeloek. To the spurious cubebs belong the poisonous var. Rinoe badak, which differs from the genuine by its mace-like odor, Piper ribesioides, Wall., P. crassipes, Korth., P. Lowong, Blume, P. venosum, C. DC. and P. mollissimum, Blume, also Tetran-thera citrata, Nees, Bridelia tomentosa and some Rhamnus-species. The fruits of Piper mollissimum are known in Java by the name of Koboe-cubebs. The berries of P. ribesioides have a somewhat pungent, those of P. crassipes a cajeput-like odor.
Preparation. When distilled with water vapor, comminuted cubebs yield 10 to 18 p. c. of volatile oil. During the process of distillation ammonia is given off to a considerable extent, the cause of which phenomenon is as little known as it is in the case of ginger, pepper, pimento and other drugs.
1) C. E. Sage, Chemist and Druggist 67 (1905), 797. - J. C. Umney and H. V. Potter, ibidem 80 (1912), 331, 443. - Perfum. and Essent. Oil Record 3 (1912), 64. - ). Small, Pharmaceutical Journ. 88 (1912), 639. - E. M. Holmes, Perfum. and Essent. Oil Record 3 (1912), 125.
Properties. Cubeb oil is viscid, light-green to bluish-green. It is colorless only when the last portions of the distillate, which are blue, are not added to the oil. It possesses a characteristic cubeb odor and a warm, camphoraceous, finally grating taste. The specific gravity lies between 0,915 and 0,930; aD - 25 to - 43°; nD20o1,4938 to 1,4958.
The solubility of the oil in 90 p.c. alcohol varies considerably. Some oils, presumably those distilled from old cubebs, are soluble in an equal volume of 90 p.c. alcohol. Others require 10 vol. of such alcohol, and in individual cases the solution does not even then become clear.
The bulk of the oil boils1) between 250 and 280°. A quantitative fractionation2) yielded the following results:
1. from 175 to 250° 9,2 p.c; 2. from 250 to 260° 26,8 p.c; 3. from 260 to 270° 47,6 p.c; 4. from 270 to 280° 7,2 p.c; above 280° 9,2 p.c
The fractions obtained by Schimmel & Co. upon distillation from a simple flask (745 mm.) were as follows: 1. 205 to 225° 4 p.c; 2. 225 to 250° 14 p.c; 3. 250 to 260° 16 p.c; 4. 260 to 265° 22 p.c; 5. 265 to 275° 24 p.c; 6. 275 to 280° 5 p.c; 7. Residue 15 p.c.
Oils distilled from old cubebs, which contain the cubeb camphor described below, are somewhat denser than the normal oils, and are recognized by their behavior towards alkali metal. If a piece of bright potassium or sodium be placed in such an oil, it loses its metallic lustre and is covered with a crust, whereas oils distilled from fresh cubebs do not attack the metal3).
Composition. From this behavior towards potassium, it is evident that the last-mentioned oils are fairly free from oxygen, and consist of terpenes and sesquiterpenes only, whereas the reaction with the metal is to be attributed to the cubeb camphor.
By means of systematic fractionation a laevogyrate terpene (aD - 35,5°) boiling between 158 to 163° can be separated from the lowest portions of the oil1). Presumably this is pinene or camphene. Moreover dipentene (in. p. of dichlorhydrate 48 to 49o) has been found in the distillate below 200°.
1) In the process of distillation oils containing cubeb camphor are decomposed in part with the formation of water. E. Schasr and G. Wyss, Arch, der Pharm. 206 (1875), 322.
2) J.C. Umney, Pharmaceutical Journ. III. 25 (1895), 951.
3) E. A. Schmidt, Arch, der Pharm. 191 (1870), 23.
As already mentioned, the bulk of the oil distils between 250 and 280o and consists of two laevogyrate sesquiterpenes-2).
One of these, which boils between 262 and 263°, has a lesser angle of rotation, does not combine with hydrogen chloride, and has not been further investigated.
The second yields a crystalline dihydrochloride3) which melts at 118° and is identical with cadinene.
Cubed camphor1) is a sesquiterpene hydrate, probably an alcohol of the composition5) C15H24H0. Optically it is laevo-gyrate, crystallizes in the rhombic system, and, according to several investigators, melts at 65"), 677) and 70°8) respectively. It is rather unstable, for when kept over sulphuric acid it is resolved into sesquiterpene and water6). It boils at 148° 9) with partial splitting off of water. Complete dehydration results upon prolonged heating from 200 to 250°. The sesquiterpene thus obtained has not been further investigated.
The circumstance that cubeb camphor is met with only in old cubebs leads to the supposition that it is formed during the storage by the absorption of water from a moist atmosphere.
1) Oglialoro, Gazz. chim. ital. 5 (1875), 467; Berl. Berichte 8 (1875), 1357.
2) Wallach, Liebig's Annalen 288 (1887), 78 ff.
3) This was first obtained by Soubeiran and Capitaine (Liebig's Annalen 34 , 323) and recognized as sesquiterpene dichlorhydrate; later it was examined and described by Schmidt, by Schaer and Wyss, also by Wallach (loc. cit).
4) Cubeb camphor was first observed by Teschemacher towards the beginning of the nineteenth century. Later it was investigated by C. Muller, Liebig's Annalen 2 (1832), 90, Blanchet and Sell, Ibidem 6 (1833), 294, Winckler, Ibidem 8 (1833), 203, E.A.Schmidt, Arch, der Pharm. 191 (1870), 23; Berl. Berichte 10 (1877), 188 and E. Schser and G. Wyss, Arch, der Pharm. 206 (1875), 316.
5) Schmidt, Schaer and Wyss, loc. cit.
°) Schmidt, loc. cit.
7) Schaer and Wyss, loc. cit.
8) Winckler, loc. cit.
") The boiling point is remarkably low for a sesquiterpene. Possibly it may be explained by decomposition that takes place during boiling.