Oleum Laurocerasi. - Kirschlorbeerol. - Essence de Laurier-Cerise.
Origin and Production. Prunus Laurocerasus L., a native of Persia and the Caucasus, is frequently cultivated in moderate climates, more particularly as an ornamental plant.
As to its properties, the oil distilled from the cherry laurel leaves closely resembles that of the bitter almonds and can be distinguished only by its slightly different odor. The method of preparation is the same as that for bitter almond oil. The cut leaves are mashed with water, the mixture allowed to stand for some time and then distilled with steam. According to Umney2) the yield amounts to about 0,05 p. c.
As with the bitter almonds, the oil results upon the hydrolysis of a glucoside, the prulaurasin3), by emulsin. This glucoside crystallizes in thin, colorless needles, has a slightly bitter taste, melts at 120 to 122° and is readily soluble in water, alcohol and acetic ether, but is well-nigh insoluble in ether and deviates the plane of polarized light to the left, ([a]D - 62,69°). Prulaurasin has the formula C14H17N06 and is hydrolyzed by emulsin into hydrocyanic acid (8,59 p.c), glucose (61,24 p.c.) and benzaldehyde.
According to older statements the oil and hydrocyanic acid were supposed to exist in part as such in the leaves and not to owe their formation to the glucoside. However, C. Ravenna and M. Tonegutti1) have proven that the leaves do not contain free hydrocyanic acid.
1) Report of Schimmel & Co. April 1895, 11.
2) Pharmaceutical Journ. III. 5 (1875), 761.
3) H. Herissey, Compt. rend. 141 (1905), 959. - Journ. de Pharm. et Chim. VI. 23 (1906), 5. - The following papers have reference to laurocerasin as the glucoside was formerly known: Lehmann, Neues Repert. f. d. Pharm. 23 (1874), 449. - Pharm. Zeitschr. f. Russl. 24 (1885), 353, 369, 385, 401; Berl. Berichte 18 (1885), 569, Abstracts. - K. )ouck, Arch, der Pharm. 243 (1905), 421.
Properties. Cherry laurel oil can be distinguished from bitter almond oil only by the odor. This distinction becomes more apparent after the benzaldehyde has been combined with sodium acid sulphite. As to all other properties there is almost perfect agreement between the two oils. d16o1,050 (in a few instances as low as 1,0457 has been observed) to 1,066; aD mostly inactive, occasionally slightly active, + 0° 12' to - 0°46'; nD20o 1,540 to 1,543; soluble in 2,5 to 4 vol. of 60 p.c. alcohol (the solubility in 60 p. c. alcohol diminishes with age) and in 1 to 2 vol. of 70 p.c. alcohol; A. V. 1,6 to 2,8; hydrocyanic acid content 0,4 to 3,6 p.c, seldom higher (up to 8 p.c. and more!).
In as much as cherry laurel oil is very poisonous because of its hydrogen cyanide content, this fact should be taken into consideration when it is used.
Composition. Like bitter almond oil, cherry laurel oil contains benzaldehyde, hydrocyanic acid and benzaldehyde cyanhydrin (phenyl hydroxyacetonitrile)2). Naturally the same quantitative variations occur here as in the case of bitter almond oil (see this).
According to W. A. Tilden3), the oil contains traces of another substance in addition to those already mentioned. It is probably due to this that the oil owes the peculiar odor that differentiates it from bitter almond oil. If the oil be shaken out with sodium acid sulphite solution, a dark colored liquid remains which, upon oxidation with chromic acid, yields benzoic acid. Tilden suspects the presence of benzyl alcohol.
Adulteration and Examination. Cherry laurel oil is subject to the same adulterations practiced on bitter almond oil. The admixtures can be tested for as indicated for bitter almond oil on p. 584.