Laurocerasi Folia. Br. Cherry-Laurel Leaves.
"Cherry-Laurel Leaves are the fresh leaves of Prunus Laurocerasus, Linn." Br.
Cherry Bay; Laurier-cerise, Fr. Cod.; Kirschlorbeer, G.; Lauroceraso, It.; Laurel-cerezo (Hoja de), Sp.
Prunus Laurocerasus is a small evergreen tree, rising 15 or 20 feet, with long, spreading branches, which, as well as the trunk, are covered with a smooth, blackish bark. The leaves are oval-oblong, petiolate, from five to seven inches in length, acute, finely toothed, firm, coriaceous, smooth, beautifully green and shining, with oblique nerves, and yellowish glands at the base. The flowers are small, white, strongly odorous, and disposed in simple axillary racemes. The fruit is an oval drupe, very similar in shape and structure to a small black cherry. The cherry-laurel is a native of Asia Minor, but is cultivated in Europe, both for medicinal use and for the beauty of its shining evergreen foliage. Almost all parts of it have more or less of the odor of hydrocyanic acid.
In their recent and entire state cherry-laurel leaves have scarcely any odor; but, when bruised, they emit the characteristic odor of the plant in a high degree. Their taste is somewhat astringent and strongly bitter, with the flavor of the peach kernel. They are officially described as "thick, coriaceous, on short, strong petioles, oblong or somewhat obovate, from twelve to eighteen centimetres long, tapering towards each end, recurved at the apex, distantly but sharply serrate and slightly revolute at the margins; dark green, smooth and shining above, much paler beneath; midrib prominent, with one or two glandular depressions on the under surface near its base. Inodorous, but emitting when bruised an odor resembling that of prussic acid." Br.
Cherry-laurel leaves are sometimes substituted by the leaves of other species of Prunus. These are readily distinguished in that they do not possess the characteristic glandular hairs which occur on the basal portion of the leaves and petioles of P. Laurocerasus. (B. P. G.) 1907, p. 325.)
Cherry-laurel leaves yield a volatile oil containing benzaldehyde and hydrocyanic acid by distillation with water, which they strongly impregnate with their flavor. One pound, avoirdupois, of the fresh leaves yields 40.5 grains of the oil. (Ph. Cb., 1855, 205.) The oil resembles that of bitter almonds, for which it is said to be sometimes sold in Europe, where it is employed to flavor liquors and various culinary preparations, but, as the glucoside of cherry-laurel leaves is decomposed more slowly than ordinary crystallized amygdalin, it is liable to hold hydrocyanic acid, and hence to be poisonous. The glucoside referred to has been termed laurocerasin, or "amorphous amygdalin." It is decomposed by emulsin into hydrogen cyanide, benzaldehyde, and sugar, but more slowly than ordinary amygdalin. Its optical activity also differs from that of ordinary amygdalin. (Jacobsen, Die Glykoside, 25.) That the oil exists already formed, to a certain extent, in the fresh leaves, is rendered probable by the fact, stated by Winckler, that they yield it in considerable quantity when distilled without water. (J. P. C.) xxv, 195.) The fresh leaves are used to flavor milk, cream, etc., and more safely than the oil, though they also are poisonous, when too largely employed.
Uses.—The leaves of the cherry-laurel possess properties similar to those of hydrocyanic acid, and the water distilled from them is much employed in various parts of Europe for the same purposes as that active medicine. But it deteriorates by age, and therefore, as kept by pharmacists, must be of variable strength. J. Broker, a Dutch pharmacologist, has satisfied himself, by numerous experiments, that the proportion of hydrocyanic acid in the leaves varies with the season, the age of the plant, the character of the soil and of the weather, and thinks that, in consequence of this variability, they are inferior for medicinal use to bitter almonds, which in this respect have a more uniform composition. He found the proportion of the acid in the leaves greatest in July, and least in February. (B. F. M. R., Oct., 1868, p. 517.) It is not, therefore, to be regretted that the want of the plant in this country has prevented the general introduction of so variable a remedy as the distilled water. (See Aqua Laurocerasi.)
Off. Prep.—Aqua Laurocerasi, Br.