Cherry-laurel leaves are obtained from Prunus Laurocerasus, Linn. (N.O. Rosaceae), an evergreen shrub indigenous to Persia and Asia Minor, but cultivated in temperate regions. They are used in the fresh state. The leaves are alternate, shortly petiolate and coriaceous in texture. They vary usually from 12 to 17 centimetres in length, and from 4 to 5 centimetres in breadth. They are oblong or nearly obovate in shape, and taper towards both base and apex, the latter being acute and somewhat recurved. The margin bears strong, distant serrations. The upper surface is dark green and glossy; the lower is paler with a prominent midrib, near the base of which on either side are from two to four sugar glands. The unbroken leaves are odourless, but when bruised emit an odour of hydrocyanic acid and bitter almond oil.
Constituents.—The chief constituent of cherry-laurel leaves is the glucoside prulaurasin (laurocerasin) which has been obtained in long, slender, acicular, bitter crystals, melting at 120° to 122°; it closely resembles amygdalin, but is not identical with it, prulaurasin being the glucoside of racemic phenylglycollic acid, whereas amygdalin is the glucoside of d-phenylglycollic acid. It is contained in the parenchymatous tissue of the leaf, while the endodermis of the midrib and veins contains the enzyme emulsin, which is capable of hydrolysing it; when, therefore, the respective cells containing these constituents are ruptured the emulsin coming into contact with the laurocerasin decomposes it, giving rise to dextrose, hydrocyanic acid, and benzaldehyde. The leaves yield on an average about 0.1 per cent. of hydrocyanic acid; young leaves yield more than old ones, and unexpanded leaves may yield as much as 2.4 per cent.
Action and Uses.—Cherry-laurel leaves are used in pharmacy for the preparation of Aqua Laurocerasi, a distilled aromatic water containing 0.1 per cent. of hydrocyanic acid.
- Aqua Laurocerasi, B.P.—CHERRY-LAUREL WATER.
- Fresh cherry-laurel leaves, crushed, 80; water, 250. Add the crushed leaves to the water in a retort, distil 100, shake the distillate, and filter if necessary. Finally, adjust the strength of the product, either by adding diluted hydrocyanic acid, or by diluting with water, so that it shall contain 0.1 per cent. of real hydrocyanic acid. Cherry-laurel water is employed for internal and external use as a sedative, in place of diluted hydrocyanic acid. It is added to eye lotions (1 in 16), and is also prescribed as a flavouring agent. It should be preserved in well-closed bottles. Dose.—2 to 8 mils (1/2 to 2 fluid drachms)
- Aqua Laurocerasi, P.I.—CHERRY-LAUREL WATER, P.I.
- Strength, 0.10 per cent.
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.