The leaves, fruit, and oil of Laurus nobilis, Linné.
COMMON NAMES: Laurel, Bay, Sweet bay, Sweet bay tree.
ILLUSTRATION: Bentley and Trimen, Med. Plants, 221.
Botanical Source.—The bay tree is either a shrub or small tree, usually growing to a height of from 20 to 30 feet. The leaves are short-petioled, oblong-lanceolate or oblong, veined, entire, or occasionally repand, somewhat acute at each end, and alternately affixed. They are smooth, leathery, glossy-green above, and paler beneath. The veins meet the midrib at an acute angle, and by means of small lateral veinlets, form a network which does not anastomose prominently near the leaf-margin. The flowers are dioecious, yellow, or yellowish-white, axillary, and borne in umbellate clusters. The fruit is an oval, deep-purple, almost black drupe.
History, Description, and Chemical Composition.—This plant, the well-known bay tree, is cultivated in Mexico, but is indigenous to the countries round about the Mediterranean. The leaves, expressed oil, and berries are employed.
I. FOLIA LAURI, Laurel leaves.—These, as well as the fruit, have been described above. When dried they are of a yellow-green or brown-green color, and possess an aromatic, bitter taste, and an aromatic agreeable odor. Their virtues are due to the presence of a volatile oil (1/3 per cent, Flückiger, Pharmacognosie, 1891; from 0.8 to 2.5 per cent, referred to dried leaves, Schimmel & Co.'s Report, October, 1893). It is probably identical with that from the fruit (which yields 0.8 per cent), but has a finer aroma. Its specific gravity is 0.924. According to Prof. Wallach (1889), the oil both from the leaves and the berries, contains for the most part cineol (eucalyptol), a terpene derivative, and small quantities of the terpene pinene. (For list of 22 essential oils in which cineol has been found to occur, see Schimmel & Co.'s Report, 1891, p. 68.)
II. FRUCTUS (or BACCAE) LAURI, Laurel or Bay-berries.—The dry berries are fragile, wrinkled, green-black, or black-brown, having a thin, friable integument enclosing an aromatic, oily, bitter, dicotyledonous kernel. Bonastre (1824) found the fruits to contain 0.8 per cent of volatile oil, 12.8 per cent of a green fatty oil., and 5.1 per cent of solid fat. According to analysis by Staub (1879) a variety of fatty matters are present, viz., the glycerides of acetic, oleic, linoleic, stearic, palmitic, myristic, and lauric acids, with small amounts of free acetic acid.
III. OLEUM LAURI, Oil of Laurel.—This is the expressed oil of the fruit, and is known also as Oleum Lauri Expressum, Oleum Laurinum, and Oleum Lauri Unguinosum. This oil is a green, granular, lard-like mixture, melting at 40° C. (104° F.), to a dark-green aromatic fluid, and consisting of a semi-solid fat (chiefly laurostearine, the glyceryl-ester of lauric acid C12H24O2), fragrant ethereal oil of bitter, balsamic taste, and green chlorophyll, which is permanent toward ammonia. An adulteration with indigo and curcuma can therefore be recognized by the formation of a red color upon the addition of ammonia water to an alcoholic extract of the oil. These coloring matters are also insoluble in ether, while oil of laurel is completely soluble with green color. Cold alcohol dissolves out essential oil and chlorophyll, leaving the fatty matter undissolved.
Action, Medical Uses, and Dosage.—The ancients valued bay leaves and laurel berries, using them as astringents, stimulants, and stomachics. In Europe pastry is at the present day flavored with the leaves, the belief prevailing that they render the food more easily digested. Active emmenagogue properties were formerly ascribed to laurel, and a decoction of the root-bark was in vogue as a remedy in dropsies and disorders of the urinary tract. Locally, in powder or decoction, the leaves and fruit were applied to insect bites and stings, scalp eruptions, and in leucorrhoea when accompanied by lax vaginal walls. All that now remains of this ancient medication is the use of the oil (both volatile and fixed) as a stimulant topical agent for rheumatic and other painful parts.
Related Species.— Ɣ Persea gratissima, Gaertner (Laurus Persea, Linné), Alligator pear. The fruit, from its long, pear shape, is also known as the Avacado pear, and from its butyraceous, rich pulp, Midshipman's butter, or Vegetable marrow. The tree closely resembles our sassafras tree, and the fruit is either green, purple, or red, the first variety being preferred by the natives who consume the fruit. If eaten before maturity the fruit is liable to induce dysenteric and febrile disorders. The seeds, which are the medicinal parts, are hard and globose, contain a milky juice which leaves a red ineffaceable mark upon a white surface when exposed to the atmosphere. The seeds contain amygdalin, and a ferment capable of producing therefrom hydrocyanic acid; fat, starch, mannit, and sugar; the fruit, gum, sugar, fixed oils, and salts of malic acid (Betancourt). The seeds are reputed anthelmintic, and are applied locally and given internally, in fluid extract, for rheumatism and intercostal neuralgia.