Robinia.—Locust Tree.
The bark and leaves of Robinia Pseudacacia, Linné.
Nat. Ord.—Leguminosae.
COMMON NAMES: Locust tree, Black locust, Yellow locust, False acacia.
Botanical Source.—This is a tree from 50 to 80 feet in height, and from 1 to 4 feet thick; the bark is rough and dark. The branches are numerous, smooth, and armed with stipular prickles. The leaves are unequally pinnate; the leaflets in from 8 to 12 pairs, ovate and oblong-ovate, thin, nearly sessile, and very smooth; the stipules minute, bristle-form, and partial. The flowers are white, fragrant, showy, and borne in numerous, axillary, pendulous racemes. Calyx 5-cleft, short, campanulate, slightly 2-lipped. Standard large and rounded, turned back, scarcely longer than the wings and keel. Stamens diadelphous; style bearded inside. The fruit is a legume, or linear, compressed pod, 2 to 4 inches in length, and about 6 lines wide, margined on the seed-bearing edge. Seed several, small, brown, and reniform (G.—W.). When young, the tree is armed with thorns, which disappear in its maturity.
History.—This tree, known by the names of Black locust and Yellow locust, is found in several parts of the United States, principally west of the Allegheny Mountains, being seldom found north of Pennsylvania, or in the Atlantic southern states; it blossoms in May. It is valued for the durability, hardness, and lightness of its wood. The bark and leaves are used, and yield their properties to water or alcohol. The bark of the root is the most active. The seeds are slightly acrid, and contain much oil., which may be obtained by expression. By steeping in water, their acridity is removed, and a very mild, useful meal may be then prepared from them. The inner bark is tough and fibrous.
Chemical Composition.—From the root of this plant Hlasiwetz (1852) isolated asparagin. The flowers, according to Zwenger and Dronke (1861; see Husemann and Hilger, Pflanzenstoffe, p. 1046), contain a yellow, crystallizable glucosid, robinin (C25H20O16), which, upon hydrolysis, is split into quercetin and a non-fermentable sugar. The bark of the locust tree, when chewed, produced violent emeto-catharsis (Amer. Jour. Pharm., 1887, p. 153; F. B. Power and Jacob Cambier, Pharm. Rundschau, 1890, pp. 29-38). The latter authors, searching for the poisonous principle, found it in an albuminous body (phytalbumose, 1.66 per cent), which is tasteless, soluble in water, insoluble in alcohol, and coagulated by heat, with complete loss of its toxic properties; for this reason some declare a decoction of the bark is inert. It is precipitated by tannic acid and by solution of potassium bismuth iodide. It is allied to ricin, the poisonous, albuminous constituent of the castor-oil seed. (For further reactions, see the original paper.) The authors, in addition, found an inert albumin (globulin, characterized by being insoluble in concentrated salt solution); small quantities of the poisonous alkaloid, choline (of the class known as ptomaïnes), fatty matter, inert resin, cane sugar (4.57 per cent, referred to air-dry bark), starch, gum, some tannin, coloring matter, and probably asparagin. The poisonous principle, in the form of an albuminous body, was likewise obtained by R. Kobert (Jahresb. der Pharm., 1891, p. 146).
Action, Medical Uses, and Dosage.—A decoction of the bark of the root is tonic in small doses, but emetic and purgative in large ones. An ounce of the bark boiled in 3 gills of water, operates as a cathartic in doses of ½ ounce, given morning and evening. The bark is supposed to possess some acro-narcotic properties, as the juice of it has been known to produce coma and slight convulsions. An overdose has produced symptoms very similar to those resulting from an improper dose of belladonna, and at the same time cured a case of fever and ague. The flowers possess antispasmodic properties, and form an excellent and agreeable syrup. The leaves, in doses of 30 grains, every 20 minutes, operate mildly and efficiently as an emetic. The drug should be tested for its effects upon gastro-intestinal and nervous affections.
