AL'KALOIDS ( Literally, resembling alkali). A term applied to all nitrogenous basic com pounds. found in plants. The alkaloids are as a rule the most important medicinal principles of the plants from which they are derived, and in moderate (loses constitute therapeutic agents of the highest value. In larger quantities, how ever, they are extremely poisonous. Most alkaloids are chemically composed of carbon, hydrogen, nitrogen, and oxygen. A very few, including the well-known nicotine of tobacco, and coniine, con tain carbon, hydrogen, and nitrogen, but no oxygen. The alkaloids that contain oxygen are non-volatile solids, and can mostly be obtained in the form of colorless crystals. Those that contain no oxygen are volatile liquids. The sep aration of the two groups of alkaloids can there fore he readily effected by simply subjecting the given mixture to a process of distillation.
Many alkaloids are chemically related to the organic bases called pyridine and ryttino/inc (qq.v.). Thus confine, nicotine, piperine, atro pine, cocaine, and others have been shown to be derivatives of pyridine: quinine, cinchonine, strychnine, brueine. etc., have been shown to be derivatives of quinoline. Other alkaloids, in cluding caffeine, or theine, and theobromine, are related to uric acid. Iuu contradistinction to these true, or alkaloids, a certain number of substances not found ready-formed in nature, but prepared artificially in the chemi cal laboratory, have been termed artificial alka loids. Antipyrine, kairine, thalline, and the ordinary acet-anilide, or autifebrine, are ex amples of artificial alkaloids, which resemble the natural alkaloids both in their chemical con stitution and physiological action. Of the natu ral alkaloids but very few have as yet been reproduced artificially. Another few, including atropine and cocaine, have been reconstructed from their decomposition products.
The separation and detection of the several alkaloids is often a matter of great importance in medico-legal examinations. The analytical
method usually employed (the so-called Stas Otto method) consists in partially separating the given mixture by the use of water, alcohol, ether, chloroform, benzine, and amyl alcohol, then applying tests depending upon the char acteristic reactions of the various constituents. Tannic, picric, and phospho-molybdic acids, potas sium-mercuric iodide, and a few other reagents form insoluble precipitates with the alkaloids.
The following are the more important natural alkaloids, their characteristic properties, and the sources from which they are obtained: A•onitinc, CJI.,,NO„; melting point, 184° C.; insoluble in water; soluble in alcohol, ether, and chloroform; a violet coloration is produced when its solution in phosphoric acid is cautiously evaporated. It is found in aconite, the tuber of Aconit napcllus Linms.
Atropine, or Maurine, melting point. 115° C.; soluble in alcohol and chloro form; sparingly soluble in hot water and in ether. It does not exist ready-formed in nature, but is produced by the transformation of the alkaloid hyoscyamine.
Berberine, melting point, 120° C.; soluble in hot water or alcohol; its aqueous solution is colored red by chlorine. It is found in yellow puecoon, the rhizome and roots of Hydrastis eanadensis Linn6; also, in Canadian moonseed, the rhizome and roots of Menispermum canadense Linne, and in other plants.
1 !I melting point, 100° C.; soluble in alcohol and in chlorofrom. It imparts to strong nitric acid a, red coloration that gradually changes to yellow; the coloration becomes violet on of stannous chloride. It is found, along with strychnine, in mix vomica.
Caffeine, or Vieille, melting point, 230.5° C.; soluble in hot water and in chloro form; sparingly soluble in hot alcohol. If its solution in chlorine water is evaporated and am monia added to the residue, the latter turns pur ple. It is found in many plants and is con tained in considerable qnantities in tea and coffee.