A. W. Sangstor ( Determination of Alkaloid Structures University College 1 of the West lndies Jamaica I I. Isolation, characterization, and physical methods There are several well-known books on the chemistry of the alkaloids (I), but these tend to discuss the detailed chemistry of particular groups of alkaloids. It is the purpose of these articles to outline the general methods of approach in alkaloid chemistry.' The term "alkaloid" (alkali-like) is applied to the large group of basic nitrogen-containing natural prod- ucts of vegetable origin. They are usually colorless (berberine is yellow), well-crystalline solids, but some from the tobacco, hemlock, and pomegranate root bark are liquids,. The bases are usually optically active (mainly levorotatory) though a few such as coniine, cinchonine, laudanosine, pilocarpine, and pelletierine are dextrorotatory,andothers like berberine,papaverine, and pilocereine are optically inactive. In most cases the nitrogen atom forms an integral part of a cyclic structure. Classifications of alkaloids usually exclude simple amines, purines, hetaines derived from amino acids of proteins, choliie, and other bases of biological importance which in contradistinction to the typical alkaloids are not limited to one or a few species of plants. Alkaloids occur most abundantly in the higher orders of the plant kingdom and have been found in over 90 different families of flowering plants (2). The majority of these families belong to dicotyl- edenous orders and the number of monocotyleden~us families showing the presence of alkaloids is relatively The present article deals with methods of isohtion and char- acterization and the applications of physics1 methods to the de- termination of alkaloid structures. The second paper, to be published in October, will describe chemical methods of .structural determination. small. The Gymnosperms and Pteridophytes are poorly represented and so far as is known alkaloids are virtually absent from the lower groups of plants with the excep tion of one or two families of the fungi (e.g., ergot) (8). Alkaloids generally occur in the plant tissue at points of intense cell activity such as the leaves, roots, bark, and seeds and are generally regarded as plant met,abolic . byproducts. There is considerable variation in the alkaloidal content in the plant depending on such factors as time of reaping and methods of cultivation and selec- tion. A knowledge of the botanical origin of an alkaloid can be useful in giving indications of the structural type of alkaloid which is likely to be present. Plants of the same family generally tend to produce alkaloids of the same structural type. This is a generalization which has to be applied with caution for there are alkaloids such as nicotine and berberine which are found in several different plant families. Also plants such as the opium poppy give a number of different structural types of alkaloids though the latter are probably bio- genetically related. Alkaloids occur usually as salts of the common plant acids. In certain plants, however, a specific acid may be found associated with certain alkaloids such as quinic acid in the cinchona group, aconitic acid in the aconitines, and meconic acid in the opium group. A few alkaloids such as narceine and narcotine are found free in nature, probably because of their low basicity. A few alkaloids as found in the solanum and veratrum groups occur as glycosides of such sugars as glucose, rhamnose, and galactose. Other alkaloids as in the 454 / Journal of Chemical Education