Elemi. Gum Elemi. Elemi, Fr.—This concrete resinous exudation is official in several of the European Pharmacopoeias. The variety which is mostly used is known as Manila elemi and is derived from Canarium commune L. and probably also from C. lusonicum Gray (Fam. Burseraceae). The name elemi is applied commercially to a large number of resins. The true elemi varieties contain from 20 to 25 per cent. of amyrin. These are further distinguished as "hard" or "soft" elemi, which are differentiated by the fact that the " soft" elemi contains from 20 to 25 per cent. of volatile oil. There are a number of other commercial varieties of elemi. The so-called carana-elemi is obtained from Protium Carana (Humb.) L. March., a tree growing in Venezuela and Northern Brazil. Brazilian Almesseya-elemi is obtained from Protium heptaphyllum March., var. Brasiliense Engl. East African elemi is probably obtained from. Boswellia Frereana Birdwood. Yucatan elemi is derived from Amyris Plumieri DC.. All these plants belong to the Burseraceae. The elemi is obtained by incisions into the trees, through which the juice flows and concretes upon the bark.
Carana-elemi occurs in masses of a greenish-yellow color, externally hard, internally soft, with a peculiar fennel-like aromatic odor. It is insoluble in water, soluble in sulphuric ether, chloroform, and benzene. According to Tschirch and Saal, carana-elemi contains 20 per cent. of exceedingly acrid resin. (A. Pharm., Bd. 241, 1903.)
Elemi is in masses of various consistence, sometimes solid and heavy like wax, sometimes light and porous; unctuous to the touch; diaphanous; of diversified colors, generally greenish with intermingled points of white or yellow, sometimes greenish-white with brown stains, sometimes yellow like sulphur; fragile and friable when cold; softening by the heat of the hand; of a terebinthinate somewhat aromatic odor, diminishing with age, and resembling to some extent that of lemon and fennel; of a warm, slightly bitter, disagreeable taste; entirely soluble, with the exception of impurities, in boiling alcohol; and affording a volatile oil by distillation. "Moistened with rectified spirit, it breaks up into small particles, which, when examined by the microscope, are seen partly to consist of acicular crystals." Br., 1885. Elemi is sometimes adulterated with rosin and turpentine.
According to Bacon (Philippine Journal of Science, 1909, iv, p. 93), the Manila elemi is derived from the Canarium luzonicum Miq. When first collected it is soft, but later becomes hard on exposure to the air and light, which has given rise to the belief that there were two varieties of the Manila gum. It is collected by incising the tree at the time when it is developing new leaves, the juice exuding through the bark and collecting in lumps at the point of the incision.
The two varieties of elemi that have been investigated chemically are the Manila, or soft elemi, and the Brazilian, or hard elemi. The Manila elemi contains 10 per cent. of an ethereal oil (made up of phellandrene and dipentene), amyrin, C30H50O, of which, according to Vesterberg, the isomeric varieties a- and b-amyrin are present, an amorphous resin, small amounts of a-manelemic acid, C37H56O4, ß-manelemic acid, C44H80O4, bryoidin, C20H38O4, and a bitter principle. The Brazilian elemi (protium elemi) contained protomyrin, 30 per cent.; protolaminic acid, 25 per cent.; and protolaresine, 37.5 per cent. The protomyrin has the same melting point and formula as the amyrin from Manila elemi.
Elemi has properties analogous to those of the turpentines, but is exclusively applied to external use. In the United States it is rarely employed even in this way, except as a constituent of plasters prepared upon the large scale. In the pharmacy of Europe it enters into the composition of numerous plasters and ointments. Unguentum Elemi (Br. Ph., 1885) was of the strength of about 20 per cent.
The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.