Tonka Bean. Coumarouna odorata, Coumarouna oppositifolia.
Tonka Bean. Feve Tonka, Fr. Tonkabohnen, G.—The seeds of Coumarouna odorata of Aublet, a large tree growing in Guiana and Northern Brazil which yields the Dutch Tonka Bean; and of C. oppositifolia (Aubl.) Taub, which is the source of the English tonka bean. The fruit is an oblong-ovate pod, enclosing a single seed, from 3 to 4 cm. long and about 1 cm. wide, usually somewhat compressed, with a dark brown, wrinkled, shining, thin, and brittle skin, and a light brown, oily kernel. The seed has a strong, agreeable, aromatic odor, and a bitterish, aromatic taste. Its active constituent is a crystallizable, odorous substance, called coumarin or cumarin, C9H6O2. It is the anhydride of coumaric acid, C9H8O2. It is capable of sublimation; but, to obtain it in crystals in this way, a low temperature is necessary. (Waddington, P. J., 1868, 410.) This substance is sometimes found in a crystalline state, between the two lobes of the kernel. Coumarin appears to be a widely spread substance which has been found in many species of plants, notably in species of Melilotus (fam. Leguminosae), sweet vernal grass (Anthoxanthum odoratum L.., and related grasses, and Trilisa odoratissima (Walt.), Cass. (Liatris odoratissima Willd.) (fam. Compositae), a plant sometimes used to protect woollens from moths. (A. J. P., 1859, 556; also 1899, 133; see also Chem. Gaz., 1852; D. C., Nov., 1887.) Gossmann obtains coumarin in the following manner. The beans, cut finely, are heated for a long time with an equal bulk of alcohol of specific gravity 0.863, nearly to boiling, and, the tincture being decanted, the residue is treated in the same manner. The tinctures are mixed, the alcohol distilled off until turbidness appears, when four times the bulk of water is added, which precipitates coumarin and fatty matter. The precipitate is then heated to boiling, and the liquid passed through a moistened filter. The fatty matter remains on the filter, and the hot solution which passes deposits the coumarin on cooling. More may be obtained by concentrating the liquid, and may be purified by animal charcoal. One pound of the beans yielded 108 grains of coumarin. Coumarin has been prepared synthetically by heating salicylic aldehyde with sodium acetate and acetic anhydride, whereby acetocoumaric acid is formed, which decomposes further into acetic acid and coumarin. It has also been obtained by the action of phenol upon the malic acid. Tonka bean is used to adulterate tincture and extract of vanilla and to flavor snuff, being either mixed with it in the state of powder or put entire into the snuff box. Coumarin adulterated with acetanilid has been found in the market. (Schim. Rep., 1893, 67.) Tonquin butter is an article of commerce in Holland. It is the fatty substance of tonka beans; it was analyzed by M. Duyk, it has the sp. gr. of 0.888, melting point is 28° C. (82.4° F.), saponification number 25.7. (Rep. de Pharm., 1908.)
Ellinger (A. E. P. P., 1908, Suppl.) found the fatal dose of coumarin for the rabbit to be 0.3 Gm. per kilo. He confirmed the statement of Kohler (Cb. M. W., 18.75) that it acted as a narcotic, but could not find evidence of cardiac depression. The fluidextract of the bean has been used with asserted advantage in whooping cough in doses equivalent to from five to eight grains (0.32-0.5 Gm.) for children five years old. (A. J. P., 1869, 27.)