Origin, Production and Properties. The seeds of Nigella damascena, L, known occasionally as Schwarzkummel, yield upon distillation 0,4 to 0,5 p. c. of an oil with a beautifully blue fluorescence, which has the agreeable odor and taste of juniper berries. d15o 0,895 to 0,9153); aD + 1°4' to - 7,8°3); n20o 1,55823). In 90 p. c. alcohol the oil is but imperfectly soluble, in absolute alcohol it is soluble in all proportions.
Composition. The principal constituent of nigella oil4) is the alkaloid damascenine, C10H13O3N, which produces the characteristic fluorescence, and which was first prepared by A. Schneider5). By shaking the oil with tartaric acid and subsequent decomposition of the tartrate with soda6), as much as 9 p.c. can be isolated from the oil. The alkaloid can also be obtained by percolating the comminuted seed with dilute hydrochloric acid, supersaturating the solution with soda and extracting with petroleum ether. From the petroleum ether solution the chlor-hydrate of the base can be shaken out in a pure condition by means of hydrochloric acid. In this manner 18 kg. of seeds yielded 110 g. of hydrochlorate1).
1) Berl. Berichte 24 (1891), 2459.
2) Report of Schimmel & Co. April 1895, 75.
3) H. Haensel, Apotheker Ztg. 15 (1911), 28.
4) The statements found in the reports on earlier investigations are largely contradictory. This is due to the fact that in some instances the seeds of Nigella damascena, L., were examined, in others those of Nigella sativa, L - H. G. Greenish, Pharmaceutical Journ. III. 12 (1882), 681. - Reinsch, Jahrbuch f. prakt. Pharm. II. 4 (1841), 385; Pharm. Zentralbl. 1842, 314. - Fluckiger, ibidem HI. 2 (1854), 161.
5) Pharm. Zentralh. 31 (1890), 173 and 191. Comp. also the inaug dissertation by the same author, Erlangen 1890.
6) Report of Schimmel & Co. October 1899, 38.
Pure damascenine boils with slight decomposition at 270° (750 mm.)'2) or in vacuum at 157° (10 mm.). It congeals in the cold and melts at 26°. According to A. Schneider it yields crystalline salts with acids. With platinum chloride, gold chloride, and mercuric chloride, crystalline double salts result. With the general alkaloidal reagents it produces characteristic precipitates: solution of iodine in potasium iodide produces a purplish-brown precipitate; potassium bismuth iodide, a brown precipitate; potassium mercuric iodide and phosphomolybdic acid yield white precipitates.
The problem of the constitution of damascenine has been attacked consecutively by Schimmel & Co.3), H. Pommerehne4) and O. Keller5). However, A.). Ewins2) first succeeded in proving the constitutional formula of damascenine by its synthesis, thus demonstrating it to be the methyl ester of a 2-methylamino-3-methoxvbenzoic acid.
The synthesis of damascenine was accomplished in the following manner: with the aid of dimethyl sulphate, m-hydroxy-benzoic acid was converted into m-methoxybenzoic acid. When nitrated, this yielded a mixture of nitro products from which the 2-nitro-3-methoxybenzoic acid could be isolated without difficulty. This was reduced to 2-amino-3-methoxybenzoic acid which, when heated with methyl iodide in a sealed tube, yielded the hydriodide of 2-methylamino-3-methoxy benzoic acid. By heating it with freshly precipitated silver chloride it was converted into the corresponding hydrochloride (m.p. 210 to 211°) which is identical with the hydrochloride of damasceninic acid. By passing hydrogen chloride into the methyl alcoholic solution of the hydrochloride, the hydrochloride of the methyl ester is produced. When hydrogen chloride is split off, this yields methyl-2-methylamino-3-methoxybenzoate or damascenine (m. p. 23 to 24°). Mixed with the natural product, this synthetic damascenine suffers no lowering of the melting point.
1) Arch, der Pharm. 237 (1899), 475.
2) Journ. chem. Soc. 101 (1912), 544.
3) Loc. cit.
4) Arch, der Pharm. 238 (1900), 546; 239 (1901), 34; 242 (1904), 295. 5) Ibidem 242 (1904), 299; 246 (1908), 1.
The seeds of other species of Nigella have also been examined for alkaloids by O.Keller1). In the seeds of Nigella aristata he is supposed to have found a new alkaloid, methyl-damascenine, in addition to damascenine. According to Ewins, however, this is an error. The methyldamascenine of Keller, C10H13O3N, is by him supposed to be identical with the dama-scenine of Nigella damascena to which the above formula should be assigned. Keller's attempts to isolate alkaloids from the seeds of Nigella sativa, N. arvensis, N. orientalis, N his-panica, N. Garidella, N. integrifolia and N. divers/folia by extraction with dilute hydrochloric acid gave negative results.