Upon steam-distillation of the dry herb of Chelidonium majus, L. (family Papaveraceae), H. Haensel2) obtained 0,013 p.c. of a brown oil with a pleasant odor which congealed in the cold and which was soluble in 45 parts of 90 p. c. alcohol. d40o0,9374.
1) Comp. also Perfum. and Essent. Oil Record 3 (1912), 111, 124, 239. 2) Apotheker Ztg. 23 (1908), 279. - Chem. Zentralbl. 1908, II. 1837.
The volatile oils obtained from the crucifers are not contained as such in the parts of plants that yield them, but in the form of glucosides. They result from a process of fermentation, the hydrolysis of the glucosides being brought about by enzymes which are present in the same organs. The products of this hydrolysis are glucose and mustard oils, the latter being esters of isothiocyanic acid (See mustard oil, p. 522). According to L. Guignardl) the cruciferous glucosides are located in the parenchymatous tissues, more particularly those of the bark and the embryo of the seeds. The enzyme, mostly myrosin, is deposited in special "myrosin cells" that are distributed throughout all the tissues, including those of the pericarp. Whether the enzyme of all crucifers is the same has not yet been determined. This much, however, has been established, that the enzymes of this family are able to hydrolyze the gluco-sides contained therein.
According to T. Bokorny2) the action of the enzyme is restricted to certain limits of temperature. Water of 75° kills the myrosin in fifteen minutes, a fact to be borne in mind when distilling the volatile oils. Moreover, the enzymes are rendered inactive by the presence of certain substances, such as formaldehyde, 1 p. c sulphuric acid, a 0,1 p. c. solution of corrosive sublimate, or silver nitrate. However, for the purpose of hydro-lyzing the glucoside, the destroyed enzyme of the plant in question can be replaced by the water-soluble ferment of comminuted white mustard.
Not all the mustard oil glucosides have been isolated in the pure state. In some instances conclusions have been drawn from the end products of the reaction as to the nature of the glucoside.
Of this group of glucosides, sinigrin, the glucoside of black mustard, has been known longest and is most thoroughly investigated. In addition to black mustard it occurs in Thlaspi arvense, L., Cochlearia Armoracia, L, Sisymbrium Alliaria, Scop., and dissolved in the aqueous distillate, it was extracted by shaking with benzene. The yield amounted to 0,115 p.c. The light-yellow crude oil became colorless upon rectification. Three-fourths of the oil boiled at 231,5°, the boiling point of phenylacetonitrile or benzyl cyanide, C6H5. Ch2cm. The identity of the oil with this substance was established by converting it into phenylacetic acid melting at 77° and by the analysis of its silver salt. The lower fractions of the oil contain small amounts of a sulphur-containing compound, the composition of which was not determined.
1) Compt. rend. Ill (1890), 249.
2) Chem. Ztg. 24 (1900), 771, 817, 832.
Brassica Rapa, L. Glucotropaeo/in (hydrolyzable to benzyl mustard oil) is found in Lepidium sativum, L. and in Tropaeolum ma/us, L. belonging to the family Tropaeo/aceae. Glucocochlearin (yielding sec. butyl mustard oil) is contained in Cochlearia officinalis, L. and Cardamine amara, L. Gluconasturtiin (yielding phenylethyl mustard oil) is found in Nasturtium officinale, R. Br., in Barbaraea praecox, in Brassica Rapa, var. rapifera, Metzg. and probably also in Reseda odorata (family Resedaceae). The glucoside of Brassica Napus, L. has been named gluconapin (yielding crotonyl mustard oil). Mustard oil-like compounds which are, no doubt, referrable to glucosides, are yielded by Iberis amara, L., Capsella bursa pastoris, Monch., Sisymbrium officinale, Scop., Matthiola annua, R. Br. and other plants1).