Oleum Amygdalarum amararum. - Bittermandelol. - Essence d'Amandes Ameres.
Origin. The almond tree, Prunus Amygdalus, Stokes (Amyg-dalus communis, L), which belongs to the family of Rosaceae, is cultivated in Europe, Asia and northern Africa, and recently also in California. In the course of time several cultural varieties have resulted, which, however, differ merely in the size of their fruits and seeds. Those trees which yield bitter almonds reveal no constant botanical differences from those that produce sweet almonds. Probably all almond trees originally produced bitter almonds and it may be that continuous cultivation resulted in the sweet variety.
Production. Of the bitter almond oil of commerce only a very small amount is obtained from bitter almonds. For its technical production the seeds of the apricot, Prunus Armeniaca, L, are used almost exclusively. Its oil in no way l) H. Haensel, Chem. Zentralbl. 1906, I. 1497.
differs from that of the bitter almond1). The apricot kernels, that is the seeds without the hard shells, were formerly imported into Europe almost exclusively from Asia Minor and Syria, the home of the tree. They were designated peach kernels2). More recently other countries, more particularly Morocco, California and Japan have acquired importance as producers3).
Before the kernels are used for the production of the volatile oil they must be deprived of their fatty oil. They are ground in a roller mill to a coarse powder and exposed to a pressure of 350 atmospheres in a hydraulic press. Upon cold expression the bitter almonds yield about 50 p.c, the apricot kernels about 35 to 38 p.c. of fatty oil.
By means of a chaser mill (vertical millstones) the press cakes are reduced to a fine powder and are then ready for the production of the volatile oil. This does not occur as such in the seeds, but results upon fermentation in a similar manner as do mustard oil and oil of wintergreen. In the presence of water the glucoside amygdalin, which is present in the bitter almond and in the apricot kernel, is changed by the enzyme, emulsin, to benzaldehyde, hydrocyanic acid and glucose.
The reaction is expressed by means of the following equation: C20H27No11 + H20 = C6H6Cho + CNH + 2C6H1206
Amygdalin Water Benzaldehyde Hydrocyanic Glucose acid.
As to the immediate products which result in this reaction, a lively controversy has arisen between K. Feist4), L. Rosen-thaler"), S. ). M. Auld6) and Bourquelot and Herissey7) which cannot here be entered into. It has been shown that emulsin is no definite chemical compound but a mixture of enzymes to which different names have been assigned. Leaving out of consideration the formation of the glucosecyanhydrin, the system amygdalin-emulsin, according to Rosenthaler's elaborate investigations1), presents the following reaction possibilities.
1) Comp. G. de Plato, On the transformation of hydrocyanic acid during the ripening process of the almond. Annali della R. Staz. chim.-agr. sperim. II. 4 (1910), 117; Report of Schimmel & Co. October 1911, 19.
2) The kernels of the peach, Prunus Persica, Jess., likewise yield an oil of equal value to that of bitter almond oil.
3) Comp. O. Tunmann, Der Drogenhandel Hamburgs. Apotheker Ztg. 26 (1911), 579.
4) Arch, der Pharm. 246 (1908), 206, 509; 247 (1909), 226, 542; 248 (1910), 101.
6) Ibidem 246 (1908), 365, 710. - Biochem. Zeitschr. 14 (1908), 238; 15 (1909), 71, 257. - Arch, der Pharm. 248 (1910), 105.
6) Journ. chem. Soc. 93 (1908), 1251, 1276; 95 (1909), 927.
7) Journ. de Pharm. et Chim. VII. 6 (1912), 246.
I. Amygdalin, when reacted upon by amygdalase-) yields mandelic nitrile glucoside and glucose. II. When acted upon by prunase3), mandelic nitrile glucoside is resolved into d-benzaldehyde cyanhydrin and glucose.
III. d-Benzaldehyde cyanhydrin, when acted on by d-hydroxynitri-lase4) resolves itself into benzaldehyde and hydrocyanic acid.
IV. Under the influence of a d-hydroxynitrilase5), benzaldehyde and hydrocyanic acid combine so as to form d-benzaldehyde cyanhydrin.
V. Benzaldehyde and hydrocyanic acid likewise combine to form inactive benzaldehyde cyanhydrin. VI. By means of d-hydroxynitrilase, inactive benzaldehyde cyan-hydrin can be broken down asymmetrically with formation of l-benzaldehyde cyanhydrin. As a result of the use of an emulsin rich in this enzyme, the benzaldehyde cyanhydrin formed upon the hydrolysis of the amygdalin may be strongly lasvogyrate.
Inasmuch as the emulsin loses its activity at boiling temperature the fermentation must be completed at a temperature below 60° before the distillation is begun. Hence the almond powder is made into a mash with 6 to 8 parts of water at from 50 to 60° and is allowed to stand for about 12 hrs. After which time the oil formed is distilled over with steam.
1 Arch, der Pharm. 248 (1910), 534; 251 (1913), 85. - Additional literature will be found in vol. I of this text-book, p. 534, footnote 3; also in the Report of Schimmel &Co. April 1913, 20.
2) According to Caldwell, Courtauld, H. E. and E. F. Armstrong and Horton; comp. H. Euler, Allgemeine Chemie der Enzyme, p. 17. According to G. Bertrand and A. Compton (Bull. Soc. chim. IV. 9 , 1071) emulsin consists of amygdalinase and amygdalase. At moderatly increased temperatures both act with about equal readiness on amygdalin. For a test period of 15 hrs. the best temperature for the action of the enzymes on amygdalin is +40°; for a period of 2 hrs. it is +56° for amygdalase and +58° for amygdalinase.
3) H. E. and E. F. Armstrong and E. Horton, Proceed. Royal Soc. London, B. 86 (1912), 359, 363; Chem. Zentralbl. 1912, II. 1292.
4) Arch, der Pharm. 248 (1910), 534.
5) Ibidem 251 (1913), 56, 85.
According to the directions of M. Pettenkofer1), 12 parts of almond powder deprived of its fatty oil are stirred into 100 to 120 parts of boiling water and the mixture kept at the boiling temperature of water for 15 to 30 minutes. It is then set aside to cool. To the cooled mixture 1 part of fresh bitter almond powder, mixed with 6 to 7 parts of water, is added and the mixture allowed to macerate for 12 hours.