145 



Cyanogenesis in Plants. 



Part IV. — The Occurrence of Phaseolunatin in Common Flax 



(Lirmm usitatissimum). 



By Wyndham E. Dunstan, M.A., LL.D., F.R.S., T. A. Henry, D.Sc, 

 Principal Assistant in the Scientific and Technical Department of the 

 Imperial Institute, and S. J. M. Auld, Ph.D. 



(Received April 11 —Read May 10, 1906.) 



In Part III of this series of papers* it was shown that the seeds of 

 Phaseolus lunatus, as produced by the uncultivated plant in Mauritius, 

 contained a new cyanogenetic glucoside, phaseolunatin, which was proved 

 to have the constitution of a dextrose ether of acetonecyanhydrin. Phaseo- 

 lunatin was further shown to undergo hydrolysis by mineral acids or by the 

 action of the characteristic, emulsin-like enzyme also present in the seeds, 

 yielding, as final products, acetone, hydrocyanic acid, and dextrose. 



This decomposition of the glucoside by the enzyme takes place when 

 the ground seeds of Phaseolus lunatus are mixed with water, and from 

 such a preparation it is comparatively easy to isolate and identify the 

 hydrolytic products, acetone and hydrocyanic acid. The simultaneous 

 production, therefore, of these two substances from plants by mere contact 

 with water may be taken as indicating the occurrence in such plants of 

 phaseolunatin or some similar derivative of acetonecyanhydrin, and of an 

 enzyme capable of decomposing this compound under the conditions specified. 



Before the isolation of phaseolunatin, it was observed by Van Romburghf 

 that various plants, on crushing with water and subsequent distillation, 

 yielded acetone, and that in some cases this was accompanied by hydrocyanic 

 acid. The plants mentioned by Van Romburgh as yielding both these 

 products are Phaseolus lunatus, Manihot utilissima (the Cassava plant from 

 which the tapioca of commerce is prepared), Manihot glaziovii (the Ceara 

 rubber tree), and Hevea brasiliensis (the Para rubber tree). This author 

 stated that he was at first inclined to associate the simultaneous production 

 of acetone and hydrocyanic acid from these plants with the occurrence in 

 them of a compound of these two substances, but his subsequent discovery 

 that several plants, notably Erythroxylon Coca, from which the " Coca leaves," 

 largely used as a stimulant in South America, are procured, and Pogostemon 

 cristatus, yielded acetone unaccompanied by hydrocyanic acid, led him to 

 * ' Boy. Soc. Proc.,' 1903, vol. 72, p. 285. 



t ' Annales du Jardin Botanique de Buitenzorg,' 1899, vol. 2, 1, p. 2. 



