Nature cf the Vesicating Constituent of Croton Oil, 2*61 



" An Enquiry into the Nature of the Vesicating Constituent of 

 Croton Oil" By Wyndham R. DUNSTAN, M.A., F.R.S., and 

 Lucy Everest Boole, F.I.C., Lecturer on Chemistry in the 

 London School of Medicine for Women. Received June 5, 

 —Read June 20, 1895. 



The nature of the vesicating, or more strictly the pustule- producing, 

 constituent, of croton oil is a long out-standing problem in chemical 

 pharmacology. Many attempts have "been made to disentangle from 

 the complicated mixture of fatty acids and glycerides expressed from 

 the seeds of Croton tiglium, known as croton oil, a single substance 

 exhibiting its remarkable power of raising pustules on the skin. 

 The conclusion first arrived at by Pelletier and Caventou that the 

 vesicating constituent is a volatile acid was afterwards proved to be 

 incorrect. The early experiments of Nimmo and of Warington 

 showed that alcohol is able approximately to separate the oil into two 

 parts, that which dissolves containing nearly the whole of the vesi- 

 cating constituent. The systematic investigation, of which an 

 extensive and somewhat involved account was published by Buch- 

 heiin* in the year 1857, confirmed and extended these observations. 

 It was then shown that the small proportion of croton oil which 

 may be dissolved by repeated extraction with alcohol (85 per cent.) 

 contains nearly the whole of the vesicating constituent. But the 

 bland oil which remains undissolved still retains the purgative power 

 of the original substance. When the solution of the vesicating 

 portion is mixed with aqueous ammonia and lead oxv-acetate, the 

 vesicating constituent remains in solution, and the precipitate con- 

 tains only the lead salts of fatty acids. The vesicating oil may be 

 saponified by alkalis the resulting soap still retaining the vesicating 

 property which is also exhibited by the magnesium, barium and lead 

 salts prepared from the soap. A partial purification of the vesicating 

 substance may be effected by extracting the lead salt with ether which 

 dissolves an inactive lead salt (lead oleate), but leaves a lead salt pos- 

 sessing powerful vesicating properties and furnishing, when decom- 

 posed with hydrochloric acid, an oily acid exhibiting the same property. 

 The ethyl salt, prepared in the usual way from this acid, is however 

 not vesicating, neither is the acid regenerated from it. From these 

 results Buchheim concluded that the vesicating property of croton 

 oil is due either to a peculiar non- volatile acid which he named 

 crotonoleic acid, or perhaps to a hydrolytic product of this acid. On 

 the other hand he suggests that the vesicating property may belong 



* Virchow's ' Archiv,' vol. 12, p. 1 ; see also his ' Lehrbuch der Arzneimittel- 

 leliie,' p. 364. 



