3 



CHAPTER 6 



ChenriLstry 



by James D. Loudon* 



6.1: Extraction and General Properties 



Colchicine is commonly extracted from the seeds and corms ot the 

 autumn crocus, Colclucum autumnale, Linn., but it is also present in 

 numerous species of Colchicum (Alboi) as well as in other Liliaceae 

 (Klein and Pollauf-) . Extraction is effected by alcohol (Zeiself 

 Chemnitius-*) and the concentrates after dilution with water are 

 freed from insoluble fats or resins. The aqueous solution is then 

 repeatedly extracted with chloroform and the colchicine is recovered 

 in the form of a crystalline addition complex with the solvent. From 

 this the chloroform is distilled off in steam or alcohol and evapora- 

 tion of the residual solution yields amorphous colchicine which may 

 be crystallized from ethyl acetate as pale yellow needles (Clewer, 

 Green, and Tutin'') . Chromatographic purification of the chloroform 

 solution on alumina greatly facilitates the procedure (Ashley and 

 Harris'") . 



Pure colchicine, CooHo-.O^X, forms fine, practically colorless needles, 



m.p. 155°; [ajo^ — 119.9° (c — 0.878 in chloroform), as determined 

 by Mr. T. Y. Johnston at Glasgow. It is readily soluble in alcohol, 

 chloroform, or in cold water, but is less soluble in hot water or in 

 cold benzene and is almost insoluble in ether. From these solvents 

 there is a tendency to crystallize with solvent of crystallization which 

 may markedly affect the melting point. Concentrated aqueous solu- 

 tions dc})osit crystals of the sesquihydrate which, despite its relatively 

 sparing solubility in water, does not crystallize from more dilute 

 solution unless induced to do so by seeding (Loudon and Speak- 

 man") . Dilute mineral acids and alkalis color colchicine an intense 

 yellow, while nitric acid (d,1.4) produces a violet color which slowly 

 changes to yellow and finally to green: other color-reactions are de- 



Lectuier in Chemistry, University of Glasgow, Scotland. 



[159] 



