THE (ESTRUS-PRODUCING HORMONE 87 



general, the recent water-soluble extracts have been prepared 

 (a) by initial aqueous extraction, and (b) by treatment of the fat 

 extract with a view to freeing the active material. 



The first successful attempt appears to have been made by 

 Zondek and Brahn (661), who were able to detach the hormone 

 from the unsaponifiable matter of the oil by the use of acid. A 

 protein-free dialysable product, giving a clear solution in 

 water and having a high activity could be obtained. More 

 recently Zondek (648) has described a modification of this 

 process for securing the hormone from urine. The essential 

 feature of this modification is that the urine is extracted 

 directly with ether or chloroform, the use of alcohol being 

 avoided. 



Soon after the work of Zondek and Brahn, Laqueur and 

 co-workers (355, 356) reported the preparation of active aqueous 

 solutions direct from liquor folliculi, without the intermediate 

 production of an oily extract. Colloidal iron was added to 

 diluted follicular fluid, and the mixture centrifuged. This 

 yielded a turbid yellow fluid, which on partial evaporation at 

 low temperatures yielded a clear fluid containing the hormone 

 and a precipitate. The weight of the unit obtained by this pro- 

 cess was very great, about 50 mgms.,and for this reason Laqueur 

 re-introduced the use of organic solvents. Later, he reported 

 (355) the preparation of ' menformon ' from placenta by initial 

 boiling with benzene, extraction of the benzene extract with 

 alcohol, and treatment with dilute HCl. After centrifuging or 

 filtering, a very active water-clear solution is obtained. The 

 process appears to be similar in principle to that of Zondek and 

 Brahn, but it has been much criticised. The yields obtained 

 are said to be 600-700 m.u. from one placenta. Laqueur 

 stipulates a minimum purity of i m.u. = •! mgm. before the 

 substance may be called ' menformon.' Glimm and Wadehn 

 (245) obtained an aqueous solution by dissolving the oil in 40% 

 methyl alcohol and evaporating down in vacuo. Activity was 

 found in the aqueous residue. They (246) mention the partial 

 solubility of the active fraction of purified oily extracts in lime 

 water, while Loewe (410) also discusses the possibilities of 

 obtaining the material in water solution. 



Dodds and co-workers, after an indifferently successful 



