VITAMIN D 305 



Hess (1925a) found that activated cholesterol did not lose its potency 

 by prolonged contact (24 hours) with acetone, chloroform, or benzene, 

 and Steenbock and Black (1924, 1925) reported that liver retained its 

 induced antirachitic potency for at least 2 months after having been 

 dried at 96° C. for 24 hours, and that activated oUve oil kept in a 

 stoppered bottle was found unimpaired in activity after 10 months, 

 while Nelson and Steenbock (1925) reported that a petroleum-ether 

 solution of the unsaponifiable fraction of cod-liver oil maintained its 

 potency for at least one and a half years. 



Results not concordant with the theory that cholesterol or phytosterol 

 can always be rendered antirachitic by ultra-violet irradiation were 

 cited by Steenbock and Black in 1925. 



Vitamin D from Ergosterol 



Schlutz and Morse (1925) considered the possibility that the 

 "substance in which the absorption spectrum is changed (and anti- 

 rachitic potency induced by irradiation) may be a small amount of 

 impurity in the cholesterol which is not removed by repeated crystalliza- 

 tions from alcohol, and which is exceedingly absorptive." 



Hess, Weinstock and Sherman (1926b) succeeded in separating 

 irradiated cholesterol into an active and inactive portion by precipitating 

 the inactive cholesterol with digitonin. The active fraction constituted 

 4 or 5 per cent of the original. 



Rosenheim and Webster ( 1927c) found both the unsaturated carbon 

 linkage and the secondary alcohol grouping essential to the precursor 

 of vitamin D. Upon fractionating irradiated cholesterol with digitonin 

 they found the active portion to be about 0.1 per cent when irradiated 

 in nitrogen. 



By recrystallizing, from acetone and hot methyl alcohol, some 

 cholesterol which had been irradiated in the air. Shear and Kramer 

 (1926a) obtained from the mother liquor about 5 per cent of crude oil, 

 40 per cent of which was not precipitable by digitonin. The cholesterol- 

 free oil gave positive reactions with the Shear aniline-hydrochloric acid 

 reagent, Lieberman-Burchard and Salkowski test, and the Lifschiitz 

 reaction for oxycholesterol. Both the crude and the cholesterol-free oil 

 obtained by these methods had antirachitic potency. When incorporated 

 in cottonseed oil the cholesterol-free oil retained its potency during two 

 months' storage. 



In 1926-1927, Hess and Windaus published evidence that cholesterol 

 or phytosterol recovered after being separated twice as the dibromide, 

 could not be activated. They questioned whether in previous work. 



