VITAMIN D 307 



be rendered antirachitic by irradiation. The sterol nature of the pro- 

 vitamin is shown by the fact that it can be concentrated through 

 precipitation with digitonin and separation from cholesterol-digitonide by 

 fractional extraction with xylene. Since such sensitiveness to oxidation 

 is characteristic of only one known sterol, ergosterol, Rosenheim and 

 Webster studied ergosterol spectroscopically and found absorption bands 

 in the same region as in cholesterol purified by ordinary means, but 

 from 1,500 to 2,000 times more intense. They summarized their findings 

 as follows : "As a result of the irradiation the absorption bands dis- 

 appear in the critical region of 280 to Z\0 ^[x just as in the case of non- 

 purified cholesterol ; at the same time the product loses its property of 

 being precipitated by digitonin. If provitamin is ergosterol, or an un- 

 saturated sterol of similar constitution the amount present in ordinary 

 cholesterol would be of the order of 0.05%." ... "A daily dose of 

 1/10000 mg. of irradiated ergosterol cured and prevented rickets in rats 

 on a rachitogenic diet. Tests with still smaller quantities, not yet com- 

 pleted, indicate that the limit of activity will prove to be less than 

 1/50000 mg." . . . "These results seem to justify the conclusion that 

 the naturally occurring parent substance of vitamin D is ergosterol or a 

 sterol highly unsaturated and of similar constitution possessing the same 

 absorption spectrum and physiological activity." Soon afterward, Rosen- 

 heim and Webster ( 1928) pointed out also that not only the typical ring 

 structure, but also the specific relative positions in which the three 

 double bonds are present in the molecule of ergosterol appear essential 

 for the photochemical conversion of a sterol into vitamin D. They 

 regard the position of ergosterol as parent substance of vitamin D to be 

 unique. 



The finding of Anderson and Shriner (1926) that different fractions 

 of sterols prepared from corn oil show decided dififerences in optical 

 rotation, stability and solubility, led Hess and Anderson (1927) to study 

 the physiological activity of irradiated sitosterol, a sterol which had 

 exhibited relative instabihty to oxidation. One kilogram of corn oil 

 yielded 0.5 gram of a-sitosterol. After irradiation 2.5 milligrams pro- 

 duced moderate to marked healing of rickets. The authors stated: 

 "Whether traces of ergosterol are present in corn oil is not known, and 

 it cannot, therefore, be definitely stated whether in our experiments 

 ergosterol was the substance extracted and activated. If ergosterol is 

 the sole antirachitic precursor, it is evident that this sterol must be 

 universally present in all fats of animal and of plant origin that are 

 capable of activation by ultraviolet radiations. . . . Considerable further 

 chemical and biologic investigations will be necessary before it can be 



