154 VITAMIN D GROUP 



have ascribed to the "spectroscopically pure" provitamin of earthworms 

 physical constants different from those of ergosterol and have further de- 

 scribed the earthworm provitamins as a "chicken provitamin D." Indeed, 

 van der Vliet^^ ascribes to earthworm provitamin D, activated, an efficacy 

 ratio of 100. 



Pollard^"^ found ergosterol in cocksfoot grass, and Windaus and Bock 

 identified it in wheat germ 011,1"^ cottonseed oil, and scopolia root sterols. ^^^ 

 The 7-dehydro derivatives of sitosterol, stigmasterol and campesterol, which 

 might have been expected in these sources, were not found and, in fact, 

 have never been found in nature. 



The foregoing chemical studies are supported and extended by chick-rat 

 assays on irradiated vegetable materials. Thus Bethke et aU^^ found the low 

 efficacy ratio characteristic of irradiated ergosterol in irradiated specimens 

 of cottonseed oil, wheat middlings, and alfalfa leaf, as well as in yeast and 

 Aspergillus. Haman and Steenbock"' found the low ratios in irradiated 

 coconut, peanut, and wheat germ oils, and Black and Sassaman^^^ got simi- 

 lar results with alfalfa unsaponifiables and maize oil phytosterol. Koch and 

 Koch,^^^ however, reported that irradiated maize oil phytosterol showed a 

 somewhat higher efficacy ratio than irradiated ergosterol. On the whole, it 

 appears that, with one exception, no provitamin D but ergosterol has yet 

 been identified in the vegetable kingdom. The exception is 22-dihydroergos- 

 terol, which Santos Rulz"^ has separated chromatographically from the 

 minor sterols of ergot. 



3. 7-Dehydrocholesterol 



In only three instances has 7-dehydrocholesterol been isolated from a 

 natural source. Boer et al.^^ obtained it from a sample of duck egg cholesterol 

 containing 4.5 % of provitamin D. That ducks' eggs should contain a differ- 

 ent provitamin D from hens' eggs is remarkable and doubtless reflects a 

 difference in diet, perhaps a predominantly fish diet in the case of the ducks. 

 Windaus and Bock^^^ isolated 7-dehydrocholesterol from pigskin, and Bock 

 and Wetter^"" obtained it from the wave horn snail, or whelk, Buccinum 

 undaium. It is noteworthy that this snail yielded 7-dehydrocholesterol, 

 whereas the two other snails studied by the same investigators gave ergos- 

 terol. 



»8 A. Pollard, Biochem. J. 30, 382 (1936). 



"fl A. Windaus and F. Bock, Hoppe-Seyler's Z. physiol. Chem. 256, 47 (1938). 



10 A. Windaus and F. Bock, Hoppe-Seyler's Z. physiol. Chem. 250, 258 (1937). 



" R. M. Bethke, P. R. Record, and O. H. M. Wilder, /. Biol. Chem. 112, 231 (1935). 



12 R. W. Haman and H. Steenbock, /. Biol. Chem. 114, 505 (1936). 



" A. Black and H. L. Sassaman, Am. J. Pharm. 108, 237 (1936). 



i« E. M. Koch and F. C. Koch, J. Biol. Chem. 116, 757 (1936). 



1* A. Santos Ruiz, Anales real acad. farm. 3, 201 (1941). 



18 A. Windaus and F. Bock, Hoppe-Seyler's Z. physiol. Chem. 245, 168 (1937). 



