II. CHEMISTRY 155 



It is assumed, on the basis of chick-rat assays, that the provitamin D in 

 the cholesterol of all mammalian sources is 7-dehydrocholesterol. Com- 

 mercial cholesterol, such as was used in Waddell's work,^^ comes from the 

 spinal cords of cattle. Bethke ei al}^^ found that activated samples of butter, 

 lard, and brain exhibit the same high efficacy ratio as cod liver oil or ir- 

 radiated ordinary cholesterol. Haman and Steenbock^^^ reported high 

 efficacy ratios for irradiated lard and chicken fat. 



4. Provitamins D of Invertebrates 



The phenomenal abundance of provitamin D in the sterols of the inverte- 

 brates has been demonstrated by a number of workers,^^' ^*-^^- los-io?, 117-121 

 whose findings are included in Table II. In several instances provitamins 

 have been isolated, which, although "pure" by spectrographic tests, do 

 not correspond in other properties to any known form of provitamin D. 

 Some of these have considerable commercial, as well as theoretical, impor- 

 tance. 



Four provitamins were described in the patents of Boer ei aL^"®' ^°^' "'' 

 The one from the earthworm, Lumbricus terrestris, has already been dis- 

 cussed and show^n to be a mixture of ergosterol with at least one other, 

 unidentified, provitamin. The one from the waterworm, Tubifex, has not 

 been further investigated chemically, but in view of the findings on Lumbri- 

 cus it seems unlikely that it is a single substance. In biological tests^^ it has 

 been found to have an efficacy ratio of 100 when activated. The one from 

 the common sea mollusk, Mytilus eduHs, has been reinvestigated by van 

 der Vliet,^" who considers it to be a mixture of three main components, 

 7-dehydrocholesterol, ergosterol, and a provitamin tentatively identified as 

 22-dehydro-7-dehydrocholesterol (i.e., A^ ''■^'^-cholestatriene-S-ol). These 

 sterols were not isolated, but their presence indicated indirectly by fraction- 

 ations, degradations, and efficacy ratios. The presence of ergosterol could 

 account for the somewhat low efficacy ratio of 71 % reported^-" for the 

 mixture. It has been suggested that the provitamin D of the periwinkle, 

 Littorina Uttorea, may be impure 7-dehydroclionasterol.^22 After irradiation 

 it is said^^ to exhibit an efficacy ratio of 100%. Such effectiveness seems 

 inconsistent with the presence of an ethyl group in the side chain. 



Van der Vliet^^ has determined the chick-rat efficacy ratios of several 

 other invertebrate provitamins D which have not been examined 



"7 A. G. Boer, J. van Niekerk, E. H. Reerink, and A. van Wijk, U. S. Pat. 2,216,719 



(1940). 

 "« P. Fantl, Australian J. Exptl. Biol. Med. Sci. 20, 55 (1942). 

 "9 W. S. Calcott, J. Waddell, and H. R. Rosenberg, U. S. Pat. 2,383,446 (1945). 

 "» H. R. Rosenberg and J. Waddell, /. Biol. Chem. 191, 757 (1951). 

 1" H. Rosenberg, U. S. Pat. 2,475,917 (1949). 

 '" C. A. Kind and S. C. Herman, J. Org. Chem. 13, 867 (1948). 



