308 THE VITAMINS 



decided whether certain sterols other than ergosterol can contribute to 

 the antirachitic activity of irradiated material." 



a-sitosterol, like ergosterol, cannot withstand purification by bromina- 

 tion. Therefore the usual method for freeing a sterol from ergosterol is 

 not open. 



Bills, Honeywell and MacNair (1928), however, found that their 

 most carefully purified (thrice brominated) cholesterols and also a 

 sample of twice brominated cholesterol prepared by Windaus, when 

 irradiated, appeared slightly active antirachitically when fed to the 

 extent of about thirty times the minimum curative dose of irradiated 

 ordinary cholesterol (mixed apparently, with about 12 parts of ergosterol 

 per 1,000). When spectrograms were taken through 20 centimeters of a 

 15 per cent solution of the thrice brominated cholesterol, absorption 

 bands with maxima at 315, 304, 293.5, 282 and 269 nn were visible. The 

 assumption that the bands characteristic of ergosterol were due to 

 ergosterol itself would account for about one-fifth of the observed 

 antirachitic potency. These authors suggested that the remaining potency 

 (associated with absorption bands at 315 and 304 /</i) was due to the 

 activatability of cholesterol itself or to an undiscovered impurity which 

 persists after 3 purifications with bromine. (See also Schlutz and Morse, 

 1925.) 



Jendrassik and Kemenyffi (1927) reported that cholesterol could 

 still be activated after purification by way of the dibromide and they 

 believed that ergosterol was not the only substance capable of being 

 activated. 



Koch, Koch and Ragins (1929) and Koch, Koch and Lemon (1929) 

 published experiments confirming the results of Bills. They found on 

 purifying cholesterol by the bromine treatment or by a triple treatment 

 with potassium permanganate that the two products upon irradiation 

 induced calcification in dosages 30 to 70 times as large as that required 

 of the original cholesterol. The two products showed no absorption bands 

 corresponding to ergosterol and showed no general absorption in the 

 ultra-violet region. These investigators do not believe this low activata- 

 bility to be due to a trace of ergosterol. When their purified products 

 were heated slightly above the melting point under conditions that 

 avoided appreciable oxidation, every one of the purified products was 

 about 25 to 70 times as active as the presumably pure cholesterol. With 

 the increase in activatability a strong general absorption was observed 

 in the ultra-violet region but since there were no bands whatever they 

 feel that the potency of the product is not due to ergosterol. They 

 believe that "provitamin D activity" may be a general property in 



