II. CHEMISTRY 183 



a. Ergosterol 



Usual, or hydrated, form, C28H440-H20, molecular weight 414.648; an- 

 hydrous, C28H44O, molecular weight 396.632. Three double bonds. Melting 

 point about 165°, unsharp, varies with conditions. In vacuo, sublimation 

 occurs at 180°,^^ heavy vapors at 185°,^^^ and distillation with slight decom- 

 position at 198°.^* Principal absorption maxima at 262, 271, 282, and 293.5 

 m^ (in alcohol). Absorption minima at 263, 277, and 289.5 m/x. Molecular 

 extinction coefficient at 282 m/x = 11,500. [a]f = -135°, and [a]546i = 



— 174° (anhydrous ergosterol in chloroform). Heat of combustion (an- 

 hydrous), 9,950 caloriesi5 per gram.^''^ Specific gravity (anhydrous), 1.040.^^* 

 Ratio of digitonide to sterol, 4.0 il.^'*^ 



Crude ergosterol as obtained from the unsaponifiable matter of the fat 

 of fungi contains other sterols in varying amounts. Tanret^*^ was the first 

 to prepare ergosterol of high purity. He made it from the crude sterols of 

 ergot by fractional crystallization in ether. The ergosterol of yeast is ac- 

 companied by a number of minor sterols to the extent of about 20 %.^^''- ^^^ 

 Bills and Honey^vell-^^ obtained from yeast a purified product identical 

 with Tanret's by recrystallizing the crude sterols from 95 % alcohol-benzene 

 2:1. Alternatively, the same degree of purification was attained by convert- 

 ing the ergosterol into ergosteryl isobutyrate, which forms massive crystals 

 easy to purify. The ester was saponified, and the ergosterol recovered. 

 Callow^* purified ergosterol via the benzoate, and by this means eliminated, 

 along with other impurities, an exceptionally persistent contaminant, 5- 

 dihydroergosterol, which may be present to the extent of about 5 %.^^^ This 

 ergosterol, hydrated, showed [a]f = —128.7°, and anhydrous, [afo = 



— 135° (in chloroform). Huber et alP'^ crystallized ergosterol from 95% 

 alcohol-benzene 1:2 (not 2:1, as used by Bills and Honeywell). They 

 obtained hydrated ergosterol which had [a]^ = —133° (in chloroform). 

 Although the ambient temperature was not stated, it would seem that this 

 value represented a sample of exceptional purity. 



Ergosterol forms snow-white crystals, the gross appearance of which 

 varies with the solvent. From 95% alcohol it crystallizes in leaflets, and 

 from ether, chloroform, and acetone in fine needles.^^^ Larger crystals are 

 obtained from ether-acetone 1:3.2^^- "2 The presence of a little water in 



24^ C. Tanret, Coni'pt. rend. 108, 98 (1889); Ann. chim. et phys. Ser. 6, 20, 289 (1890). 



=«5 H. P^nau and Z. Hardy, /. pharm. chim. Ser. 8, 9, 145 (1929). 



24« C. Tanret, Ann. chim. et phys. Ser. 8, 15, 313 (1908). 



"■" A. Castillo and E. Ruppol, Bull. acad. roy. med. Belg. Ser. 5, 13, 48 (1933). 



2^8 W. Halden, Hoppe-Seyler's Z. physiol. Chem. 225, 249 (1934). 



243 C. E. Bills and E. M. Honeywell, /. Biol. Chem. 80, 15 (1928). 



"0 R. K. Callow, Biochem. J. 25, 87 (1931). 



2" W. Huber, G. W. Ewing, and J. Kriger, /. Am. Chem. Soc. 67, 609 (1945). 



"2 C. E. Bills, U. S. Pat. 1,775,548 (1930). 



