PHYTOSTEROLS 49 



kingdom : in addition to the higher plants, they occur in 

 Sphagnum, Pelvetia, Laminaria, Agaricus, Lactarius, and 

 Polyporus* 



Ergosterol is the name given to a sterol isolated from 

 ergot by Tanret ; f this substance, melting at 154°, to which 

 he assigned the formula C27H42O, HgO, was accompanied by 

 a second sterol which he described as fungisterol of the 

 formula C25H40O, HgO, m.p. I44°- Both these sterols are 

 regarded as belonging to a class characteristic of crypotogams 

 and differing from cholesterol and phytosterol in their reaction 

 in chloroform solution with sulphuric acid ; whereas in the 

 case of the ordinary sterols the chloroform solution acquires a 

 red colour, it is the acid which turns red in the case of the 

 fungus sterols. Yeast has been shown to contain a mixture 

 of sterols — namely ergosterol and zymosterol, m.p. 99-104°.$ 

 The work of Webster and others has shown that the irradia- 

 tion of ergosterol with ultra violet light gives rise to 

 vitamin D. 



Phytosterols crystallize from alcohol in elongated plates 

 and from ether in slender needles. The melting-point 

 varies somewhat according to the source from which it 

 is prepared; it lies somewhere between 135 and 137° or 

 it may be as high as 144°. The reason for this may be 

 that the various substances obtained from different sources 

 and described as one and the same substance are in reality 

 different substances but all of a phytosterol nature. The 

 colour reactions of phytosterols resemble those of cholesterol. 



DISTINCTION BETWEEN CHOLESTEROL AND PHYTOSTEROL. 



In examining the unsaponifiable matter of a fat for sterols, 

 the unsaponifiable residue remaining after evaporation of the 

 ether is dried over a water bath and then dissolved in the 

 least possible quantity of absolute alcohol and allowed to 

 crystallize. The crystals which separate should be examined 



♦Ellis: "Biochem. Journ.," 1918, 12, 154. 160, 173. 



t Tanret : " Compt. rend.," 1889, 108, 98, and 1908, 147, 75. 



t Smedley-Maclean : "Biochem. Journ.," 1928,22, 22. 



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