THE FOLIC ACID COMPLEX 



One process used for the isolation of vitamin Be conjugate from 

 yeast was as follows : ® A plasmolysed extract of brewers' yeast was 

 dissolved in warm water and the liquor acidified to pK 3 and filtered. 

 The filtrate was stirred with norit, and the adsorbate was eluted with 

 hot aqueous alcoholic ammonia. The eluate was concentrated and 

 re-adsorbed on norit and the adsorbate eluted as before. The con- 

 centrated eluate was extracted at pH 5*5 to 6 with butanol, the extract 

 discarded, and the aqueous solution re-extracted at pH 3. The activity 

 remaining in the aqueous solution was due almost entirely to vitamin 

 Be conjugate, the solution having scarcely any activity towards L. 

 helveticus or S. faecalis. It was converted by digestion with hog 

 kidney into vitamin Be, which was isolated by the procedure described 

 above. 



Another method used to prepare vitamin Be conjugate ^" was to 

 percolate dried brewers' yeast with 60 % alcohol, which extracted 

 inert material, and then to percolate with slightly acid 45 to 50 % 

 alcohol, which extracted the conjugate. A further quantity of inert 

 material was removed from the extract by addition of alcohol to a 

 concentration of 70 % and adjusting the pYi to 3 ; the conjugate 

 was then precipitated by adjusting the ^H of the filtrate to 5-5 

 to 6-0. 



SLR Factor 



The best source of the SLR factor was the liquor from Rhizopus 

 nigricans fmnaric acid fermentations.® The factor was isolated by 

 adsorption on charcoal, elution, chromatographic purification and 

 crystallisation. It was shown to be a pterine for which the name 

 rhizopterine was proposed. 



Xanthopterine 



Xanthopterine was isolated from a liver extract ^° by precipitation 

 with silver hydroxide and silver nitrate, regeneration with hydro- 

 chloric acid, adsorption on fuller's earth, elution with 20 % pjnridine, 

 evaporation to dryness, precipitation of the barium salt, and regenera- 

 tion with hydrochloric acid and sodium carbonate. 



References to Section 2 



1. H. K. Mitchell, E. E. Snell and R. J. WilHams, /. Amer. Chem. 



Soc, 1941, 63, 2284 ; 1944, 66, 267. 



2. E. H. Frieden, H. K. Mitchell and R. J. Williams, ibid., 269. 



3. E, E. Snell and W. H. Peterson, /. Bact., 1940, 36, 273. 



4. E. L. R. Stokstad, /. Biol. Chem., 1941, 139, 475. 



470 



