Chapter VIII 



THE FOLIC ACID COMPLEX 



I. INTRODUCTION 

 Folic Acid 



One of the most complicated chapters in the story of the vitamin 

 B complex is that relating to folic acid. When certain fastidious 

 micro-organisms, such as Lactobacillus helveticus (frequently referred 

 to, especially in U.S.A., as L. casei c) and Streptococcus faecalis R 

 (previously called S. lactis R), are transferred to a synthetic medium 

 containing, in addition to amino acids, all the members of the vitamin 

 B complex so far discussed, little or no growth occurs. The addition 

 of certain concentrates prepared from natural sources produces 

 optimal growth, however, and folic acid is the name given to one 

 such factor obtained in 1941 from spinach leaves (hence its name) by 

 H. K. Mitchell, E. E. Snell and R. J. Williams.^ 



The two essential steps in the preparation of this substance were 

 adsorption on charcoal and elution of the active principle from the 

 adsorbate by means of aqueous ammonia, steps also used in the pre- 

 paration of several other growth factors, since shown to be closely 

 related, chemically and biologically, to folic acid. It is convenient, 

 therefore, to discuss all these substances together and refer to them 

 collectively as the folic acid complex. 



Norit Eluate Factor or L. casei Factor 



One of these substances is the factor first called the norit eluate 

 factor and subsequently known as the L. casei factor. This was first 

 described by E. E. Snell and W. H. Peterson, ^ who stated that certain 

 lactic acid bacteria, when grown in a medium containing amino acids 

 and all the known growth factors, required in addition two new growth 

 factors isolated from liver, one adsorbed and the other not adsorbed, 

 on norit. They were accordingly distinguished as the norit eluate 

 factor and norit filtrate factor respectively. The former was con- 

 centrated by a series of additional steps, giving a product that resembled 

 the naturally occurring purines in several respects. 



The best source of the new factor was " solubilised liver ", which 

 was also used by E. L. R. Stokstad ^ in making a somewhat purer 



457 



