THE FOLIC ACID GROUP 573 



Lactobacillus bulgaricus 05, and Lactobacillus delbruckii LD50 require 

 folic acid for growth, but cannot utilize formylpteroic acid. 96 



Formylfolic acid, which is utilized as effectively as folic acid by Strep- 

 tococcus faecalis R and Lactobacillus casei 37 produces reticulocytosis and 

 increases the hemoglobin and the number of red and white blood cells and 

 platelets in pernicious anemia patients, but is reported to be less active 

 than folic acid when administered orally. 53 



N-[p-(4-Quinazolyl) benzoyl] glutamic acid is reported to be approxi- 

 mately 1 to 10 per cent as active as folic acid in stimulating the growth 

 of Streptococcus faecalis R. However, the results indicate that consider- 

 able growth was obtained in the absence of exogenous folic acid, at least 

 one-half that which was obtained by addition of either folic acid or the 

 analogue. 97 The possibility of a sparing action of the analogue on folic 

 acid cannot be excluded on the basis of the data presented; however, 

 analogues of vitamins can, in many instances, carry out the metabolic 

 functions of the vitamins. This quinazolyl analogue does not produce a 

 hematologic response in patients with pernicious anemia. 53 



N 10 -Methylpteroylglutamic acid, which is inhibitory to some organisms 

 (p. 580), replaces folic acid in stimulating the virus causing the Rous 

 sarcoma in folic acid-deficient chicks. 77 



An x-methylfolic acid (p. 575) , 2-desamino-2-hydroxypteroic acid, 

 2-desamino-2-hydroxypteroylglutamic acid, and pteroylaspartic acid are 

 all inactive clinically in treatment of the anemias responding to folic 

 acid. 53 



The diamide of folic acid neither increases the urinary folic acid con- 

 centrations in human subjects nor appreciably stimulates the growth of 

 Lactobacillus casei or Streptococcus faecalis R. 38 However, the methyl 

 ester of folic acid is approximately 10 per cent as active as the free acid 

 for Lactobacillus casei, 13 but probably somewhat less active for Strepto- 

 coccus faecalis R. 19 



Xanthopterin and Related Pterins. The hemopoietic effect of xanthop- 

 terin in alleviating the anemia resulting from the maintenance of rats 

 on a diet of goat's milk was reported almost a decade before the structure 

 of folic acid was known. 98 Xanthopterin has also been reported to relieve 

 the anemia produced by feeding a high-protein diet to fingerling Chinook 

 salmon. 99 Treatment of cytopenic monkeys maintained on a vitamin 

 M-deficient diet with synthetic xanthopterin gave a reticulocyte response 

 and increased the number of red and white blood cells. 100 The growth 

 inhibition and leucopenia in rats maintained on a purified diet deficient 

 in folic acid and containing succinylsulfathiazole has been reported to 

 respond partially to xanthopterin. 101 Attempts to reproduce these results 

 have been only partially successful; however, incubation of rat livers 



