INTESTINAL SYNTHESIS 



ic. T. D. Spies, G. G. Lopez, R. E. Stone, F. Milanes, R. O. Branden- 

 burg and T. Aramburu, Int. Z. Vit. Forsch., 1947, 19, i. 



2. A. D. Welch, R. W. Heinle, E. M. Nelson and H. V. Nelson, Ann. 



N. Y. Acad. Sci., 1946, 48, 347. 



3. A. L. Franklin, E. L. R. Stokstad and T. H. Jukes, Proc. Soc. Exp. 



Biol. Med., 1947, 66, 576. 



4. C. W. Denko, W. E. Grundy, J. W. Porter, G. H. Berryman. T. E. 



Friedemann and J. B. Youmans, Arch. Biochem., 1946, 10, 33. 



5. B. C. Johnson, T. S. Hamilton and H. H. Mitchell, /. Biol. Chem., 



1945. 159, 425. 



6. B. S. Schweigert, /. Lab. Clin. Med., 1948, 33, 1271. 



7. G. Toennies and D. L. Gallant, ibid., 1949, 34, 501. 



8. R. E. Simpson and B. S. Schweigert, Arch. Biochem., 1949, 20, 32 ; 



R. Wolff, L. Drouet and R. Karlin, Science, 1949, 109, 612. 



12. INTESTINAL SYNTHESIS OF FOLIC ACID 



Reference has already been made (page 461) to the production of 

 folic acid deficiency in rats by administration of sulphas nxidihe and 

 other sulphonamides,^"^ and to the fact that large amounts of folic 

 acid are excreted in human faeces * (see page 504). The faecal excre- 

 tion is largely independent of the dietary intake of folic acid and so, 

 apparently, is the urinary excretion, which decreased only slightly on 

 a restricted diet. This may be taken to indicate that some at least of 

 the folic acid synthesised by the intestinal flora may be utilised in 

 man. The rat may also be able to utilise the folic acid so produced ^ 

 although, even in the rat, symptoms of folic acid deficiency can cor 

 exist with a high faecal elimination of folic acid.^ Rabbits can ap- 

 parently utilise folic acid synthesised by the intestinal flora, as the 

 administration of sulphasuxidine markedly reduced the urinary 

 excretion of folic acid.^" If humans can, in fact, utilise folic acid 

 from this source, then patients with pernicious anaemia are not only 

 unable to utilise conjugated folic acid derived from the diet, but also 

 folic acid produced by intestinal synthesis. Similarly, patients with 

 nutritional macrocytic anaemia must be suffering not only from a 

 dietary deficiency but also from an inability to absorb the vitamin 

 from the gut. 



In point of fact, the only direct evidence on the extent to which 

 folic acid synthesised by the intestinal flora can be utilised in man is 

 an observation by Grundy et al.'^ that absorption does not take place. 

 These workers found that when phthalylsulphathiazole was given for 

 several days to volunteers maintained on carefully controlled diets, 

 the faecal excretion of L. casei factor fell to about 10 % of its original 

 value and increased again when administration of the drug ceased. 

 The amount of folic acid excreted in the urine did not fall with the 



