VII. OrCURKENCE IN FOODS 27 



reaction wliich rtMiuiros Ihr i)rcs(Mic(' of PABA to the extent of at. least one 

 part per million. 



VII. Occurrence in Foods 



LEMUEL D. WRIGHT and PETER A. TAVORMINA 



A variety of natural materials of both plant and animal origin have been 

 found to contain PABA (Table V). The vitamin occurs not only as such 

 but also in conjugated form. Thompson and his colleagues' ha\^e reported 

 that approximately 80% of the PABA content of animal tissues is in the 

 bound form, whereas in plants the bound form represents only 44 % of the 

 total PABA. 



Several procedures have been utihzed for the liberation of the PABA 

 from the conjugate form. Autolysis,^"^ enzymes,^' ^ and acid'-^- * and alka- 

 Une'- ^' 6' ^ hydrolysis all have been employed. Although it is generally ac- 

 cepted that autolytic and enzymatic methods free only part of the bound 

 PABA,2- ^- ^ there is little agreement concerning which of the two alterna- 

 tive procedures is the more desirable. Thompson et al} reported that pure 

 PABA is destroyed in part by either acid or basic hydrolysis. Lampcn and 

 Peterson* obtained maximum values for hver PABA, using 5 A'^ alkali. 

 Pure PABA added to a liver sample prior to hydrolysis is recovered in 92 

 to 100 % yields. Lampen and Peterson suggest that part of the bound PABA 

 in natural materials is in a form which resists acid hydrolysis. On the other 

 hand, Pennington^ reports that tissue PABA, but not pure PABA, is \'irtu- 

 ally completely destroyed by alkahne hydrolysis. 



The first indication that not all of the PABA of yeast is in the free state 

 was the report by Loomis and his associates^ of an antisulfanilamide frac- 

 tion from yeast which was ether-insoluble, not diazotizable, and not inac- 

 tivated by acetylation. Blanchard^ observed that yeast has a higher PABA 

 content after autolysis, and he attributes this to the presence in yeast of a 



' R. C. Thompson, E. R. Isbell, and H. K. Mitchell, J. Biol. Chem. 148, 281 (1943). 



2 H. K. Mitchell, E. R. Isbell, and R. C. Thompson, /. Biol. Chem. 147, 485 (1943). 



3 J. O. Lampen and W. H. Peterson, J. Biol. Chem. 153, 193 (1944). 

 ^ K. C. Blanchard, J. Biol. Chem. 140, 919 (1941). 



5D. Pennington, Science 103, 397 (1946). 



« J. C. Lewis, /. Biol. Chem. 146, 441 (1942). 



^ T. Ekstrand and B. Sjogren, Xalure 156, 476 (1945). 



8 A. J. Haagen-Smit, A. G. R. Strickland, C. E. P. Jeffreys, and J. G. Kirchnor, 



Food Research 11, 142 (1946). 

 'T. A. Loomis, R. S. lluijhard, and E. Neter, Pruc. Soc. E.cptl. liinl. Mai. 47, l.'i!) 



(1941). 



