INTERCONVERSIONS OF POLYUNSATURATED FATTY ACIDS 



815 



of the administration of linolenate is probably an inactive isomer. The 

 whole subject must be considered to be in a state of flux, in view of the find- 

 ing of Thomasson^^ that 7-isolinolenic acid (6,9,12-octadecatrienoic acid) 

 is the active essential fatty acid (131 U. per gram), and that ordinary lino- 

 lenic acid (9,12,15-octadecatrienoic acid) possesses no significant biopotency 

 (9 U. per gram) . 



(3) Intercom versio'hs of Elaeostearic Acid 



Miller and Burr'^^ found that, when the conjugated isomer of linolenic 

 acid, namely, elaeostearic acid (9,11,13-octadecatrienoic acid), is given to 

 rats, it rapidly loses its absorption band at 270 m/x, and that a new maximum 

 appears at 235 m/z. This is interpreted to mean that one double bond has 

 been saturated, with the resultant formation of a dienoic acid. According 

 to Reiser,^" a similar change of trienoic acid to dienoic acid occurs in the 

 case of the hen when tung oil, which contains principally a-elaeostearic 

 acid, is fed. In another test of Reiser ei al.,^^ it was noted that ct-elaeo- 

 stearic acid was transformed to acids having two to six double bonds. 



(4) Interconversions of the More Highly Unsaturated Acids 



Information regarding the changes of the tetraenoic and more highly 

 unsaturated acids is quite limited. Holman and Taylor ^^"^ presented some 



Diene 



hen, chick, dog, rat, mouse 



hen, chick 



-♦ Tetraene^ 



Pentaene 



> Hexaene 



Fig. 1. The biologic interconversions of polyunsaturated fatty acids. 



' Dienoic acid is formed from diene-free fatty acids of cod-liver oil, by the chick. 



^ Trienoic acid increases upon depletion of other acids, and may be formed from 

 arachidonic acid. 



^ The tetraenoic acid formed from trienoic acid appears to be a biologically inactive 

 isomer of arachidonic acid. 



* Uncertain, because the tetraene used was impure. 



1" E. S. Miller and G. O. Burr, Proc. Exptl. Biol. Med., 36, 726-72!) (1937). 

 '80 R. T. Holman and T. S. Taylor, Arch. Biochem., 29, 295-301 (1950). 



