TRIGLYCERIDES AND FATTY ACIDS 75 



fatty acids in which a partial oxidation at the /3-carbon atom had occurred 

 were likewise isolated. Accordiiig to Dakin/^ when phenylvaleric acid 

 (Cells •(CH2)4-COOH) was oxidized, the side chain was degraded by the 

 removal of the four carbons in two pairs, which he suggested might be 

 termed "successive beta-oxidation." The benzoic acid resulting from the 

 oxidation of phenylvaleric acid was also shown by Dakin to be excreted 

 as hippuric acid. 



Dakin^ observed that, when ammonium butyrate was oxidized in vitro 

 with H2O2 under conditions approaching those in the body, acetoacetate 

 and acetone were end-products. On the other hand, when the reaction 

 temperature was higher, the acetoacetate was decarboxylated to acetone. 

 In longer-chain fatty acids, ^^ the terminal products were aldehydes having 

 one less carbon atom than the original acid. 



In later work, Dakin ^^ was able to isolate a number of intermediate com- 

 pounds of caproic acid (CH3-CH2-CH2-CH2-CH2-COOH) from the per- 

 fusate, after perfusing a surviving liver with Ringer solution containing 

 this acid. The intermediates included: 



2-hexenoic acid (CH3CH2-CH2-CH:CH-COOH), 



^-hydroxycaproic acid (CHa-CHzCHa-CHOH-CHz-COOH), 



/3-ketocaproic acid (CHaCIIaCHaCO-CHa-COOH). 



In addition to the aforementioned acids, acetoacetic acid and /3-hydroxy- 

 butyric acid were always present. When 2-hexenoic acid, /S-hydroxy- 

 caproic acid, or /3-ketocaproic acid was fed, acetoacetate and /8-hydroxy- 

 butyrate were formed, as well as some of the other intermediates. 



Further support for the /3-oxidation theory can be deduced from the 

 results with unsaturated and hydroxy acids. As early as 1842, Erdmann 

 and Marchand'^ disclosed that cinnamic acid (CeHs-CHrCH-COOH) was 

 eliminated as hippuric acid by the organism, while v. Graebe and Schultzen^® 

 and Dakin^^ confirmed this fact and demonstrated, possibly erroneously, 

 that mandelic acid (CfiHs-CHOH-COOH), in contradistinction to phenyl- 

 acetic acid, could also give rise to hippuric acid. On the other hand, 

 Quick^^ noted that the benzoic acid formed after phenylpropionic acid or 

 after the corresponding a,j8-unsaturated acid (cinnamic) was given was 

 conjugated largely with glucuronic acid.'^-^^ The ratio of benzoate ex- 

 creted as glucuronate to that as hippurate was 3:1. In sharp contrast to 



" H. D. Dakin, /. Biol. Chem., 56, 4.3-51 (1923). 



^ O. L. Erdmann and R. F. Marchand, /. prakt. Chem., 26, 494-498 (1842). 



16 C. V. Graebe and O. Schultzen, Ann. Chem. Pharm., U2 [n.s.GG], 345-350 (1867). 



" A. J. Quick, J. Biol. Chem., 77, 581-593 (1928). 



18 A. J. Quick, J. Biol. Chem., 80, 515-526 (1928). 



