III. OXIDATION AND METABOLISM 



occurs during the formation of dicarboxylic acids has been suggested by 

 Stadie^ as follows : 



-CH3 



-CH, 



-CHO 



-COOH 



When tricaprin is metabolized in man by co-oxidation, the hydrolysis of 

 the triglyceride occurs first, followed by the oxidation of the free fatty 

 acid, capric acid, to the dicarboxylic acid with the same number of carbons. 

 Tn this case, sebacic acid is formed. The newly-formed dicarboxylic acid 

 is then subjected to /3-oxidation from one or from both ends, yielding a 

 series of dicarboxylic acids which have two, four, or six carbons less than 

 does the original acid.^^ It is possible that the simplest dicarboxylic acid, 

 oxalic acid (HOOC-COOH), which is normally present in the urine of man 

 to the extent of 20 to 40 mg. per day,^^ may owe its origin to a reaction of 

 this nature. A similar suggestion is made that food fats are the "parent 

 substances of the C4 system," which includes succinic acid (H00C-CH2-- 

 CH2-C00H). In the experiments of Verkade and van der Lee,^^ the 

 dicarboxylic acids, sebacic, suberic, and adipic, were isolated from the urine 

 after tricaprin had been ingested. A probable scheme of oxidation is 

 illustrated below: 



O 



H2C— O— C-(CH2)8-CH3 



11 3HOH 



HC— O— C(CH2)8-CH3 



O 



H2COH 

 > HCOH + 3CH3(CH.,)8COOH 



H2C— O— C(CH2)8-CH3 

 Tricaprin 



H2COH 

 Glycerol 



CH3(CHo)3-COOH 

 Capric acid 



O2 



Capric acid 

 O2 



-> H(X)C(CH2)8C()OH 

 Sebacic acid 



HOOC(CH2)6C()()H + CH3COOH 

 Suberic acid Acetic acid 



HOOC(CH2)4-COOH + CH3COOH 

 Adipic acid Acetic acid 



The Oxidation of Tricaprin in Man as an Example of co-()xid:ition of Fatty Acids 



68 P. E. Verkade and J. van der Lee, Z. physiol. Chem., 227, 213-222 (1934). 

 «8 P. Miiller, Verhandl. Ver. schweiz. Physiol., 11, 8-9 (1937); Chem. Abstr., 32, 6308 

 (1938); Physiol. Abst., 22, 349 (1937). 



