Catabolism of fish furan fatty acids to urofuran acids in the rat.

A mixture of long-chain furan fatty acids was prepared as methyl esters from testes lipids of Northern pike (Esox lucius). Upon feeding these esters to rats, dicarboxylic acids, which still contained the furan structure, were found in the urine. The first phase of a rapid but incomplete catabolism is beta-oxidation of the proximal chain of the furan fatty acids. It proceeds to a distance of three carbon atoms from the ring. omega-Oxidation of the terminal alkyl chain, followed by alpha-oxidation gives rise to a second alkylcarboxyl chain with five carbon atoms or less. The ring methyl substituents of the precursor acids seem to be more resistant to oxidation than the alkyl substituent with three or five carbon atoms. The urinary catabolites from furan fatty acids in the rat are similar to furan acids found in human urine, but only one of the structures occurs in both sources.