Furan fatty acids: Occurrence, synthesis, and reactions. Are furan fatty acids responsible for the cardioprotective effects of a fish diet?

Furan FA (F‐acids) are tri‐or tetrasubstituted furan derivatives characterized by either a propyl or pentyl side chain in one of the α‐positions; the other is substituted by a straight long‐chain saturated acid with a carboxylic group at its end. F‐acids are generated in large amounts in algae, but they are also produced by plants and microorganisms. Fish and other marine organisms as well as mammals consume F‐acids in their food and incorporate them into phospholipids and cholesterol esters. F‐acids are catabolized to dibasic urofuran acids, which are excreted in the urine. The biogenetic precursor of the most abundant F‐acid, F6, is linoleic acid. Methyl groups in the β‐position are derived from adenosylmethionine. Owing to the different alkyl substituents, synthesis of F‐acids requires multistep reactions. F‐acids react readily with peroxyl radicals to generate dioxoenes. The radical‐scavenging ability of F‐acids may contribute to the protective properties of fish and fish oil diets against mortality from heart disease.