Furan fatty acids (FFA) are characterized by a furan ring, which carries an unbranched fatty acid chain with 9, 11 or 13 carbon atoms in one α-position and a short straight-chain alkyl group with 3 or 5 carbon atoms in the other α-position. The β-positions of the furan ring can be substituted with two methyl residue or just with one methyl group in the β-position adjacent to the long aliphatic chain. The structure of furan fatty acids is similar to that of some prostaglandins (a five-membered ring with an alkyl chain and an alkyl carboxylic chain). The biological role of the FFA is still not clear, but it has been pointed out that FFA act as antioxidants as they prevent linoleic acid oxidation. The connection between consumption of fish rich in FFA and protection against coronary heart disease mortality has been confirmed in several research studies. In the present study, the fatty acid profile of six species of Adriatic fishes (european pilchard, european anchovy, european hake, horse mackerel, common sole, atlantic mackerel), three species of freshwater fish (perch, indigenous catfish, trout) and three molluscs (clam, mussel, oyster) were determined. The identification of different FFA obtained from muscle, liver, testes, ovaries, eyes and brain was carried out using comprehensive bidimensional gaschromatography coupled on-line with mass spectrometry. The identified FFA were both the saturated series 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid [MonoMe(9,5)], 10,13-epoxy-11,12-dimethyloctadeca-10,12-dienoic acid [DiMe(9,5)], 12,15-epoxy-13,14-dimethyloctadeca-12,14-dienoic acid [DiMe(11,3)], 12,15-epoxy-13-methyleicosa-12,14-dienoic acid [MonoMe(11,5)], 12,15-epoxy-13,14-dimethyleicosa-12,14-dienoic acid [DiMe(11,5)], 14,17-epoxy-15,16-dimethyldocosa-14,16-dienoic acid [DiMe(13,5)], and the unsaturated series 12,15-epoxy-13,14-dimethyleicosa-12,15,16-trienoic acid [DiMe(11,5:1)], 12,15-epoxy-13,14-dimethyleicosa-10,12,14-trienoic acid [DiMe(11:1,5)]. The ubiquitary FFA were [MonoMe(9,5)], [DiMe(11,3)], [MonoMe(11,5)] and [DiMe(11,5)]. FFA were absent in the molluscs and in the indigenous catfish. The unsaturated FFA were absent in the testes and ovaries of european anchovy and european hake
