New Δ5 and Δ4 unsaturated medium- and long-chain fatty acids in the freshwater sponge Baicalospongia bacilifera

The composition of Δ5(Δ4) unsaturated medium- and long-chain fatty acids (FAs) of the freshwater sponge Baicalospongia bacilifera was selectively determined by means of the analytical iodolactonization reaction and the structures of FAs were identified by gas chromatography-mass spectrometry (GC-MS), spectrophotometry, and particular chemical degradation. The presence of several unusual monoenoic branched-chain FAs iso -15:1 Δ4, anteiso -15:1 Δ4, iso -17:1 Δ4, anteiso -17:1 Δ4, non-methylen interrupted tetraenoic acid 18:4 Δ5,9,12,15 and isomeric eicosapentaenoic acid (IEPA) with a trans double bond (20:5 Δ5 c ,8 c ,11 t ,14 c ,17 c ) was shown.