サメガレイClidoderma asperrimum の筋肉脂質における全-cis-5,8,11,14,17,20,23-ヘキサコサヘプタエン酸（26:7n-3）の存在

摘要

Fatty acid analysis of roughscale sole Clidoderma asperrimum flesh lipids was carried out by gas chromatography. An unidentified peak appeared in the chromatogram in the elution region of ≥C24 fatty acids. After enrichment by solvent partitioning, reversed-phase thin-layer chromatography (TLC), and argentation TLC, the peak component was subjected to structural analyses. The partially hydrogenated products after reaction with hydrazine hydrate gave seven isomers of cis-hexacosenoic acid (26:1). Gas chromatography-mass spectrometry (GC–MS) analyses of their dimethyl disulfide adducts identified the monounsaturates as 5-, 8-, 11-, 14-, 17-, 20-, and 23-26:1. The peak component was assigned to all-cis-5,8,11,14,17,20,23-hexacosaheptaenoic acid (26:7n-3). GC–MS analyses of the 4,4-dimethyloxazoline derivative and methyl ester confirmed this structure. This fatty acid is a rare, very long-chain polyunsaturated fatty acid (VLCPUFA). The concentrations of the acid found in roughscale sole were 0.69 ± 0.34% (N = 5) of total fatty acids in flesh lipids. Roughscale sole appears to be characterized by the occurrence of 26:7n-3, which is lacking in popular sources of methylene-interrupted VLCPUFA, such as vertebrate retina, spermatozoa, and herring. 　北海道産サメガレイの筋肉脂質の脂肪酸をGC で分析したところ，炭素数24 以上の領域に未知のピークが出現した。この成分を濃縮後，数種の誘導体に変換してGC-MSに供した結果，同成分は全-cis-5,8,11,14,17,20,23-ヘキサコサヘプタエン酸（26:7n-3）と同定された。総脂肪酸中の含有量は供試5 個体の平均で0.69±0.34％であった。サメガレイは，n-3 系およびn-6 系超長鎖ポリエン酸の給源として一般的な高等動物の網膜，精子，ニシン油などには見られない26:7n-3 を含む点で特徴的である。