C20–C24 Monounsaturated fatty acid isomers in the lipids of flathead flounder, Hippoglossoides dubius

Simultaneous Treatment of Long-chain Monounsaturated Fatty Acid and n-3 Polyunsaturated Fatty Acid Decreases Lipid and Cholesterol Levels in HepG2 Cell

The n-3 type polyunsaturated fatty acids (n-3PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), from fish oil exhibit health benefits such as triacylglycerol- and cholesterol-lowering effects. Some pelagic fishes contain long-chain monounsaturated fatty acids (LC-MUFAs) such as eicosenoic acid (C20:1), which exert health-promoting effects. However, no study has evaluated beneficial effects of n-3PUFA and LC-MUFA combination. Here, we investigated effects of simultaneous treatment with n-3PUFA (EPA and DHA) and LC-MUFA (cis-5-C20:1 and cis-7-C20:1) and found that n-3PUFA and LC-MUFA combination significantly decreased lipid accumulation and reduced total cholesterol in HepG2 cells. Cholesterol level was significantly lower in DHA + cis-7-C20:1 group than in DHA + EPA group. These results suggest the importance of LC-MUFA as a functional molecule in fish oil.

Quantitative Analysis of the Distribution of cis-Eicosenoic Acid Positional Isomers in Marine Fishes from the Indian Ocean

This study investigated the occurrence and distribution of cis-eicosenoic acid (c-20:1) positional isomers in fishes from the Indian Ocean and compared to those from the Pacific and Atlantic Ocean. Lipids were extracted from the edible part of the fish and then methylated. The eicosenoic acid methyl ester fraction was separated from total fatty acid methyl esters by reversed-phase HPLC and quantitatively analyzed using a GC-FID fitted with the SLB-IL111 highly polar GC column. c14-20:1 was used as an internal standard. The results indicated that the highest levels of c-20:1 positional isomers were found in fishes from the Pacific Ocean (saury, 166.95±12.4 mg/g of oil), followed by the Atlantic Ocean (capelin, 162.7±3.5 mg/g of oil), and lastly in fishes from the Indian Ocean (goatfish, 34.39 mg/g of oil). With only a few exceptions, the most abundant 20:1 positional isomer found in fishes of the Indian and Atlantic Ocean was the c11-20:1 isomer (>50%) followed by the c13-20:1 isomer (<25%). Unusually, the c7-20:1 isomer was predominantly found in a few fishes such as the tooth ponyfish, longface emperor, and commerson's sole. The c9, c5, and c15-20:1 isomers were the least occurring in fishes from the Indian and Atlantic Ocean. In contrast, the c9-20:1 isomer was the principal isomer identified in fishes from the Pacific Ocean. The results revealed that the content and distribution of c-20:1 positional isomers varied among fishes in different oceans. The data presented in the current study are the first to report on the distribution of c-20:1 positional isomers in fishes from the Indian Ocean.

Identification of novel nonmethylene-interrupted fatty acids, 7E,13E-20:2, 7E,13E,17Z-20:3, 9E,15E,19Z-22:3, and 4Z,9E,15E,19Z-22:4, in Ophiuroidea (brittle star) lipids

Fatty acids of Ophiuroidea (brittle star) Ophiura sarsi have been investigated by gas-liquid chromatography (GLC). About 2-13% of four unidentified fatty acids were found in total fatty acids from a sample caught at a depth of 1,100 m. Structural analyses were undertaken after partial hydrogenation of their concentrates with hydrazine hydrate and subsequent isolation of the monoenoate products by argentation thin-layer chromatography. The structures of the unidentified fatty acids were determined as 7E,13E-eicosadienoic (20:2), 7E,13E,17Z-eicosatrienoic (20:3), 9E,15E,19Z-docosatrienoic (22:3), and 4Z,9E,15E,19Z-docosatetraenoic (22:4) acids by gas chromatography-mass spectrometry of dimethyl disulfide adducts and GLC of the monoenoates on a polar column. These fatty acids belong to a family of nonmethylene-interrupted (NMI) polyunsaturated fatty acids frequently observed in marine invertebrates and conifer seeds. As far as the authors know, however, these NMI fatty acid types with mixed geometry of ethylenic bonds have not been reported previously.