Occurrence and distribution of cis-7-icosenoic acid in the lipids of Japanese marine fish, shellfish, and crustaceans

Abstract

This paper reports the concentration and composition of the isomers of cis-icosenoic 26 acid (20:1) in the fatty acids of various species of Japanese marine animals. The main purpose 27 of this study is to reveal the distribution of a positional isomer, cis-7-20:1 (c7-20:1), in marine 28 animals. Because this isomer overlaps with the c9-20:1 isomer in gas chromatography (GC) on 29 the commonly used polar capillary columns, less information is available on its occurrence and 30 distribution. In this study, the monounsaturated fatty acids isolated by argentation thin-layer 31 chromatography were analyzed by GC using a highly polar capillary column, SLB-IL111 (100-32 m long), with the highest polarity among the commercially available GC columns. A clear 33 separation between the c7-and c9-20:1 isomers enabled the analysis of all the isomers of 20:1 34 present in marine animals. The results confirmed that the c7 isomer was a minor component of 35 the 20:1 in the pelagic fish, which is rich in the c9 and/or c11 isomers as reported previously. In 36 contrast, the c7 isomer was one of the major isomers in flatfish, shellfish, crabs, and brittle star. 37In these samples, the c13 isomer also occurred at higher concentrations rather than the c9 isomer. 38Because such a specific pattern of the 20:1 positional isomers was generally observed in both 39 benthic fish and its dietary animals, the c7 isomer in the benthic fish probably originated from 40 its diet. These marine animals are used as food in Japan, and therefore the c7-20:1 isomer is 41 consumed by humans. 42 43

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

“…It was reported that c7-20:1 was a minor component in the total c-20:1 content of most pelagic fish, which is rich in either c11 or c9-20:1 isomers. In contrast, the c7-20:1 isomer was one of the major isomers contributing to the total c-20:1 content in benthic fishes and also their dietary animals 14 . In the current study, a high content of c7-20:1 was mainly recorded in benthic fish 28 .…”

“…2 and 12 and Nakamura et al 14 for the same GC column and Ando and Sasaki 15 for the SLB-IL100 GC column. The IS c14-20:1 eluted Fig.…”

“…Some researchers have reported that in the majority of pelagic fish, the main isomer is c11-20:1, except in the northwest pacific fishes in which the c9-20:1 isomer contributes the highest proportion of the total c-20:1 14 . Results from the current study are in accordance with the above observation.…”

“…A few studies have investigated the distribution of positional isomers of c-20:1 and c-22:1 in fishes captured from the Pacific Ocean and Atlantic Ocean. In these studies, c-20:1 positional isomer was separated from flathead flounder and used as a reference 14 . Nakamura et al reported the distribution of c-20:1 in the lipids of 38 species, including Japanese pelagic fish, benthic fish, shellfish, and crustaceans 10,14,15 .…”

“…In these studies, c-20:1 positional isomer was separated from flathead flounder and used as a reference 14 . Nakamura et al reported the distribution of c-20:1 in the lipids of 38 species, including Japanese pelagic fish, benthic fish, shellfish, and crustaceans 10,14,15 . To date, no research has been conducted on the distribution of positional isomers of LCMUFAs in fishes from the Indian Ocean.…”