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. 2017 Aug 30;7(1):9944.
doi: 10.1038/s41598-017-09637-9.

Lipids, fatty acids and hydroxy-fatty acids of Euphausia pacifica

Hidetoshi Yamada  1 , Yuya Yamazaki  2 , Seiji Koike  2 , Mayuka Hakozaki  3 , Nozomi Nagahora  3 , Sayaka Yuki  3 , Akira Yano  3 , Koichiro Tsurumi  4 , Takuji Okumura  5
Affiliations

Lipids, fatty acids and hydroxy-fatty acids of Euphausia pacifica

Hidetoshi Yamada et al. Sci Rep. .

Abstract

Euphausia pacifica is a good candidate for a resource of marine n-3 PUFA. However, few reports exist of the lipid and fatty acid composition of E. pacifica. To examine the potential of E. pacifica as a resource of marine n-3 PUFA, we analyzed E. pacifica oil. We extracted lipids from E. pacifica harvested from the Pacific Ocean near Sanriku, Japan. Lipid classes of E. pacifica oil were analyzed by TLC-FID and the fatty acid composition of the oil was analyzed by GC/MS. Free fatty acids and hydroxy-fatty acids were analyzed by LC/QTOFMS. The lipid content of E. pacifica ranged from 1.30% to 3.57%. The ratios of triacylglycerols, phosphatidylcholine, phosphatidylethanolamine and free fatty acids in E. pacifica lipids were 5.3-23.0%, 32.6-53.4%, 8.5-25.4% and 2.5-7.0%, respectively. The content of n-3 PUFA in E. pacifica lipids was 38.6-46.5%. We also showed that E. pacifica contains unusual fatty acids and derivatives: C16-PUFAs (9,12-hexadecadienoic acid, 6,9,12-hexadecatrienoic acid and 6,9,12,15-hexadecatetraenoic acid) and hydroxy-PUFAs (8-HETE and 10-HDoHE). E. pacifica is a good resource of marine n-3 PUFA. Moreover, E. pacifica can provide C16-PUFA and hydroxy-PUFAs.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
Extract chromatogram of free fatty acids contained in E. pacifica. Fatty acids in E. pacifica oil were analyzed by LC/QTOFMS. Fatty acids were predicted form the extracted ionized compounds by exact mass and molecular formula, and compounds were confirmed by using fatty acid standards. The compounds identified by using standards are shown with their molecular formula and structure. The compounds that were not identified by standards are shown with molecular formula only.
Figure 2
Figure 2
Structure analysis of 9,12-hexadecadienoic acid. We purified and analyzed the compound predicted as a C16H28O2 fatty acid. The exact mass and molecular formula of the compound were identified by using LC/QTOFMS. Fatty acid structure was identified by GC/MS. (A) Mass to charge (m/z) acquisition by LC/QTOFMS. (B) Mass spectra acquisition by GC/MS. (C) The result to access mass spectra for NIST2.0 library.
Figure 3
Figure 3
Structure analysis of 6,9,12-hexadecatrienoic acid. We purified and analyzed the compound predicted as a C16H26O2 fatty acid. (A) Mass to charge (m/z) acquisition by LC/QTOFMS. (B) Mass spectra acquisition by GC/MS. (C) The result to access mass spectra for NIST2.0 library.
Figure 4
Figure 4
Structure analysis of 6,9,12,15-hexadecatetraenoic acid. We purified and analyzed the compound predicted as a C16H24O2 fatty acid. (A) Mass to charge (m/z) acquisition by LC/QTOFMS. (B) Mass spectra acquisition by GC/MS. (C) The result to access mass spectra for NIST2.0 library.
Figure 5
Figure 5
MS/MS analysis of 8-HETE and 10-HDoHE. (A–D) Chromatogram of LC/QTOFMS. (E–H) MS/MS spectra acquisition by LC/QTOFMS. (A and E) Compound C20H32O3 purified from E. pacifica. (B and F) 8-HETE standard. (C and G) Compound C22H32O3 purified from E. pacifica. (D and H) 10-HDoHE standard.
Figure 6
Figure 6
8-HEPE is produced from EPA by an enzymatic reaction. BSA, E.pacifica protein or boiled E pacifica protein (50 µg) was incubated with 2 nmol of EPA at 20 °C for 1 hour. The concentration of 8-HEPE produced was measured by LC/QTOFMS. Values are the mean and s.d. of five individual experiments. ** indicates p < 0.01.
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