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<p>Accurate identification of <i>trans</i>-18:3 fatty acid isomers remain challenging due to the co-elution of structurally diverse <i>cis</i> isomers, particularly non-methylene-interrupted fatty acids (NMIFAs). GC–FID analysis of pine nut using an SP™-2560 column revealed unusually high peak areas (&gt; 13%) in the 18:3t region. However, a peak reduction in the 18:3t region after nitric acid-induced isomerization reaction, suggested the presence of <i>cis</i> isomers in native pine nut. GC–MS data identified the disappearing peak as pinolenic acid (5Z,9Z,12Z-octadecatrienoic acid; Δ5, 9, 12–18:3), while FT–IR and Raman spectroscopy confirmed hardly detectable <i>trans</i> fatty acid content prior to isomerization. Further, comparative analysis with perilla oil, rich in α-linolenic acid, under identical conditions aided in clarifying <i>trans</i> isomer positions in the 18:3t region. These findings demonstrate the limitation of retention-time-based identification alone to distinguish geometric isomers within polyunsaturated fatty acid subclasses.</p> Graphical abstract <p></p>

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Co-elution of Cis-NMIFAs in the 18:3t region: analytical approach in trans fatty acid identification

  • 期刊论文

  • 发表日期：

    2025年7月22日

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  • Vivian Prayitno,
  • Hae-Se Lee,
  • Min-Jeong Kim,
  • Se-Young Kim,
  • Ki-Teak Lee

摘要

Accurate identification of trans-18:3 fatty acid isomers remain challenging due to the co-elution of structurally diverse cis isomers, particularly non-methylene-interrupted fatty acids (NMIFAs). GC–FID analysis of pine nut using an SP™-2560 column revealed unusually high peak areas (> 13%) in the 18:3t region. However, a peak reduction in the 18:3t region after nitric acid-induced isomerization reaction, suggested the presence of cis isomers in native pine nut. GC–MS data identified the disappearing peak as pinolenic acid (5Z,9Z,12Z-octadecatrienoic acid; Δ5, 9, 12–18:3), while FT–IR and Raman spectroscopy confirmed hardly detectable trans fatty acid content prior to isomerization. Further, comparative analysis with perilla oil, rich in α-linolenic acid, under identical conditions aided in clarifying trans isomer positions in the 18:3t region. These findings demonstrate the limitation of retention-time-based identification alone to distinguish geometric isomers within polyunsaturated fatty acid subclasses.

Graphical abstract