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Trans and positional ethylenic bonds in two dominant isomers of eicosapentaenoic acid from the freshwater sponge Baicalospongia bacillifera
Author(s) -
Imbs Andrey B.,
Rodkina Svetlana A.
Publication year - 2005
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-005-1457-2
Subject(s) - chemistry , sponge , double bond , eicosapentaenoic acid , methylene , structural isomer , cis–trans isomerism , column chromatography , stereochemistry , medicinal chemistry , fatty acid , polyunsaturated fatty acid , chromatography , organic chemistry , botany , biology
Reinvestigation of the current FA composition of the regional freshwater sponge Baicalospongia bacillifera showed that the main measured isomer of EPA (14% of the total FA now detected) is, in fact, an unusual 5 Z ,8 Z ,11 Z ,14 Z ,18 E ‐EPA. Two other isomers of this acid also present were identified as a novel 5 Z ,8 Z ,11 Z ,15 Z ,18 E ‐EPA and the common methylene‐interrupted 5 Z ,8 Z ,11 Z ,14 Z ,17 Z ‐EPA (usually written simply as EPA). Isolation of these acids as their methyl ester derivatives was accomplished with the use of a combination of silver‐ion column chromatography and HPLC. The structure of the two new compounds was deduced from GC‐MS and detailed NMR data. Partial hydrazine reduction of all three isolated EPA esters followed by separation of cis/trans isomers of the resulting monoenoic acids and GC‐MS analysis of their dimethyl disulfide adducts were used for determination of the configuration and position of the double bonds. We may assume that the sponge B. bacillifera cannot receive these unusual EPA isomers directly from food sources (e.g., algal diatoms), and accordingly restructuring of ordinary EPA to novel acids may take place in the sponge tissue.