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Stereospecific analysis of triacylglycerols rich in long‐chain polyunsaturated fatty acids
Author(s) -
Myher J. J.,
Kuksis A.,
Geher K.,
Park P. W.,
DiersenSchade D. A.
Publication year - 1996
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/bf02522622
Subject(s) - lipidology , clinical chemistry , polyunsaturated fatty acid , stereospecificity , chemistry , long chain , food science , organic chemistry , biochemistry , chromatography , fatty acid , polymer science , catalysis
Six oils of marine, algal, and microbial origin were analyzed for stereospecific distribution of component fatty acids. The general procedure involved preparation of sn ‐1,2‐(2,3)‐diacylglycerols by partial deacylation with ethylmagnesium bromide or pancreatic lipase, separation of X‐1,3‐ and sn ‐1,2(2,3)‐diacylglycerols by borate thin‐layer chromatography, resolution of the sn ‐1,2‐ and sn ‐2,3‐enantiomers by chiral phase high‐performance liquid chromatography following preparation of dinitrophenylurethane derivatives, and determination of the fatty acid composition by gas chromatography. Unexpected complications arose during a stereospecific analysis of triacylglycerols containing over 33% of either 20∶4 or 22∶6 fatty acids. The sn ‐1,2(2,3)‐diacylglycerols made up of two long‐chain polyunsaturated acids migrated with the X‐1,3‐diacylglycerols and required separate chiral phase resolution. Furthermore, the enzymatic method yielded sn ‐1,2(2,3)‐diacylglycerols, overrepresenting the polyenoic species due to their relative resistance to lipolysis, but prolonged digestion yielded correct composition for the 2‐monoacylglycerols. The final positional distribution of the fatty acids was established by pooling and normalizing the data from subfractions obtained by norman‐ and chiral‐phase separation of diacylglycerols. The molecular species of X‐1,3‐, sn ‐1,2‐ and sn ‐2,3‐diacylglycerol dinitrophenylurethanes were identified by chiral‐phase liquid chromatography/mass spectrometry with electrospray ionization, which demonstrated a preferential association of the paired long‐chain acids with the sn ‐1,2‐ and sn ‐2,3‐diacylglycerol isomers.