Multi-component analysis of marine lipids in fish gonads with emphasis on phospholipids using high resolution NMR spectroscopy

High resolution NMR has been applied for assessment of lipid classes and acyl stereospecific positions of fatty acids in marine phospholipids and triacylglycerols. 1D and 2D NMR techniques in combination with recording of a number of reference standards have been used to interpret the 1H and 13C NMR spectra of fish gonads. 13C NMR spectra gave information regarding the polyunsaturated fatty acids (PUFAs) in phosphatidylcholine (PC) and phoshatidylethanolamine (PE). The carbonyl resonances showed that n − 3 PUFAs primarily were esterified in the sn-2 position of PC and PE. The glycerol resonances showed that the PC/PE ratio was higher in roe than in milt and that roe comprised more triacylglycerols than milt. Thin layer chromatography showed that milt contained 2.4 times more cholesterol than roe, which was also found by integrating the 1H NMR spectra. Concentration (mol%) of n − 3 fatty acids were calculated from the 1H NMR data and showed 44.8 and 36.3% in roe and milt, respectively.