ACYL STEREOSPECIFIC ANALYSIS OF TUNA PHOSPHOLIPIDS VIA HIGH-RESOLUTION C-13-NMR SPECTROSCOPY

High resolution C-13-NMR spectra of the carbonyl region was recorded on fish phospholipids (PL), in order to study the acyl positional distribution. PLs obtained from skipjack tuna (Katsuwonus pelamis) showed poorly resolved spectra in organic solutions and an alternative approach, based on phospholipase C hydrolysis of PLs followed by C-13-NMR analysis of sn-1,2-diacylglycerols, was developed. Phospholipase C hydrolysis was specifically monitored using C-13-NMR and high resolution carbonyl spectra of sn-1,2-diacylglycerols assigned to different fatty acids attached to the sn-1 and sn-2 position of PLs. A selective enrichment of saturated and monounsaturated fatty acids in the sn-1 position, and a corresponding sn-2 location of polyunsaturated fatty acids (PUFA) was found. NMR-derived quantitative data were compared with the acyl profile determined using gas chromatography.