Simultaneous determination of molecular species of monoacylglycerols, diacylglycerols and triacylglycerols in human very-low-density lipoproteins by reversed-phase liquid chromatography.

The aim of the present study was to investigate the applicability of a previously developed method for the analysis of triacylglycerol molecular species to the simultaneous determination of triacylglycerols, diacylglycerols and monoacylglycerols of human very-low-density lipoproteins (VLDL). Ten elderly women were recruited for the study. Blood was obtained in fasting conditions and VLDL were isolated by ultracentrifugation. Neutral lipids were separated by solid-phase extraction and were subsequently injected on a reversed-phase HPLC system, with an elution system composed of acetone in acetonitrile. The method allowed the separation of four monoacylglycerols, 18 diacylglycerols and 24 triacylglycerols, including the resolution of positional isomers of diacylglycerols. Monoacylglycerols were composed of oleic, linoleic, palmitic and stearic acids. The major diacylglycerols were 1,2-dilinoleoyl-glycerol and 1,3-dilinoleoyl-glycerol (14.24+/-1.02 and 17.93+/-1.42%, respectively). The main triacylglycerols quantified were dioleoyl-stearoyl-glycerol (OOS), oleoyl-dipalmitoyl-glycerol (OPP), trilinoleoyl-glycerol (LLL) and linoleoyl-distearoyl-glycerol (LSS), accounting for 11.25+/-2.15, 10.14+/-2.05, 9.35+/-2.30 and 8.56+/-1.56%, respectively. An inverse relationship between polarity and fatty acid disappearance from triacylglycerols (r(2)=0.82, P<0.05) and from diacylglycerols (r(2)=0.93, P<0.01) was discovered. In conclusion, the method allowed, for the first time, the easy, rapid and simultaneous determination in a single chromatogram of triacylglycerol, diacylglycerol and monoacylglycerol molecular species of human VLDL by reversed-phase HPLC.