Simultaneous Determination of Molecular Species of Monoacylglycerols, Diacylglycerols and Triacylglycerols in Human Very-Low-Density Lipoproteins by Reversed-Phase High-Performance 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 a elution system composed of acetone in acetonitrile. The method allowed the separation of 4 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-stearoylglycerol (OOS), oleoyl-dipalmitoyl-glycerol (OPP), trilinoleoyl-glycerol (LLL) and linoleoyldistearoyl-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=0.82, p<0.05) and from diacylglycerols (r=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. Non-standard abbreviations: Fatty acids: A: arachidonic acid (20:4); Ln: Linolenic acid (18:3); L: linoleic acid (18:2); O: oleic acid (18:1); P: palmitic acid (16:0); S: stearic acid (18:0). Monoacylglycerols : L: monolinoleoyl-glycerol; O:monooleoyl-glycerol; P: monopalmitoylglycerol; S: monostearoyl-glycerol. Diacylglycerols: LL: dilinoleoyl-glycerol; OP: oleoyl-palmitoyl-glycerol. Triacylglycerols: LLL: trilinoleoyl-glycerol; OOP: dioleoyl-palmitoyl-glycerol; AOP: arachidonoyl-oleoyl-palmitoyl-glycerol. ECN: equivalent carbon number; CN: carbon number; DB: number of double bonds; NUFA: number of unsaturated fatty acids.