High-Resolution NMR Spectroscopy: An Alternative Fast Tool for Qualitative and Quantitative Analysis of Diacylglycerol (DAG) Oil

Multinuclear (H-1, C-13, P-31) and multidimensional NMR spectroscopy was employed for the analysis of diacylglycerol (DAG) oil and the quantification of its acylglycerols and acyl chains composition. A number of gradient selected two dimensional NMR techniques (TOCSY, HSQC-DEPT, HSQC-TOCSY, and HMBC) facilitated the assignment of the complex one dimensional H-1- and C-13-NMR spectra. In several cases, the aforementioned 2D-NMR techniques offered solid proof of earlier assignments based on chemical shift changes induced by the presence and relative positions of double bonds within the acyl chains. Integration of the appropriate signals in the NMR spectra of the three nuclei allowed the determination of DAG oil composition, which was found to be within the limits accepted for this oil, namely 1-monoacylglycerols 0.40-0.60%; 2-monoacylglycerols 0.40-0.50%; 1,3-diacylglycerols 57-62%; 1,2-diacylglycerols 28-32%; triacylglycerols 9-11%; saturated fatty acids 3-5%; oleic acid 37-45%; linoleic acid 49-53%; and linolenic acid 5-6.5%; tocopherols 0.24-0.27%. The compositional results obtained from the NMR spectra of the three nuclei were compared and discussed in terms of repeatability and ease of performance.