Submitted to: Analytical and Bioanalytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2015
Publication Date: 4/9/2015
Publication URL: http://handle.nal.usda.gov/10113/61936
Citation: Byrdwell, W.C. 2015. The updated bottom up solution applied to mass spectrometry of soybean oil in a dietary supplement gelcap. Analytical and Bioanalytical Chemistry. 407:5143-5160.
Interpretive Summary: A new method for obtaining information about the structures of triacylglycerols (fats and oils) has been developed. The relative ratios of fragments of the fats are used to figure out structural information about the fats, in a process called 'lipidomics'. One ratio tells about whether they are saturated, monounsaturated or polyunsaturated fats. Another ratio tells about where the fats that make up the triacylglycerols are located within the fat, specifically, which fatty acid is in the middle position of the fat or oil, to determine if it is available for the body to digest and absorb. Another ratio provides information about the fatty acids on the left and right sides of the fats. Not only do these ratios provide information about the structure of the fats, but they also constitute a 'reduced data set' from which a library of mass spectra (plots of the masses of the fragments of the fat or oil) can be produced.
Technical Abstract: Among the goals of lipidomics applied to triacylglycerols (TAGs) is identification of molecular species, degree and location of unsaturation, and positions of fatty acyl chains (i.e., identification of regioisomers). Toward those ends, we define one, two, and three ‘Critical Ratios’ for Type I, II, and III TAGs that provided different aspects of the desired information. Critical Ratio 1, [MH]+/Sum[DAG]+, is correlated to the degree of unsaturation ([MH]+ is the protonated molecule and Sum[DAG]+ is the sum of diacylglycerol-like ions, [DAG]+); Critical Ratio 2, [AA]+/[AB]+ for Type II TAGs (‘ABA/AAB/BAA’) and [AC]+/([AB]++[BC]+) for Type III TAGs (‘ABC/CBA/BAC/CAB/ACB/BCA’) is correlated to identification of regioisomers; and Critical Ratio 3, [BC]+/[AB]+, provides information about those [DAG]+ from Type III TAGs. Furthermore, Critical Ratios are used in the Updated Bottom-Up Solution (UBUS) to reproduce the mass spectra of TAGs by atmospheric pressure chemical ionization (APCI) mass spectrometry (MS), electrospray ionization (ESI) MS, and atmospheric pressure photoionization (APPI) MS applied to analysis of soybean oil in a dietary supplement gelcap. We present a new model for the [MH]+/Sum[DAG]+ ratio, quantify regioisomers using the [AA]+/[AB]+ ratio, and describe trends for [BC]+/[AB]+ that have never been reported before. The UBUS is also applied to other classes of molecules, i.e., vitamin D and DAGs. The amount of Vitamin D3 in the gelcap fell from 2011±22 when received to 1689±33 just prior to expiration. The Critical Ratios constitute a reduced data set that can provide structural information and also act as a library of mass spectra.