Monoacylglycerol analysis

Keusgen, M., Curtis, J.M. and Ayer, S.W. (1996) The use of nicotinates and sulfo-quinovosyl monoacylglycerols in the analysis of monounsaturated n-3 fatty acids by mass spectrometry. Lipids, 31 (2), 231-8. 

The CB used was a standard factory product originating from the Ivory Coast. Its composition, determined by gas chromatography and HPLC for TAG analysis and by atomic absorption for phospholipid content, was as follows TAG 97% diacyl-glycerols 1.1% monoacylglycerols 0.2% free fatty acids 1.3% phosphatides 0.15% and others 0.25% (4). The TAG composition which is given in detail elsewhere (4) is for main TAG, POP 17.3%, POS 37.3%, and SOS 27.3% saturated TAG represented 2.3%. 

Key Words Bonnd water esterification ethanolysis glycerolysis immobilized glycerol lipase monoacylglycerol regiospecific analysis. 

Monoacylglycerols and diacylglycerols. The early GC/MS methods of analysis of MGs and DGs utilized TMS ethers, which were unstable and could... 

The incorporation of [ C]glycerol and [ CJglycerol phosphate into lipids was studied by Barron and Stumpf (1962). The active fraction obtained from avocado Persea americana L.) fruit mesocarp was purified by density gradient centrifugation, and most of the activity was found in the microsomal fraction. The first product was PA [but analysis at early time points detected lysophosphatidic acid (LPA)], followed by monoacylglycerol, diacylglycerol, and triacylglycerol in that order. 

According to Oomah et al. (1996), extraction of residual oil from commercially available flaxseed meal with hexane alone resulted in a higher oil recovery than methanol/hexane or methanol-ammonia-water/hexane. However, it should be noted that their starting material was meal and not seeds of flax. Analysis of the extracted lipids from the meal showed (Table 3) that hexane preferentially extracted the neutral lipids primarily composed of triacylglycerols (TAG). Neutral lipid fraction of oil extracted with methanol/hexane solvent system contained more monoacylglycerols (MAG), diacylglycerols (DAG) and free fatty acids (FFA) than the lipids extracted by other solvent systems (Table 3). Methanol/hexane solvent system extracted more polar lipids than methanol-water-am-monia/hexane system and this lipid fraction was composed mainly of phosphotidylcholine (PC). Polar lipids of methanol-ammonia-water/hexane extracted lipids contained also phosphotidylethanolamine (PE), lysophosphatidylcholine (LPC) and some unidentified compounds. 

Chiral chromatography is widely used for the resolution of chiral isomers of eicosanoids and enantiomeric isomers of di- and monoacylglycerols. The technique and its applications were extensively reviewed by Prof. Ian Blair in relation to the targeted analysis of these lipid classes and individual species employing LC-MS [87-89]. 

Adlof RO. Analysis of fatty acid monoacylglycerol and diacylglycerol positional isomers by silver ion high-performance liquid chromatography. J Chromatogr A 1996 741 135-8. 

The right-hand side shows how compounds from a lane on the chromatogram that has not been sprayed with sulphuric acid can be removed for analysis of the fatty acids on positions 1/3 and 2. The area of silica gel corresponding to each species is removed from the plate, the compound eluted with ether and subjected to lipase hydrolysis which releases fatty acids 1 and 3. These are converted into methyl esters for analysis by GLC. The fatty acid remaining in the monoacylglycerol after lipase hydrolysis representing position 2 can be released by saponification and also analysed by GLC. 

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