REACTION OF LIPIDS CONTAINING HYDROXY-GROUPS WITH TRIMETHYLSULFONIUM HYDROXIDE - FORMATION OF O-METHYL DERIVATIVES

Base-catalyzed transesterification of acyl lipids with trimethylsulfon ium hydroxide (TMSH) is an easy and convenient method for the preparat ion of fatty acid methyl esters (FAME) for gas chromatography (GC) ana lyses. We have found, however, that lipids containing hydroxy groups a re partially converted to the corresponding O-methyl ether derivatives which may interfere with FAME in GC separations. For example, long-ch ain alcohols are found to be converted to alkyl methyl ethers, rac-1-O -alkylglycerols to the corresponding 2-O- and 3-O-monomethyl ethers, a s well as 2,3-di-O-methyl ethers, hydroxy fatty acids to methoxy FAME, and cholesterol to cholesteryl 3 beta-methyl ether. From our results, it is obvious that TMSH derivatization method is not recommended with out limitation for lipids containing hydroxy groups; it may be, howeve r, of some diagnostic value for the analysis of such lipids by GC/mass spectrometry.