ABSTRACT
Objective To indentify monogalactosylmonoacylglycerol (MGMG) and analyze the chemical characteristics of sn-1 and sn-2 type isomers in Marine TCM Sargassum fusiforme. Methods The MGMG compounds were isolated by multiple chromatography methods and their structures were determined by spectroscopic methods such as NMR and HRESI-MS. The interconversion and chromatography-mass spectrometry feature of MGMG positional isomers were analyzed through HPLC and HPLC-ESI-MS/MS. Results Five MGMGs were isolated from Sargassum fusiforme, and the fatty acyl compositions were stearidonoyl, linolenoyl, arachidoyl, linoleyl, and oleyl. The sn-1 and sn-2 type of MGMG were unstable. The interconversion tended to be sn-1 type rapidly, and kept balanced content at 85:15. The relative retention time of sn-2 type was less than sn-1 type on C18 reverse phase chromatography. The abundant fragment ions of MS/MS were significantly differences. The base peak was [M+Na-Gal]+ (100%), and the peak intensity of [M+Na-RCOOH]+ was always more than 50% from sn-2 type while less than 20% from sn-1 type. Conclusion Five MGMGs were isolated from brown algae for the first time. This was the first report about the interconversion and chromatography-mass spectrometry feature of sn-1 and sn-2 type. It can use to determine the fatty acyl attachment in each MGMG.