Rapid and Easy Identification of Isomers of Coumaroyl- and Caffeoyl-D-quinic Acid by Gas Chromatography/Mass Spectrometry

Abstract

The 3-O-, 4-O- and 5-O-isomers of caffeoyl-D-quinic acid and the corresponding ethyl esters were separated by high-performance liquid chromatography and the structures were verified by NMR spectrometry. Trimethylsilylation of the compounds allowed a rapid and easy identification of isomers from the proportions of the characteristic key ions at m/z345 and 307. Coumaroyl-D-quinic acids show analogous fragmentation for ions at m/z345 and 219. Stereochemical considerations explain the fragmentation of the isomers.