Evaluation of quadrupole time-of-flight tandem mass spectrometry and ion-trap multiple-stage mass spectrometry for the differentiation of C-glycosidic flavonoid isomers

LC-MS-MS is becoming a very important tool for the on-line identification o f natural products in crude plant extracts. For an efficient use of this te chnique in the dereplication of natural products, a careful study of the pa rameters used to generate informative MS-MS spectra is needed. In this pape r, the collision-induced dissociation (CED) MS-MS spectra of ubiquitous C-g lycosidic flavonoids have been systematically studied using hybrid quadrupo le time-of-flight and ion-trap (IT) mass analysers under various CID energy conditions. Efficient differentiation of flavonoid C-glycoside isomers was possible, based on the comparison of CID-MS-MS spectra of particular C-gly coside unit fragments. Striking differences between 6-C and 8-C flavonoid g lycosides were especially observed in the product ion spectra of their X-0, 2(+) fragments ([M+H-120](+)). Some guidelines for the on-line characterisa tion of C-glycosidic flavonoids by LC-MS-MS or LC-multiple-stage MS are giv en. (C) 2001 Elsevier Science B.V. All rights reserved.