Abstract: HPLC-ESI-MS/MS is becoming one of the most important tools for the on-line identification of natural products in crude plant extracts. In this paper, a combined HPLC-ESI-MS/MS method was developed to character two flavonoid C-glycoside isomers in Scutellaria baicalensis Georgi. Using tandem mass spectrometry, useful fragments of the two flavonoid C-glycoside isomers were obtained. The experimental results demonstrate that cross-ring ions of [M-H-60]^-, [M-H-90]^-, [M-H-120]^- are characteristic ions of flavonoid C-glycoside. By analyzing the differences of the retention time and the relative abundance of ions [M-H-60]^-, the two isomers can be distinguished conveniently.

Key words: HPLC-ESI-MS/MS, Scutellaria baicalensis Georgi, Flavonoid C-glycoside isomers