Determination of Diterpenoids and Flavonoids in Isodon rubescens by LC-ESI-MS-MS

The diterpenoids and flavonoids in Isodon rubescens were analyzed simultaneously by high-performance liquid chromatography coupled with electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS-MS) for the first time. The fragmentation pathway of rubescensin A (oridonin) and rubescensin B (ponicidin) in an electrospray ion trap mass spectrometer was also investigated. A total of 10 compounds, including five diterpenoids and five flavonoids, were identified or preliminarily characterized based on their mass spectra. Six of them were reported from Isodon species for the first time.