Identification of flavonoids of Rhodiola rosea by liquid chromatography-tandem mass spectrometry

Phenolic compounds from the aerial parts of medicinal plant Rhodiola rosea were identified using LC/MS experiments with time-of-flight and triple quadrupole instruments, providing accurate mass and CID fragmentation data about the compounds. Supercritical fluid extraction (SFE) was used to remove non-polar compounds from the samples, followed by liquid extraction of the flavonoids. Flavonoids were the main constituents in aerial parts of the plant, and no phenylpropanoids were detected. In addition to usual fragment ions providing the size of the attached glycosides in flavonoids, ions due to radical cleavage of glycosides were observed in the negative ion mode with relatively high collision energies. Use of these ions for elucidating the glycosylation site in the aglycone part was evaluated and was found to give some tentative information, but their use in unambiguous identification of unknown flavonoids is not recommended. Fifteen flavonoids, of which 10 were previously unreported from the plant, were identified.