Identification of three types of O‐glycosylated flavonoids in Dendrobium loddigesii, Dendrobium primulinum, Dendrobium crepidatum, Dendrobium porphyrochilum, and Dendrobium hancockii using mass spectrometry

Flavonoids, representing the pharmacologically active ingredients, are found widely in Dendrobium species. The biodiversity of Dendrobium makes the identification of its varieties all the more complicated. Previous studies showed that C-glycosylated flavones and a few O-glycosylated flavonols could be used in the identification of various Dendrobium species. Accordingly, this study further explores the significance of the identification of various types of O-glycosylated flavonoids in Dendrobium species.High-performance liquid chromatography coupled with electrospray ionization multistage tandem mass spectrometry (HPLC-ESI-MSn ) was used to identify the chemical constituents in five types of Dendrobium: Dendrobium loddigesii, Dendrobium primulinum, Dendrobium crepidatum, Dendrobium porphyrochilum, and Dendrobium hancockii.A total of 41 O-glycosylated flavonoids and 3 C-glycosylated flavones were identified, among which O-glycosylated dihydroflavones were the main flavonoids in D. loddigesii and D. primulinum, O-Glycosylated flavonols were rich in both D. crepidatum and D. porphyrochilum characterized by the main aglycone, substituted sugars, and their structural characteristics, and O-glycosylated flavones were the main constituents in D. hancockii.In this study, three types of O-glycosylated flavonoids in the five Dendrobium species were determined to have certain significance. This also provides a reference for the identification of other O-glycosylated flavonoids in Chinese herbs.