Identification of flavonoids in Dendrobium huoshanense and comparison with those in allied species of Dendrobium by TLC, HPLC and HPLC coupled with electrospray ionization multi-stage tandem MS analyses

Dendrobium huoshanense, a unique species in the genus Orchidaceae, is only found in China and is known as "mihu". Due to the lack of quality control, the use of D. huoshanense in the herbal market has been limited. In this study, methods based on thin-layer chromatography, high-performance liquid chromatography and high-performance liquid chromatography coupled with electrospray ionization multi-stage tandem mass spectrometry were used to identify the flavonoids in D. huoshanense and distinguish this species from other Dendrobium species. Using thin-layer chromatography, a characteristic band was observed for D. huoshanense, and this band was absent from the thin-layer chromatography plates of other Dendrobium species. Then, using high-performance liquid chromatography, nine peaks of flavonoids were observed in the chromatograms of ten batches of D. huoshanense. Ultimately, 22 flavonoids in D. huoshanense were identified by multi-stage tandem mass spectrometry, and 11 of these compounds are being reported from D. huoshanense for the first time. In addition, two compounds both with molecular weights of 710, were identified as being unique to D. huoshanense; one of these compounds, apigenin-6-C-alpha-L-rhamnosyl-(1 -> 2)-beta-D-glucoside-8-C-alpha-L-arabinoside, was proven to be responsible for the characteristic thin-layer chromatography band of D. huoshanense. These analysis methods can be applied for the identification and quality control of D. Huoshanense.