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‐α‐L‐rhamnosyl‐(1→2)‐β‐D‐glucoside‐8‐C‐α‐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.
Dendrobium hercoglossum Rchb. f. (D. hercoglossum), as one of the origins of medicinal Dendrobium, has been widely used as a health food and nutrient source promoting fluid production. Due to a lack of quality control, it is often counterfeited or mixed with other Dendrobium. In this study, a highperformance liquid chromatography characteristic chromatogram method is established for the quality evaluation of D. hercoglossum. Based on the highperformance liquid chromatography characteristic chromatogram, D. hercoglossum is divided into two classes, each with different flavone peaks. These flavone peaks were identified using high-performance liquid chromatography coupled with electrospray ionization multistage tandem mass spectrometry. Among them, the acylated (3-hydroxy-3-methylglutaryl, p-coumaroyl, feruloyl, or sinapoyl) flavones-C-glycosides are first found in D. hercoglossum in this study. In addition, one unique band was found in D. hercoglossum by thin-layer chromatography, which can be used to distinguish it from other Dendrobium species as a characteristic marker of this plant. Combining the high-performance liquid chromatography characteristic chromatogram and high-performance liquid chromatography coupled with electrospray ionization multistage tandem mass spectrometry, the unique band was identified as 4,5-dihydroxy-3,3′dimethoxybibenzyl. These analysis methods can be applied for the quality control and identification of D. hercoglossum as well as providing reference for the identification of similar constituents in other Dendrobium species. K E Y W O R D S flavonoids, high-performance liquid chromatography, mass spectrometry, thin-layer chromatography, traditional Chinese medicine Article Related Abbreviations: ESI-MS n , ESI multistage MS/MS; HCA, hierarchical cluster analysis; OPLS-DA, orthogonal partial least square discriminant analysis; PCA, principal analysis analysis; TCM, traditional Chinese medicine; VIP, variable importance plot 1 INTRODUCTION Dendrobium, also called "shihu" in China, is the second largest genus in Orchidaceae, whose medicinal history was originally recorded in "Shen Nong's Materia Medica." At present, Dendrobium is widely used as an edible
Flickingeria fimbriata is commonly applied in China as a traditional Chinese medicine (TCM), however the quality control of it is incomplete. In this work, we aim to identify and quantify the structures of C -glycosyl flavones in F. fimbriata . High performance liquid chromatography-diode array detector (HPLC-DAD) and High performance liquid chromatography–electrospray ionization–multiple stage tandem mass spectrometry (HPLC–ESI–MS n ) methods were combined to identify C -glycosyl flavones and determine their contents. Twenty acylated C -glycosyl flavones and ten non-acylated C -glycosyl flavones were identified for the first time in F. fimbriata on systematic MS n analysis via HPLC–ESI–MS n . The aglycones of all of these compounds were apigenin or chrysoeriol and were acylated with p -coumaric, ferulic, 3,4-dimethoxycinnamic or 3,4,5-trimethoxycinnamic acids. Furthermore, the quantification result suggest that two C -glycosyl flavones (vicenin-I and vicenin-III) with relative high contents were revealed to be more strongly acylated in F. fimbriata . The method is sufficiently precise, accurate, and sensitive for the qualitative and quantitative analysis of C -glycosyl flavones, which is expected to establish a standard for quality control and identification in this plant.
Flavones are widely used in traditional Chinese medicine (TCM) and are the pharmacologically active ingredients of many medicinal plants, such as Dendrobium. With the increasing demand for medicinal Dendrobium, the identification of characteristic flavones that can serve as chemical markers for quality control is critical step for quality assurance and safety in the TCM industry. Methods: High-performance liquid chromatography coupled with electrospray ionization multi-stage tandem mass spectrometry (HPLC/ESI-MS n ) was used to identify the chemical constituents in five types of Dendrobium: D. crystallinum, D. falconeri, D. strongylanthum, D. moniliforme, and D. gratiosissimum. Results: A total of seventy-six C-glycosyl flavones and three O-glycosyl flavones were identified, of which fifteen C-glycosyl flavones were found in D. crystallinum, twenty four were found in D. falconeri, thirty were found in D. strongylanthum, seven were found in D. moniliforme (also called "Huangtongpi", from Anhui, China), fifteen were found in D. moniliforme (also called "Zitongpi", from Yunnan, China) and seventeen were found in D. gratiosissimum. Additionally, three flavone O-glycosides were all found in D. strongylanthum. Conclusions: The results of this study may be useful for the quality assessment and for the application of D. crystallinum, D. falconeri, D. strongylanthum, D. moniliforme, and D. gratiosissimum. This study provides comprehensive information for identification of flavones from other Chinese herbs. | INTRODUCTIONDendrobium, also known as "Shihu", belongs to the orchid family. 1,2 Although seventy-four species and two varieties are known, only about forty species have medicinal value. Furthermore, some of these species with high medicinal values are now endangered. 3 Fortunately, artificial planting of Dendrobium species has been a great success in China. Some Dendrobium species have been used in traditional Chinese medicine (TCM) for centuries. At present, it is demonstrated that Dendrobium has comprehensive bioactivities, involving antioxidant, anti-cancer, anti-inflammatory and immunomodulatory. 4 According to the Chinese Pharmacopoeia (2020 version), several Dendrobium species such as, D. nobile, D. huoshanense, D. chrysotoxum, D. fimbriatum and similar species are all used as "Shihu". Nowadays, Dendrobium is not only used as medicine, but is also used as food and a tonic to condition the body. 5 Because many Dendrobium species have similar appearance and the species are more difficult to identify after processing, the market is flooded with inexpensive Dendrobium that is used as a counterfeit for precious Dendrobium. To prevent counterfeiting, it is necessary to establish an accurate and efficient identification method, such as fingerprinting method based on chromatographic techniques. The
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. Methods: High-performance liquid chromatography coupled with electrospray ionization multistage tandem mass spectrometry (HPLC-ESI-MS n ) was used to identify the chemical constituents in five types of Dendrobium: Dendrobium loddigesii, Dendrobium primulinum, Dendrobium crepidatum, Dendrobium porphyrochilum, and Dendrobium hancockii. Results: 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. Conclusions: 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.
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