Biochemical Systematics and Ecology
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The phytochemical study of the leaves of Rhododendron amesiae (Ericaceae) led to the isolation and identification of 19 compounds, including six diterpenoids (1–6), six triterpenoids (7–12) and seven flavonoids (13–19). The chemical structures of these compounds were identified by spectroscopic data, as well as by comparison with previously reported data in literature. This is the first systematic study on the chemical constituents of Rhododendron amesiae. All the compounds were isolated from this plant for the first time. Compounds 12, 14 and 15 were first isolated and reported from the genus Rhododendron and the family Ericaceae. Furthermore, the chemotaxonomic significance of these compounds was discussed.
Subject and source
The genus of Rhododendron, belonging to the family Ericaceae, is one of the largest and most valuable genera of woody plants (Chamberlain et al., 1996). The genus consisted of approximately 1025 species, which is mainly distributed in East and Southeast Asia, but sparsely populated in North America and Europe (Popescu and Kopp, 2013). China is considered to be the Rhododendron distribution center in the world with 571 species (Fang et al., 2005). In addition to being important horticultural
Phytochemical studies on species belonging to the genus Rhododendron revealed the presence of diterpenoids (Zhou et al., 2018), triterpenoids (Wang et al., 2020), monoterpenoids (Liao et al., 2015), flavonoids (Ye et al., 2019), phenolic compounds (Olennikov and Tankhaeva, 2010) and chromane derivatives (Ye et al., 2020). Among them, diterpenoids are considered to be the major characteristic and bioactive secondary metabolites (Li et al., 2019). To the best of our knowledge, to date there is no
The air-dried leaves of R. amesiae (2.4kg) were powdered and extracted with 95% EtOH four times at 50°C (3h for each time). After removing the solvent in vacuum, the crude extraction (547.2g) was suspended in H2O and then successively partitioned with petroleum ether, EtOAc, and n-BuOH. After evaporated to dryness under reduced pressure, the petroleum ether extract (87.1g), EtOAc extract (150.0g) and n-BuOH extract (130.0g) were obtained, respectively.
The petroleum ether extract (87.1g)
The present study reported the isolation and characterization of 19 secondary metabolites from the leaves of R. amesiae, including six diterpenoids (1–6), six triterpenoids (7–12) and seven flavonoids (13–19). To the best of our knowledge, compounds 12, 14 and 15 were first isolated from the genus Rhododendron as well as the family Ericaceae. All the compounds were isolated from this plant for the first time.
The diterpenoids isolated in this study were grayanane diterpenoids, which possess a
Credit authorship contribution statement
Ke Zeng: Investigation. Shurong Ban: Writing - review and editing. Zhiwei Cao: Writing - original draft. Pengkun Cao: Data curation. Xujing Luo: Investigation. Rong Wang: Investigation. Zhengbao Zhao: Supervision. Jinfang Xu: Funding acquisition, Project administration, Writing - review and editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
This research was supported by the National Natural Science Foundation of China (31700306), Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi (201802065), and Shanxi Province Science Foundation for Youths (201701D221256).
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Grayanoids are natural diterpenoids that are mostly found in the Ericaceae family, such as Rhododendron molle (Blume) G. Don (Relevant herb: nao yang hua), Rhododendron micranthum Turcz (also known as: zhao shan bai), which have traditionally been used to treat abdominal pain, cephalgia, and rheumatoid arthritis.
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