Traditional uses, chemical constituents, pharmacological activities, and toxicological effects of Dendrobium leaves: A review.

ETHNOPHARMACOLOGICAL RELEVANCE: In China, shi hu (stems of Dendrobium chrysotoxum Lindl, D. fimbriatum Hook. D. huoshanense Z.Z. Tang & S.J. Cheng, or D. nobile Lindl) and tie pi shi hu (stems of D. officinale Kimura et Migo) are famous traditional medicines and are listed in the Chinese Pharmacopoeia. However, the leaves of these Dendrobium plants are largely discarded. AIM OF THE STUDY: To better utilize Dendrobium leaves, we summarize their traditional uses, chemical constituents, pharmacological activities, and toxicological effects. MATERIALS AND METHODS: "Orchidaceae", "Dendrobium", "leaf", "traditional use", and "ethnobotany" were used as search terms to screen the literature. Cited references were collected between 1960 and 2020 from the Web of Science, China National Knowledge Internet (CNKI), SciFinder, and Google Scholar, primarily in English and Chinese. RESULTS: Traditional uses of leaves from 16 Dendrobium species were identified in the literature. The major uses of Dendrobium leaves include treatments for dermatologic disorders, metabolic syndromes, nervous system disorders, and musculoskeletal system disorders. More than 50 chemical compounds have been identified in the leaves of 10 Dendrobium species, which primarily include flavonoids, bibenzyls, coumarins, N-containing compounds, and polysaccharides. Antihyperlipidemia, antihypertensive, antihyperuricemia, anti-inflammatory, antimicrobial, antioxidant, cytotoxic and antitumor, hepatoprotective, immunomodulatory, lipase-inhibitory, and/or tyrosinase-inhibitory activities have been reported for the leaves of six Dendrobium species. D. officinale leaves have been shown to exhibit no reproductive toxicity against male rats, while D. speciosum Sm. leaves have been observed to exhibit slight genotoxicity in an in vitro study. Among Dendrobium species, D. officinale leaves are the most widely studied. CONCLUSIONS: D. officinale leaves represent a good example of the utilization of leaf resources of the Dendrobium genus. In the future, more extensive research for the development of Dendrobium leaves is needed.

The Cocultured Nigrospora oryzae and Collectotrichum gloeosporioides, Irpex lacteus, and the Plant Host Dendrobium officinale Bidirectionally Regulate the Production of Phytotoxins by Anti-phytopathogenic Metabolites.

The distinctive nature of the endophyte Irpex lacteus, host plant, and the phytopathogen Collectotrichum gloeosporioides resulted in both negative and positive regulation of the production of phytotoxins from Nigrospora oryzae. The coculture of nonhomologous I. lacteus and N. oryzae resulted in a greater number of anti-phytopathogenic metabolites from the dominant endophyte than the coculture of homologous I. lacteus and N. oryzae. The coculture of the phytopathogen N. oryzae and either the nonhomologous (isolation of I. lacteus and N. oryzae from the different plants) or homologous (isolation of I. lacteus and N. oryzae from the same plant) endophyte I. lacteus from different sources indicated that the nonhomologous I. lacteus grew faster than the homologous I. lacteus, and the production of phytotoxic azaphilone from the phytopathogenic N. oryzae decreased due to the inhibition resulting from being cocultured with nonhomologous I. lacteus. On the other hand, the production of phytotoxic azaphilone was promoted by the coculture of two phytopathogens, N. oryzae and C. gloeosporioides. The extract of the host plant, Dendrobium officinale, also increased anti-phytopathogenic metabolite production. Six new phytotoxic azaphilones from N. oryzae, four new tremulane sesquiterpenes from I. lacteus, and a new polyketone were isolated. The endophyte-phytopathogen, phytopathogen-phytopathogen, and endophyte-phytopathogen-host interactions can induce the chemical diversity of novel anti-phytopathogenic metabolites.