Two unusual dendrobine-type alkaloids from Dendrobium findlayanum

Exploring the Biomedical Potential of Terpenoid Alkaloids: Sources, Structures, and Activities

Terpenoid alkaloids are recognized as a class of compounds with limited numbers but potent biological activities, primarily derived from plants, with a minor proportion originating from animals and microorganisms. These alkaloids are synthesized from the same prenyl unit that forms the terpene skeleton, with the nitrogen atom introduced through β-aminoethanol, ethylamine, or methylamine, leading to a range of complex and diverse structures. Based on their skeleton type, they can be categorized into monoterpenes, sesquiterpenes, diterpenes, and triterpene alkaloids. To date, 289 natural terpenoid alkaloids, excluding triterpene alkaloids, have been identified in studies published between 2019 and 2024. These compounds demonstrate a spectrum of biological activities, including anti-inflammatory, antitumor, antibacterial, analgesic, and cardioprotective effects, making them promising candidates for further development. This review provides an overview of the sources, chemical structures, and biological activities of natural terpenoid alkaloids, serving as a reference for future research and applications in this area.

Two new sesquiterpene glycosides from Dendrobium findleyanum

One new ylangene-type sesquiterpene glycoside, findlayanoside C (1), and one new picrotoxane-type sesquiterpene glycoside, findlayanoside D (3), together with five known sesquiterpene glycosides, dendrofindlayanoside C (2), dendronobiloside B (4), dendronobiloside A (5), dendroside F (6) and dendromoniliside D (7), have been isolated from the stems of Dendrobium findleyanum. The structures of compounds 1 and 3 were elucidated by means of extensive spectroscopic analyses, and their absolute configuration were confirmed by electronic circular dichroism (ECD) calculations. Cytotoxic activity assays against SMMC-7721, A-549 and MCF-7 human cancer cell lines revealed IC50 values of 10.12, 12.32 and 14.13 μM for compound 1, and of 9.25, 13.16 and 16.26 μM for compound 2. This study enriches the anti-tumour sesquiterpenoids composition of D. findleyanum.

Phytochemical Profile of Alkaloid Extract from Dendrobium huoshanense and Inhibitory Effects against Oxidative Stress in H2 O2 -Induced PC12 Cells

This study aimed to explore the alkaloid profile of Dendrobium huoshanense and determine the potential protective effect against oxidative damage. The crude D. huoshanense alkaloid extract (DHAE) was obtained by 70 % ethanol extraction and liquid-liquid partition. DHAE contained specific alkaloid components with abundant 6-hydroxynobiline (58.15 %) and trace dendrobine (3.23 %) in the preliminary HPLC fingerprint and GC-MS analysis, which was distinguished from D. officinale or D. nobile. Subsequently, six alkaloids including 6-hydroxynobiline, 2-hydroxy dendrobine, nobilonine, dendrobine, Findlayines D and trans-dendrochrysanine were identified in the purified DHAE (namely DHSAE-3, DHSAE-3') via further solid phase extraction coupled with UPLC-MS/MS analysis. Meanwhile, pretreatment with DHAE or DHSAE (0.5, 5 μg/mL) increased cell viability by 14.0-57.4 % compared to that of H2 O2 -induced PC12 Model cells. Among them, 5 μg/mL DHSAE-3-treated cells displayed a pronounced reversion than the positive vitamin E (p<0.01). Furthermore, a clear cellular morphological restoration and 38.4 % reduction in intracellular reactive oxidative species level were achieved. Our findings suggest that D. huoshanense has a characteristic alkaloid profile represented by abundant 6-hydroxynobiline, and DHAEs exhibit obvious protection against oxidative neuronal damage. Overall, this study indicates that DHAEs might be used to inhibit oxidative stress and provide a source to develop novel neuroprotective drugs.

Two new cadinene-type sesquiterpene glycosides from Dendrobium findlayanum

Two new and one known cadinene-type sesquiterpene glycosides, findlayanosides A-B (1-2) and dendronobiloside D (3), were isolated from the stems of Dendrobium findlayanum. This is the first report that cadinene-type sesquiterpene glycosides were isolated from D. findlayanum. The structures of compounds 1 and 2 were elucidated by extensive spectroscopic analyses, and their absolute configurations were confirmed by electronic circular dichroism (ECD) calculations. The obtained compounds were evaluated for their cytotoxicity against HL-60, SMMC-7721, A-549 and MCF-7 human cancer cells, and no obvious cytotoxic activity was observed at the concentration of 25 μΜ.

Two new alkaloids from Dendrobium nobile Lindl. exhibited neuroprotective activity, and dendrobine alleviated Aβ1-42 -induced apoptosis by inhibiting CDK5 activation in PC12 cells

Dendrobium nobile Lindl. is registered in the Chinese Pharmacopoeia as a traditional medicine. Phytochemical investigation of the ethanol extract of D. nobile Lindl. stems yielded three alkaloid compounds, including two new compounds dendroxine B (2) and denrine B (3) as well as one known compound dendrobine (1). Here, we identified the structure of these compounds using spectroscopic analyses and compared them with those described in previous studies. Compounds 1-3 were found to show protective effect against amyloid-β 1-42 (Aβ_1-42 )-induced neurotoxicity in rat pheochromocytoma (PC12) cells, among which dendrobine exhibited the most significant neuroprotective effect. Hoechst 33342/propidium iodide staining indicated that dendrobine ameliorated Aβ_1-42 -induced apoptosis. Moreover, quantitative real-time polymerase chain reaction and western blot analysis analysis demonstrated that dendrobine suppressed the activation of cyclin-dependent kinase 5 (CDK5), upregulated Bcl-2 expression, and downregulated Bax, cyto-c, and caspase-3 expression. Molecular docking analysis and surface plasmon resonance assay suggested that dendrobine directly bound to CDK5 protein with a KD value of 2.05 × 10^-4  M. In summary, alkaloids are the neuroprotective constituents of D. nobile Lindl., and dendrobine protected PC12 cells against Aβ_1-42 -induced apoptosis by inhibiting CDK5 activation.

Picrotoxane sesquiterpenoids: chemistry, chemo- and bio-syntheses and biological activities

Covering: up to December 2021Picrotoxane sesquiterpenoids are a special category of natural products known to have a picrotoxane skeleton and are characterised by a highly oxidised cis-hydrindene core, lactone rings, and epoxide functionalities. Ever since the first picrotoxane was isolated from Menispermum cocculus in the early 19^th century, these compounds have long attracted the attention of natural product chemists, synthetic chemists, and pharmacologists for their particular structures and powerful biological activities. This review extensively summarizes a total of 132 naturally occurring picrotoxane sesquiterpenoids, taking into account their distributions, structural classifications, chemical and bio-synthetic researches, and bioactivities. It provides a comprehensive and in-depth perspective for further investigation on picrotoxane sesquiterpenoids.

Alkaloids from Dendrobium and their biosynthetic pathway, biological activity and total synthesis

BACKGROUND

Dendrobium Sw. has been used for thousands of years in China as a precious traditional Chinese medicine. It is derived from stems of various Dendrobium plants and has the functions of nourishing Yin and clearing heat, activating water and nourishing the stomach, moistening the lung and relieving cough. Modern phytochemical studies show that the main components of Dendrobium include alkaloids, polysaccharides, terpenoids, diphenylbenzene, and phenanthrene. Alkaloids are natural products with obvious biological activity and are important effective components of the medicinal activity or toxicity of plants. At present, dozens of alkaloids with various structures have been isolated from Dendrobium plants, and the alkaloid contents in Dendrobium plants of different species are quite different. From the perspective of food safety, the type, molecular structure, content and potential physiological activity or toxicity of alkaloids are important bases for evaluating the safety of edible plants. Studies have shown that the alkaloids isolated from Dendrobium have neuroprotective, anti-inflammatory and antitumor activities, showing that these alkaloids with potential medicinal activity are important sources of lead compounds in innovative drug development.

PURPOSE

To summarize the research progress on alkaloids in Dendrobium and provide a reference for research on the food safety and medicinal development of Dendrobium.

METHOD

Information about alkaloids from Dendrobium was collected from the scientific databases Web of Science, PubChem and PubMed. We discuss the biosynthetic pathway, biological activities and total synthesis of alkaloids from Dendrobium from 1964 to 2020 and summarize the knowledge of alkaloids from Dendrobium, the biosynthetic pathway, biological activities and total synthesis. We chose publications on their chemistry, drug effects, pharmacology, metabolism and biosynthesis, physiology and toxicity. Alkaloids, Dendrobium, biosynthetic pathway and biological activities were used as keywords to extract the relevant literature.

CONCLUSION

In this paper, the structural classification, biological activity, target and toxicology and synthesis of the alkaloids in Dendrobium were systematically reviewed, which will provide a reference for the safety, development and application of Dendrobium.

Orchidaceae-Derived Anticancer Agents: A Review

Simple Summary

Orchids are commonly used in folk medicine for the treatment of infections and tumors but little is known about the actual chemical composition of these plants and their anticancer properties. In this paper, the most recent literature on orchid-derived bioactive substances with anticancer properties is reviewed. According to the published data, numerous species of orchids contain potential antitumor chemicals. Still, a relatively insignificant number of species of orchids have been tested for their bioactive properties and most of those studies were on Asian taxa. Broader research, ’including American and African species, as well as the correct identification of samples, is essential for evaluating the usefulness of orchids as a plant family with huge anticancer potential.

Abstract

Species of orchids, which belong to the largest family of flowering plants, are commonly used in folk medicine for the treatment of infections and tumors. However, little is known about the actual chemical composition of these plants and their anticancer properties. In this paper, the most recent literature on orchid-derived bioactive substances with anticancer properties is reviewed. For the assessment, previous papers on the anticancer activity of Orchidaceae published since 2015 were considered. The papers were found by exploring electronic databases. According to the available data, many species of orchids contain potential antitumor chemicals. The bioactive substances in a relatively insignificant number of orchids are identified, and most studies are on Asian taxa. Broader research on American and African species and the correct identification of samples included in the experiments are essential for evaluating the usefulness of orchids as a plant family with vast anticancer potential.

Natural Composition and Biosynthetic Pathways of Alkaloids in Medicinal Dendrobium Species

Dendrobium is the second biggest genus in the Orchidaceae family, some of which have both ornamental and therapeutic values. Alkaloids are a group of active chemicals found in Dendrobium plants. Dendrobine has emerged specific pharmacological and therapeutic properties. Although Dendrobium alkaloids have been isolated and identified since the 1930s, the composition of alkaloids and their biosynthesis pathways, including metabolic intermediates, alkaloid transporters, concrete genes involved in downstream pathways, and associated gene clusters, have remained unresolved scientific issues. This paper comprehensively reviews currently identified and tentative alkaloids from the aspect of biogenic pathways or metabolic genes uncovered based on the genome annotations. The biosynthesis pathways of each class of alkaloids are highlighted. Moreover, advances of the high-throughput sequencing technologies in the discovery of Dendrobium alkaloid pathways have been addressed. Applications of synthetic biology in large-scale production of alkaloids are also described. This would serve as the basis for further investigation into Dendrobium alkaloids.

Identification, Biological Activities and Biosynthetic Pathway of Dendrobium Alkaloids

Dendrobium is a genus of flowering plants belonging to the Orchidaceae family with more than 1,400 species. Many Dendrobium species have been used as medicinal plants in several Asian countries for thousands of years. Alkaloids were reported as the major biological markers due to their complex chemical compositions and various types. In this review, we summarized the structural types of alkaloids, their pharmacological activities, as well as the mechanisms of biological activities. More than sixty alkaloids were isolated and identified from the Dendrobium genus. Moreover, the pharmacological effects of Dendrobium alkaloids as hepatic lipid and gluconeogenesis regulation, as neuroprotection, and as anti-tumor, anti-inflammatory, anti-diabetes, and anti-virus factors were described. Besides, the total chemical synthesis of dendrobine is provided, while the biosynthetic pathway of dendrobine has been proposed based on the functions of associated genes. For applications of these invaluable herbs, more researches on the extraction of biological markers from compounds are needed. Further confirmation of the proposed biosynthetic pathways is anticipated as well.