Stelleraguaianone B and C, two new sesquiterpenoids from Stellera chamaejasme L

Characterization of SchTPSs Enables Construction of Yeast for the Bioproduction of α-Cadinol and the Related Sesquiterpenes

Plant volatile sesquiterpenes (PVSs) play important roles in chemical plant defense. However, it is difficult to isolate sufficient PVSs for deep investigations due to their low contents and chemical and physical properties close to those of other lipids. The extracts of Stellera chamaejasme L. exhibit insecticidal, fungicidal, and allelopathic activities. In this study, we identified three sesquiterpene synthase genes (SchTPS5, SchTPS6, and SchTPS7) from S. chamaejasme L. SchTPS7 is an α-farnesene synthase. SchTPS5 and SchTPS6 are two catalytically promiscuous sesquiterpene synthases, and α-cadinol and τ-muurolol are the predominant products for both of them in Saccharomyces cerevisiae. This study, for the first time, reports plant sesquiterpene synthases capable of producing α-cadinol and/or τ-muurolol in a heterologous host. More intriguingly, seven out of eight products of SchTPS6 in S. cerevisiae possess various insecticidal, fungicidal, and herbicidal activities. Building on this finding, we used SchTPS6 to construct an engineered S. cerevisiae for the production of these sesquiterpenes. The titers of two major products α-cadinol and τ-muurolol, respectively, reached 46.2 ± 4.0 and 11.2 ± 1.4 mg/L in a flask. This study lays a foundation for the development of new agrochemical mixtures.

Terpenoids from the Roots of Stellera chamaejasme (L.) and Their Bioactivities

An undescribed diterpene, stellerterpenoid A (1), and two undescribed sesquiterpenoids, stellerterpenoids B and C (2-3), together with six known compounds, prostratin (4) stelleraguaianone B (5), chamaejasnoid A (6), auranticanol L (7), wikstronone C (8), and oleodaphnone (9), were isolated from the roots of Stellera chamaejasme L. Their structures were elucidated by extensive spectroscopic data (1D, 2D NMR, IR, UV, and HR-ESI-MS). The absolute configuration of 1-3 was elucidated based on ECD calculation. Among them, stellerterpenoid A was a rare 13, 14-seco nortigliane diterpenoid and stellerterpenoid B was a guaiacane-type sesquiterpenoid with an unusual 1, 2-diketone moiety. The known stelleraguaianone B (5) exhibited moderate activity for suppressing NO production in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages cells with an IC50 value of 24.76 ± 0.4 μM. None of the compounds showed anti-influenza virus or anti-tumor activity in vitro.

Daphnane-type diterpenoids from Stellera chamaejasme L. and their inhibitory activity against hepatocellular carcinoma cells

Daphnane-type diterpenoids, which are scarce in nature, exhibit potent growth-inhibitory activities against various cancer cells. To identify more daphnane-type diterpenoids, the phytochemical components in the root extracts of Stellera chamaejasme L. were analysed in this study using the Global Natural Products Social platform and the MolNetEnhancer tool. Three undescribed 1α-alkyldaphnane-type diterpenoids (1-3; named stelleradaphnanes A-C) and 15 known analogues were isolated and characterised. The structures of these compounds were determined using ultraviolet and nuclear magnetic resonance spectroscopy. The stereo configurations of the compounds were determined using electronic circular dichroism. Next, the growth-inhibitory activities of isolated compounds against HepG2 and Hep3B cells were examined. Compound 3 exhibited potent growth-inhibitory activities against HepG2 and Hep3B cells with half-maximal inhibitory concentration values of 9.73 and 15.97 μM, respectively. Morphological and staining analyses suggested that compound 3 induced apoptosis in HepG2 and Hep3B cells.

Diversity of sesquiterpenoids from Stellera chamaejasme with neuroprotective effects

Chromatographic fractionation of the 95% EtOH extract of the roots of Stellera chamaejasme yielded 20 sesquiterpenoids of four different types, guaiane-, carotane-, sesquicarane-, and alpiniane-types. Among them, sesquistrachanoids A-F were previously undescribed ones, whose structures including absolute configurations were elucidated by spectroscopic methods, the Mo₂(OAc)₄-induced ECD experiment, and analysis of experimental and calculated 1D NMR and ECD data. Sesquistrachanoid A is a 2,3-seco-guaiane-type sesquiterpenoid with a α-pyrone core and sesquistrachanoid B is the first example of 8,9-seco-guaiane-type sesquiterpenoid featured with an 1,8-δ-lactone core. Sesquistrachanoid C is a guaiane sesquiterpenoid characterized by a peroxide bridge between C-8 and C-10. All sesquiterpenoids were evaluated for their neuroprotective effects on cell damage induced by sodium nitroprusside in PC-12 cells. The bioassay results showed that six compounds at 10 μM could restore the cell viability, being comparable to that of the positive control edaravone. The mechanistic study on the most pronounced activity compound, stelleraguaianone B, demonstrated that it played a neuroprotective role by promoting the mRNA expression of antioxidant enzymes to reduce oxidative stress.

Stellerasespenes A‒E: Sesquiterpenoids from Stellera chamaejasme and their anti-neuroinflammatory effects

Five undescribed sesquiterpenoids stellerasespenes A‒E and four reported congeners were isolated from the roots of Stellera chamaejasme. The structures were elucidated by comprehensive spectroscopic analyses together with X-ray single crystal diffraction and theoretical calculations. The structure of holosericin B was revised. All the isolated compounds were evaluated for NO production in murine microglial BV2 cells induced by LPS. Stellerasespene A showed better inhibitory activity than the positive control minocycline, inhibiting NO production and overexpression of pro-inflammatory cytokine IL-1β in LPS-activated BV2 cells.

Effects of Allelochemicals, Soil Enzyme Activities, and Environmental Factors on Rhizosphere Soil Microbial Community of Stellera chamaejasme L. along a Growth-Coverage Gradient

Allelochemicals released from the root of Stellera chamaejasme L. into rhizosphere soil are an important factor for its invasion of natural grasslands. The aim of this study is to explore the interactions among allelochemicals, soil physicochemical properties, soil enzyme activities, and the rhizosphere soil microbial communities of S. chamaejasme along a growth-coverage gradient. High-throughput sequencing was used to determine the microbial composition of the rhizosphere soil sample, and high-performance liquid chromatography was used to detect allelopathic substances. The main fungal phyla in the rhizosphere soil with a growth coverage of 0% was Basidiomycetes, and the other sample plots were Ascomycetes. Proteobacteria and Acidobacteria were the dominant bacterial phyla in all sites. RDA analysis showed that neochamaejasmin B, chamaechromone, and dihydrodaphnetin B were positively correlated with Ascomycota and Glomeromycota and negatively correlated with Basidiomycota. Neochamaejasmin B and chamaechromone were positively correlated with Proteobacteria and Actinobacteria and negatively correlated with Acidobacteria and Planctomycetes. Allelochemicals, soil physicochemical properties, and enzyme activity affected the composition and diversity of the rhizosphere soil microbial community to some extent. When the growth coverage of S. chamaejasme reached the primary stage, it had the greatest impact on soil physicochemical properties and enzyme activities.

Stelleranoids A-M, guaiane-type sesquiterpenoids based on [5,7] bicyclic system from Stellera chamaejasme and their cytotoxic activity

Thirteen previously undescribed guaiane-type sesquiterpenoids based on [5,7] bicyclic system, stelleranoids A-M (1-13), along with six known analogues (14-20), were isolated from the roots of Stellera chamaejasme with chromatographic techniques. Their structures including absolute configurations were determined by HRESIMS and spectroscopic data, quantum chemical calculations, as well as X-ray crystallographic analysis. Cytotoxicity test in three cell lines indicated that compound 14 had relatively stronger cytotoxic effect against MKN-45, SKOV3, and Du145 cell lines with IC₅₀ of 9.8, 17.4 and 7.3 μM, respectively; compounds 3 and 8 displayed moderate cytotoxic effect against MKN-45 and Du145 cell lines with IC₅₀ ranged from 14.5 to 18.8 μM, comparable to those of the positive control. As determined by fluorescent microscopy and flow cytometry in Du145 cell line, compound 14 could promote cell apoptosis and cause cell cycle arrest at the G0/G1 phase, leading to the inhibition of cell proliferation. Further Western blot analysis revealed that this inhibitory effect was accompanied by upregulating pro-apoptosis proteins cleaved-PARP, cleaved-Caspase-9 and tumor suppressor protein p53 while downregulating anti-apoptotic protein Bcl-2 in 14-treated Du145 cells.

Guaiane-type sesquiterpenoids from the roots of Stellera chamaejasme L. and their neuroprotective activities

Nine undescribed guaiane-type sesquiterpenoids stelleraterpenoids A‒I, along with seven reported congeners, were isolated and identified from the 70% EtOH extract of the roots of Stellera chamaejasme L. Their chemical structures were elucidated on the basis of various spectral data. The relative configurations were determined by their NOESY spectra and comparison between their experimental and calculated NMR data. The absolute configurations were established by the comparison between the experimental and calculated ECD spectra and further by X-ray single-crystal diffraction analysis. The neuroprotective effects of these compounds on the H₂O₂-induced damage in human neuroblastoma SH-SY5Y cells were evaluated. Stelleraguaianone B exhibited the better activity with 71.62% cell viability compared to the positive control Trolox (65.05%) at 12.5 μM, which might be achieved by inhibiting the apoptosis of SH-SY5Y cells based on an annexin V-FITC/PI staining experiment.

Ethnopharmacology, phytochemistry, pharmacology, clinical applications and toxicology of the genus Stellera Linn.: A review

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Stellera Linn. consists of species of perennial herbs and shrubs, and is mainly distributed in the temperate regions of east Asia to west Asia. There are 10∼12 species in the world, two species in China: Stellera chamaejasme Linn. and Stellera formosana Hayata ex Li. As recorded, the roots of Stellera species are used to dissipate phlegm and relieve pain. The roots and the barks can be used for papermaking.

AIM OF THIS REVIEW

This review aims to summarize the ethnopharmacological uses, chemical constituents, pharmacological activities, clinical applications and toxicology of the genus Stellera to better understand their therapeutic potential in the future.

MATERIALS AND METHODS

The relevant information of the genus Stellera was collected from scientific databases (Pubmed, ACS website, SciFinder Scholar, Elsevier, Google Scholar, Web of Science and CNKI). Information was also gathered from 'Flora Republicae Popularis Sinicae (〈〈〉〉)', folk records, conference papers on ethnopharmacology, Ph.D. and Masters' Dissertation.

RESULTS

Stellera plants have been studied as traditional folk medicines all around the world. The chemical constituents of Stellera species mainly comprise terpenoids, flavonoids, coumarins, lignans, and so on. Extracts and compounds of Stellera species exhibit extensive pharmacological activities, such as anti-tumor, anti-viral, anti-convulsive, anti-epileptic, anti-bacterial and anti-insect activities, etc. Clinical applications have suggested that the genus Stellera has the effects in treating several skin diseases and cancers, however, the results should be further verification. The genus Stellera plants are toxic and should be used reasonable.

CONCLUSION

This paper reviewed the ethnopharmacological uses, chemical constituents, pharmacology, clinical applications and toxicology of the genus Stellera. The genus Stellera has broad application prospects. However, further in-depth studies are needed to determine the medical uses of the genus and its chemical constituents, pharmacological activities, clinical applications and toxicology.

A new 11,10-guaiane-type sesquiterpenoid from the roots of Stellera chamaejasme Linn

Chamaejasmone F, a new 11,10-guaiane-type sesquiterpenoid, is isolated from the roots of Stellera chamaejasme Linn., along with four known compounds including two guaiane sesquiterpenoids and two lignans. The structure of the new compound is elucidated by extensive spectroscopic analysis, especially two-dimensional nuclear magnetic resonance spectroscopy and high-resolution electrospray ionization mass spectrometry. The known compounds 1β-hydroxy-10βH-guaia-4,11-dien-3-one and (+)-hinokinin are isolated from the genus Stellera for the first time. In an in vitro assay, chamaejasmone F shows moderate cytotoxic activity against the human triple negative breast cancer cell line MB-MDA-231.

Antiallergic Effects of Phenolic Compounds Isolated From Stellera chamaejasme on RBL-2H3 Cells

The current study was undertaken to isolate and identify anti-inflammatory and antiallergic active compounds in the ethyl acetate and butanol fractions of an ethanolic extract of the aerial parts of Stellera chamaejasme (SCAE). A new maltol glucoside, maltol 3-(6″-(2-( E)-butenoyl)-glucoside) and benzoic acid, daphnoretin (a coumarin), 6 flavonoids (apigenin, genkwanin, taxifolin, apigenin 7- O-glucoside, luteolin 7- O-sambubioside, genkwanin 5- O-glucoside), and 2 lignans (matairesinoside and lariciresinol) were isolated from SCAE by chromatographic separation. Their chemical structures were elucidated by analyzing spectroscopic data, including 1-dimensional and 2-dimensional nuclear magnetic resonance (Fig1). Maltol 3-(6″-(2-( E)-butenoyl)-glucoside) significantly inhibited β-hexosaminidase release by 85.5% in immunoglobulin E and dinitrophenyl/bovine serum albumin (DNP/BSA)-induced RBL-2H3 cells. Benzoic acid from S. chamaejasme inhibited β-hexosaminidase release (by 80.2%) in IgE and DNP/BSA-induced RBL-2H3 cells and interleukin-4 messenger ribonucleic acid expression (by 21.9% inhibition) in propidium iodide-induced RBL-2H3 cells.

Characterization of Guaiene Synthases from Stellera chamaejasme L. Flowers and Their Application in De novo Production of (-)-Rotundone in Yeast

Four terpene synthases for the biosynthesis of volatile terpenoids were identified from the transcriptome of Stellera chamaejasme L. flowers, including SchTPS1, SchTPS2, SchTPS3, and SchTPS4. Their functions were characterized by synthetic biology approaches in Escherichia coli and in vitro enzymatic assays. SchTPS1, SchTPS2, and SchTPS3 are guaiene synthases, while SchTPS4 is an (E,E)-geranyl linalool synthase. Next, SchTPS1 and α-guaiene 2-oxidase VvSTO2 were co-expressed in Saccharomyces cerevisiae to reconstruct the biosynthetic pathway of (-)-rotundone, which is a unique aroma compound in fruits, vegetables, and wines. This is the first report for the construction of a (-)-rotundone-producing microbial platform.