Highly oxidized cuparene-type sesquiterpenes from a mycelial culture of Flammulina velutipes

Catalytic asymmetric intramolecular propargylation of cyclopropanols to access the cuparane core

The catalytic asymmetric propargylation of enol(ate) intermediates is a well-established method for the synthesis of α-propargyl-substituted carbonyl compounds. However, the propargylation of homo-enol(ate) or its equivalents for the synthesis of β-propargyl-substituted carbonyl compounds remains underdeveloped. A catalytic enantioselective decarboxylative intramolecular propargylation of cyclopropanols has been developed using a PyBox-complexed copper catalyst. This reaction offers an effective approach to assemble a cyclopentanone skeleton bearing an all-carbon quaternary stereogenic center and an adjacent quaternary gem-dimethyl carbon center, which is the core scaffold of the naturally occurring cuparenoids. Key to the success of this protocol is the use of a new structurally optimized PyBox ligand. This study represents the first example of catalytic asymmetric intramolecular propargylation of cyclopropanols.

Molecular and Functional Analyses of Characterized Sesquiterpene Synthases in Mushroom-Forming Fungi

Sesquiterpenes are a type of abundant natural product with widespread applications in several industries. They are biosynthesized by sesquiterpene synthases (STSs). As valuable and abundant biological resources, mushroom-forming fungi are rich in new sesquiterpenes and STSs, which remain largely unexploited. In the present study, we collected information on 172 STSs from mushroom-forming fungi with experimentally characterized products from the literature and sorted them to develop a dataset. Furthermore, we analyzed and discussed the phylogenetic tree, catalytic products, and conserved motifs of STSs. Phylogenetic analysis revealed that the STSs were clustered into four clades. Furthermore, their cyclization reaction mechanism was divided into four corresponding categories. This database was used to predict 12 putative STS genes from the edible fungi Flammulina velutipes. Finally, three FvSTSs were selected to experimentally characterize their functions. FvSTS03 predominantly produced Δ-cadinol and FvSTS08 synthesized β-barbatene as the main product; these findings were consistent with those of the functional prediction analysis. A product titer of 78.8 mg/L β-barbatene was achieved in Saccharomyces cerevisiae via metabolic engineering. Our study findings will help screen or design STSs from fungi with specific product profiles as functional elements for applications in synthetic biology.

Liverwort-Derived Metabolites Retard Endophyte Growth and Inspire Antifungal Application

Liverwort secondary metabolites play an important role in the peaceful relationship between liverwort endophytic fungi and the host. This study identified potential antifungal agents based on interactions between host plants and endophytic fungi. Two endophytic fungi strains and 25 metabolites, including nine new compounds, were isolated from the Chinese liverwort Herbertus herpocladioides. Endophytic fungi were identified using internal transcribed spacer and whole-genome sequencing, and the compound structures were determined using comprehensive spectroscopic analysis coupled with electronic circular dichroism calculations. Among these compounds, compounds 10-13 exhibited potent antifungal activities. Compound 10, the most potent antifungal agent, disrupted fungal mitochondrial respiration by inhibiting the activity of mitochondrial complexes I and IV and resulted in the intracellular ATP content of endophytic fungi being significantly reduced. The in vivo results show that compound 10 protected fruits and animals from infection by phytopathogen Alternaria citriarbusti and human pathogen Candida albicans, respectively.

Two new sesquiterpenoids from plant endophytic fungus Flammulina velutipes

Two new sesquiterpenoids, flammupin A (1) and flammupin B (2), along with two known compounds, enokipodin C (3) and 5,5'-dibuthoxy-2,2'-bifuran (4) were obtained from Flammulina velutipes, an endophytic fungus isolated from the roots of Caulophyllum robustum Maxim. The structures were elucidated by the combination of HR-ESI-MS, NMR, and ECD analyses. Compound 3 exhibited moderate to potent cytotoxicity against A549, HeLa, and SMMC-7721 cells with IC₅₀ values ranged from 3.69 to 11.84 μM.

A Combined Molecular Docking and Density Functional Theory Nuclear Magnetic Resonance Study of Trans-Dehydrocrotonin Interacting with COVID-19 Main Protease and Severe Acute Respiratory Syndrome Coronavirus 2 3C-Like Protease

For the development of drugs that treat SARS-CoV-2, the fastest way is to find potential molecules from drugs already on the market. Unfortunately, there is currently no specific drug or treatment for COVID-19. Among all structural proteins in SARS-CoV, the spike protein is the main antigenic component responsible for inducing host immune responses, neutralizing antibodies, and/or protecting immunity against virus infection. Molecular docking is a technique used to predict whether a molecule will bind to another. It is usually a protein to another or a protein to a binding compound. Natural products are potential binders in several studies involving coronavirus. The structure of the ligand plays a fundamental role in its biological properties. The nuclear magnetic resonance technique is one of the most powerful tools for the structural determination of ligands from the origin of natural products. Nowadays, molecular modeling is an important accessory tool to experimentally got nuclear magnetic resonance data. In the present work, molecular docking studies aimed is to investigate the limiting affinities of trans-dehydrocrotonin molecule and to identify the main amino acid residues that could play a fundamental role in their mechanism of action of the SARS-CoV spike protein. Another aim of this work is all about to evaluate 10 hybrid functionalities, along with three base pairs using computational programs to discover which ones are more reliable with the experimental result the best computational method to study organic compounds. We compared the results between the mean absolute deviation (MAD) and root-mean-square deviation (RMSD) of the molecules, and the smallest number between them was the best result. The positions assumed by the ligands in the active site of the spike glycoprotein allow assuming associations with different local amino acids.

Synthesis of Cyclopentenones with C4-Quaternary Stereocenters via Stereospecific [3,3]-Sigmatropic Rearrangement and Applications in Total Synthesis of Sesquiterpenoids

A cationic gold(I)-catalyzed asymmetric [3,3]-sigmatropic rearrangement of sulfonium leads after cyclization to cyclopentenones with a C4-quaternary stereocenter. Starting with simple vinyl sulfoxides and propargyl silane, numerous compounds were isolated with moderate to good yields and excellent enantiomeric excesses (26 examples). The application of this simple methodology allowed the efficient total synthesis of five natural sesquiterpenoids, including enokipodin A and B, hitoyopodin A, lagopodin A, and isocuparene-3,4-diol.

Base-Free Catalytic Wittig-/Cross-Coupling Reaction Sequence as Short Synthetic Strategy for the Preparation of Highly Functionalized Arylbenzoxepinones

The facile synthesis of highly functionalized building blocks with potential biological activity is of great interest to medicinal chemistry. The benzoxepinone core structures commonly exhibit biological activity. Thus, a short and efficient synthetic route towards benzoxepine containing scaffold, which enables late stage modification was developed. Namely, base-free catalytic Wittig reactions enabled the synthesis of bromobenzoxepinones from readily available starting materials. Subsequent, Suzuki–Miyaura and Stille reactions proved to be suitable methods to access a variety of benzoxepinone diaryl derivatives by late stage modification in only three steps. This three-step reaction sequence is suitable for high throughput applications and gives facile access to highly complex molecular structures, which are suitable for further functionalization. The antiproliferative properties of selected arylbenzoxepinones­ were tested in vitro on monolayer tumor cell line A549. Notably, in this initial screening, these compounds were found to be active in the micromolar range.

Identification of Secondary Metabolites in Flammulina velutipes by UPLC-Q-Exactive-Orbitrap MS

Flammulina velutipes is the fourth largest edible fungus in China with high nutritional value. In this paper, ultrahigh-performance liquid chromatography tandem hybrid quadrupole-Orbitrap mass spectrometry (UPLC-Q-Exactive-Orbitrap MS) was used to identify the secondary metabolites of F. velutipes. The metabolites were identified by comparing the retention time, accurate molecular weight, and MS2 data with standard databases of mzVault and mzCloud (compound: 17,000+) and BGI high-resolution accurate mass plant metabolome database (plant metabolite: 2500+). Finally, 26 secondary metabolites were preliminarily identified, including flavonoids, phenylpropanoids, organic acids, and steroids.

Bioactive small secondary metabolites from the mushrooms Lentinula edodes and Flammulina velutipes

Mushrooms have been attracting attention as a source of bioactive compounds for the development of dietary supplements and medicines. Many researchers have reported pharmacological effects of edible mushrooms, and have isolated and identified bioactive substances. Lentinula edodes (shiitake) and Flammulina velutipes (enokitake) are the cultivated edible mushrooms that are popular throughout the world. In L. edodes, polyacetylenes and sulfur compounds have been shown to display antimicrobial activity. In F. velutipes, many types of bioactive terpenes have been reported from mycelium culture filtrate or solid culture substrate. This article reviews the bioactive metabolites of low-molecular weight from L. edodes and F. velutipes.

Stepwise approach for sterically hindered Csp3-Csp3 bond formation by dehydrogenative O-alkylation and Lewis acid-catalyzed [1,3]-rearrangement towards the arylalkylcyclopentane skeleton of sesquiterpenes

A stepwise dehydrogenative cross-coupling method was developed for the formation of sterically hindered Csp3-Csp3 bonds. Intramolecular dehydrogenative O-alkylation of a β-ketoester by 2,3-dichloro-5,6-dicyano-p-benzoquinone to form an oxolane followed by Lewis acid-catalyzed [1,3]-rearrangement furnished the sesquiterpene arylmethylcyclopentane skeleton. The formal syntheses of herbertane-type β-herbertenol, cuparane-type enokipodins A and B were also achieved.

Productivity and bioactivity of enokipodins A-D of Flammulina rossica and Flammulina velutipes

Enokipodins are antimicrobial sesquiterpenes produced by Flammulina velutipes in a mycelial culture medium. To date, enokipodin production has not been reported in other members of the genus Flammulina. Hence, in this study, the production of enokipodins A, B, C, and D by F. velutipes and F. rossica was investigated. Some strains of F. rossica were confirmed to produce at least one of the four enokipodins in the culture medium. However, some strains of F. velutipes did not produce any of the enokipodins. In an antibacterial assay using liquid medium, enokipodin B showed the strongest growth inhibitory activity against Bacillus subtilis among the four types of enokipodins. Enokipodin B inhibited the spore germination of some plant pathogenic fungi. Enokipodins B and D exerted moderate anti-proliferative activity against some cancer cell lines, and enokipodins A and C inhibited the proliferation of the malarial parasite, Plasmodium falciparum.

Fe(III)-Catalyzed Diastereoselective Friedel-Crafts Alkylation-Hemiketalization-Lactonization Cascade for the Synthesis of Polycyclic Bridged 2-Chromanol Lactones

An unprecedented Fe(III)-catalyzed Friedel-Crafts alkylation-hemiketalization-lactonization cascade of electron-rich hydroxy arenes and distinctively functionalized unsaturated 4-keto esters is developed for the construction of polycyclic bridged 2-chromanol lactones. Following this simple and facile protocol, a broad range of products was prepared in good to excellent yields as a single diastereomer. An unusual conglomerate (enantiomerically pure polymorph) of 3ac is reported along with the absolute stereochemistry, and the remaining products were rigorously confirmed by single-crystal X-ray analysis and analogy.

Golden Needle Mushroom: A Culinary Medicine with Evidenced-Based Biological Activities and Health Promoting Properties

Flammulina velutipes (enoki, velvet shank, golden needle mushroom or winter mushroom), one of the main edible mushrooms on the market, has long been recognized for its nutritional value and delicious taste. In recent decades, research has expanded beyond detailing its nutritional composition and delved into the biological activities and potential health benefits of its constituents. Many bioactive constituents from a range of families have been isolated from different parts of the mushroom, including carbohydrates, protein, lipids, glycoproteins, phenols, and sesquiterpenes. These compounds have been demonstrated to exhibit various biological activities, such as antitumour and anticancer activities, anti-atherosclerotic and thrombosis inhibition activity, antihypertensive and cholesterol lowering effects, anti-aging and antioxidant properties, ability to aid with restoring memory and overcoming learning deficits, anti-inflammatory, immunomodulatory, anti-bacterial, ribosome inactivation and melanosis inhibition. This review aims to consolidate the information concerning the phytochemistry and biological activities of various compounds isolated from F. velutipes to demonstrate that this mushroom is not only a great source of nutrients but also possesses tremendous potential in pharmaceutical drug development.

Structural determination of complex natural products by quantum mechanical calculations of (13)C NMR chemical shifts: development of a parameterized protocol for terpenes

Nuclear magnetic resonance (NMR) spectroscopy is one of the most important tools for determining the structures of organic molecules. Despite the advances made in this technique, revisions of erroneously established structures for natural products are still commonly published in the literature. In this context, the prediction of chemical shifts through ab initio and density functional theory (DFT) calculations has become a very powerful tool for assisting with the structural determination of complex organic molecules. In this work, we present the development of a protocol for (13)C chemical shift calculations of terpenes, a class of natural products that are widely distributed among plant species and are very important due to their biological and pharmacological activities. This protocol consists of GIAO-DFT calculations of chemical shifts and the application of a parameterized scaling factor in order to ensure accurate structural determination of this class of natural products. The application of this protocol to a set of five terpenes yielded accurate calculated chemical shifts, showing that this is a very attractive tool for the calculation of complex organic structures such as terpenes.

Evaluation of the α-phenylvinyl cation as a chemical ionization reagent for the differentiation of isomeric substituted phenols in an ITMS

Ion-molecule reactions between the α-phenylvinyl cation and isomeric naturally occurring phenols were investigated using a quadruple ion trap mass spectrometer. The α-phenylvinyl cation m/z 103, generated by chemical ionization from phenylacetylene, reacts with neutral aromatic compounds to form the characteristic species: [M + 103](+) adduct ions and the trans-vinylating product ions [M + 25](+) , which correspond to [M + 103](+) adduct after the loss of benzene. Isomeric differentiation of several ring-substituted phenols was achieved by using collision-induced dissociation of the [M + 103](+) adduct ions. This method also showed to be effective in the differentiation of 4-ethylguaiacol from one of its structural isomers that displays identical EI and EI/MS/MS spectra. The effects of gas-phase alkylation with phenylvinyl cation on the dissociation behavior were examined using mass spectrometry(n) and labeled derivatives. Copyright © 2015 John Wiley & Sons, Ltd.

Enantioselective palladium catalyzed conjugate additions of ortho-substituted arylboronic acids to β,β-disubstituted cyclic enones: total synthesis of herbertenediol, enokipodin A and enokipodin B

Palladium catalyzed asymmetric conjugate addition of ortho-substituted arylboronic acids to cyclic enones and its application in natural product synthesis.

Use of P450 cytochrome inhibitors in studies of enokipodin biosynthesis

Enokipodins A, B, C, and D are antimicrobial sesquiterpenes isolated from the mycelial culture medium of Flammulina velutipes, an edible mushroom. The presence of a quaternary carbon stereocenter on the cyclopentane ring makes enokipodins A-D attractive synthetic targets. In this study, nine different cytochrome P450 inhibitors were used to trap the biosynthetic intermediates of highly oxygenated cuparene-type sesquiterpenes of F. velutipes. Of these, 1-aminobenzotriazole produced three less-highly oxygenated biosynthetic intermediates of enokipodins A-D; these were identified as (S)-(-)-cuparene-1,4-quinone and epimers at C-3 of 6-hydroxy-6-methyl-3-(1,2,2-trimethylcyclopentyl)-2-cyclohexen-1-one. One of the epimers was found to be a new compound.

Enhanced oral bioavailability of a sterol-loaded microemulsion formulation of Flammulina velutipes, a potential antitumor drug

PURPOSE

To investigate the growth inhibition activity of Flammulina velutipes sterol (FVS) against certain human cancer cell lines (gastric SGC and colon LoVo) and to evaluate the optimum microemulsion prescription, as well as the pharmacokinetics of encapsulated FVS.

METHODS

Molecules present in the FVS isolate were identified by gas chromatography/mass spectrometry analysis. The cell viability of FVS was assessed with methyl thiazolyl tetrazolium (MTT) bioassay. Based on the solubility study, phase diagram and stability tests, the optimum prescription of F. velutipes sterol microemulsions (FVSMs) were determined, followed by FVSMs characterization, and its in vivo pharmacokinetic study in rats.

RESULTS

The chemical composition of FVS was mainly ergosterol (54.8%) and 22,23-dihydroergosterol (27.9%). After 72 hours of treatment, both the FVS (half-maximal inhibitory concentration [IC(50)] = 11.99 μg · mL(-1)) and the standard anticancer drug, 5-fluorouracil (IC(50) = 0.88 μg · mL(-1)) exhibited strong in vitro antiproliferative activity against SGC cells, with IC(50) > 30.0 μg · mL(-1); but the FVS performed poorly against LoVo cells (IC(50) > 40.0 μg · mL(-1)). The optimal FVSMs prescription consisted of 3.0% medium chain triglycerides, 5.0% ethanol, 21.0% Cremophor EL and 71.0% water (w/w) with associated solubility of FVS being 0.680 mg · mL(-1) as compared to free FVS (0.67 μg · mL(-1)). The relative oral bioavailability (area-under-the-curve values of ergosterol and 22,23-dihydroergosterol showed a 2.56-fold and 4.50-fold increase, respectively) of FVSMs (mean diameter ~ 22.9 nm) as against free FVS were greatly enhanced.

CONCLUSION

These results indicate that the FVS could be a potential candidate for the development of an anticancer drug and it is readily bioavailable via microemulsion formulations.

Bioactive sesquiterpenoids from the solid culture of the edible mushroom Flammulina velutipes growing on cooked rice

The edible mushroom Flammulina velutipes was cultivated on cooked rice. Six new cuparene sesquiterpenes, enokipodins E-J (1-6), and two new sterpurane sesquiterpenes, sterpurols A (10) and B (11), with four known sesquiterpenes, 2,5-cuparadiene-1,4-dione (7), enokipodins B (8) and D (9), and sterpuric acid (12), were isolated from the solid culture of F. velutipes. The structures of new metabolites were elucidated by NMR experiments. The absolute configurations in new compounds were assigned by X-ray crystallographic analysis, the modified Mosher method, and CD data analysis. Bioactivity screening indicated that compounds 5-9 displayed weak antibacterial activity against Bacillus subtilis; 2, 3, and 5 showed weak antifungal activity against Aspergilus fumigatus; 6-9 showed both moderate cytotoxicity against the human tumor cell lines (HepG2, MCF-7, SGC7901, and A549) and antioxidant activity in DPPH scavenging assay. These results suggest that the solid culture of F. velutipes on cooked rice could be a good functional food.

Antineoplastic agents. 556. Isolation and structure of Coprinastatin 1 from Coprinus cinereus

Cancer cell line bioassay-guided separation of an ethyl acetate extract prepared from a plant-associated fungus, Coprinus cinereus, led to the isolation of three new sesquiterpenes, coprinastatin 1 (1), coprinol (2), and the epimer (4a), of the known sesquiterpene triol (4b). The previously described sesquiterpene 3 and oxazolinone 5 were also isolated. The structure and relative configuration of coprinastatin 1 (1) were determined by HRMS and by 1D- and 2D-NMR spectroscopic analyses. The structure of terpene 2 was elucidated by single-crystal X-ray diffraction experiments. The remaining structures were similarly determined, structure 3 by spectroscopic analyses and both 4a and 5 by X-ray crystal structure determination. Coprinastatin 1 (1) was found to inhibit growth of the murine P388 lymphocytic leukemia cell line and the pathogenic bacterium Neisseria gonorrhoeae.

Diversity of sesquiterpene synthases in the basidiomycete Coprinus cinereus

Fungi are a rich source of bioactive secondary metabolites, and mushroom-forming fungi (Agaricomycetes) are especially known for the synthesis of numerous bioactive and often cytotoxic sesquiterpenoid secondary metabolites. Compared with the large number of sesquiterpene synthases identified in plants, less than a handful of unique sesquiterpene synthases have been described from fungi. Here we describe the functional characterization of six sesquiterpene synthases (Cop1 to Cop6) and two terpene-oxidizing cytochrome P450 monooxygenases (Cox1 and Cox2) from Coprinus cinereus. The genes were cloned and, except for cop5, functionally expressed in Escherichia coli and/or Saccharomyces cerevisiae. Cop1 and Cop2 each synthesize germacrene A as the major product. Cop3 was identified as an alpha-muurolene synthase, an enzyme that has not been described previously, while Cop4 synthesizes delta-cadinene as its major product. Cop6 was originally annotated as a trichodiene synthase homologue but instead was found to catalyse the highly specific synthesis of alpha-cuprenene. Coexpression of cop6 and the two monooxygenase genes next to it yields oxygenated alpha-cuprenene derivatives, including cuparophenol, suggesting that these genes encode the enzymes for the biosynthesis of antimicrobial quinone sesquiterpenoids (known as lagopodins) that were previously isolated from C. cinereus and other Coprinus species.

Volatile terpenoids of endophyte-free and infected peppermint (Mentha piperita L.): chemical partitioning of a symbiosis

The study reports the effects on volatiles of an endophytic fungus inhabiting asymptomatically the leaves of peppermint. By means of headspace solid-phase microextraction (HS-SPME) and gaschromatography-mass spectrometry (GC-MS) terpenoids were sampled in time course from the head space of peppermint leaves and roots. After removal of the mycelium from peppermint tissues, fungal volatiles were analyzed and compared with those of pure fungal cultures. In the presence of the endophyte, the relative amount of all main compounds increased in leaves. Starting from the first 14 d of culture, (-)-menthone and (+)-neomenthol were consistently higher than in control plants. On the contrary, (+)-menthofuran increased only by 28 d of culture. Root volatiles were also dramatically altered by the presence of the fungus, with (+)-pulegone accounting for at least 44% of the total volatile emission. (+)-Pulegone was also the main compound of PGP-HSF mycelium isolated from peppermint roots. The sesquiterpenoid cuparene was found as a novel compound of peppermint leaf headspace and was a main volatile of ex planta and pure culture mycelia. The chemical spectrum of terpenoids and their distribution among peppermint roots, leaves, and mycelia are likely to account for a fine regulation of the mutualism in planta and for the acquisition by the fungus of novel metabolic competences.

Enantioselective total synthesis of enokipodins A-D, antimicrobial sesquiterpenes produced by the mushroom, Flammulina velutipes

The first enantioselective total synthesis of enokipodins A, B, C and D, highly oxidized alpha-cuparenone-type sesquiterpenoids possessing antimicrobial activity, was accomplished in 8-28% overall yields from methyl (2,5-dimethoxy-4-methylphenyl)acetate by applying Meyers' diastereoselective alkylation protocol for the construction of their C7-quaternary asymmetric center. The present synthesis confirmed the absolute configuration of the enokipodins, and also constitutes a formal enantioselective synthesis of (S)-1,4-cuparenediol and (S)-cuparene-1,4-quinone.

2,2-Dimethyl cyclopentanones by acid catalyzed ring expansion of isopropenylcyclobutanols. A short synthesis of (±)-α-cuparenone and (±)-herbertene

2,2-dimethyl cyclopentanones are readily prepared by acid catalyzed ring expansion of isopropenylcyclobutanols; the method allows ready access to the family of sesquiterpenes cuparanes and herbertanes, as demonstrated by the synthesis of (+/-)-alpha-cuparenone and the direct precursor of (+/-)-herbertene.

Antimicrobial cuparene-type sesquiterpenes, enokipodins C and D, from a mycelial culture of Flammulina velutipes

Two new cuparene-type sesquiterpenes, enokipodins C (1) and D (2), were isolated from culture medium of an edible mushroom, Flammulina velutipes, along with enokipodins A (3) and B (4). The structures of 1 and 2 were determined using spectroscopic methods (HRMS, (1)H and (13)C, and 2D NMR). The absolute configuration of enokipodin C was determined from the observed (1)H NMR chemical shifts and NOEs in NOESY experiments after conversion into the corresponding esters with the chiral reagent 2-(2'-methoxy-1'-naphthyl)-3,4-dichlorobenzoic acid. All the metabolites showed antimicrobial activity against a fungus, Cladosporium herbarum, and Gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus.