Sesquiterpene Skeleton Research Articles

Medullins A-H, Sesquiterpenes from Perenniporia medulla-panis, and Their Cellular Signaling Mechanism in HDF Cells.

A chemical investigation of an ethyl acetate-soluble layer in the culture broth of Perenniporia medulla-panis resulted in the isolation of eight novel sesquiterpenes conjugated Gly (1), l-Val (2), l-Ala (3), l-Tyr (4), l-Thr (5), l-Ile (6), l-Leu (7), and l-Phe (8). Elucidation of their structures was performed through comprehensive spectroscopic analysis. The absolute configuration of the sesquiterpene skeleton was ascertained using modified Mosher's methods. The configurations of the amino acid units in compounds 2-8 were identified through acid hydrolysis followed by LC-MS analysis employing Marfey's method. Compounds 1-3 and 5-8 showed significant regulating effect on MAP kinase activity (p-ERK and p-JNK) in human diploid fibroblast (HDF) cells.

Novel Radical Cyclization Cascade for the Unified Synthesis of the Cedrane and Clovane Sesquiterpene Skeletons

AbstractRadical cyclization cascade reactions of epoxycyclohexanes possessing alkene and alkyne side chains have been achieved. Sequential 5‐ or 6‐exo‐trig/5‐exo‐dig reactions triggered by epoxide ring opening with Cp2TiCl were found to provide a useful unified synthetic method for generating the carbon skeletons of clovane and cedrane, two tricyclic sesquiterpenes. The factors responsible for the development of stereoselectivity during cyclization are also discussed.

Functional Characterization of Sesquiterpene Synthases and P450 Enzymes in Flammulina velutipes for Biosynthesis of Spiro [4.5] Decane Terpene.

Flammulina velutipes, a popular edible mushroom, contains sesquiterpenes with potential health benefits. We characterized 12 sesquiterpene synthases and one P450 enzyme in F. velutipes using Aspergillus oryzae as a heterologous expression system, culminating in the biosynthesis of 16 distinct sesquiterpene compounds. An enzyme encoded by the axeB gene responsible for the synthesis of the spiro [4.5] decane compound axenol was discovered, and the mechanism of spirocycle formation was elucidated through quantum mechanical calculations. Furthermore, we delineated the role of a P450 enzyme colocated with AxeB in producing the novel compound 3-oxo-axenol. Our findings highlight the diverse array of sesquiterpene skeletons and functional groups biosynthesized by these enzymes in F. velutipes and underscore the effectiveness of the A. oryzae system as a heterologous host for expressing genes in the Basidiomycota genome. These insights into the biosynthesis of bioactive compounds in F. velutipes have significant implications for functional food and drug development.

Acremosides A-G, Sugar Alcohol-Conjugated Acyclic Sesquiterpenes from a Sponge-Derived Acremonium Species.

Seven new sugar alcohol-conjugated acyclic sesquiterpenes, acremosides A-G (1-7), were isolated from the cultures of the sponge-associated fungus Acremonium sp. IMB18-086 cultivated with heat-killed Pseudomonas aeruginosa. The structures were determined by comprehensive analyses of 1D and 2D NMR spectroscopic data. The relative configurations were established by J-based configuration analysis and acetonide derivatization. The absolute configurations were elucidated by the Mosher ester method and ECD calculations. The structures of acremosides E-G (5-7) featured the linear sesquiterpene skeleton with a tetrahydrofuran moiety attached to a sugar alcohol. Acremosides A (1) and C-E (3-5) showed significant inhibitory activities against hepatitis C virus (EC50 values of 4.8-8.8 μM) with no cytotoxicity (CC50 of >200 μM).

Systematic Mining and Evaluation of the Sesquiterpene Skeletons as High Energy Aviation Fuel Molecules.

Sesquiterpenes have been identified as promising ingredients for aviation fuels due to their high energy density and combustion heat properties. Despite the characterization of numerous sesquiterpene structures, studies testing their performance properties and feasibility as fuels are scarce. In this study, 122 sesquiterpenoid skeleton compounds, obtained from existing literature reports, are tested using group contribution and gaussian quantum chemistry methods to assess their potential as high-energy aviation fuels. Seventeen sesquiterpene compounds exhibit good predictive performance and nine compounds are further selected for overproduction in yeast. Through fed-batch fermentation, all compounds achieve the highest reported titers to date. Subsequently, three representative products, pentalenene, presilphiperfol-1-ene, and α-farnesene, are selected, produced, purified in large quantities, and tested for use as potential fuels. The performance of pentalenene, presilphiperfol-1-ene, and their derivatives reveals favorable prospects as high-energy aviation fuels.

An HMM approach expands the landscape of sesquiterpene cyclases across the kingdom Fungi.

Sesquiterpene cyclases (STC) catalyse the cyclization of the C15 molecule farnesyl diphosphate into a vast variety of mono- or polycyclic hydrocarbons and, for a few enzymes, oxygenated structures, with diverse stereogenic centres. The huge diversity in sesquiterpene skeleton structures in nature is primarily the result of the type of cyclization driven by the STC. Despite the phenomenal impact of fungal sesquiterpenes on the ecology of fungi and their potentials for applications, the fungal sesquiterpenome is largely untapped. The identification of fungal STC is generally based on protein sequence similarity with characterized enzymes. This approach has improved our knowledge on STC in a few fungal species, but it has limited success for the discovery of distant sequences. Besides, the tools based on secondary metabolite biosynthesis gene clusters have shown poor performance for terpene cyclases. Here, we used four sets of sequences of fungal STC that catalyse four types of cyclization, and specific amino acid motives to identify phylogenetically related sequences in the genomes of basidiomycetes fungi from the order Polyporales. We validated that four STC genes newly identified from the genome sequence of Leiotrametes menziesii, each classified in a different phylogenetic clade, catalysed a predicted cyclization of farnesyl diphosphate. We built HMM models and searched STC genes in 656 fungal genomes genomes. We identified 5605 STC genes, which were classified in one of the four clades and had a predicted cyclization mechanism. We noticed that the HMM models were more accurate for the prediction of the type of cyclization catalysed by basidiomycete STC than for ascomycete STC.

Sesquiterpenes from the soil-derived fungus Trichoderma citrinoviride PSU-SPSF346.

Two new sesquiterpenes, trichocitrinovirenes A (1) and B (2), and five known compounds including four structurally related sesquiterpenes and one γ-lactone were isolated from the soil-derived fungus Trichoderma citrinoviride PSU-SPSF346. The structures were identified by analysis of their spectroscopic data. The relative configuration was assigned based on NOEDIFF data. The absolute configuration of compound 1 was established according to specific rotations and ECD data while that of compound 2 was proposed based on biosynthetic considerations. Compound 2 possesses a rare bicyclic sesquiterpene skeleton. The antimicrobial and cytotoxic activities of the isolated compounds were evaluated.

Structures, Occurrences and Biosynthesis of 11,12,13-Tri-nor-Sesquiterpenes, an Intriguing Class of Bioactive Metabolites.

The compounds 11,12,13-tri-nor-sesquiterpenes are degraded sesquiterpenoids which have lost the C3 unit of isopropyl or isopropenyl at C-7 of the sesquiterpene skeleton. The irregular C-backbone originates from the oxidative removal of a C3 side chain from the C15 sesquiterpene, which arises from farnesyl diphosphate (FDP). The C12-framework is generated, generally, in all families of sesquiterpenes by oxidative cleavage of the C3 substituent, with the simultaneous introduction of a double bond. This article reviews the isolation, biosynthesis and biological activity of this special class of sesquiterpenes, the 11,12,13-tri-nor-sesquiterpenes.

Anti-tumor mechanism of sesquiterpenoids from Cryptoporus volvatus based on molecular docking

To identify the target genes mediating anti-tumor effect of sesquiterpenoids from Cryptoporus volvatus and explore the possible mechanism using molecular docking and molecular dynamics simulation. Based on the chemical structure of sesquiterpenes from C. volvatus, we explored the online reverse target finding websites PharmMapper, SEA, Target Hunter and related literature for preliminary prediction of possible anti-tumor targets. Discovery Studio 4.0 (Libdock function) and Maestro 12.3 were used to connect sesquiterpenes with the possible targets, and the potential targets were selected according to the scores. The interaction between the sesquiterpenes and the targets were analyzed using 2D interaction diagram, and the influence of different sesquiterpene skeletons on their activity was inferred based on their activity measurements in experiment. Kinetic simulation was performed for front-end protein sequence (1UNQ) of the Akt (protein kinase B) and for the complex formed by 1UNQ and compound 4 (which had the best cytotoxic activity in vitro) in its optimal conformation, and the root mean square deviation (RMSD) value and root mean square float (RMSF) value of the complex and 1UNQ were measured to evaluate the stability of the binding of compound 4 to the target. The sesquiterpenes showed optimal binding with 1UNQ. Analysis of 2D interaction diagram suggested that the hydrogen bonding and electrostatic force were the most important forces mediating the interaction between the sesquiterpenes and 1UNQ. Analysis of the optimal 3D conformation showed that for different sesquiterpenes, a slight change of the molecular framework produced a steric hindrance effect and caused changes in their bioactivity. Kinetic simulation showed that the complex formed by compound 4 and1UNQ had a lower RMSD than the target pure protein sequence, indicating that compound 4 could stably bind to 1UNQ. The anti-tumor effect of the sesquiterpenoids from C. volvatus was associated with their ability to cause Lys-144 acetylation, which blocks Akt binding to the downstream PIP3 and thus affects the proliferation of tumor cells. 1UNQ is the target of sesquiterpenoids from C. volvatus, which affects the proliferation of tumor cells by acetylating Lys-14.

Terpenoids with α-glucosidase inhibitory activity from Rhododendron minutiflorum Hu

Five undescribed triterpenoids, two unusual omphalane-type sesquiterpenoids together with twenty-five known compounds were isolated from the leaves and stems of Rhododendron minutiflorum Hu. The absolute configurations of 1–3 and 6 were established by single-crystal X-ray diffraction analysis and electronic circular dichroism (ECD). Compounds 6–7 feature the rare omphalane-type sesquiterpene skeleton and are verified by single-crystal X-ray diffraction analysis for the first time. In the biological activity assay, most of the triterpenoids have different degrees of inhibitory effects on α-glucosidase, with IC50 values ranging from 6.97 to 229.3 μM (the positive control drug acarbose has an IC50 value of 3.07 × 10−3 μM). Structure and activity relationship (SAR) study reveals that the oxidation degrees of C-3, C-8, or C-11 to C-13 of the ursane-type triterpenoid influence the inhibitory activity dramatically.

Hybrid of the 1,2,3‐triazole nucleus and sesquiterpene skeleton as a potential antitumor agent: Hemisynthesis, molecular structure, Hirshfeld surface analysis, density functional theory, and in vitro cytotoxic and apoptotic effects

AbstractA new 1,2,3‐triazole sesquiterpenic named (4aR,5aS,7aR,10aR,10bR)‐10‐benzyl‐5,5‐dichloro‐1,1,4a,7a‐tetramethyl‐1,2,3,4,4a,5,7a,10,10a,10b decahydrocyclopropa[2′,3′]cyclohepta [1′,2′:3,4]benzo[1,2‐d][1,2,3]triazol‐7(6H)‐one was synthesized by a dipolar cycloaddition 1,3 between benzyl azide and α,β‐unsaturated sesquiterpene ketone catalyzed by titanium tetrachloride TiCl4. It was obtained with a good yield and characterized using single‐crystal X‐ray diffraction technique, infra red (IR) spectroscopy, High Resolution Mass Spectrometry (HRMS), UV‐Visible, and 1H and 13C NMR spectroscopies. The optimization by the density functional theory (DFT) method was carried out to study the formation mechanism of the derivative. The selected compounds 1–4 exhibited anticancer activities in vitro against namely fibrosarcoma (HT‐1080), lung carcinoma (A‐549), and breast (MCF‐7 and MDA‐MB‐231 cell lines with IC50 in the range of 10.02–44.71 μM). In addition to using flow cytometry and the apoptosis assay, cell cycle arrest at the S phase (10 μM) and G2/M arrest in (5 and 10 μM) was performed for compound 4 in fibrosarcoma (HT‐1080) cancer cells. Results suggested that compound 4 test with good activity against HT‐1080 cells with IC50 value from 10.02 μM and induced the apoptotic effect. Theoretical studies were realized to estimate the molecular proprieties that lead to a high potential of cytotoxic effect, which is in agreement with the experimental results.

Research advances in methods of cyclezation mechanism of sesquiterpenes

Terpenes are the largest group of natural products and contain the widest assortment of structural types. Terpene cyclization is also the most complex reaction found in nature. For a long time, terpenoids with diverse structures have attracted natural product chemists to explore their biosynthesis mechanism. Such a large number of terpene skeletons are catalyzed by enzymes called terpene synthase. Sesquiterpene synthase is a kind of terpene synthase, which can catalyze the cyclization of linear precursor farnesyl pyrophosphate(FPP) to sesquiterpene skeletons. Sesquiterpene synthase cyclize a single precursor FPP into many sesquiterpene skeletons. With the continuous discovery of sesquiterpene synthase, the cyclization mechanism of sesquiterpene synthase has been studied deeply. In recent years, with the development and improvement of isotope labeling of substrate FPP and structural analysis of sesquiterpene synthase, the structure and cyclization mechanism of sesquiterpene synthase have been studied more systematically and accurately. In this review, we reviewed the progress of the research methods on the mechanism of sesquiterpene cyclization by substrate isotope labeling and protein structure, as well as the summary and prospect of sesquiterpene synthase research.

Molecular and Functional Evolution of the Spermatophyte Sesquiterpene Synthases.

Sesquiterpenes are important defense and signal molecules for plants to adapt to the environment, cope with stress, and communicate with the outside world, and their evolutionary history is closely related to physiological functions. In this study, the information of plant sesquiterpene synthases (STSs) with identified functions were collected and sorted to form a dataset containing about 500 members. The phylogeny of spermatophyte functional STSs was constructed based on the structural comparative analysis to reveal the sequence–structure–function relationships. We propose the evolutionary history of plant sesquiterpene skeletons, from chain structure to small rings, followed by large rings for the first time and put forward a more detailed function-driven hypothesis. Then, the evolutionary origins and history of spermatophyte STSs are also discussed. In addition, three newly identified STSs CaSTS2, CaSTS3, and CaSTS4 were analyzed in this functional evolutionary system, and their germacrene D products were consistent with the functional prediction. This demonstrates an application of the structure-based phylogeny in predicting STS function. This work will help us to understand evolutionary patterns and dynamics of plant sesquiterpenes and STSs and screen or design STSs with specific product profiles as functional elements for synthetic biology application.

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.

Essential oil composition of the sub-aerial parts of eight species of Cymbopogon (Poaceae)

The genus Cymbopogon (Poaceae) comprised of many species of grasses that grow in tropical and subtropical regions around the world. Some of the commercially important aromatic species of Cymbopogon are cultivated for the extraction of the essential oils from their aerial-parts. In spite of wide distribution and large scale cultivation, the essential oils of the sub-aerial parts (root/rhizome) of these species have not been systematically studied so far. In this study, the hydro-distilled essential oils from the sub-aerial parts of eight species, including a hybrid of Cymbopogon, namely C. flexuosus (Nees ex Steud.) W.Watson, C. khasianus (Hack.) Stapf ex Bor, C. pendulus Nees ex Steud., C. khasianus × C. pendulus, C. winterianus Jowitt ex Bor, C. martini (Roxb.) W.Watson, C. distans (Nees ex Steud.) W.Watson, and C. jwarancusa (Jones) Schult. and their varieties/chemotypes were analyzed by gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GCMS). A total of thirty-three terpene C-skeleton types (six monoterpene skeletons, twenty-seven sesquiterpene skeletons) were identified. Among these p-menthane, myrcane, elemane, eudesmane, and agarospirane C-skeletons dominated in the examined species of Cymbopogon. A multivariate statistical comparison by principal component analysis and agglomerative hierarchical clustering grouped the examined essential oils in to four clusters (cluster I: geraniol, and piperitone/ geraniol chemotypes; cluster II: high elemol and low elemol chemotypes; cluster III: limonene chemotype; and cluster IV: 5-epi-7-epi-α-eudesmol/ eudesmanediol/ hinesol, and cis-p-menth-2-en-1-ol/ trans-p-menth-2-en-1-ol/ eudesmanediol chemotypes). The sub-aerial parts, a waste product of cultivation can serve as good source of valuable and rare lead molecules, such as elemol, 5-epi-7-epi-α-eudesmol, β-eudesmol, eudesmanediol, hinesol, agarospirol, 7-epi-α-eudesmol, α-eudesmol, γ-eudesmol, shyobunol, selina-6-en-4-ol, and p-menth-2-en-1-ols.

An integrated strategy to identify genes responsible for sesquiterpene biosynthesis in turmeric.

Metabolic module, gene expression pattern and PLS modeling were integrated to precisely identify the terpene synthase responsible for sesquiterpene formation. Functional characterization confirmed the feasibility and sensitivity of this strategy. Plant secondary metabolite biosynthetic pathway elucidation is crucial for the production of these compounds with metabolic engineering. In this study, an integrated strategy was employed to predict the gene function of sesquiterpene synthase (STS) genes using turmeric as a model. Parallel analysis of gene expression patterns and metabolite modules narrowed the candidates into an STS group in which the STSs showed a similar expression pattern. The projections to latent structures by means of partial least squares model was further employed to establish a clear relationship between the candidate STS genes and metabolites and to predict three STSs (ClTPS16, ClTPS15 and ClTPS14) involved in the biosynthesis of several sesquiterpene skeletons. Functional characterization revealed that zingiberene and β-sesquiphellandrene were the major products of ClTPS16, and β-eudesmol was produced by ClTPS15, both of which indicated the accuracy of the prediction. Functional characterization of a control STS, ClTPS1, produced a small amount of β-sesquiphellandrene, as predicted, which confirmed the sensitivity of metabolite module analysis. This integrated strategy provides a methodology for gene function predictions, which represents a substantial improvement in the elucidation of biosynthetic pathways in nonmodel plants.

Essential oil of the malagasy grass Elionurus tristis Hack. contains several undescribed sesquiterpenoids

Essential oils (EOs) obtained from aerial parts and roots of Elionurus tristis were investigated by GC, GC-MS, pc-GC and NMR. Both aerial parts and roots EOs contained common molecules such as α-pinene, camphene, trans-α-bergamotene and calarene. Moreover, we identified several unusual sesquiterpenes and four undescribed compounds, 7-epi-khusian-2-ol, 4,8-di-epi-acorone, 2-epi-ziza-5-en-2-ol and antsorenone. The last one exhibits an undescribed natural sesquiterpene skeleton. All undescribed compounds were isolated and fully characterized by MS, 1D and 2D-NMR. Furthermore, the formation pathway of the Antsorane skeleton is discussed.

Eucalypglobulusals A-J, Formyl-Phloroglucinol-Terpene Meroterpenoids from Eucalyptus globulus Fruits.

Ten new formyl-phloroglucinol-terpene meroterpenoids, eucalypglobulusals A-J (1-10), andtenknown analogues were isolated from Eucalyptus globulus fruits. The structures of 1-10 were determined by spectroscopic analysis, while their absolute configurations were established using calculated and experimental electronic circular dichroism (ECD) spectra. Eucalypglobulusal A was assigned as a new formyl-phloroglucinol-terpene meroterpenoid with a rearranged sesquiterpene skeleton, and an aldol condensation between C-3 and C-5 of the germacrene C moiety was proposed to be a key step in its putative biosynthetic pathway. Eucalypglobulusal F exhibited cytotoxicity against the human acute lymphoblastic cell line (CCRF-CEM) with an IC50 value of 3.3 μM, while eucalypglobulusal A, eucarobustol C, macrocarpal A, macrocarpal B, and macrocarpal D exhibited DNA topoisomerase I (Top1) inhibition. The compounds eucalypglobulusal A and macrocarpal A act as Top1 catalytic inhibitors and delay Top1 poison-mediated DNA double-strand damage.

Volatile Metabolomic Composition of Vitex Species: Chemodiversity Insights and Acaricidal Activity.

The Vitex genus (Lamiaceae) produces a plethora of metabolites that include ecdysteroids and terpenoids, some of which have demonstrated insect repellent properties. The volatile composition of several members of this genus has not been chemically defined, as many taxa are endemic to remote ecosystems. In this study, leaves were collected from the northeast of Brazil from Vitex capitata, V. megapotamica, V. gardneriana, and V. rufescens plants and examined for their chemical profile via GC-MS/FID of essential oil extracts. The analyses showed a diversity of terpenoids. Of particular note were seven-member ring sesquiterpenes which were present in great abundance; a dendrogram showed clades separating by the production of bicyclogermacrene, aromadendrane and 5,10-cycloaromadendrane sesquiterpenoids for the four species. Comparison of volatile metabolite profiles to 13 other Vitex species showed strong similarities in the production of some monoterpenes, but varied by their production of larger terpenes, especially those with gem-dimethylcyclopropyl subunits on seven-member ring compounds. From this work, we suggest that the sesquiterpene skeleton with seven member rings is a good chemosystematic biomarker candidate for the Vitex genus. Separation using this biomarker was then validated using Inter-Simple Sequence Repeat profiling. Lastly, experiments examining the toxicity of these four oils against the coconut mite Aceria guerreronis showed that only the oil of V. gardneriana had strong acaricidal activity, with an LC50 of 0.85 mg/mL, thus demonstrating its potential for use as a natural pesticide.

Gold(i)-catalyzed access to neomerane skeletons

The gold(i) catalyzed cycloisomerization of an enynyl propargylic ester, featuring a 1,2-acyloxy migration/intramolecular cyclopropanation sequence, opens a straightforward access to the 5,7,3-tricyclic skeleton of neomerane sesquiterpenes. The first total synthesis of 5-epi-valeneomerin B in 12 steps with an overall yield of 5.3% is reported.