Dimeric Sesquiterpene Research Articles

Targeted isolation of dimeric sesquiterpene lactones and sesquiterpene derivatives from the roots of Inula helenium

LC-HRMS/MS-based molecular networking was applied to investigate the bioactive sesquiterpene lactones and their analogs contained in Inula helenium, enabling the isolation of four undescribed eudesmane-eudesmane sesquiterpene dimers (1–4), a sesquiterpene-amino acid adduct (5), and 17 known sesquiterpenes (6–22). The structures were determined based on 1D, 2D NMR, and HRESIMS data analysis, as well as DP4+ probability analyses and ECD calculations. The biosynthetic pathway of the sesquiterpene dimers is postulated to proceed via the Diels-Alder reaction as the key step. The inhibitory activity of all isolates on LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages was evaluated. Compounds 4, 17, and 20 exhibited significant inhibitory activity against NO production, with IC50 values of 8.4, 5.5, and 9.1 μM, respectively.

Anti-inflammatory Lindenane Sesquiterpene Dimers from the Roots of Chloranthus fortunei.

In this study, eight lindenane-type sesquiterpene dimers, including five previously undescribed sesquiterpene dimers (1-5), were isolated from the roots of Chloranthus fortunei, and their structures were elucidated using 1D/2D NMR, HRESIMS, and ECD calculations. Compound 1 presents the second example of a type of novel 8,9-seco lindenane-type sesquiterpene dimer, considered a product of 8/9-diketone oxidation. Compounds 2 and 3 represent the third and fourth examples, respectively, of this kind of C-11 methine dimer. Furthermore, compound 4 was considered as an artifact generated from the radical reaction of a known compound chlojaponilide F (6), which was explained by the density functional theory quantum calculation. All isolates were evaluated for their protective activity against the LPS-induced pulmonary epithelial cell line with compound 7 exhibiting the most potent bioactivity. Further in vitro biological evaluation demonstrated that 7 reduced the production of reactive oxygen species and interleukin-1β, further regulated by the expression of the NLRP3. These results show that compound 7 exhibits therapeutic potential for lung inflammatory diseases.

Sesquiterpene dimers with a rare skeleton from Chloranthus holostegius exhibiting multidrug resistance reversal activity in vitro and in vivo

Two previously unreported lindenane sesquiterpene dimers (1 and 2) with a rare skeleton containing an oxaspiro[4.5]decane moiety were isolated from the roots of Chloranthus holostegius var. trichoneurus. Their structures were elucidated by HRESIMS, NMR, ECD, and NMR quantum chemical calculations, along with DP4+ probability analysis. In bioassay, compound 1 exhibited significant activity to reverse the multidrug resistance (MDR)in MCF-7/ADR cells, with an IC50 value of 4.4 μM. Further mechanistic studies revealed that compound 1 combined with doxorubicin could induce apoptosis of MCF-7/ADR cells and block the cell cycle in the G2/M phase. Mechanistically, compound 1 could inhibit the efflux function of P-glycoprotein (P-gp) using the zebrafish model. Finally, the enhanced chemotherapeutic effects of doxorubicin were further confirmed by in vivo zebrafish xenograft experiments.

Characterization of Sesquiterpene Dimers from the Flowers of Inula japonica and the Structural Revisions of Related Compounds.

Sesquiterpene dimers are mainly found in the Asteraceae family. However, conflicting reports on the structures of these compounds can be found in the literature. Herein, we describe ten sesquiterpene dimers isolated from the flowers of Inula japonica, including configurational revisions of japonicone H (1-1), japonicone D (2-1), inulanolide A (4-1), japonicone X (5-1), and inulanolide F (5-2) to compounds 1, 2, 4, and 5, respectively. Five new related metabolites (3 and 6-9) are also described. Application of GIAO NMR/DP4+ analyses and ECD/OR calculations enabled us to revise the absolute configurations of an additional 13 sesquiterpene dimers isolated from plants of the genus Inula. Compounds 1, 2, 4, and 6 exhibited inhibition of nitric oxide production in lipopolysaccharide activated RAW264.7 macrophages with IC50 values of 4.07-10.00 μM.

A pair of cadinane-type sesquiterpene enantiomers and other chemical constituents from the whole plants of Chloranthus henryi

Continual phytochemical investigation on the whole plants of Chloranthus henryi Hemsl afforded fourteen compounds (1–14), including eight sesquiterpene monomers (1–8), four sesquiterpene dimers (9–12), a diterpene (13), and a simple coumarin (14). The structures of these compounds were assigned by means of spectroscopic techniques and ECD calculations. Compounds 1a and 1b are a pair of cadinane-type sesquiterpene enantiomers, while compounds 3–7 and 11–14 are isolated from C. henryi for the first time. Moreover, the chemotaxonomic significance corresponding to the aforementioned compounds was investigated.

Research progress on natural guaiane-type sesquiterpenoids and their biological activities

Guaiane-type sesquiterpenoids are a class of terpenoids with [5,7] ring-fused system as the basic skeletal structure composed of three isoprene units, which are substituted by 4,10-dimethyl-7-isopropyl. According to the difference in functional groups and degree of polymerization, they can be divided into simple guaiane-type sesquiterpenoids, sesquiterpene lactones, sesquiterpene dimers, and sesquiterpene trimers. Natural guaiane-type sesquiterpenoids are widely distributed in plants, fungi, and marine organisms, especially in families such as Compositae, Zingiberaceae, Thymelaeaceae, Lamiaceae, and Alismataceae. Guaiane-type sesquiterpenoids have good antibacterial, anti-inflammatory, anticancer, and neuroprotective effects. In this paper, the novel guaiane-type sesquiterpenoids isolated and identified in recent 10 years(2013-2022) and their biological activities were reviewed in order to provide refe-rences for the research and development of guaiane-type sesquiterpenoids.

Chlorahololide D, a Lindenane-Type Sesquiterpenoid Dimer from Chloranthus holostegius Suppressing Breast Cancer Progression.

Aimed at discovering small molecules as anticancer drugs or lead compounds from plants, a lindenane-type sesquiterpene dimer, chlorahololide D, was isolated from Chloranthus holostegius. The literature review showed that there were few reports on the antitumor effects and mechanisms of chlorahololide D. Our biological assay suggested that chlorahololide D blocked the growth and triggered apoptosis of MCF-7 cells by stimulating the reactive oxygen species (ROS) levels and arresting the cell cycle at the G2 stage. Further mechanism exploration suggested that chlorahololide D regulated apoptosis-related proteins Bcl-2 and Bax. Moreover, chlorahololide D inhibited cell migration by regulating the FAK signaling pathway. In the zebrafish xenograft model, chlorahololide D was observed to suppress tumor proliferation and migration significantly. Considering the crucial function of angiogenesis in tumor development, the anti-angiogenesis of chlorahololide D was also investigated. All of the research preliminarily revealed that chlorahololide D could become an anti-breast cancer drug.

Aquilariperoxide A, a Sesquiterpene Dimer from Agarwood of Aquilaria sinensis with Dual Antitumor and Antimalarial Effects.

Aquilariperoxide A (1), an unprecedented sesquiterpene dimer characterized by a dioxepane ring connecting two sesquiterpene units via a C-C bond, was isolated from agarwood of Aquilaria sinensis-containing resins. The structure was elucidated by spectroscopic and computational methods. A bioassay revealed that 1 significantly inhibits cell proliferation and migration in human cancer cells. The mechanism of 1 against cancer cells was briefly discussed by analysis of RNA sequence data and epithelial-mesenchymal transition. Besides, the antimalarial activity of 1 was also evaluated.

In Vitro and In Vivo Therapeutic Potential of 6,6'-Dihydroxythiobinupharidine (DTBN) from Nuphar lutea on Cells and K18-hACE2 Mice Infected with SARS-CoV-2.

We have previously published research on the anti-viral properties of an alkaloid mixture extracted from Nuphar lutea, the major components of the partially purified mixture found by NMR analysis. These are mostly dimeric sesquiterpene thioalkaloids called thiobinupharidines and thiobinuphlutidines against the negative strand RNA measles virus (MV). We have previously reported that this extract inhibits the MV as well as its ability to downregulate several MV proteins in persistently MV-infected cells, especially the P (phospho)-protein. Based on our observation that the Nuphar extract is effective in vitro against the MV, and the immediate need that the coronavirus disease 2019 (COVID-19) pandemic created, we tested here the ability of 6,6'-dihydroxythiobinupharidine DTBN, an active small molecule, isolated from the Nuphar lutea extract, on COVID-19. As shown here, DTBN effectively inhibits SARS-CoV-2 production in Vero E6 cells at non-cytotoxic concentrations. The short-term daily administration of DTBN to infected mice delayed the occurrence of severe clinical outcomes, lowered virus levels in the lungs and improved survival with minimal changes in lung histology. The viral load on lungs was significantly reduced in the treated mice. DTBN is a pleiotropic small molecule with multiple targets. Its anti-inflammatory properties affect a variety of pathogens including SARS-CoV-2 as shown here. Its activity appears to target both pathogen specific (as suggested by docking analysis) as well as cellular proteins, such as NF-κB, PKCs, cathepsins and topoisomerase 2, that we have previously identified in our work. Thus, this combined double action of virus inhibition and anti-inflammatory activity may enhance the overall effectivity of DTBN. The promising results from this proof-of-concept in vitro and in vivo preclinical study should encourage future studies to optimize the use of DTBN and/or its molecular derivatives against this and other related viruses.

Lindenane-Type Sesquiterpene Dimers Mitigate Lipopolysaccharide-Induced Inflammation by Inhibiting Toll-Like Receptor Signaling.

Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns and trigger an inflammatory response via the myeloid differential factor 88 (MyD88)-dependent and toll-interleukin-1 receptor domain-containing adapter-inducing interferon-β (TRIF)-dependent pathways. Lindenane type sesquiterpene dimers (LSDs) are characteristic metabolites of plants belonging to the genus Sarcandra (Chloranthaceae). The aim of this study was to evaluate the potential anti-inflammatory effects of the LSDs shizukaol D (1) and sarcandrolide E (2) on lipopolysaccharides (LPS)-stimulated RAW264.7 macrophages in vitro, and explore the underlying mechanisms. Both LSDs neutralized the LPS-induced morphological changes and production of nitric oxide (NO), as determined by CCK-8 assay and Griess assay, respectively. Furthermore, shizukaol D (1) and sarcandrolide E (2) downregulated interferon β (IFNβ), tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β) mRNA levels as measured by reverse transcription polymerase chain reaction (RT-PCR), and inhibited the phosphorylation of nuclear factor kappa B p65 (p65), nuclear factor kappa-Bα (IκBα), Jun N-terminal kinase (JNK), extracellular regulated kinase (ERK), mitogen-activated protein kinase p38 (p38), MyD88, IL-1RI-associated protein kinase 1 (IRAK1), and transforming growth factor-β-activated kinase 1 (TAK1) proteins in the Western blotting assay. In conclusion, LSDs can alleviate the inflammatory response by inhibiting the TLR/MyD88 signalling pathway.

A DFT study of the endo-selectivity mechanism of the Diels-Alder reaction in lindenane dimeric sesquiterpene synthesis promoted by pyridines.

The lindenane dimeric sesquiterpenoids with versatile biological activities are accessible via biometric synthesis, in which the endo-selective Diels-Alder reaction plays an important role. To explore the endo-selectivity of the Diels-Alder reaction between lindenane sesquiterpenes promoted by pyridines, density functional theory (DFT) calculations were performed to explore the reaction mechanism between pyridines and D-A monomers. The calculations performed on the reaction pathways explain why pyridines can promote endo-selectivity via hydrogen bonding, and the hydrogen bond strength is a key factor driving the Diels-Alder reaction in major biochemical systems. These DFT-level insights will pave the way for designing better promoters for Diels-Alder reactions in biometric synthesis applications.

Targeted isolation of sesquiterpene lactone dimers from Aucklandia lappa guided by LC-HRMS/MS-based molecular networking

An LC-HRMS/MS-based molecular networking strategy was applied to investigate the potential sesquiterpene dimers of Aucklandia lappa, leading to the isolation of three undescribed guaiane-guaiane dimers and one guaiane-eudesmane dimer together with six known sesquiterpenes. The structures were determined by analyzing their 1D, 2D NMR, and HRESIMS data as well as ECD calculations. The biogenetic pathway of the sesquiterpene dimers was postulated to involve the Diels-Alder cycloaddition as the key step. All compounds exhibited their inhibitory effects on LPS-induced nitric oxide production in RAW 264.7 macrophages with IC50 values ranging from 0.3 to 25.1 μM.

Ethnobotanical Uses, Phytochemical Composition, Biosynthesis, and Pharmacological Activities of Carpesium abrotanoides L. (Asteraceae).

Carpesium abrotanoides L. (Asteraceae) is a medicinal plant with immense therapeutic importance and bioactivities. It is commonly encountered in various Asian regions. It has numerous ethnomedicinal uses for curing diverse ailments such as toothache, stomach ulcer, boils, tonsillitis, bronchitis, bacterial infection, bruises, swelling, virus infection, fever, and amygdalitis, as well as an anthelmintic versus round-, tape-, hook-, and pinworms. Different classes of phytoconstituents such as sesquiterpenes, sesquiterpene dimers, monoterpenes, and nitrogenous compounds have been reported from this plant. These phytoconstituents have proved to possess anti-inflammatory, cytotoxic, antimicrobial, and insecticidal capacities. The present review aims to summarize all published data on C. abrotanoides including traditional uses, phytoconstituents, bioactivities, and toxicological aspects, as well as the synthesis and biosynthesis of its metabolites through an extensive survey on various databases and various publishers. These reported data could draw the attention of various natural-metabolite-interested researchers and medicinal chemists towards the development of this plant and/or its metabolites into medicine for the prevention and treatment of certain illnesses. Despite the diverse traditional uses of C. abrotanoides, there is a need for scientific evidence to support these claims. Clinical trials are also required to further assure these data and validate this plant utilization in treating several diseases.

Vlasouliodes A-D, four new C30 dimeric sesquiterpenes exhibiting potential inhibition of MCF-7 cells from Vladimiria souliei

As our ongoing interest to search bioactive dimeric sesquiterpenes from the genus Vladimiria (Asteraceae), the plant of Vladimiria souliei was studied. Based on the repetitive chromatographic fractionation, a chemical investigation on the roots of Vladimiria souliei led to the isolation and the identification of four previously undescribed sesquiterpene dimers, vlasouliodes A-D (1–4). Their chemical structures were elucidated by comprehensive analysis of spectroscopic data, including HRESIMS, 1D and 2D NMR spectroscopic data. The absolute configurations of them were unambiguously established by the experimental and calculated ECD data. In the in vitro biological activity evaluation, 1 and 3 displayed pronounced inhibitory activity against human breast adenocarcinoma cell lines (MCF-7) with IC50 values of 17.12 ± 0.42 μM and 13.12 ± 0.10 μM, respectively. Additionally, treatment with 1 and 3 induced cell apoptosis in MCF-7 cells, down-regulated the expression of Caspase-3 and up-regulated the expression of Cleaved-caspase-3.

Terpenoids from Nardostachys jatamansi and their cytotoxic activity against human pancreatic cancer cell lines

Five previously unreported terpenoids, together with fifteen known analogs, were isolated from a methanol extract of the roots and rhizomes of Nardostachys jatamansi. Their structures, including absolute configurations, were elucidated by spectroscopic data and electronic circular dichroism (ECD) spectra analyses, as well as single-crystal X-ray diffraction for crystalline compounds. Structurally, (4R,5S,6S,7R)-1(10)-aristolane-8,9-diacid is a novel 8,9-dicarboxylic acid derivative of aristolane-type sesquiterpenoid. (4R,6S,7R,10S)-10-Hydroxyguaia-1(5)-6,7-epoxy-2-one is an undescribed analogue of nardoguaianone K, with a rare 6,7-epoxide group. (4R,5R,6R,8R)-1(10)-Isonardosinone-8-ol-9-one-7,11-lactone is an isonardosinane-type sesquiterpene bearing a γ-lactone ring. Dinardokanshone F is a rare example of a sesquiterpene dimer from N. jatamansi connected by an oxo bridge. The isolates were evaluated for their cytotoxic activity against four human pancreatic cancer cell lines (CFPAC-1, PANC-1, CAPAN-2 and SW1990). Compound epoxynardosinone exhibited significant cytotoxicity against CAPAN-2 cell lines with IC50 value of 2.60 ± 1.85 μM. 1-Hydroxylaristolone displayed comparable cytotoxicity on CFPAC-1 cell lines (IC50 1.12 ± 1.19 μM), compared to Taxol (IC50 0.32 ± 0.13 μM). 1-Hydroxylaristolone, 1(10)-aristolane-9β-ol, 1(10)-aristolen-2-one, alpinenone, valtrate isovaleroyloxyhydrine and nardostachin displayed stronger cytotoxicity against PANC-1 cell lines with IC50 values ranging from 0.01 ± 0.01 to 6.50 ± 1.10 μM. 1(10)-Aristolane-9β-ol, 10-hydroxyguaia-1(5)-6,7-epoxy-2-one, nardoguaianone K, nardonoxide, epoxynardosinone, 1(10)-isonardosinone-8-ol-9-one-7,11-lactone, valtrate isovaleroyloxyhydrine and nardostachin showed remarkable cytotoxicity against SW1990 cell lines with IC50 values ranging from 0.07 ± 0.05 to 4.82 ± 6.96 μM. Furthermore, the primary mechanistic study of nardostachin demonstrated that it induced cell apoptosis via the mitochondria-dependent pathway, and induced SW1900 cell arrest at G2/M phase.

Retusone A, a Guaiane-Type Sesquiterpene Dimer from Wikstroemia retusa and Its Inhibitory Effects on Histone Acetyltransferase HBO1 Expression.

Retusone A (1), a new sesquiterpene dimer consisting of two guaiane-type sesquiterpenoids, and oleodaphnal (2) were isolated from heartwood of Wikstroemia retusa (Thymelaeaceae). The planar structure of 1 was elucidated on the basis of HRESIMS and NMR spectroscopic data, and the relative stereochemistry was established by X-ray diffraction analysis. The absolute configuration of 1 was determined by electronic circular dichroism. Compound 1 suppressed luciferase reporter gene expression driven by the HBO1 (histone acetyltransferase binding to ORC1) gene promoter in human breast cancer MCF7 cells. Compound 1 also decreased the expression of endogenous HBO1 mRNA and protein, and inhibited proliferation of the cells. These results suggest that retusone A (1), which has a unique dimeric sesquiterpenoid structure with inhibitory activity against HBO1 expression, may contribute to the development of a novel therapeutic candidate for the treatment of breast cancer.

Sarglafuran A, a lindenane-type sesquiterpene dimers with unique furan ring from the leaves of Sarcandra glabra

Sarglafuran A (1), a new [4 + 2] type lindenane sesquiterpene dimer with an unique furan ring moiety, and a pair of new [2 + 2] type dimeric lindenane epimers, sarglalactones N and O (2 and 3), were isolated from the leaves of Sarcandra glabra. Their structures were elucidated by comprehensive spectroscopic analyses, and the absolute configurations of these compounds were determined by single crystal X-ray diffraction or CD exciton chirality method. In addition, a possible biosynthetic pathway of the unique furan ring moiety in 1 had been proposed. Their cytotoxicity against MCF-7 and MDA-MB-231, together with the inhibitory activity against nitric oxide (NO) production of LPS-induced RAW264.7 macrophages were evaluated.

Meroterpenoids and sesquiterpene dimers from Sarcandra glabra with anti-neuroinflammatory activity

Sarcandra glabra (Thunb.) Nakai is abundantly artificially cultivated for industrial use as an essential pharmaceutical and chemical raw material in China. In this work, five new meroterpenoids (1–5), along with one analog (6) and six known sesquiterpene dimers (7–12) were isolated from Sarcandra glabra. The chemical structures, including absolute configurations, were deduced by extensive spectroscopic methods combined with quantum mechanical electronic circular dichroism (ECD) and nuclear magnetic resonance (NMR) calculations, Mo2(OAc)4-induced ECD experiments, and customizable DP4 + probability analysis. Compounds 1–6 are biogenetically assembled by the cyclization of gentisicacid and monoterpene, featuring a novel 6/6/6 -fused ring system. Compounds 4 and 5 possess significant inhibitory effects on nitric oxide (NO) production against lipopolysaccharide (LPS)-induced microglia (BV2) cells, while compounds 8 and 9 displayed an approximately equal effect to Dexamethasone. The analysis of the protein-protein interaction (PPI) network and molecular docking showed 4 and 5 could play an anti-neuroinflammatory role by regulating heat shock proteins 90AA1 (Hsp90AA1). This study provided evidence for further research and utilization of S. glabra in anti-neuroinflammatory medicinal products.

Sesquiterpene dimers from Chloranthus fortunei and their protection activity against acute lung injury

Chloranthus fortunei (family Chloranthaceae), a perennial herb, widely distributed in south China with an altitude of 170–340 m. The whole plants were used as an anti-inflammatory agent for the treatment of cough, arthritis and tumor. Five previously unreported compounds fortulactones A-E were isolated from the aerial part of Chloranthus fortunei. Their structures were elucidated using 1D/2D NMR and HRESIMS and their absolute configuration were determined using the ECD excitron chirality method. All isolates were tested for inhibitory effects on the NO production of liposaccharide (LPS)-induced RAW 264.7 macropahges. The most potent compound 1 was further evaluated its protective activity against LPS stimulated A549 cells, the ELISA kits results showed the abnormal states of MDA and SOD were corrected to a certain extent. Meanwhile, the pro-inflammatory cytokine, such as TNF-α, IL-6 and IL-1β were also attenuated. In conclusion, these results showed that 1 exhibited therapeutic potential for ameliorating ALI.

Synthetic Studies on Small Molecule Natural Products with Neurotrophic Activity

Neurotrophic factors have been shown to potentially be beneficial for the treatment of neurodegenerative diseases such as Alzheimer's disease, because endogenous neurotrophic factors (NGF, BDNF) have been recognized to play critical roles in the promotion of neurogenesis, differentiation, and neuroprotection throughout the development of the central nervous system. However, high-molecular-weight proteins are unable to cross the blood-brain barrier and are easily decomposed under physiological conditions. Thus, small molecules that can mimic the functions of neurotrophic factors are promising alternatives for the treatment of neurodegenerative disease. Since 1990, the author has been involved in searching for natural products with typical neurotrophic properties that can cause neurogenesis, enhance neurite outgrowth, and protect against neuronal death by using three cellular systems (PC12, rat cortical neurons, and MEB5 cells). Through these research activities on neurotrophic natural products, the author has tried to induce a paradigm shift from the discipline of natural products chemistry to science disciplines. This review focuses on our independent synthetic studies of the neurotrophic natural products discovered in the plants. The following synthetic elaborations are described: syntheses of dimeric isocuparane-type sesquiterpenes mastigophorenes A and B, macrocyclic bis-bibenzyls plagiochins A-D and cavicularin through a Pd-catalyzed Stille-Kelly reaction; the formal synthesis of merrilactone A and jiadifenin, which are seco-prezizaane-type sesquiterpenes, through intramolecular Pd-catalyzed Mizoroki-Heck and Tsuji-Trost reactions; and finally the first enantioselective synthesis of neovibsanin B, a vibsane-type diterpene, through a Pd-catalyzed cyclic carbopalladation-carbonyl tandem reaction.