Discovery of eudesmane-type sesquiterpenoids with neuroprotective effects from the roots of Chloranthus serratus.

Seven eudesmane-type sesquiterpenoids, including three pairs of racemic compounds (1a-3a and 1b-3b) and a sesquiterpenoid lactone (4), were obtained from the roots of Chloranthus serratus. The structures of these sesquiterpenoids were characterized based on spectroscopic analyses, ECD calculations, and X-ray diffraction experiment. Neuroprotection assays of the isolated eudesmane-type sesquiterpenoids were conducted on H2O2 damaged PC12 cells. At the concentration of 10 µM, compounds 1b and 4 increased cell viability from 54.8 ± 3.3% to 76.8 ± 2.3 and 72.7 ± 8.2%, respectively.

Anti-inflammatory Eudesmane Sesquiterpenoids from Artemisia hedinii.

Fourteen new eudesmane sesquiterpenoids (1, 3-5, 7-16) and seven known analogues were isolated from the whole plant of Artemisia hedinii. Their structures were elucidated by spectroscopic data analysis and comparison with published NMR data, and their absolute configurations were confirmed by X-ray diffraction experiments and TDDFT ECD calculation. Compounds 1-15 were identified as eudesmane acids, which represent a kind of lactone ring-opening eudesmane-type sesquiterpenes with an acetoxyl or a hydroxy group attached to C-9. Compounds 1 and 2, 5 and 6, and 7 and 8 are three pairs of epimers isomerized at C-3, C-5, and C-11, respectively. Compounds 1-9, 11-13, 15-19, and 21 could influence the proinflammatory phenotype of the M1 macrophage. Among them, compounds 5, 8, 9, 12, 16, and 19 consistently exhibited anti-inflammatory effects, as evidenced by downregulating classic pro-inflammatory cytokines TNF-α, IL-12, IL-6, and IFN-γ in LPS-induced primary bone marrow derived M1 macrophages.

Therapeutic potential and pharmacological activities of ß-eudesmol.

Herbal medicines are attracting the attention of researchers worldwide. ß-Eudesmol is one of the most studied and major bioactive sesquiterpenes, mainly extracted from Atractylodes lancea (Thunb) DC. rhizomes. It has potential anti-tumor and anti-angiogenic activities and is an inhibitor of tumor growth by inhibiting angiogenesis by suppressing CREB activation of the growth factor signaling pathway. It also stimulates neurite outgrowth in rat pheochromocytoma cells with activation of mitogen-activated protein kinases. It may be a promising lead compound for enhancing neural function, and it may help to explain the underlying mechanisms of neural differentiation. In this review, we summarized the currently available clinical and preclinical studies describing the therapeutic applications of ß-eudesmol.

Oxygenated Geosmins and Plant-like Eudesmanes from a Bacterial Mangrove Endophyte.

Geosmin (1) is a microbial terpene metabolite that is responsible for the typical smell of soil and causes an off-odor of food and water. Eudesmane sesquiterpenes are commonly found in plant essential oils. Here we describe the discovery of four geosmin-type metabolites, 7R-hydroxygeosmin (2), 3-oxogeosmin (3), 2R-hydroxy-7-oxogeosmin (4), 5-deoxy-7ß,9ß-dihydroxygeosmin (5), the plant-like eudesmanes 4ß,10α-eudesmane-5ß,11-diol (6) and (1S,5S,6S,7S,10S)-10α-eudesm-4(15)-ene-1α,6α-diol (7), and the known 1(10)E,5E-germacradiene-2,11-diol (8) from a bacterial endophyte (Streptomyces sp. JMRC:ST027706) of the mangrove plant Bruguiera gymnorrhiza. By means of NMR, MS, and ECD spectroscopy, all chemical structures as well as the absolute configurations for the new compounds were elucidated. Compounds 2-5 represent the first geosmin-related metabolites directly as bacterial natural products. The plant-derived eudesmane-5ß,11-diol (6) and (1S,5S,6S,7S,10S)-10α-eudesm-4(15)-ene-1α,6α-diol (7) are also now reported as bacterial products. The broad antimicrobial activities of 6 against a suite of fungal and bacterial pathogens including methicillin-resistant Staphylococcus aureus suggest that this terpene could be an important active principle of the medicinal plant Cymbopogon distans. The discovery of geosmin metabolites from one actinomycete indicated that these bacteria could possess enzymes for modifying geosmin and offer a possibility for bioremediation.

Nitric Oxide Production Inhibitory Eudesmane-Type Sesquiterpenoids from Artemisia argyi.

Six new eudesmane-type sesquiterpene derivatives, artemargyinins A-F were isolated from the leaves of Artemisia argyi. Their structures were elucidated based on the extensive analysis of spectroscopic data. Artemargyinins A-F feature a lactone ring-opening eudesmane-type sesquiterpene with an isoprenoid group at C(8). All compounds were tested for their inhibitory effects on lipopolysaccharide-induced nitric oxide (NO) production in RAW264.7 macrophages. Artemargyinins A-F showed more potent NO production inhibitory activity with IC50 values ranging from 7.66±0.53 to 61.19±2.54 µM than the positive control quercetin (IC50 =74.34±1.39 µM). Among them, artemargyinins C and D exhibited strong inhibitory activity with IC50 values of 8.08±0.21 and 7.66±0.53 µM, respectively.

Dodelates A-E: Five dimeric eudesmane sesquiterpenoids from Dobinea delavayi.

Dodelates A-E (1-5), five angeloylated eudesmane sesquiterpenoid dimers were isolated from the roots of Dobinea delavayi. Their structures were elucidated by extensive spectroscopic data and single-crystal X-ray diffraction analyses. A possible biosynthetic pathway of these five compounds was proposed. Compounds 1 and 3 exhibited moderate antimalarial activities against Plasmodium yoelii BY265RFP.

Sesquiterpenoids from the herbs of Solanum lyratum and their cytotoxicity on human hepatoma cells.

Eleven sesquiterpenoids including four new eudesmane sesquiterpenoids, solanoids A-D (1-4), and seven known compounds (5-11) were isolated from the herbs of Solanum lyratum. By analyzing the UV, MS and NMR data, the gross structures of all isolates were established. The absolute configurations of these new compounds were determined by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. The in vitro cytotoxicity of all isolates against the hepatocellular carcinoma Hep3B and HepG2 cell lines was evaluated. Among them, compounds 7 and 11 exhibited moderate cytotoxicity against two cell lines.

[A new eudesmane type sesquiterpene from cultivated Clerodendranthus spicatus in Hainan].

Six compounds were isolated from the aerial part of cultivated Clerodendranthus spicatus in Hainan with various chromatographic techniques,and their structures were determined as:1-dehydroxy-1-oxo-rupestrinol(1),N-trans-feruloyltyramine(2),methyl 3,4-dihydroxyphenyllactate(3),caffein acid(4),methyl caffeate(5) and ethyl caffeate(6),via analysis of physicochemical properties and spectroscopic evidence.Compound 1 was a new compound,while compounds 2 and 3 were isolated from C.spicatus for the first time.Biological activity results showed that compounds 2-4 exhibited α-glucosidase inhibitory activity with different inhibition ratio.

Potent inhibition of gastric cancer cells by a natural compound via inhibiting TrxR1 activity and activating ROS-mediated p38 MAPK pathway.

Thioredoxin reductase 1 (TrxR1) has emerged as a potential target for cancer therapy, because it is overexpressed in several types of cancers and associated with increased tumour growth and poor patient prognosis. Alantolactone (ALT), a natural sesquiterpene lactone originated from traditional folk medicine Inula helenium L., has been reported to exert antitumor activity in various tumours. However, the effect of ALT on human gastric cancer cells and its underlying mechanism remains unknown. In this study, we showed that ALT inhibited cell proliferation and induced cell apoptosis in gastric cancer cells. Mechanistically, our data found that ALT induced reactive oxygen species (ROS) production by inhibiting TrxR1 activity, resulting in the activation of p38 mitogen-activated protein kinase (MAPK) pathway and eventually cell apoptosis in gastric cancer cells. And the effects of ALT were reversed by pre-treatment with NAC (a scavenger of ROS). Further investigation revealed that ALT displayed synergistic lethality with erastin against gastric cancer cells, which demonstrating combined inhibition of TrxR1 and glutathione (GSH) leads to a synergistic effect in gastric cancer cells. More importantly, ALT treatment markedly reduced the activity of TrxR1 in vivo and inhibited the growth of gastric cancer xenografts without exhibiting significant toxicity. Taken together, these findings suggest that ALT may be used as a novel therapeutic agent against human gastric cancer.

Intestinal Absorption of Isoalantolactone and Alantolactone, Two Sesquiterpene Lactones from Radix Inulae, Using Caco-2 Cells.

BACKGROUND: Isoalantolactone and alantolactone are the main sesquiterpene lactones in Radix Inulae (dried root of Inula helenium L. or I. racemosa Hook. F.), which is a frequently utilized herbal medicine. They also occur in several plants and have various pharmacologic effects. However, they have been found to have poor oral bioavailability in rats. OBJECTIVES: To understand the intestinal absorptive characteristics of isoalantolactone and alantolactone as well specific influx and efflux transporters in their absorption. METHODS: Bidirectional permeabilities of isoalantolactone and alantolactone were investigated across Caco-2 cell monolayers. Transport assays were performed using different concentrations of two lactones and specific inhibitors of ATP-binding cassette transporters and influx transporters. RESULTS: The absorption permeability of isoalantolactone and alantolactone was high at the tested concentrations (5, 20 and 80 µmol/l), and the major permeation mechanism of both lactones was found to be passive diffusion with active efflux mediated by multidrug resistance-associated proteins (MRPs) and breast cancer resistance protein (BCRP). CONCLUSION: Our results demonstrated that the absorption permeability of isoalantolactone and alantolactone was good in the Caco-2 cell model. The isoalantolactone and alantolactone absorption elucidated in this study provides useful information for further pharmacokinetics studies. Since low intestinal absorption can now be ruled out as a cause, further studies are needed to explain the low oral bioavailability of the two sesquiterpene lactones.

LC-MS guided isolation of gracilistones A and B, a pair of diastereomeric sesquiterpenoids with an unusual tetrahydrofuran-fused tricyclic skeleton from Acanthopanax gracilistylus and their potential anti-inflammatory activities.

Gracilistones A (1) and B (2), two new eudesmane-type sesquiterpenoids with an unusual tetrahydrofuran-fused 6/6/5 tricyclic ring system, were obtained from Acanthopanax gracilistylus under the guidance of LC-MS investigation. Their structures and absolute configurations were assigned by extensive spectroscopic analyses and quantum calculation methods. Compounds 1 and 2 showed potent inhibitory activity against LPS-induced nitric oxide production in RAW 264.7 macrophages, compared with the positive control L-NMMA. In addition, compounds 1 and 2 were also evaluated for their antioxidant (DPPH• and ABTS•+) and xanthine oxidase (XO) inhibitory activities, and they exhibited weak inhibitory effects at 100 µM.

Silver perchlorate in the mobile phase for rapid separation and determination of a pair of positional isomers in Inula racemosa Hook.f. with RP-HPLC.

Alantolactone and isoalantolactone isolated from many species of plants are a pair of positional isomers of CC bond. Previously, alantolactone and isoalantolactone have been proved to be good lead compounds for future anticancer agent development. Similarity of their molecular structures increases the separation difficulty for these two isomers on a conventional C18 column. Silver perchlorate (AgClO4) as mobile phase additives with RP-HPLC for improving the separation was developed for rapid determination of the positional isomers in Inula racemosa Hook.f. The effects of the concentration of silver perchlorate on the separation of the analytes were investigated. The composition of acetonitrile and water containing 5.0% silver perchlorate in a 65:35 (v/v) ratio was used as mobile phase, in which they were well separated within a short period of time on the C18 column. The method was successfully applied to determine them in an extract of Inula racemosa Hook.f. root. Silver perchlorate in mobile phase can efficiently improve the separation of the positional isomers and could be applied to rapidly determinate their content in this plant.

Isolation of eudesmanes from Pluchea odorata and evaluation of their effects on cancer cell growth and tumor invasiveness in vitro.

The traditionally used Central American medicinal plant Pluchea odorata, known as an anti-inflammatory and cancer cell growth-inhibiting remedy, was subjected to bioassay-guided isolation. Structure elucidation by 1D- and 2D-NMR and MS techniques supported by ECD and UV spectroscopic data revealed seven structurally previously undescribed and eight known eudesmane-type sesquiterpenes. Furthermore, one previously undescribed and one known phytol-like alcohol were identified. All compounds were tested for their cytotoxicity in cancer cells and for their anti-invasive effects. Among the eudesmanes, 3α-(2',3'-epoxy-2'-methylbutyryloxy)-4α-hydroxy-11-hydroperoxy-eudesm-6-en-8-one exhibited the most potent cytotoxic activity with an IC50 value of 8.8 µM (after 48 h). Also in an in vitro model measuring the tumor-triggered breaching of the adjacent lymph endothelial cell barrier (3S*,4R*,5S*,10S*,2'R*,3'R*)-3-(2',3'-epoxy-2'-methylbutyryloxy)-4,7-dihydroxy-eudesm-11-en-8-one (IC75 = 47 µM) and (3S*,4R*,5R*,10S*,2'R*,3'R*)-3-(2',3'-epoxy-2'-methylbutyryloxy)-4-acetyloxy-6-methoxy-11-hydroxy-eudesm-6-en-8-one (IC75 = 73 µM) showed inhibitory activities. Furthermore, preliminary structure-activity relationships (SARs) of the eudesmanes were developed.

Chlorajaponols A-F, sesquiterpenoids from Chloranthus japonicus and their in vitro anti-inflammatory and anti-tumor activities.

Two new eudesmane sesquiterpenoids, chlorajaponols A-B (1-2), two new guaiane sesquiterpenoids, chlorajaponols C-D (3-4), a new germacrane sesquiterpenoid, chlorajaponol E (5), and a new lindenane sesquiterpenoid, chlorajaponol F (6), along with 8 known sesquiterpenoids and 6 known disesquiterpenoids, were isolated from the whole plant of Chloranthus japonicus. Their structures were established by extensive analysis of NMR spectroscopic data in combination with mass spectrometry. The structures of compounds 1-4 were confirmed by single crystal X-ray diffraction (CuKα radiation). The possible biogenetic pathways of compounds 1-6 were discussed. Chlorajaponol B (2) showed significant inhibition against nitric oxide (NO) release in LPS-induced RAW264.7 macrophages with the IC50 value of 9.56±0.71µM, comparable to that of positive control amino guanidine (8.50±0.35µM). Shizukaol C (18) strongly suppressed the proliferation of three human tumor cell lines MGC803, HepG2, and HL-60 with IC50 values of 4.60±1.05µM, 3.17±0.66µM, and 1.57±0.27µM, respectively.

New Eudesmane Sesquiterpenoids from Salvia plebeia R. Br.

Three new sesquiterpenoids, salplebeones A - C (1 - 3), were isolated from the ethanol-soluble extract of the aerial part of Salvia plebeia R. Br. Their structures were established by detailed analysis of NMR and MS spectra. Salplebeone A was an eudesmane lactone, while salplebeones B and C were rare eudesmane sesquiterpenoids, containing 12,8-lactam groups. Antiproliferative activities of salplebeones A - C to myeloid leukemia cell lines were evaluated.

Sesquiterpenoids from the cultured mycelia of Ganoderma capense.

Eleven new sesquiterpenoids, including eight cadinane-type sesquiterpenoids, Ganodermanol A-H (1-8), and three eudesmane-type sesquiterpenoids, Ganodermanol I-K (9-11), together with three known compounds (12-14), were isolated from the cultured mycelia of Ganoderma capense. Their structures and absolute configurations were identified through combined extensive spectroscopic analysis, circular dichroism (CD), and Mo2(AcO)4-induced CD. Compounds 4 and 9 exhibited moderate cytotoxic activity against the human cancer cell line HCT116 with IC50 values of 16.6 and 12.2µM, respectively.

Sesquiterpenoids from the twigs and leaves of Fokienia hodginsii.

A rare carotane-type sesquiterpenoid, forkienin A (1), a new eudesmane-type sesquiterpenoid, forkienin B (2), and a new natural eudesmane-type sesquiterpenoid, forkienin C (3), were isolated from the twigs and leaves of Fokienia hodginsii, along with eight known sesquiterpenoids. The structures of the new compounds were elucidated on the basis of their spectroscopic analysis, including 1D and 2D NMR methods. All compounds were evaluated for cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cell lines.

Sesquiterpenes from the whole plants of Parasenecio roborowskii.

Six eremophilane-type (parasenolide A-F) and an eudesmane-type (parasenin) sesquiterpenoids, along with eight known sesquiterpenes, were isolated from the whole plants of Parasenecio roborowskii. The structures and absolute configurations of new compounds were elucidated using extensive spectroscopic analysis, including HRESIMS, 1D and 2D NMR experiments, the CD exciton chirality methods, and single-crystal X-ray crystallography. All isolated compounds were evaluated for cytotoxicity against five human cancer (HeLa, HepG2, K562, MDA231, and NCI-H460) cell lines and a murine melanoma B16 F10 cell line by MTT assay. Compounds 1-15 showed cytotoxic activities, especially compounds 3, 4, 8, 10, and 12. These five compounds showed broad spectrum activities against all the tested cancer cell lines with IC50 ranging from 9.2 to 35.5µM. The study supports that eremophilenolides and eudesmane-type sesquiterpenes occur mainly in the genus Parasenecio and can be used as a chemosystematic marker of the genus.

Eight new eudesmane- and eremophilane-type sesquiterpenoids from Atractylodes lancea.

Phytochemical and pharmacological study on the rhizomes of Atractylodes lancea led to the identification of twenty-one compounds: six new eudesmane-type sesquiterpenoids (1-6), two new eremophilane-type sesquiterpenoids (7, 8), and thirteen known compounds (9-21). These new compounds were elucidated using extensive spectroscopic analyses with experimental and calculated electronic circular dichroism (ECD) for the configurational assignments. Notably, this study was the first report on the isolation of two eremophilane-type sesquiterpenoids (7, 8) from the genus Atractylodes. Compounds 5, 7, and 16 showed potent hepatoprotective activities against N-acetyl-p-aminophenol (APAP)-induced HepG2 cell injury at a concentration of 10µM (bicyclol as the positive drug).

A new rearranged eudesmane sesquiterpene and bioactive sesquiterpenes from the twigs of Lindera glauca (Sieb. et Zucc.) Blume.

A new rearranged eudesmane sesquiterpene, named eudeglaucone (1), and five known sesquiterpenes including (+)-faurinone (2) and four eudesmane-type sesquiterpenes (3-6), were isolated from the twigs of Lindera glauca (Sieb. et Zucc.) Blume. The structure of 1 was elucidated by a combination of extensive spectroscopic analyses, including extensive 2D NMR (1H-1H COSY, HMQC, HMBC, and NOESY) and HR-MS. Compound 1 was a relatively rare rearranged eudesmane sesquiterpene in terpenoids. All isolates were evaluated for their antiproliferative activities against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15). Compounds 3 and 6 showed significant cytotoxicity against SK-MEL-2 and HCT-15 cell lines with IC50 values ranging from 9.98 to 12.20 µM. We also investigated the anti-neuroinflammatory activities of the isolates (1-6) in the lipopolysaccharide (LPS)-stimulated murine microglia BV-2 cell line by measuring nitric oxide (NO) levels. All isolates significantly inhibited NO production with IC50 values of 3.67-26.48 µM without inducing cell toxicity.