Cytotoxic activity of some natural and synthetic guaianolides

The essential oil composition of the endemic plant species Centaurea vandasii and chemotaxonomy of section Phalolepis (Asteraceae)

In the present study, the chemical composition of the essential oil from aerial parts of the endemic plant species, Centaurea vandasii Velen (sect. Phalolepis, Asteraceae), collected in its locus classicus in Rhodope Mts, Bulgaria, was evaluated by GC-MS. The main components of the oil were hexadecanoic acid (18.3%), tetradecanoic acid (13.8%), caryophyllene oxide (12.1%) and germacrene D (8.4%). Furthermore, a complete literature review on the composition of the essential oils of all the other taxa of Centaurea, belonging to section Phalolepis, studied so far, was performed. HCA (Hierarchical Cluster Analysis) and PCA (Principal Component Analyses) were used in order to demonstrate chemotaxonomical variations in the composition of the essential oils.

A new cytotoxic sesquiterpene lactone from Euphorbia microsphaera Boiss against human breast cancer (MCF-7) and human fibrosarcoma (HT1080) cells

A new guaianolide sesquiterpene lactone with cytotoxic properties was isolated from Euphorbia microsphaera Boiss. To determine the highest active fraction and isolate bioactive compounds, a bioassay guided fractionation approach was used. The general toxicity properties of the plant's extracts and fractions (fr_1-10) were assessed against Artemia salina, Oryzeaphilus mercator, and Tribolium castaneum. Cytotoxic activities were investigated against normal human foreskin fibroblasts and two malignant cell lines, including human breast cancer (MCF-7) and human fibrosarcoma cells (HT1080) using the MTT assay at different time points of 24, 48, and 72 h. Single crystal X-ray diffraction (SC-XRD) and mass spectrometry data were used to determine the structure of the active guaianolide sesquiterpene lactone (3aR,4S,4aS,5R,7aS,9aS)-5-hydroxy-5,8-dimethyl-3-methylene-2-oxo-2,3,3a,4,4a,5,6,7,7a, 9a decahydroazuleno [6,5-b] furan-4-yl acetate (named aryanin). Chloroformic fraction 7 (fr₇, LC₅₀ = 93.50 μg/mL for general toxicity) had the highest toxicity result, with a mortality rate of more than 50% for both insect species after 12 h at 15 mg/mL. The highest cytotoxicity of aryanin was observed on 24 h treated MCF-7 with an IC₅₀ of 13.81 μg/mL. After 24 h, the inhibition of MCF-7 cell proliferation was 92%-94% at concentrations of 25-50 μg/mL, respectively. On MCF-7, the IC₅₀ was found to be 49.35 μg/mL after 72 h. This compound had a considerable cytotoxicity (IC₅₀ ≤ 12.5 μg/mL, 24 h) on human foreskin fibroblasts. In contrast to the MCF-7 cell line, the proliferation of human foreskin fibroblasts was increased after 72 h.

The essential oil composition of Centaurea immanuelis-loewii Degen growing wild in Bulgaria and chemotaxonomy of section Acrocentron

In the present study, the chemical composition of the essential oil from aerial parts of the Balkan endemic, Centaurea immanuelis-loewii Degen (sect. Acrocentron, Asteraceae), collected in Bulgaria was evaluated by GC-MS. The main components of the oil were β-caryophyllene (23.2%), germacrene D (13.7%) and caryophyllene oxide (12.4%). Furthermore, a complete literature review on the composition of the essential oils of all the other taxa of Centaurea, belonging to section Acrocentron, studied so far, was performed and the chemotaxonomical variations in the composition of the essential oils is discussed.

Chlorinated Guaiane-Type Sesquiterpene Lactones as Cytotoxic Agents against Human Tumor Cells

Guaiane-type sesquiterpene lactones are naturally occurring compounds which have attracted attention due to their array of biological activities. In this study, chlorinated guaianolides 1-8, isolated from plants of the genus Centaurea, were evaluated against the human leukemia cell lines HL-60, U-937, a specific U-937 cell line that overexpresses the anti-apoptotic Bcl-2 protein and the human melanoma cell line SK-MEL-1. This established the relevant structure-growth inhibition relationships. Chlorohyssopifolins A (1), C (3) and D (4) and linichlorin A (6) were the most potent compounds in terms of inducing growth inhibition in the four cell lines. IC₅₀ values were below 10 μM in all cases. Chlorohyssopifolins A (1) and D (4) and linichlorin A (6) were potent apoptotic inducers in human U-937 leukemia cells, as determined by fluorescent microscopy and flow cytometry, and their mechanism of action was associated with cytochrome c release, caspase activation and poly(ADP-ribose)polymerase cleavage. Overall this study shows that guaianolides induce cytotoxicity against human tumor cells and provides important insights into the cell death pathways that are involved.

The investigation of the potential antidepressant-like activity of Xanthium orientale subsp. italicum (Moretti) Greuter in rodents

ETHNOPHARMACOLOGICAL RELEVANCE

Ethnobotanical surveys revealed that Xanthiumorientale subsp. italicum (Moretti) Greuter has been used against central nervous system disorders in Turkish folk medicine. The aim of the present study is to verify the folkloric assertion on this plant. The compounds responsible for the activity were investigated using bioassay-guided fractionation procedures.

MATERIALS AND METHODS

The antidepressant activity of the aqueous, n-hexane, ethyl acetate (EtOAc), methanol (MeOH) extracts; fractions and isolated compounds from active MeOH extract were evaluated by using the in vitro MAO inhibition assay and three different in vivo models namely forced swimming test, tail suspension test, and antagonism of tetrabenazine-induced ptosis, hypothermia, and suppression of locomotor activity. The results were compared with control and reference groups, and active compounds of the plant have been determined. Through the bioassay-guided fractionation procedures, two compounds were isolated from the active fraction and their structures were elucidated by spectroscopic methods.

RESULTS

The MeOH extract of the plant was found to possess antidepressant-like activity. This extract was then subjected to chromatographic techniques. Isolated sesquiterpene lactones were elucidated as xanthatin (1) and xanthinosin (2), which were responsible for the antidepressant-like activity.

CONCLUSIONS

This study discovered the antidepressant potential of X. orientale subsp. italicum. Using bioassay-guided fractionation and isolation techniques, xanthatin (1) and xanthinosin (2) were determined as the main active components of the leaves.

Epoxide containing molecules: A good or a bad drug design approach

Functional group modification is one of the main strategies used in drug discovery and development. Despite the controversy of being identified for many years as a biologically hazardous functional group, the introduction of an epoxide function in a structural backbone is still one of the possible modifications being implemented in drug design. In this manner, it is our intention to prove with this work that epoxides can have significant interest in medicinal chemistry, not only as anticancer agents, but also as important drugs for other pathologies. Thus, this revision paper aims to highlight the biological activity and the proposed mechanisms of action of several epoxide-containing molecules either in preclinical studies or in clinical development or even in clinical use. An overview of the chemistry of epoxides is also reported. Some of the conclusions are that effectively most of the epoxide-containing molecules referred in this work were being studied or are in the market as anticancer drugs. However, some of them in preclinical studies, were also associated with other different activities such as anti-malarial, anti-arthritic, insecticidal, antithrombotic, and selective inhibitory activity of FXIII-A (a transglutaminase). As for the epoxide-containing molecules in clinical trials, some of them are being tested for obesity and schizophrenia. Finally, drugs containing epoxide groups already in the market are mostly used for the treatment of different types of cancer, such as breast cancer and multiple myeloma. Other diseases for which the referred drugs are being used include heart failure, infections and gastrointestinal disturbs. In summary, epoxides can be a suitable option in drug design, particularly in the design of anticancer agents, and deserve to be better explored. However, and despite the promising results, it is imperative to explore the mechanisms of action of these compounds in order to have a better picture of their efficiency and safety.

Guaianolides from the Aerial Parts of Centaurea Hololeuca

Seven guaianolides were isolated from the acetone extract of the aerial parts of Centaurea hololeuca Boiss. The antifeedant activity of the natural compounds (1–7) and of four chloro derivatives (8–11), synthesized from repin (1) and janerin (3) were tested against larvae of Spodoptera littoralis. Cebellin J (6) and chlorojanerin (11) showed significant antifeedant activity at 100 ppm, whereas at this concentration cebellin G (4) and 15-deschloro-15-hydroxychlorojanerin (7) stimulated feeding. Cebellin G (4) stimulated larvae of S. littoralis to feed at low concentration, but deterred feeding at high concentrations. The addition of chlorine to repin (1) resulted in an increase in antifeedant activity.

Chemical Composition of the Essential Oil of the Local Endemics Centaurea davidovii and C. parilica (Asteraceae, sect. Lepteranthus) from Bulgaria

In the present study the chemical compositions of the essential oils from aerial parts of Centaurea davidovii Urum. and C. parilica Stoj. & Stef., both endemic to Bulgaria, were evaluated by GC and GC-MS. The main components of C. davidovii were β-eudesmol (13.9%), spathulenol (13.3%), caryophyllene oxide (10.1%) and ( Z)-phytol (5.4%). The main components of C parilica were hexadecanoic acid (39.2%), ( Z, Z)-9,12-octadecadienoic acid (11.9%), caryophyllene oxide (6.8%) and spathulenol (6.6%). In order to compare the essential oils composition of these taxa and of related species a PCA analysis was carried out.

Sesquiterpenoids in subtribe Centaureinae (Cass.) Dumort (tribe Cardueae, Asteraceae): distribution, (13)C NMR spectral data and biological properties

Asteraceae Bercht. & J. Presl is one of the biggest and most economically important plant families. The taxonomy and phylogeny of Asteraceae is rather complex and according to the latest and most reliable taxonomic classification of Panero & Funk, based on the analysis of nine chloroplast regions, the family is divided into 12 subfamilies and 35 tribes. One of the largest tribes of Asteraceae is Cardueae Cass. with four subtribes (Carlininae, Echinopinae, Carduinae and Centaureinae) and more than 2500 species. Susanna & Garcia-Jacas have organized the genera of Centaureinae (about 800 species) into seven informal groups, which recent molecular studies have confirmed: 1. Basal genera; 2. Volutaria group; 3. Rhaponticum group; 4. Serratula group; 5. Carthamus group; 6. Crocodylium group; 7. Centaurea group. This review summarizes reports on sesquiterpenoids from the Centaureinae subtribe of the Asteraceae family, as well as the (13)C NMR spectral data described in the literature. It further reviews studies concerning the biological activities of these metabolites. For this work, literature data on sesquiterpenes from the Centaureinae subtribe were retrieved with the help of the SciFinder database and other similar data banks. All entries from 1958 until the end of 2011 were considered. This review is addressed to scientists working in the metabolomics field such as chemists, botanists, etc., the spectroscopic data reported make this work a good tool for structural elucidation, the biological section gives useful information to those who wish to study the structure activity relationships.

An allenic Pauson-Khand approach to 6,12-guaianolides

Cyclocarbonylation of α-methylene butyrolactone-containing allene-ynes affords 6,12-guaianolide ring systems. Incorporation of the α-methylene butyrolactone early in a synthetic sequence is rare for reactivity reasons; however, this moiety proves to be beneficial to the allenic Pauson-Khand reaction. The three double bonds and the ketone in the resulting 5-7-5 ring system bear significant differences in their reactivity and are ideally positioned for synthetic application to 6,12-guaianolides and analogs.

The antidepressant-like effect of Hedyosmum brasiliense and its sesquiterpene lactone, podoandin in mice: evidence for the involvement of adrenergic, dopaminergic and serotonergic systems

We have recently shown that the ethanol extract of the leaves of Hedyosmum brasiliense exhibits an antidepressant-like effect in the tail suspension and forced swimming tests in mice. The present study investigates the mechanisms involved in the antidepressant-like effect of H. brasiliense extract, together with the antidepressant potential of podoandin, an isolated sesquiterpenoid. H. brasiliense (50mg/kg, i.p.) and podoandin (10mg/kg, i.p.) decreased the immobility time in the forced swimming test, without any accompanying changes in ambulation in the open-field test. The anti-immobility effect of the H. brasiliense extract was prevented by pre-treating the mice with ondansetron, NAN 190, pindolol, prazosin, yohimbine, haloperidol, SCH23390, and sulpiride. On the other hand, pre-treating the mice with: p-chlorophenylalanine (4 consecutive days), ketanserin, naloxone, naltrindole, bicuculline, phaclofen, or l-arginine did not block the antidepressant-like effect of H. brasiliense. In addition, pre-treatment of the animals with methylene blue, NG-nitro-l-arginine or 7-nitroindazole, at subeffective doses, did not cause a synergistic effect with H. brasiliense extract at an effective dose in the forced swimming test. The anti-immobility effect of podoandin was also prevented by pre-treating the mice with NAN-190, ondansetron, prazosin, yohimbine, sulpiride and haloperidol. The results indicate that the antidepressant-like effect of H. brasiliense (and podoandin) is dependent on the serotonergic, noradrenergic and dopaminergic systems, but not on the GABAergic, opioid and oxidonitrergic systems.

Synthesis of (-)-β-caryophyllene oxide via regio- and stereoselective endocyclic epoxidation of β-caryophyllene with Nemania aenea SF 10099-1 in a liquid-liquid interface bioreactor (L-L IBR)

Nemania aenea SF 10099-1, a basidiomycete isolated from a forest soil sample, regio- and stereoselectively epoxidized β-caryophyllene (Car) to (-)-β-caryophyllene oxide (Car-Ox) in a liquid-liquid interface bioreactor (L-L IBR) consisted of a liquid medium (a bottom phase), a fungus-ballooned microsphere (MS) mat (a middle phase), and an organic phase containing Car (a top phase). The cultivation conditions, such as carbon and nitrogen sources, kind of MS, initial medium pH and Car concentration, were optimized in the L-L IBR system. The best carbon and nitrogen sources were xylose and tryptone, respectively. The most suitable polyacrylonitrile MS was MMF-DE-1 (former MFL-80SDE; non-coated type). Although the strain could not grow below pH 5.5, the endocyclic epoxidation of Car efficiently proceeded at a wide range of initial medium pH (6.0 to 9.0). The bioconversion system exhibited an excellent alleviation effect toward substrate and product inhibitions. While Car could be added into an organic phase (KF-96L-1CS, dimethyl silicone oil) at 50% (w/v), the accumulation of Car-Ox reached over 30g/l in spite of these strong microbial toxicities. Moreover, the epoxidation reaction smoothly proceeded in a novel L-L IBR system, a multistory L-L IBR systems, consisted of 5 stacked reactor units. The optical rotation of Car-Ox produced was (-) and the enantiomeric excesses of (-)-β-Car-Ox purified by 1st and 2nd recrystallization from methanol reached 97.51 and 99.33%, respectively.

Cytotoxic geranylflavonoids from Bonannia graeca

The analysis of the aerial parts of Bonannia graeca led to the isolation and characterization of polar geranylated flavonoids (6 and 7). The structure elucidation was performed by extensive spectroscopic methods (1D and 2D NMR) and comparison with literature data. All natural flavonoids isolated from B. graeca (1-7) and some synthetic derivatives (8-11) were tested for cytotoxic activity against four human tumor cell lines. Preliminary structure-activity relationship correlations are discussed.

What made sesquiterpene lactones reach cancer clinical trials?

Sesquiterpene lactones (SLs) are plant-derived compounds often used in traditional medicine against inflammation and cancer. This review focuses on the chemical and biological properties of SLs that lead to enhanced anticancer and anti-inflammatory effects. The chemical properties comprise alkylating center reactivity, lipophilicity, and molecular geometry and electronic features. SLs in clinical trials are artemisinin, thapsigargin and parthenolide and many of their synthetic derivatives. These drugs are selective toward tumor and cancer stem cells by targeting specific signaling pathways, which make them lead compounds in cancer clinical trials.

The Cytotoxic Properties of Natural Coumarins Isolated from Roots of Ferulago campestris (Apiaceae) and of Synthetic Ester Derivatives of Aegelinol

Grandivittin (1), agasyllin (2), aegelinol benzoate (3) and felamidin (20), four natural coumarins isolated from Ferulago campestris, and several synthetic ester derivatives of aegelinol (4) were tested against four tumor cell lines. Some of them were shown to be marginally cytotoxic against the A549 lung cancer cell line.

Antiproliferative effect of flavonoids and sesquiterpenoids from Achillea millefolium s.l. on cultured human tumour cell lines

The antiproliferative activities of n-hexane, chloroform, aqueous-methanol and aqueous extracts of the aerial parts of the Achillea millefolium aggregate on three human tumour cell lines were investigated by means of MTT assays. The chloroform-soluble extract exerted high tumour cell proliferation inhibitory activities on HeLa and MCF-7 cells, and a moderate effect on A431 cells; accordingly, it was subjected to detailed bioactivity-guided fractionation. As a result of the multistep chromatographic purifications (VLC, CPC, PLC, gel filtration), five flavonoids (apigenin, luteolin, centaureidin, casticin and artemetin) and five sesquiterpenoids (paulitin, isopaulitin, psilostachyin C, desacetylmatricarin and sintenin) were isolated and identified by spectroscopic methods. The antiproliferative assay demonstrated that centaureidin is the most effective constituent of the aerial parts of yarrow: high cell growth inhibitory activities were observed especially on HeLa (IC(50) 0.0819 microm) and MCF-7 (IC(50) 0.1250 microm) cells. Casticin and paulitin were also highly effective against all three tumour cell lines (IC(50) 1.286-4.76 microm), while apigenin, luteolin and isopaulitin proved to be moderately active (IC(50) 6.95-32.88 microm). Artemetin, psilostachyin C, desacetylmatricarin and sintenin did not display antiproliferative effects against these cell lines. This is the first report on the occurrence of seco-pseudoguaianolides (paulitin, isopaulitin and psilostachyin C) in the Achillea genus.

Cytotoxic activity of some natural and synthetic ent-kauranes

Atractyligenin (1) and several synthetic derivatives were tested and found to be active against tumor cell replication. Compound 1 was readily converted to the 2,15-diketo (3) or 15-keto (4) derivatives, which contain an alpha,beta-unsaturated ketone. Compounds 3 and 4 showed significant cytotoxic activity against all six tested cancer cell lines and were most potent against 1A9 ovarian cancer cells with EC50 values of 0.2 and 0.3 microM, respectively. These two 1-analogues are promising lead compounds for further investigation.

Natural sesquiterpenoids

This review covers the isolation, structural determination, synthesis and chemical and microbiological transformations of natural sesquiterpenoids. The literature from January to December 2005 is reviewed,and 386 references are cited.