Chemical Composition and Antioxidant Activity of Essential Oils and Hexane Extract of Onopordum arenarium from Tunisia.

In the present study, volatile oils from Onopordum arenarium fresh flowers and stems were obtained by hydrodistillation and the non-polar aerial part hexane extract was prepared using a Soxhlet apparatus. The constituents of different organs were identified for the first time by gas chromatography equipped with flame ionization detector and gas chromatography coupled to mass spectrometry. A total of 29 and 25 compounds were identified constituting over 91.6 and 89.2% of the whole constituents from flower and stem volatile oils, respectively. Both organs were constituted mainly of long-chain hydrocarbons (23.3-36.4%) followed by oxygenated long-chain hydrocarbons (31.5-33.8%) and oxygenated monoterpenes (14.4-6.6%). The major identified compound was palmitic acid [25.5% in O. arenarium flower essential oil (EO) and 28.7% in the stem EO]. Eighteen compounds representing 80.7% of the whole constituents were identified in the n-hexane extract, which was characterized by high amounts of triterpenoids (39.6%) and dominated by lupeol acetate (19.2%) and ß-amyrin acetate (10.1%). Moreover, all extracts were evaluated for antioxidant potential using 1,1-diphenyl-2-picrylhydrazyl radical assay. The obtained results demonstrated that the EOs and the hexane extract could be a new source of natural potentially bioactive molecules.

Evaluation of angiotensin converting enzyme inhibitors by SPR biosensor and theoretical studies.

Surface plasmon resonance (SPR) biosensor has been utilized for monitoring analyte-ligand interactions in modern drug discovery processes. SPR biosensors measure the change in refractive indexes over the course of analyte molecules' binding to a specific immobilized ligand on sensor chip. This effort highlights a comprehensive SPR study besides enzymatic assay for discovery of new Angiotensin Converting Enzyme (ACE) inhibitors via screening of medicinal plants. At first, five medicinal plants were selected as potential sources for developing new ACE inhibitors through hydrolyzing hippuryl-L-histidyl-L-leucine (HHL) assay. The interaction of selected extracts with immobilized ACE on the sensor chip (500D) confirmed that the Onopordum acanthium L. had the greatest ACE inhibition activity among the set of compounds and its active compound (onopordia) was isolated. SPR biosensor used to evaluate binding affinity of onopordia and ACE. Equilibrium constant (KD), and changes in Gibb's free energy of the binding (ΔGbinding) values for the interaction of onopordia with ACE were found to be 10.24 µM and -28.48 kJ/mol, respectively. Computational analysis supported the binding of onopordia to the ACE active site. Kinetic and thermodynamic parameters of binding revealed that onopordia is an acceptable ACE inhibitor and could treat hypertension. SPR biosensor can be used to improve the drug discovery process for many important classes of drug targets due to its great sensitivity.

The hydro-alcoholic extracts of Sardinian wild thistles (Onopordum spp.) inhibit TNFα-induced IL-8 secretion and NF-κB pathway in human gastric epithelial AGS cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Thistles species (Family: Compositae) are traditionally used in the Mediterranean area, particularly in Sardinia. They are usually gathered from the wild and used for both food and therapeutic purposes, including gastrointestinal disorders. AIM OF THE STUDY: This work aims to evaluate the anti-inflammatory activity of eight wild thistles from Sardinia, in an in vitro model of gastric inflammation, and to identify the major active compounds in the extracts. MATERIALS AND METHODS: The hydro-alcoholic extract of the aerial part of each species was prepared. After the induction of inflammation by the addition of tumor necrosis factor-α (TNFα) (10ng/mL), AGS cells were treated with extracts/pure compounds under study. The inhibition of interleukin-8 (IL-8) release, IL-8 and NF-κB promoter activities and NF-κB nuclear translocation were evaluated. Extracts main components were identified by HPLC-PDA-MS/MS. RESULTS: Only Onopordum horridum Viv. and Onopordum illyricum L. hydro-alcoholic extracts reduced, in a concentration-dependent fashion, the IL-8 release and promoter activity in human gastric epithelial cells AGS. The effect was partially due to the NF-κB pathway impairment. Onopordum hydro-alcoholic extracts were also chemically profiled, and caffeoylquinic acid derivatives were the main compounds identified in the extract. Further investigations showed that 3,5 dicaffeoylquinic acid highly inhibited IL-8 secretion in AGS cells (IC50 0.65µM), thus suggesting that this compound contributed, at least in part, to the anti-inflammatory activity elicited by O. illyricum extracts. CONCLUSIONS: Our results suggest that Onopordum species may exert beneficial effects against gastric inflammatory diseases. Thus, these wild plants deserve further investigations as preventive or co-adjuvant agents in gastric diseases.

Layer chromatography-bioassays directed screening and identification of antibacterial compounds from Scotch thistle.

The antibacterial profiling of Onopordum acanthium L. leaf extract and subsequent targeted identification of active compounds is demonstrated. Thin-layer chromatography (TLC) and off-line overpressured layer chromatography (OPLC) coupled with direct bioautography were utilized for investigation of the extract against eight bacterial strains including two plant and three human pathogens and a soil, a marine and a probiotic human gut bacteria. Antibacterial fractions obtaining infusion-transfusion OPLC were transferred to HPLC-MS/MS analysis that resulted in the characterization of three active compounds and two of them were identified as, linoleic and linolenic acid. OPLC method was adopted to preparative-scale flash chromatography for the isolation of the third active compound, which was identified after a further semi-preparative HPLC purification as the germacranolide sesquiterpene lactone onopordopicrin. Pure onopordopicrin exhibited antibacterial activity that was specified as minimal inhibitory concentration in the liquid phase as well.

Anti-inflammatory sesquiterpene lactones from Onopordum illyricum L. (Asteraceae), an Italian medicinal plant.

Onopordum illyricum L. is a medicinal plant used in the Mediterranean area as antipyretic for the treatment of respiratory and urinary inflammations and to treat skin ulcers. Repeated chromatographic purification of O. illyricum aerial parts led to the isolation of six known sesquiterpenes, which were evaluated for the inhibition of the pro-inflammatory transcription factors NF-κB and STAT3 and for the activation of the transcription factor Nrf2, which regulates the cellular antioxidant response. Structure-activity relationships were interpreted by the NMR-based cysteamine assay. The sesquiterpene lactone vernomelitensin significantly inhibited NF-κB and STAT3, showing also a significant Nrf2 activation. Accordingly, the cysteamine assay selected vernomelitensin as the most reactive of the isolated sesquiterpenes, identifying the α,ß-unsaturated aldehyde moiety as responsible for the higher (re)activity.

Investigation of the Antiproliferative Properties of Natural Sesquiterpenes from Artemisia asiatica and Onopordum acanthium on HL-60 Cells in Vitro.

Plants and plant extracts play a crucial role in the research into novel antineoplastic agents. Four sesquiterpene lactones, artecanin (1), 3ß-chloro-4α,10α-dihydroxy-1α,2α-epoxy-5α,7αH-guaia-11(13)-en-12,6α-olide (2), iso-seco-tanapartholide 3-O-methyl ether (3) and 4ß,15-dihydro-3-dehydrozaluzanin C (4), were isolated from two traditionally used Asteraceae species (Onopordum acanthium and Artemisia asiatica). When tested for antiproliferative action on HL-60 leukemia cells, these compounds exhibited reasonable IC50 values in the range 3.6-13.5 µM. Treatment with the tested compounds resulted in a cell cycle disturbance characterized by increases in the G1 and G2/M populations, while there was a decrease in the S phase. Additionally, 1-3 elicited increases in the hypodiploid (subG1) population. The compounds elicited concentration-dependent chromatin condensation and disruption of the membrane integrity, as revealed by Hoechst 33258-propidium staining. Treatment for 24 h resulted in significant increases in activity of caspases-3 and -9, indicating that the tested sesquiterpenes induced the mitochondrial pathway of apoptosis. The proapoptotic properties of the sesquiterpene lactones were additionally demonstrated withannexin V staining. Compounds 1 and 2 increased the Bax/Bcl-2 expression and decreased the expressions of CDK1 and cyclin B2, as determined at the mRNA level by means of RT-PCR. These experimental results indicate that sesquiterpene lactones may be regarded as potential starting structures for the development of novel anticancer agents.

Inhibition of COX-2 and NF-κB1 Gene Expression, NO Production, 5-LOX, and COX-1 and COX-2 Enzymes by Extracts and Constituents of Onopordum acanthium.

The present study focused on the investigation of the inhibition of cyclooxygenase-2 and nuclear factor kappa B1 gene expression, nitric oxide production, leukotriene biosynthesis (5-lipoxygenase), and cyclooxygenase-1 and cyclooxygenase-2 enzymes of Onopordum acanthium, and the isolation and identification of its active compounds. From the chloroform soluble part of the MeOH extract prepared from aerial parts, lignans [pinoresinol (1), syringaresinol (2), and medioresinol (3)] and flavonoids [hispidulin (4), nepetin (5), apigenin (6), and luteolin (7)] were isolated by a combination of different chromatographic methods. The structures of the compounds were determined by means of mass spectrometry and 1D- and 2D-nuclear magnetic resonance spectroscopy, and by comparison of the spectral data with literature values. Extracts of different polarity and the isolated compounds obtained from the aerial parts, together with those previously isolated from the roots of the plant [4ß,15-dihydro-3-dehydrozaluzanin C (8), zaluzanin C (9), 4ß,15,11ß,13-tetrahydrozaluzanin C (10), nitidanin diisovalerianate (11), 24-methylenecholesterol (12), and 13-oxo-9Z,11E-octadecadienoic acid (13)], were evaluated for their inhibitory effects on cyclooxygenase-2 and nuclear factor kappa B1 gene expression, inducible nitric oxide synthase, 5-lipoxygenase, and cyclooxygenase-1 and cyclooxygenase-2 enzymes in in vitro assays. It was found that O. acanthium extracts exert strong inhibitory activities in vitro and some lignans, flavonoids, and sesquiterpenes may play a role in these activities. 4ß,15-Dihydro-3-dehydrozaluzanin C and zaluzanin C at 20 µM were the most active constituents tested against lipopolysaccharide/interferon-γ-induced nitric oxide production (100.4 ± 0.5 % and 99.4 ± 0.8 %) in the inhibition of cyclooxygenase-2 (98.6 ± 0.2 % and 97.0 ± 1.1 %) and nuclear factor kappa B1 gene expression (76.7 ± 7.3 % and 69.9 ± 3.4 %). Furthermore, it was shown that these inhibitory effects are not due to cytotoxicity of the compounds.

Standardization of solvent extracts from Onopordum acanthium fruits by GC-MS, HPLC-UV/DAD, HPLC-TQMS and 1H-NMR and evaluation of their inhibitory effects on the expression of IL-8 and E-selectin in immortalized endothelial cells (HUVECtert).

In this work we have characterized and standardized the solvent extracts of the fruits of Onopordum acanthium, a plant widely distributed from Europe to Asia and used in different traditional medicines. Fruits were extracted with methanol (ME) and n-hexane (HE) and the extract compositions determined by GC-MS, HPLC-UV/DAD, HPLC-TQMS and 1H NMR spectroscopy. Anti-inflammatory activity (IL-8 and E-selectin, qPCR and ELISA) was investigated in HUVECtert cells stimulated with TNF-alpha and LPS. Arctiin and isochlorogenic acid were found in ME (87 +/- 2%, w/w, and 10.2 +/- 0.2%, w/w; 38.0 +/- 3.2 mg/gFRUITS and 3.5 +/- 0.4 mg/gFRUITS) and (ii) paraffins in the HE (195.6 +/- 5.6 mg/g). A dose dependent (from 15 to 40 microgME/mL corresponding to 20-75 microM arctiin) inhibition of E-selectin and of the induction of IL-8 was induced by LPS. The results of this study support the use of O. acanthium fruits in traditional medicine as an anti-inflammatory agent and for cancer prevention and treatment.

Phytotoxic potential of Onopordum acanthium L. (Asteraceae).

Onopordum acanthium L. (Asteraceae) is a plant native to southern Europe and southwestern Asia, but it is invasive in disturbed areas and agricultural fields around the world, causing many agronomic problems by interfering with crops or preventing animals from grazing on pastures. Allelopathy could be one of the reasons that this plant has spread over different continents. The aim of the present study was to bioprospect O. acanthium leaf extracts through the isolation and purification of allelopathic secondary metabolites with phytotoxicity to explain their invasive behavior. Phytotoxic activity was tested using etiolated wheat coleoptiles. The most active extract was selected to perform a bioassay-guided isolation of two flavonoids, pectolarigenin (1) and scutellarein 4'-methyl ether (2), and two sesquiterpene lactones, elemanolide 11(13)-dehydromelitensin ß-hydroxyisobutyrate (3) and acanthiolide (4). All compounds were isolated for the first time from O. acanthium, and acanthiolide (4) is described for the first time. Compound 3 strongly inhibited the growth of wheat coleoptiles and 1 showed an intermediate effect. The results indicate that these compounds could contribute to the invasion of O. acanthium in ecological systems and agricultural fields.

Variation in oil content, fatty acid and phytosterols profile of Onopordum acanthium L. during seed development.

This study has determined oil, fatty acid (FA) and phytosterols content during the ripening of the Tunisian Onopordum acanthium L. seeds. In total, nine FAs and six phytosterols were identified. The main FAs were linoleic acid (0.18-8.06 mg/g of seed) followed by oleic acid (0.051-2.45 mg/g of seed), palmitic acid and stearic acid. Pentadecanoic acid was detected, for the first time, in unripe fruits and the two last stages of development were characterised by a relative abundance of erucic acid. Overall, ß-sitosterol (34.5-77.79% of total sterols) was the major 4-desmethylsterols during maturation. The first episodes of growth were characterised by the best amounts of stigmasterol and campesterol, while stigmastanol and Δ7 sitosterol had quoted the semi-ripe and fully ripe fruits; however, cholesterol was absent. These findings are useful in understanding a potential new source of important natural compounds (Phytosterols and USFA) found in this fruit and when harvest should be undertaken to optimise desired FA and phytosterols content.

Effects of catalysts and solvents on liquefaction of Onopordum heteracanthum for production of bio-oils.

Milled Onopordum heteracanthum stalks were converted to liquid products in organic solvents (methanol, ethanol and acetone) with (KOH and ZnCl2) and without catalyst in an autoclave at temperatures of 523, 543 and 563 K. Effects of liquefaction parameters such as catalyst and solvent were investigated. The percentage yields from supercritical methanol, ethanol and acetone conversions were 48.2, 50.4 and 66.2 at 563 K in the non-catalytic runs, respectively. In the catalytic run with ZnCl2, the highest conversion (70.2%) was obtained in acetone at the same temperature. The obtained liquid products at 563 K were analyzed and characterized by elemental, Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry. 106 different compounds have been identified by GC-MS in the liquid products obtained in methanol at 563 K.

Bioactivity-guided isolation of antiproliferative compounds from the roots of Onopordum acanthium.

Onopordum acanthium has been considered in traditional medicine to be effective against different cancers. The chloroform extracts of the root, which displayed antiproliferative effect against human tumor cell lines, was subjected to bioactivity-guided multistep chromatographic separation. This experiment resulted in the isolation of the sesquiterpene lactones 4beta,14-dihydro-3-dehydrozaluzanin C (1), zaluzanin C (2) and 4beta,15,11beta,13-tetrahydrozaluzanin C (3), the neolignan nitidanin-diisovalerianate (4), besides 13-oxo-9Z,11 E-octadecadienoic acid (5), 24-methylenecholesterol (6), alpha-linolenic acid, linoleic acid, stigmasterol and beta-sitosterol. The structures of the isolated compounds were established through analytical data (NMR, MS), and by comparison of these with those reported in the literature. All the aforementioned compounds were detected for the first time from this plant. The antiproliferative activities of compounds 1-6 were assessed on cervix adenocarcinoma HeLa, breast adenocarcinoma MCF7 and skin epidermoid carcinoma A431 cells by using the MTT assay. It was found that, 4beta,14-dihydro-3-dehydrozaluzanin C (1), the most active antiproliferative compound of the extract, exerted remarkable tumor cell growth inhibitory activity (IC50 2.7-15.1 microM).

Sesquiterpenes from Onopordum illyricum and their antifeedant activity.

Phytochemical investigation of the acetone extract of the aerial parts of Onopordum illyricum L. afforded five known sesquiterpenoids: compounds 3 and 4 already isolated from O. illirycum, and 8alpha-[4'-hydroxymethacryloyloxy]-sonchucarpolide (1), 8alpha-[4'-hydroxymethacryloyloxy]-4-epi-sonchucarpolide (2) and 8-(4'-hydroxymethacryloyl)-dehydromelitensin (5), not previously detected in this species. Compounds 4 and 5 showed moderate antifeedant activity against larvae of Spodoptera littoralis.

Phytochemical profile and apoptotic activity of Onopordum cynarocephalum.

A phytochemical investigation of acetone and chloroform extracts of the aerial parts of Onopordum cynarocephalum Boiss. et Blanche was carried out. It led to the isolation of two new sesquiterpenes, the elemane aldehyde (2) and the eudesmane (11), together with 15 known compounds: two lignans (1 and 15) and 13 sesquiterpenes (3-10, 12-14, 16, 17). The structures were elucidated by spectroscopic analyses, especially 1D and 2D NMR spectra. The anti-growth effect against three human melanoma cell lines, M14, A375, and A2058, of the different extracts and compounds of O. cynarocephalum was also investigated. Among them, the chloroform extract exhibited the strongest biological activity, while the most active compounds were the lignan arctigenin (1), and the sesquiterpenes, compounds 3, 5, and 6 belonging to the elemane type, and 7 belonging to the eudesmane type. Our data also demonstrate that acetone and chloroform extracts induce, in the A375 cell line, apoptotic cell death that could be related to an overall action of the compounds present, but in particular to the lignans arctigenin (1) and the sesquiterpenes compounds 3-8 and 16. In fact, these molecules were able to induce a high DNA fragmentation, correlated to a significant increase of the caspase-3 enzyme activity. Furthermore, apoptosis appears to be mediated, at least in part, via PTEN activity and the inhibition of Hsp70 expression.

A new hepatoprotective flavone glycoside from the flowers of Onopordum alexandrinum growing in Egypt.

A bioactivity-guided fractionation of the ethyl acetate fraction of the flowers of Onopordum alexandrinum L. (Asteraceae) yielded a new flavonoidal glycoside designated as acacetin-7-O-galacturonide (9), alongside with nine known flavonoids; 6-methoxy-apigenin (hispidulin) (1), acacetin (2), apigenin (3), luteolin (4), kaempferol (5), eriodictyol (6), apigenin-7-O-glucoside (7), luteolin-7-O-glucoside (8), and kaempferol-3-O-rutinoside (10). The compounds were assayed for their hepatoprotective activity against CCl4-induced hepatic cell damage in rats and free radical scavenging activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH). Compounds 4, 6, 9, and 10 have not been previously reported from flowers of O. alexandrinum L., and this is the first report of acacetin-7-O-galacturonide (9) in nature which has also shown significant hepatoprotective and free radical scavenging effects. The isolated compounds were identified using different spectroscopic methods (UV, 1H NMR, 13C NMR, HMQC, HMBC, and COSY).

Onopordum cynarocephalum induces apoptosis and protects against 1,2 dimethylhydrazine-induced colon cancer.

The potential chemopreventive properties of the crude extract of Onopordum cynarocephalum were evaluated. Growth inhibition was investigated in FHs74Int human normal intestinal cells and ModeK mouse normal intestinal cell line and in two human colon cancer cells HCT-116 (p53+/+) and HT-29 (p53+/-). The extract was not cytotoxic to FHs74Int cells at concentrations 2-fold higher than the IC50 of HCT-116 cells. The extract inhibited dose-dependently the growth of HCT-116 cells (IC50=0.18 mg/ml) to a greater extent than HT-29 cells (IC50=1.8 mg/ml). The p53 wild-type HCT-116 cells were more sensitive than p53 mutant HT-29 cells to the pro-apoptotic effects of the plant extract; five times lower concentrations were needed to induce apoptosis in HCT-116 cells. Apoptosis induction by the extract was associated with an increase in the expression of pro-apoptotic proteins such as p53 and Bax, and a significant inhibition of the anti-apoptotic protein Bcl-2. Significant decrease in cyclin D1 protein and increase in p21 protein was observed in extract-treated HCT-116 cells. In vivo, the crude extract injected intra-peritoneally reduced the number of tumors by 64% (p<0.0001) and decreased the mean size of aberrant crypt foci in the DMH model of colon cancer. These data collectively suggest that O. cynarocephalum has potential anti-colon cancer effects.

Isolation and structural characterization of a water-soluble germination inhibitor from Scotch thistle (Onopordum acanthium) cypselas.

Cypsela dormancy in Scotch thistle (Onopordum acanthium) may be affected by the presence of chemical inhibitors. To investigate this phenomenon, a leachate from O. acanthium cypselas was tested for its ability to inhibit germination of the cypselas from which it was derived (i.e., autoinhibition). Leachates varied in their degree of autoinhibition, depending on the cypsela population from which they were prepared. Overall, removal of leachate from a group of O. acanthium cypselas increased their germinability. Using lettuce (Lactuca sativa) cypselas as an indicator species, bioactivity-guided fractionation was used to isolate a water-soluble, para-substituted benzamide from O. acanthium cypselas, which caused germination inhibition. Various chromatographic, spectroscopic, and spectrometric techniques were applied to the characterization of the bioactive compound.