Defoliation of Centaurea solstitialis Stimulates Compensatory Growth and Intensifies Negative Effects on Neighbors

Efforts to arrest the spread of invasive weeds with herbivory may be hindered by weak effects of the herbivores or strong compensatory responses of the invaders. We conducted a greenhouse experiment to study the effects of defoliation and soil fungi on competition between the invasive weed Centaurea solstitialis and C. solstitialis and Avena barbata, a naturalized Eurasian annual grass, and Nassella pulchra, a native California bunchgrass. Surprisingly, considering the explosive invasion of grasslands by C. solstitialis, Avena and Nassella were strong competitors and reduced the invader’s biomass by 80.2% and 80.1% over all defoliation and soil fungicide treatments, respectively. However, our experiments were conducted in artificial environments where competition was probably accentuated. When fungicide was applied to the soil, the biomass of C. solstitialis was reduced in all treatment combinations, but reduction in the biomass of the invader had no corollary impact on the grasses. There was no overall effect of defoliation on the final biomass of C. solstitialis as the invader compensated fully for severe clipping. In fact, the directional trend of the clipping effect was +6.4% over all treatments after eight weeks. A significant neighbor × soil fungicide × clipping effect suggested that the compensatory response was the strongest without soil fungicide and when C. solstitialis was alone (+ 19%). Our key finding was that the compensatory response of C. solstitialis in all treatments was associated with an increase in the weed’s negative effects on Nassella and Avena – there was a significant decrease in the total biomass of both grasses and the reproductive biomass of Avena in pots with clipped C. solstitialis. Our results were obtained in controlled conditions that may have been conducive to compensatory growth, but they suggest the existence of mechanisms that may allow C. solstitialis, like other Centaurea species, to resist herbivory.     

Composition and antimicrobial activity of essential oils from Centaurea sessilis and Centaurea armena

The essential oils of air-dried Centaurea sessilis and Centaurea armena obtained by hydrodistillation were analyzed by gas chromatography-mass spectrometry (GC-MS). Forty and twenty components were identified in the essential oils and the main component of these taxons was beta-eudesmol in the ratios of 12.4% and 19.3% from C. sessilis and C. armena, respectively. The antimicrobial activity of the isolated essential oil of the plants was also investigated. They showed moderate antibacterial activity against Gram-positive and Gram-negative bacteria, but no antifungal activity was observed against two yeastlike fungi.     

Biotransformation of monoterpenoids and their antimicrobial activities

Biotransformation is an economically and ecologically viable technology which has been used extensively to modify the structures of many classes of biologically active products. The discovery of novel antimicrobial metabolites from biotransformation is an important alternative to overcome the increasing levels of drug resistance by plant and human pathogens. Monoterpenes, the main constituents of essential oils, are known for their antimicrobial activities. In 2004, Farooq, Atta-Ur-Rahman and Choudhary published a review on fungal transformation of monoterpenes which covers papers published up to 2002. The present review not only updates the previous one but also discusses the antimicrobial activities (antibacterial, antifungal and antiviral) of biotransformed compounds.     

Antibacterial, antifungal, and antiviral activities of the lipophylic extracts of Pistacia vera

In the present study, antibacterial, antifungal, and antiviral properties of 15 lipohylic extracts obtained from different parts (leaf, branch, stem, kernel, shell skins, seeds) of Pistacia vera were screened against both standard and the isolated strains of Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, Candida albicans and C. parapsilosis by microdilution method. Both Herpes simplex (DNA) and Parainfluenza viruses (RNA) were used for the determination of antiviral activity of the P. vera extracts by using Vero cell line. Ampicilline, ofloxocine, ketoconazole, fluconazole, acyclovir and oseltamivir were used as the control agents. The extracts showed little antibacterial activity between the range of 128-256 microg/ml concentrations whereas they had noticeable antifungal activity at the same concentrations. Kernel and seed extracts showed significant antiviral activity compared to the rest of the extracts as well as the controls.     

Antimicrobial activities of sesquiterpene lactones and inositol derivatives from Hymenoxys robusta

Six compounds from the aerial parts of the Argentinean plant Hymenoxys robusta (Rusby) Parker were isolated and their structures elucidated using extensive spectroscopic analyses. These compounds comprise two inositol derivatives and four 3,4-seco-pseudoguaianolides, including vermeerin. Bioactivity assays of these compounds against bacterial and fungal pathogens showed that only vermeerin possessed antimicrobial activity specific against Staphylococcusaureus, and showed no toxicity when exposed to human-derived macrophages.     

Phytochemical and Cytogenetic Characterization of Centaurea solstitialis L. (Asteraceae) from Croatia

The cytogenetic characterization of Centaurea solstitialis L. (Asteraceae) showed a chromosome number of 2n = 16. Karyotype is composed by four pairs of metacentric, two pairs of submetacentric and two pairs of subtelocentric chromosomes. Physical mapping of two rDNA probes revealed two loci of 35S and one locus of 5S rRNA genes. Chromomycin fluorochrome banding revealed that all rDNA loci were GC rich. The genome size (2C‐value) of 1.95 pg classes this species in the group of very small genomes. Chemical composition of C. solstitialis volatile oil (VO) from Croatia, studied with gas chromatography–mass spectrometry showed dominant components as it follows: hexadecanoic acid, α‐linolenic acid, germacrene D and heptacosane. Antioxidant capacity, measured by ferric reducing power assay and 2,2‐diphenyl‐1‐picrylhydrazyl methods, as well as inhibition of acetyl‐ and butyrylcholinesterase of VO was lower comparing to a standard solutions. Volatile oil tested with disc diffusion method showed good inhibitory potential against Pseudomonas aeruginosa, Escherichia coli and all tested fungi: Candida albicans, Penicillium funiculosum and Aspergillus fumigatus. The microdilution method showed best activity against Chronobacter sakazakii and A. fumigatus.     

Elemanolide sesquiterpenes and eudesmane sesquiterpene glycosides from Centaurea hierapolitana

Two elemanolide sesquiterpenes and two eudesmane-type sesquiterpene glycosides named hierapolitanins A-D, were isolated, together with five known compounds, two flavones; hispidulin and jaceosidin, a flavon-C-glycoside, shaftoside, a flavonol glycoside, kaempferol-3-O-rutinoside and a neolignan, dehydrodiconiferyl alcohol from the aerial parts of Centaurea hierapolitana Boiss. (Asteraceae). Structure elucidations were based on spectroscopic evidence.     

Inhibition of elongation growth by two sesquiterpene lactones isolated from Helianthus annuus L.

Two sesquiterpene lactones belonging to the germacranolides were isolated from the leaves and stems of Helianthus annuus L. Their formation in the plant is light-dependent. Both sesquiterpene lactones (SL) strongly inhibit indole-3-acetic acid (IAA)-induced elongation growth of Avena sativa L. coleoptile segments and Helianthus annuus L. hypocotyl segments. Both SL do not, however, inhibit acid-induced growth nor growth triggered by fusicoccin at all. In the presence of dithiothreitol (DTT), the inhibitory effect of SL in the Avena-segment-test can be completely neutralized. This can be attributed to the binding of DTT to both SL. Using thin-layer-chromatography it could be shown that the inhibitors build adducts with SH-rich compounds, e.g., cysteine, glutathione, mercapto-ethanol, and DTT, whose R_f-value significantly differs from those of the primary substances. If the coleoptile segments are first treated with an inhibitor and the inhibitor is subsequently washed out, close to normal elongation growth can be induced by adding an IAA-solution. If the segments are simultaneously treated with inhibitor and IAA, no notable growth can be initiated for an extended amount of time, after the removal of both substances and the anewed addition of IAA. Fusicoccin, however, can immediately neutralize the induced growth inhibition. The same irreversible inhibition is observed when 2,4-dichlorophenoxyacetic acid (2,4-D) is used: If coleoptile segments are treated with an inhibitor plus 2,4-D or an inhibitor plus 3,5-dichlorophenoxyacetic acid (3,5-D), respectively, IAA-induced growth after removal of the substances can only be observed by those coleoptiles which had previously been treated with the non-auxin, 3,5-D plus an inhibitor. Based on these results, a possible mechanism describing how the inhibitor functions is discussed. The binding of an auxin to an auxin receptor sets a SH-group free (possibly due to a change in the conformation of the receptor); a site is given to which the inhibitor can bind irreversibly (via a S-bond). The IAA-receptor-inhibitor-complex is then no longer able to initiate elongation growth. If auxin is not present, no lasting bond between the inhibitor and the receptor can occur, since the essential SH-group remains masked. The inhibitor can be washed out again. Consequently, the SL's have to be able to intervene at the beginning of the IAA-induced reaction sequence, while the following steps remain uninfluenced, i.e. namely, the active excretion of protons into the cell wall compartments, which is directly induced by fusicoccin and causes elongation growth.Abbreviations 2,4-D 2,4-dichlorophenoxy-acetic acid - 3,5-D 3,5-dichlorophenoxy-acetic acid - DTT dithiothreitol - FC Fusicoccin - GA₃ gibberellic acid - IAA indole-3-acetic acid - MES 2-(N-morpholino)-ethane sulfonic acid - SL sesquiterpene lactone(s)     

aug-MIA-QSAR modeling of antimicrobial activities and design of multi-target anilide derivatives

The antibacterial activity against Bacillus subtilis, Staphylococcus aureus and Escherichia coli, as well as the antifungal activity against Aspergillus niger of a series of anilide derivatives have been modeled using augmented multivariate image analysis applied to quantitative structure–activity relationship (aug-MIA-QSAR). This QSAR approach is based on 2D molecular shape, as well as atomic sizes and colors to encode chemical, physical and biological properties. Predictive models with r² from 0.65 to 0.83 were used to estimate the antimicrobial activities of novel anilide analogs, which were built from the combination of substructures of the most active antimicrobial compounds along the series. Given the synergistic effect of different substituents to provide new molecules, promising compounds were proposed, highlighting a considerable multi-antimicrobial activity.     

Synthesis of acyl thiourea derivatives of chitosan and their antimicrobial activities in vitro

Three different acyl thiourea derivatives of chitosan (CS) were synthesized and their structures were characterized by FT-IR spectroscopy and elemental analysis. The antimicrobial behaviors of CS and its derivatives against four species of bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Sarcina) and four crop-threatening pathogenic fungi (Alternaria solani, Fusarium oxysporum f. sp. vasinfectum, Colletotrichum gloeosporioides (Penz.) Saec, and Phyllisticta zingiberi) were investigated. The results indicated that the antimicrobial activities of the acyl thiourea derivatives are much better than that of the parent CS. The minimum value of MIC and MBC of the derivatives against E. coli was 15.62 and 62.49 microg/mL, respectively. All of the acyl thiourea derivatives had a significant inhibitory effect on the fungi in concentrations of 50-500 microg/mL; the maximum inhibitory index was 66.67%. The antifungal activities of the chloracetyl thiourea derivatives of CS are noticeably higher than the acetyl and benzoyl thiourea derivatives. The degree of grafting of the acyl thiourea group in the derivatives was related to antifungal activity; higher substitution resulted in stronger antifungal activity.     

Antimicrobial activities of someN-alkylmaleimides

Summary A variety ofN-alkylmaleimides have been prepared and screened for antimicrobial activity using various fungi, yeasts and bacteria.N-Methyl,N-octyl andN-decylmaleimide showed antifungal activities. All test compounds showed antibacterial activity.     

Enhanced synthesis and antimicrobial activities of bacteriocins produced by Mexican strains of Bacillus thuringiensis

Recently, we reported the synthesis of five bacteriocin-like inhibitor substances (Bt-BLIS: morricin 269, kurstacin 287, kenyacin 404, entomocin 420, and tolworthcin 524) by Mexican strains of Bacillus thuringiensis. Here we show that, collectively, these Bt-BLIS have a moderate to broad spectrum of antibacterial activity, being toxic to clinically significant against Gram-positive and Gram-negative bacteria, including common etiological agents of human diseases, such as strep throat and scarlet fever, septicemia, pneumonia, urinary tract infection, and emetic and gastrointestinal syndromes. Although synthesis of the five Bt-BLIS was independent of the presence of a target inducing bacterium, we demonstrated for the first time that a proteinaceous component(s) secreted by, or liberated by proteolytic cleavage of Bacillus cereus 183 following treatment with proteinase K, enhanced Bt-BLIS synthesis.     

In vitro propagation of Centaurea spachii from inflorescence stems

Procedures for micropropagation of Centaureaspachii (Compositae), an endangered rosulate plantendemic from the mediterranean Spain area, have beendeveloped using inflorescence nodal segments asexplants for in vitro establishment. Only 15%of explants remained contaminated using this materialto start the in vitro axenic cultures. Higherproliferation of shoots and multiplication coefficientwas obtained on Murashige and Skoog (MS) mineralmedium supplemented with 1.0 mg l^{minus 1}6-benzyladenine. However, shoot elongation decreasedwith the addition of this cytokinin.Rooting of shoots with only one auxin was very lowafter 6 weeks on the majority of rooting media tested.The best rooting result (60%) was obtained on MSmedium with a combination of 2 mg l^{minus 1}indole-3-acetic acid plus 2 mgl^{minus 1} indole-3-butyric acid. Moreover, in thisculture medium 50% of shoots rooted during the thirdweek of culture. High survival, over 80%, wasobtained when the plantlets were transferred togreenhouse conditions. The endangered Centaureaspachii can be successfully micropropagatedbeginning with a single inflorescence stem and withoutsignificant damage to the mother plant.     

Allelopathic potential of two sesquiterpene lactones from Magnolia grandiflora L.

The allelopathic effects of the two sesquiterpene lactones, costunolide and parthenolide, isolated from the leaves of Magnolia grandiflora L. were evaluated on the wheat (Triticum aestivum L.), lettuce (Lactuca sativa L.), radish (Raphanus sativus L.) and onion (Allium cepa L.). Seed germination of the test species was significantly reduced at 500 μg/ml by both compounds. Both sesquiterpenes showed pronounced inhibition of root length of the test species and the inhibitory effect was concentration-dependent. In addition, shoot growth of the four species was significantly inhibited at all the concentrations tested (10–500 μg/ml). Parthenolide reduced germination and inhibited seedling growth more than costunolide. Inhibition of root growth was generally greater than that of shoot growth. The results encourage the use of these sesquiterpenes as models for development of new herbicides.     

Occurrence ofBacillus popilliae and two nematode pathogens in populations ofAmphimallon solstitialis (Col.: Scarabaeidae) near darmstadt,Germany

Populations of the June beetle,Amphimallon solstitialis (Coleoptera: Scarabaeidae), were sampled from grasslands near Darmstadt, Germany, and found to be infected by a number of diseases and parasitic nematodes. Several milky diseased larvac were found, andBacillus popilliae type A 1 isolated as the causative agent. The bacterium readily infected healthy larvae ofA. solstitialis when administeredper os in the laboratory, but was not infective to larvae ofMelolontha hippocastani by this route. A large mermithid nematode was found parasitising 10% of theA. solstitialis larvae at one site andHeterorhabditis bacteriophora was found infecting larvae at the other.

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Résumé Des populations deAmphimallon solstitialis (Col.: Scarabaeidae) ont été échantillonnées dans deux prairies distinctes près de Darmstadt (Allemagne) et se sont révélées infestées par des maladies et des nématodes parasites. Plusieurs larves dans chaque site étaient infectées par la maladie laiteuse etBacillus popillae, type A1 a été isolé comme étant l'agent responsable. La bactérie infeste facilement des larves saines deA. solstitialis quand elle est administrée par voie orale au laboratoire mais n'a pas d'effet infectieux pour les larves deMelolontha hippocastani par cette même voie. Un grand nématode mermithide a été trouvé parasite de 10% des larves deA. solstitialis sur un seul site, mais comme seuls les jeunes ont été trouvés, la détermination à l'espèce n'a pu être faite.Heterorhabditis bacteriophora était responsable de l'infection de 1,5% des larves sur seulement un site. Plusieurs larves deA. solstitialis présentaient une couleur ambrée, identique à celle trouvée sur le scarabéeCostelytra zealandica infecté parSerratia spp., et ne se nourrissaient pas de carotte au laboratoire. Les bactéries isolées à partir de ces larves ne provoquent aucun effet visible quand elles sont données en nourriture à des larves saines.

     

Antioxidant and antiviral activities ofEuphorbia thymifolia L.

The antioxidant and antiviral activities ofEuphorbia thymifolia L. (Euphorbiaceae) were investigated in this study. The results showed that all of the fractions (MeOH, CHCl₃, EtOAc, n-butanol and water) and pure compounds (3-O-galloyl-4,6-(S)-HHDP-D-glucose, rugosin B and 1,3,4,6-tetra-O-galloyl-K--D-glucose)tested possessed antioxidant activities, with the exception of the organic aqueous fraction in the anti-lipid and anti-super-oxide formation assays. The range of IC₅₀ of anti-lipid formation, anti-superoxide formation and free radical scavenging assays for all fractions and pure compounds were 2.81–7.63, 0.03–2.18 and 0.013–2.878 mg/ml, respectively. Electron spin resonance studies showed that water extract and pure compounds ofE. thymifolia exhibited superoxide radical and hydroxyl radical scavenging activities. Besides antioxidant activities, 3-O-galloyl-4,6-(S)-HHDP-D-glucose and EtOAc fraction also showed anti-HSV-2 activity. Thus,E. thymifolia was concluded to possess antioxidant and anti-HSV-2 activities.     

黄星蓟在我国的适生性分析及风险评估

【目的】黄星蓟是一种极具危险性的杂草,在美国和澳大利亚等地区被列为有毒有害杂草并加以控制。目前在我国新疆等局部区域,已发现有黄星蓟的定殖,且呈蔓延危害加剧的趋势。对黄星蓟进行适生性分析及风险评估,可为该有害生物的预警防控提供理论依据。【方法】利用MaxEnt模型对黄星蓟在我国的潜在适生区进行预测,并采用多指标赋值运算,对其入侵的风险进行定量分析。【结果】黄星蓟在我国的潜在适生区达32.96%,其中高度适生区、中度适生区和低度适生区的面积分别为11.21万、34.16万、272.28万km²。其危险性综合评估风险值R为2.01,为高度危险。【结论】我国很多区域均属于黄星蓟的适生区,需要高度重视,其预测结果为建立黄星蓟长效预警与防控机制提供必要的理论基础。     

Antimicrobial activities of 2-arylthio-N-alkylmaleimides

Summary A variety of 2-arylthio-N-alkylmaleimides were prepared, and their antimicrobial activities were examined. Almost all of these compounds exhibited antibacterial activity against Gram-positive bacteria such asBacillus subtilis andStaphylococcus aureus. Some compounds such as 2-(halogeno-phenyl)-thio-N-methylmaleimides (4, 5, 6, 8 and 10) and 2-(2-carbamoylphenyl)thio-N-methylmaleimide(35) exhibited antibacterial activity againstEscherichia coli. All compounds tested were inactive againstPseudomonas aeruginosa except 2-(2-carbamoylphenyl)thio-N-methylmaleimide(35) which was marginally active. Activities against Gram-positive bacteria were not due to the effect of the substituent on the benzene ring, except in the instances 2-carboxy, 2-carbomethoxy, 2-amino groups and alkyl chains, however, activities against Gram-negative bacteria were due to phenylthio and the alkyl substituents. Some of 2-arylthio-N-alkylmaleimides were examined for their antifungal activities using eight strains of fungi, and they showed activity against these.     

Chemical composition and antimicrobial activity of volatile compounds of Tamarix boveana (Tamaricaceae)

The chemical composition of the Tamarix boveana volatile oils obtained from the whole aerial part, flowers, leaves and stems by steam distillation was analysed using gas chromatograph (GC)-flame ionization detectors (FID) and GC-MS. Sixty-two components were identified. Hexadecanoic acid (18.14%), docosane (13.34%), germacrene D (7.68%), fenchyl acetate (7.34%), Benzyl benzoate (4.11%) were found to be the major components in the whole aerial parts. This composition differed according to the tested part: 2.4 Nonadienal was the main compound in the flowers (12.13%) while germacrene D was the major component in leaves (31.43%) and hexadecanoic acid in the stems (13.94%). To evaluate in vitro antimicrobial activity, all volatile oils were tested against six Gram-positive and Gram-negative bacteria and four fungi. The T. boveana volatile oils exhibited an interesting antibacterial activity against all strains tested except Pseudomonas aeruginosa but no antifungal activity was detected.     

Antimicrobial, antioxidant, and antiviral activities of Retama raetam (Forssk.) Webb flowers growing in Tunisia

Antimicrobial, antioxidant, and antiviral activities of flower extracts of Retama raetam Forssk. Webb (Fabaceae) were screened both from standard and isolated Gram-positive and Gram-negative bacteria by solid medium technique. Oxacillin, Amoxicillin, Ticarcillin, Cefotaxim, and Amphotericin were used as the control agents. The antiviral activity was evaluated against human cytomegalovirus (HCMV) strain AD-169 (ATCC Ref. VR 538) and coxsackie B virus type 3 (CoxB-3) using a cytopathic effect (CPE) reduction assay. The antioxidant activity was evaluated using two tests: 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging and the ammonium thiocyanate methods. All extracts were characterized quantitatively for the presence of polyphenols, flavonoids, and tannins. Of the extracts tested, butanol and ethyl acetate extracts showed important antibacterial activity against Gram-positive and Gram-negative bacteria but only moderate antifungal activity. Methanol extract exhibited moderate antiviral activity against HCMV with IC₅₀ of 250 μg/ml. Ethyl acetate, chloroform, and methanol fractions were found to cause significant free-radical-scavenging effects in both assays. These results may suggest that R. raetam flowers could be used as a natural preservative ingredient in the food and/or pharmaceutical industries.