Thesis (Ph. D.)--Oregon State University, 1994. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

This thesis, which is divided into four chapters, represents an account on the isolation, identification and the assessment of bioactivity of cytotoxic compounds from the genus Centaurea (Family: Asteraceae alto Compositae), a large genus of about 500 species. The first three chapters deal with an introduction of natural products and Centaurea species, followed by the isolation and characterisation of compounds from twelve Centaurea species. The last chapter describes the bioactivities of extracts and isolated compounds from these species. A total of 45 compounds were isolated from twelve Centaurea species, and only C. americana, C. cyanus, C. dealbata and C. macrocephala had previously been studied. Four of these are novel compounds. Four lignans arctiin, matairesinoside, matairesinol and lappaol A were isolated fromthe methanol extract of C. macrocephala seeds. Arctiin and matairesinoside were also isolated from the methanol extract of C. americana, C. bornmuel/eri, C. dealbata, C. huber-morathii, C. mucronifera, C. pamphylica, C. schischkinii and C. urvillei. The methanol extract of C. americana also afforded 20-hydroxyecdysone, 24-hydroxyecdysone, lappaol A, arctigenin and a novel compound, 3"-O-caffeoyl(9"'→3")-arctiin. The methanol extract of C. cyanus produced lariciresinol 4-0-B-D-glucoside, berchemol, moschamine and cis-moschamine. Arctigenin, astragalin, afzelin, matairesinol and a novel indole alkaloids, schischkiniin, were isolated from the methanol extract of C. schischkinii. Extract from C. bornmuelleri afforded arctigenin, astragalin, afzelin and matairesinol. The methanol extract of C. mon/ana yielded berchemol, berchemol 4'-O-B-D-glucoside, p-coumaroylquinic acid, cis-pcoumaroylquinic acid, pinoresinol, pinoresinol mono methyl ether, pinoresinol dimethyl ether, pinoresinol 4-0-B-D-glucoside, pinoresinol 4,4'di-0-B-D-glucoside, pinoresinol 4-0-apiose-(1→2)-B-D-glucoside, centcyamine, cis-centcyamine, N-(4-hydroxycinnamoyl)-5-hydroxytryptamine, cis-N-(4-hydroxycinnamoyl)-5-hydroxytryptamine, moschamine, cis-moschamine, tryptamine and two novel compounds, flavanone-apiose-glucuronic acid and montamine. C. gigantea afforded arctiopicrin, 8-0-(4-hydroxy-3-methylbutanoyl)-salonitenolide, chlorogenic acid, cirsiliol, isoquercetrin, orientin, isoorientin and 4"-hydroxybenzoyl-isoorientin. General toxicity, cytotoxicity and antioxidant activity of the extracts and isolated compounds were evaluated, respectively, by the brine shrimp lethality assay, MTT assay on human colon cancer cell line (CaCo-2) and DPPH assay. Among all the species, the methanol extract of C. bornmuelleri, C. gigantea, C. huber-morathii and C. montana were the most toxic extracts in brine shrimp lethality and MTT assay. Arctigenin (IC50=7.0 mM), matairesinol, montamine (IC50=43.9 mM) and lappol A, schischkiniin, arctiopicrin (IC50=8.5 mM) and 8-0-(4-hydroxy-3-methylbutanoyl)-salonitenolide (IC50=26.4 mM) showed higher cytotoxicity against MTT assay. Matairesinoside (IC50=2.2 x 10-3 mg/mL), matairesinol (IC50=2.0 x 10-3 mg/mL) and schischkiniin (lC50=3.8 x 10-3 mg/mL) exhibited significant free radical scavenging activities towards DPPH assay.

Centaurea macroptilon group includes taxa Centaurea macroptilon, Centaurea oxylepis, Centaurea indurata and hybrids. In this master thesis we compared morphological and genetic variation among taxa of this group. Based on the results of morphometric and molecular analyzes we re-considered current taxonomic concept of studied species and suggested changes.

Thesis (Ph. D.)--Washington State University, May 2009. / Title from PDF title page (viewed on Apr. 20, 2010). "School of Biological Sciences." Includes bibliographical references.

Invasive plants may leave enemies behind when they colonize a new habitat, allowing selection to favor increased investment in growth and/or reproduction over defensive traits. Previous studies have identified reduced diversity of potential bacterial pathogens and evolutionary increases in growth and reproduction in invading populations of yellow starthistle (Centaurea solstitialis). This study leverages a recently developed high-throughput assay of immune function to test for evidence of a trade-off between increased growth and defense against bacterial pathogens in yellow starthistle's invasion of California (USA). Seven bacterial strains were cultured from infected leaf tissue in the native range. Healthy leaf tissue from five native European collections and six invading collections were exposed to these native bacterial strains. A standardized assay of peroxidase activity was used measure the oxidative burst immune response to pathogen recognition by the leaf. Immune responses were compared to plant growth within and between ranges to assess evidence for a trade-off. Plant genotypes from the native range demonstrated a higher immune response to bacterial strains than did invading genotypes, consistent with a trade-off with plant growth across regions. The same trade-off was also apparent across genotypes from the native range, but not across genotypes from the invaded range. Our results provide evidence that increased growth in a highly invasive plant species may come at a cost to immune function, consistent with the hypothesis that escape from enemies can provide opportunities for shifts in resource allocation that favor the proliferation of non-native species.

Invasive species are often successful and problematic because of their ability to persist in disturbed and undisturbed environments despite weed management practices. Understanding reproduction and dispersal strategies in these species can aid in developing management approaches to help control their spread. Centaurea melitensis, a nonnative invasive with European origins, is found in disturbed areas of southern California. It produces three different types of flower heads that develop at different times and at different locations on the plant during the growing season. The chasmogamous (CH) flower heads are located at the top of the plant, the initial cleistogamous (iCL) heads are located at the base of the plant and at some branch and axillary points, and the final cleistogamous (fCL) heads are located along the stem and at some branch points. This pattern differs from that in Centaurea solstitialis, its most closely related congener, which develops one type of flower head with two morphologically distinct achenes within each flower head: peripheral and center achenes. The overall objective of this study was to examine potential differences between peripheral and center achenes of Centaurea melitensis, including morphological differences in dispersal features, potential differences in response to temperature, tendency to disperse, dormancy and viability. The approach involved selecting whole plants from the field and separating peripheral and center achenes from each of the three head types. Morphological differences were assessed by measuring mass, fruit length, fruit width, pappus length, pappus width, and elaiosome features. Temperature response patterns were evaluated by exposing peripheral and center achenes to temperatures ranging from 5 C to 30 C and measuring germination. Tendency of different achene types to remain in the flower heads was assessed by comparing ratios of peripheral to center achenes in heads immediately after maturation (March to June) to the ratios remaining in heads in early fall (September). Viability and dormancy testing was performed using a cut test and tetrazolium chloride tests in conjunction with germination tests. Results of these studies indicate that peripheral achenes of Centaurea melitensis were lighter and narrower, with shorter pappi and smaller elaiosomes than center achenes. Peripheral achenes responded similarly to their center counterparts in germination response to temperature, but the pattern differed among head types. Broad temperature optima were observed within the fCL and CH heads and a narrow optimum was observed in iCL. There was no evidence that the peripheral achenes remained in the heads longer than the center achenes. Ratios of peripheral to center achenes were 3.8:1 in CH heads, 2.23:1 in iCL heads, and 1.94:1 in fCL heads. Peripheral achenes were more likely to be dormant while maintaining viability than center achenes were. The results of this study, therefore, indicate that peripheral and center achenes of Centaurea melitensis differ morphologically. Dispersal features, such as pappi and elaiosomes, were more highly developed in center achenes than in peripheral achenes, but these differences were not reflected in differences in behavior to the extent we could measure it (i.e., the tendency to remain in heads or the germination responses to temperature). Differences between peripheral and center achenes of Centaurea melitensis trended in the same direction as differences seen in its closely related congener, Centaurea solstitialis, which has center achenes that disperse more readily than peripheral achenes. However, the differences observed in Centaurea melitensis were not as pronounced as those seen in Centaurea solstitialis.

Faschingbauer J.: Cytotoxic and cholinesterase inhibitory activity of extracts from selected species of the Centaurea L. genus. Diploma thesis, Charles University, Faculty of Pharmacy in Hradec Králové, Department of Pharmaceutical Botany, Hradec Králové, 2019. During the screening of biologically active secondary metabolites of plants carried out at the Department of Pharmaceutical Botany FAF UK, selected taxa of the genus Centaurea (Asteraceae) were investigated. This study is focused on a basic phytohemical research of extracts prepared from Centaurea cyanus, Centaurea jacea, Centaurea scabiosa, Centaurea pseudophrygia, Centuarea stoebe, Centaurea solstitialis a Centaurea benedicta. Extracts were prepared for evidence of the proof reactions of TLC and MS analysis (EI, ESI) to clarify a potential presence of alkaloids. EtOAc and ethanol extracts were evaluated for potential inhibitory activity against human erythrocyte acetylcholinesterase (AChE) and plasma butyrylcholinesterase (BChE) and cytotoxicity against selected 9 tumor lines. C. cyanus alkaloid extract had interesting cholinesterase activity which selectively inhibited BChE (IC50 BChE = 22.62 ± 3.62 μg / ml, IC50 AChE = 221.50 ± 44.56 g / ml). Other EtOAc extracts of selected Centaurea species were considered inactive (IC50 > 100 μg/ml)....

Climate change is a major threat to global biodiversity, and will alter species ranges, plant and animal phenology, and species interactions within ecosystems. Climate mediates plant-insect interactions, and consequently has the potential for positive or negative effects on biological control systems. Observational evidence suggests that a recent dramatic reduction in the density of diffuse knapweed, Centaurea diffusa Lamarck, in sites in British Columbia, Canada is attributed to the biological agent Larinus minutus Gyllenhal (Coleoptera: Curculionidae). This decline took place over several years of late spring and summer drought which suggested an association between dry conditions and successful biological control. To explore this, I conducted field experiments using rain shelters and watering treatments to assess the effectiveness of plant attack by L. minutus under moist and dry conditions. I found that L. minutus reduced seed production regardless of moisture conditions, with a trend towards greater seed reduction under dry conditions. Two or more species of insects in the same genera have been introduced in some weed biocontrol programs. If the species are ecological equivalents and compete the introduction of both species may be detrimental and reduce their impacts. If however the species vary in their distributions, the introduction of congeners may be advantageous. I review the following cases of species pair releases: the beetles Chrysolina quadrigemina (Suffrian) and Chrysolina hyperici (Forster) for St. John’s wort (Hypericum perforatum L.); the gallflies Urophora affinis Frfld. and Urophora quadrifasciata (Meig.) for Centaurea species; the weevils Neochetina bruchi Hustache and Neochetina eichhorniae Warner for water hyacinth (Eichhornia crassipes (Mart.) Solms.) and the beetles Galerucella pusilla Duftschmidt and Galerucella calmariensis L. for purple loosestrife (Lythrum salicaria L.). I found that congeneric agents can offer complementary control of target weeds in slightly different habitats. Given the increasing focus on possible non-target effects of biological control introductions, I recommend that greater care be taken to avoid mixed species introductions and that judicious use be made of controlled field experimentation to determine species impacts. Molecular studies of species before introduction could help prevent the accidental introduction of multiple species.

La tesis está compuesta por un compendio de artículos. El objetivo principal es la clarificación de las relaciones filogenéticas del subgrupo Acrolophus del género Centaurea. Este grupo, predominantemente mediterráneo y con más de 200 especies descritas, se divide tradicionalmente en tres secciones basadas en la morfología: Centaurea, Phalolepis y Willkommia. Artículo 1: En este estudio intentamos resolver el problema de la subdivisión seccional y consolidar la circunscripción y delimitación del grupo entero. Incluimos la mayoría de las especies descritas, usando una región nuclear (ITS) y una región cloroplástica (rpl32-trnL). Nuestros resultados no apoyan la división seccional tradicional. No hemos podido establecer una división taxonómica clara dentro del grupo debido a las fuertes incongruencias entre los dos marcadores y entre los datos genéticos y la morfología. Artículo 2: Centaurea subtilis del sureste de Italia y C. exarata del suroeste de la Península Ibérica fueron clasificadas anteriormente en el grupo Acrolophus-Phalolepis y dentro de él en la sect. Maculosae. Una revisión molecular basada en secuencias de la región ITS indica que ambas deberían clasificarse en el grupo Jacea-Lepteranthus. Este cambio es coherente con el número cromosómico de las dos especies, que tienen x = 11 como el resto de las especies del grupo Jacea-Lepteranthus y no x = 9 como las especies del grupo Acrolophus-Phalolepis. Artículo 3: Investigamos la diversificación espacio-temporal del grupo de Centaurea cineraria, a partir de marcadores AFLP y ADN plastídico. A pesar de su singularidad morfológica, no pudimos apoyar la monofilia del grupo de C. cineraria. Se define un linaje distinto, sobre todo restringido a Sicilia (el “Sicily group”), que contiene algunos miembros del grupo de C. cineraria, pero también incluye C. parlatoris, considerada miembro del grupo C. dissecta. La datación molecular apoya una diversificación reciente, presumiblemente alopátrica, iniciada hace menos de 250.000 años. Túnez, las islas Eólicas y la isla Ventotene del mar Tirreno fueron probablemente colonizadas desde Sicilia. La diversificación reciente del “Sicily group” descarta la posibilidad de vicarianza a través de puentes terrestres en favor de una dispersión transoceánica. Artículo 4: Hemos usado un muestreo amplio de C. alba y especies próximas de todo el Mediterráneo para averiguar si el tratamiento taxonómico actual es congruente con un enfoque de coalescencia. Para lograr este objetivo, hemos secuenciado una región cloroplástica, la región nuclear ITS y cinco regiones nucleares de copia única. Hemos usado el programa *BEAST basado en coalescencia para deducir el árbol de especies y hemos examinado el árbol buscando eventos de especiación con el programa BPP. Se han probado distintas clasificaciones mediante el Factor de Bayes. Las clasificaciones que unían varias especies en una única son las que nos dieron resultados significativamente mejores que las que usaron la delimitación actual. Se discute el papel de la hibridación. Finalmente, explicamos las posibles consecuencias prácticas de nuestro enfoque. Artículo 5: Centaurea corensis, especie de Cerdeña recientemente descrita y hasta ahora sólo conocida de una única localidad, fue encontrada en la isla de Procida, en el golfo de Nápoles. La afiliación a la misma especie de las dos poblaciones se confirma a través de una comparación morfológica, recuentos cromosómicos y secuenciación de ADN. Se propone la hipótesis de una poliploidización reciente y se discute la curiosa disyunción, subrayando la posibilidad de una dispersión humana reciente. Apéndice: Lista de especies del subgrupo Acrolophus con informaciones geográficas, números cromosómicos, evidencia molecular y literatura.

Centaurea tchihatcheffii Fisch. &amp / Mey. is a critically endangered annual endemic plant found only in Ankara. This study aimed to determine its distributional range, metapopulation status, the effects of agricultural activities, and assess conservation options. Occurrences and population size estimates were carried out by ground surveys. Two adjacent subpopulations were intensively studied during 2004-2008. Plant and seed demographic data were collected in the field and by laboratory tests. Field experiments simulated the effects of agricultural practices. Risks of extinction and possible impacts of different management actions were investigated through a population viability analysis (PVA) by constructing a two-stage stochastic model. Six scenarios involving different management actions were run with 10,000 replications each using RAMAS Metapop. A total of 14 patchily distributed subpopulations were found to have an extent of occurrence of &gt / 700 km2. Herbicide applications caused extreme mortality and reduced germination success, and were shown to be the major anthropogenic threat against long-term survival of C. tchihatcheffii. Tillage led to an increase in density and reproductive success in the following year. PVA simulations for most scenarios predicted extinction of both subpopulations within 4 to 95 years, but a conservation management scenario involving delayed tillage ensured viable populations with a combined size of 21 million individuals. PVA results demonstrated that timing and frequency of tillage is crucial. Therefore, we propose tillage to be carried out after seed set every other year for protected subpopulations to ensure their long term persistence. Alternatively, unprotected subpopulations elsewhere can benefit from organic or nature-friendly farming.