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At least 73 records · Page 4Linked to original sources
PubMed2002

Bioactive sesquiterpene lactones from Centaurea species and their cytotoxic/cytostatic activity against human cell lines in vitro.

Sesquiterpene lactones isolated from the aerial parts of various species of the genus Centaurea were examined for their in vitro cytotoxic/cytostatic activity against five human cell lines (i. e., DLD1, SF268, MCF7, H460 and OVCAR3). Compounds 1 - 4 were isolated from C. zuccariniana, 5 and 6 from C. achaia, 7 from C. thessala ssp. drakiensis and compounds 8 and 9 from C. deusta. Compound 1, 8alpha- O-(3,4-dihydroxy-2-methylenebutanoyloxy)dehydromelitensine was found to be the most active, exhibited a considerable growth inhibiting activity against three of the cell lines tested, while compound 5 8alpha- O-(3-hydroxy-2-methylenepropanoyl)dehydromelitensin exhibited a growth inhibiting effect against most of the tested cell lines. A new eudesmanolide (8alpha-hydroxysonchucarpolide, 4) was isolated from C. zuccariniana and its structure was elucidated by spectroscopic methods.

Antineoplastic Agents↗
PubMed1998

Preliminary study of the potential vasodilator effects on rat aorta of centaurein and centaureidin, two flavonoids from Centaurea corcubionensis.

In this work, the potential vasorelaxant activity of centaurein and centaureidin, two flavonoids from Centaurea corcubionensis, were studied for the first time in rat aorta. Centaureidin (10 microM-0.1 mM) totally relaxed, in a concentration-dependent manner and with almost equal effectiveness, the contractions induced by NA (IC50 = 16.7 +/- 1.9 microM) or by a high K+ concentration (IC50 = 16.1 +/- 3.1 microM) in intact rat aortic rings. Mechanical removal of endothelium did not significantly modify the vasoralexant effects of this flavone (IC50 = 20.8 +/- 2.4 microM for NA; IC50 = 21 +/- 2.9 microM for K+). On the other hand, centaurein (1 microM-0.1 mM) had no effect on NA- and high K(+)-induced contractions in rubbed and intact rat aortic rings. These results indicate that substitution by glucose in the chemical structure of centaureidin leads to the loss of its vasodilator activity.

Animals↗
PubMed1997

Centaurea corymbosa, a cliff-dwelling species tottering on the brink of extinction: a demographic and genetic study.

Centaurea corymbosa (Asteraceae) is endemic to a small area (< or = 3 km2), and < 500 individuals reproduce in any given year. Nevertheless, enzyme polymorphism was found within and among the six local extant populations, the most distant at 2.3 km. Levels of gene flow among populations and seed and pollen dispersal data indicated very low dispersal capacity. Rarity of long distance dispersal events coupled with traits such as prolonged juvenile period, monocarpy, and self-incompatibility precludes the establishment of new populations and thus the evolution toward colonization ability through increased dispersal rate, polycarpy, or self-compatibility. The species thus appears to be trapped on an evolutionary dead-end toward extinction, even though, from a preliminary introduction experiment, we conclude that several nearby unoccupied sites would be suitable for the species.

Biological Evolution↗
PubMed2002

Role of within-individual variation in capitulum size and achene mass in the adaptation of the annual Centaurea eriophora to varying water supply in a Mediterranean environment.

To clarify the adaptive value of variation in capitulum size and achene mass, plants of Centaurea eriophora were studied in a glasshouse and in a natural population. C. eriophora plants consist of a basal leaf rosette from which an erect stem grows, with lateral branches of various orders ending in capitula of different orders. Primary, secondary and tertiary capitula are comparable in size and they produce similar numbers of achenes, which are similar in weight (large achenes). These capitula are formed during April, May and early June, and constitute the normal or primary flowering. Following ripening of tertiary capitula, leaves senesce, but, later during June and the first half of July, a secondary flowering of a variable number of smaller capitula may occur if wet conditions persist for longer than usual. Plants that have almost senesced develop small lateral branches 1-2 cm long bearing a few small leaves and ending in a capitulum about half the diameter of capitula from the primary flowering period. The number of achenes produced in these capitula (small achenes) and their weight are 70 and 30% less, respectively, than those of capitula formed during primary flowering. These reductions appear to result from restricted availability of resources. Large and small achenes have similar dispersal characteristics and possess similar germination potential. However, large achenes produce seedlings that are capable of emerging from greater burial depths, providing the resulting plants with a potential advantage. The normal flowering period coincides with the optimum time of year for flowering and fruiting in the south of Spain, and only if rainfall lasts longer than usual does secondary flowering occur. Secondary flowering extends the normal flowering and fruiting periods, thereby providing a supplementary crop of smaller, yet viable, fruits. It can be considered to be an adaptive response to the unpredictable Mediterranean climate, optimizing the use of available resources.

Adaptation, Physiological↗
PubMed1978

RNA synthesis in whole cells and protoplasts of centaurea: a comparison.

Protoplasts enzymically isolated from suspension cultures of Centaurea cyanus L. incorporate radioactive precursors into RNA with kinetics similar to that of whole cells. There are differences, however, in several other aspects of RNA metabolism. The proportion of total RNA that contains poly(A) sequences (25 to 30%) is similar in both freshly isolated protoplasts and whole cells after a 20-minute pulse with [(3)H]adenosine. After a 4-hour pulse, however, poly(A)-containing RNA makes up 30% of the total RNA in protoplasts whereas it drops to 8% in whole cells. There appears to be a faulty processing of ribosomal precursor into the mature ribosomal species, as the precursor seems to accumulate to higher levels relative to the mature 18S and 25S rRNAs in protoplasts as compared to whole cells. Additional differences are seen in the size distributions of poly(A)-containing RNA, although the length of the poly(A) segment is similar in both protoplasts and whole cells. Within 24 hours protoplasts appear to have resumed a pattern of RNA synthesis similar to that of whole cells.

Journal Article↗
PubMedDate not supplied

Secondary metabolites from Centaurea deusta with antimicrobial activity.

The aerial parts of Centaurea deusta Ten. afforded in addition to several known compounds, mainly sesquiterpene lactones, one new eudesmanolide and one new elemane derivative. Structures of the new compounds were elucidated by spectroscopic methods. The in vitro antifungal and antibacterial activities of the isolated compounds was tested, using the microdilution method. All compounds tested showed high antifungal activity.

Anti-Infective Agents↗
PubMed2001

Patterns of allozyme variation in diploid and tetraploid Centaurea jacea at different spatial scales.

The extent and spatial patterns of genetic variation at allozyme markers were investigated within and between diploid and autotetraploid knapweeds (Centaurea jacea L. sensu lato, Asteraceae) at contrasted geographic scales: (1) among populations sampled from a diploid-tetraploid contact zone in the northeastern part of the Belgian Ardennes, and (2) within mixed populations from that zone where diploids and tetraploids coexist. Our data were also compared with a published dataset by Sommer (1990) describing allozyme variation in separate diploid and tetraploid knapweeds populations collected throughout Europe. Genetic diversity was higher in tetraploids. In the Belgian Ardennes and within the mixed populations, both cytotypes had similar levels of spatial genetic structure, they were genetically differentiated, and their distributions of allele frequencies were not spatially correlated. In contrast, at the European scale, diploids and tetraploids did not show differentiated gene pools and presented a strong correlation between their patterns of spatial genetic variation. Numerical simulations showed that the striking difference in patterns observed at small and large geographic scales could be accounted for by a combination of (1) isolation by distance within cytotypes; and (2) partial reproductive barriers between cytotypes and/or recurrent formation of tetraploids. We suggest that this may explain the difficulty of the taxonomic treatment of knapweeds and of polyploid complexes in general.

Asteraceae↗
PubMedDate not supplied

[Alteration of polymorphic systems of Centaurea scabiosa L. under chronic irradiation].

Isoenzyme and morphological polymorphism alteration in populations of perennial grass Centaurea scabiosa L. (scaly cornflower) has been studied. These populations exist on the territory of East Ural Radioactive Trace more than 40 years and are chronically exposed to beta-irradiation. Directional shift of allele frequencies on the loci Per1, Pgi2, Sod1, Lap has been detected. The fact of accumulating genetic load by chronically irradiated populations has been demonstrated. Possible reasons of discovered alterations are discussed. The analysis of the obtained data shows that the irradiated populations have greater similarity with one another than with a control, but relation between genetic distances and accumulated doses hasn't been revealed. The hypothesis is that an extra factor--gene flow from a "clean" territory influences the genetic structure of irradiated populations.

Asteraceae↗
PubMed2000

Cleistogamous capitulum in Centaurea melitensis (Asteraceae): heterochronic origin.

Cleistogamous capitula formed by Centaurea melitensis display a number of morphological and functional changes with respect to chasmogamous capitula that ensure self-fertilization. Because no studies have hitherto addressed the evolution of cleistogamy in Asteraceae, it was considered useful to ascertain whether these changes are attributable to one or more of the heterochronic processes reported in the literature. Bivariate allometric analyses were performed, and changes were represented graphically using Gould's clock models for size, shape, and age of several capitulum and floret structures. Results suggest that the partially paedomorphic appearance of cleistogamous with respect to chasmogamous capitula is attributable to three processes: (1) early onset of floral development (predisplacement), (2) decreased growth rate of the whorls studied (except gynoecium width) and (3) early offset time (progenesis). The latter appears to play the most significant role in the origin of the cleistogamous capitulum.

Journal Article↗
PubMed1976

[Hypoglycaemic activity of centaurea aspera L (author's transl)].

Two aquous crude extracts of Centaurea aspera L. flowers were tested for hypoglycaemic activity in normal and alloxan-diabetic rats. Both extracts exert a significant hypoglycaemic effect by oral route and chronic administration in diabetic rats, but only the extract obtained by exhaustion with hot water displayed an acute hypoglycaemic activity in normal animals. All plant-treated groups were compared against glibenclamide as a standard. The acute toxicity by oral and intravenous routes was determined in mice.

Administration, Oral↗
PubMed2003

Intraspecific and interspecific interactions mediated by a phytotoxin, (-)-catechin, secreted by the roots of Centaurea maculosa (spotted knapweed).

Centarea maculosa Lam. (spotted knapweed) is one of the most destructive invasive weeds in the western United States, particularly in pastures and rangelands. One of the components that may contribute to its invasiveness is the naturally produced, root-secreted allelochemical (-)-catechin. This compound has been shown to have broad-spectrum phytotoxic activity, possibly assisting C. maculosa in displacing native plant communities. As a recently characterized phytochemical, little is known about the specific effect of (-)-catechin on either C. maculosa or other plant species. We have found that, in vitro, C. maculosa begins to secrete phytotoxic levels of (-)-catechin within 2-3 weeks of seedling emergence. Furthermore, (-)-catechin concentrations consistent with those naturally secreted by C. maculosa were sufficient to inhibit germination in all species tested, including C. maculosa. These concentrations were also often either phytotoxic or growth inhibitory to seedlings in a range of plant species, while having no negative effects on the growth of C. maculosa seedlings. However, our results also indicate that different levels of resistance and susceptibility to (-)-catechin exist in plant populations, suggesting that the capability of C. maculosa to invade an area through allelochemistry may be dependent on the age and species composition of plants in that area.

Catechin↗