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At least 19 recordsLinked to original sources

PubMed2006

Antioxidant and antiaggregatory effects of an extract from Conyza canadensis on blood platelets in vitro.

The antioxidative activity of the polysaccharide extract from Conyza canadensis in blood platelets treated with peroxynitrite (ONOO-) was studied. Peroxynitrite as a strong biological oxidant has toxic effects on blood platelets and induces the oxidation of thiols, carbonylation and nitration of platelet proteins and lipid peroxidation. Therefore, the aim of our study was to assess if the natural extract from herbal plant, Conyza Canadensis, may protect platelet proteins against nitrative and oxidative damage induced by ONOO-. In our study we measured oxidative damage of platelet proteins induced by peroxynitrite and protectory effects of this extract by estimation of the level of carbonyl groups and nitrotyrosine (a marker of platelet protein nitration). We also used cytochrome c reduction method to test the ability of this extract to change O2-* generation in platelets. Moreover, we determined the effects of the extract on blood platelet aggregation induced by ADP. We observed that the extract from Conyza canadensis distinctly reduced oxidation and nitration of proteins in blood platelets treated with ONOO-(0.1mM) and O2-* production in these cells. The extract from Conyza canadensis also inhibited platelet aggregation. The ability of the extract to decrease O2-* generation in blood platelets supports the importance of free radicals in platelet functions, including aggregation process. The present study suggests that the natural polysaccharide extract from Conyza canadensis has antiaggregatory and antioxidative activities, and therefore may be beneficial in the prevention of peroxynitrite-related diseases, such as cardiovascular or inflammatory diseases.

Analysis of Variance↗

PubMed2005

[Responses of Conyza canadensis to different concentrations of copper in soil].

Through pot experiment and physiological-biochemical analysis, the study showed that the electric conductivities of Conyza canadensis collected from heavy Cu pollution (I), light Cu pollution (II) and control (III) sites were enhanced, while the chlorophyll (a + b) contents were reduced with increasing Cu concentration. The protein and proline contents in I were increased at first and then reduced, but those in II and III were reduced with increasing Cu concentration. The activities of SOD, POD and CAT were intensified under Cu stresses. When the Cu concentration was 1 200 mg x kg(-1), their activities in I, II and III were increased 194.1%, 206.2% and 118.6%, 170.1%, 182.9% and 111.3%, and 115.1%, 155.4% and 107.3%, respectively, in comparing with the control, which illustrated that the tolerance of Conyza canadensis was in order of heavy Cu pollution site > light Cu pollution site > control site, and the three ecotypes showed distinct differences in tolerance.

Biomass↗

PubMed1985

Paraquat resistance in conyza.

A biotype of Conyza bonariensis (L.) Cronq. (identical to Conyza linefolia in other publications) originating in Egypt is resistant to the herbicide 1,1'-dimethyl-4,4'-bipyridinium ion (paraquat). Penetration of the cuticle by [(14)C]paraquat was greater in the resistant biotype than the susceptible (wild) biotype; therefore, resistance was not due to differences in uptake. The resistant and susceptible biotypes were indistinguishable by measuring in vitro photosystem I partial reactions using paraquat, 6,7-dihydrodipyrido [1,2-alpha:2',1'-c] pyrazinediium ion (diquat), or 7,8-dihydro-6H-dipyrido [1,2-alpha:2',1'-c] [1,4] diazepinediium ion (triquat) as electron acceptors. Therefore, alteration at the electron acceptor level of photosystem I is not the basis for resistance. Chlorophyll fluorescence measured in vivo was quenched in the susceptible biotype by leaf treatment with the bipyridinium herbicides. Resistance to quenching of in vivo chlorophyll fluorescence was observed in the resistant biotype, indicating that the herbicide was excluded from the chloroplasts. Movement of [(14)C] paraquat was restricted in the resistant biotype when excised leaves were supplied [(14)C]paraquat through the petiole. We propose that the mechanism of resistance to paraquat is exclusion of paraquat from its site of action in the chloroplast by a rapid sequestration mechanism. No differential binding of paraquat to cell walls isolated from susceptible and resistant biotypes could be detected. The exact site and mechanism of paraquat binding to sequester the herbicide remains to be determined.

Journal Article↗

PubMed1998

[Chemical constituents of Conyza blinii Lévl].

OBJECTIVE: To study the chemical constituents in the air-dried part of Conyza blinii. METHOD: The constituent isolation was done by solvent-extraction together with column chromatography. Several methods, such as IR, 1HNMR, 13CNMR and MS, were used to determine the structures of the isolated constituents. RESULT: Three compounds were isolated from the air-dried part of Conyza blinii and identified as friedelinol, n-triacontanol and daucosterol on the basis of physical and chemical properties and spectroscopic analysis. CONCLUSION: These compounds have not been discovered previously in this plant.

Asteraceae↗

PubMed2004

Inheritance of evolved glyphosate resistance in Conyza canadensis (L.) Cronq.

N-(phosphonomethyl)glycine (glyphosate) resistance was previously reported in a horseweed [Conyza (=Erigeron) canadensis (L.) Cronq.] population from Houston, DE (P (0) (R) ). Recurrent selection was performed on P (0) (R) , since the population was composed of susceptible (5%) and resistant (95%) phenotypes. After two cycles of selection at 2.0 kg ae glyphosate ha(-1), similar glyphosate rates that reduced plant growth by 50%, glyphosate rates that inflicted 50% mortality in the population, and accumulations of half of the maximum detectable shikimic acid concentration were observed between the parental P (0) (R) and the first (RS(1)) and second (RS(2)) recurrent generations. In addition, RS(1) and RS(2) did not segregate for resistance to glyphosate. This suggested that the RS(2) population comprised a near-homozygous, glyphosate-resistant line. Whole-plant rate responses estimated a fourfold resistance increase to glyphosate between RS(2) and either a pristine Ames, IA (P (0) (P) ) or a susceptible C. canadensis population from Georgetown, DE (P (0) (S) ). The genetics of glyphosate resistance in C. canadensis was investigated by performing reciprocal crosses between RS(2) and either the P (0) (P) or P (0) (S) populations. Evaluations of the first (F(1)) and second (F(2)) filial generations suggested that glyphosate resistance was governed by an incompletely dominant, single-locus gene (R allele) located in the nuclear genome. The proposed genetic model was confirmed by back-crosses of the F(1) to plants that arose from achenes of the original RS(2), P (0) (P) , or P (0) (S) parents. The autogamous nature of C. canadensis, the simple inheritance model of glyphosate resistance, and the fact that heterozygous genotypes (F(1)) survived glyphosate rates well above those recommended by the manufacturer, predicted a rapid increase in frequency of the R allele under continuous glyphosate selection. The impact of genetics on C. canadensis resistance management is discussed.

Alleles↗

PubMed2006

Tissue culture and transient transformation of Marestail (Conyza canadensis (L.) Cronquist).

Glyphosate resistant crops are useful to agriculture by facilitating the use of nonselective herbicides, such as RoundUp, that have low human and environmental toxicity. The occurrence of glyphosate resistant weeds, however, has raised concern about the future utility of these crops. Conyza canadensis (L.) Cronquist (marestail or horseweed) is one such glyphosate resistant weed that has yet to be fully analyzed or established in tissue culture. Tissue culture enables the examination of physiological characteristics of a plant in an aseptic and controlled environment. For the present study, mairstail was cultured on a Murashige and Skoog based medium supplemented with 6-benzylaminopurine, and alpha-naphthaleneacetic acid. Plant regeneration was achieved on the same basal medium supplemented with only gibberellic acid. Glyphosate resistance could be demonstrated in the cultured tissues. The cultures could also be transformed with Agrobacterium tumefaciens without chemically inducing virulence using phenolics or glucose and resulting in a transformation frequency (transgenic events per total number of explants used) of about 13%. The tissue culture growth, preliminary glyphosate resistance data and genetic transformation data gathered in this project provide the means to further evaluate the mode of glyphosate resistance expressed by marestail.

Agrobacterium tumefaciens↗

PubMed2005

Ferritin2 gene in paraquat-susceptible and resistant biotypes of horseweed Conyza canadensis (L.) Cronq.

Ferritins, the multimeric iron storage proteins, are the main regulators of the cellular level of uncomplexed iron. Ferritins are encoded by small gene families and expressed differentially under various developmental conditions depending on iron availability, effect of hormones or oxygen radical generating agents. In the present work the primary structure of the ferritin2 gene from resistant and susceptible biotypes of horseweed Conyza canadensis was determined. This gene was found to exhibit great similarity and possess all the structural characteristics of known plant ferritin2 genes. The C. canadensis ferritin2 genes had identical primary structure in the two biotypes and were upregulated by paraquat (Pq) in both susceptible and resistant plants. The enhanced expression level was probably connected with defence reactions in the plants after Pq treatment.

Amino Acid Sequence↗

PubMed2002

Sphingolipids from Conyza canadensis.

Sphingolipid 1 and its corresponding beta-D-glucopyranoside derivative 2 have been isolated from the ethylacetate fraction of Conyza canadensis along with beta-sitosterol 3, stigmasterol 4, beta-sitosterol 3-O-beta-D-glucoside 5 and harmine 6, reported for the first time from this species. The structures of 1 and 2 were elucidated through spectroscopy including two-dimensional NMR.

Conyza↗

PubMed2003

Shikimate accumulates in both glyphosate-sensitive and glyphosate-resistant horseweed (Conyza canadensis L. Cronq.).

Horseweed (Conyza canadensis) is a cosmopolitan weed that commonly grows throughout North America. Horseweed that is not completely controlled by normal applications of glyphosate has been reported in western Tennessee. This research had three objectives: (1) to develop and validate an analytical procedure for the quantitative determination of shikimate, an important indicator of glyphosate activity in plants; (2) to confirm resistance to glyphosate in a horseweed population; and (3) to examine the accumulation of shikimate in both glyphosate-resistant and glyphosate-susceptible horseweed plants. The analytical procedure to determine shikimate used extraction with 1 M HCl for 24 h, followed by liquid chromatography using photodiode array detection, and shikimate recoveries were >or=82%. Glyphosate applications of both 0.84 kg ae/ha (the standard application rate) and 3.8 kg ae/ha to susceptible plants caused complete plant death. The same glyphosate applications to putative resistant populations caused less than 15% growth reduction as determined by visual evaluations, and fresh weights of these resistant plants 17 days after glyphosate treatment (DAT) were reduced an average of 45% in one population and were not affected in a different population. This direct comparison conclusively confirms that horseweed plants collected in western Tennessee in 2002 are resistant to 4 times the normal application dosage of glyphosate. The glyphosate-resistant horseweed biotypes still exhibited some herbicidal effects from the glyphosate, such as yellowing in the most actively growing, apical shoot meristems. The yellowing in the shoot apexes was transitory, and the plants recovered from this damage. Shikimate concentrations in all untreated horseweed plants were less than 100 microg/g, which was significantly less than that in all plants which had been treated with 0.84 kg ae/ha of glyphosate. Unexpectedly, shikimate accumulated (>1000 microg/g) in both resistant populations and the susceptible population. However, there were differences in shikimate accumulation patterns between resistant and susceptible horseweed biotypes. Shikimate concentrations in resistant populations declined about 40% from 2 to 4 DAT, while shikimate concentrations in the susceptible horseweed plants increased about 35% from 2 to 4 DAT. The confirmed resistance of a widespread weed implies that alternative control strategies for glyphosate-resistant horseweed will be needed in those no-tillage production systems where it commonly occurs.

Conyza↗

PubMed2004

Response of selected horseweed (Conyza canadensis (L.) Cronq.) populations to glyphosate.

Horseweed (Conyza canadensis (L.) Cronq.) seed was collected in Illinois, Indiana, Kentucky, Mississippi, Missouri, and Ohio to determine susceptibility of different horseweed biotypes to glyphosate. Horseweed resistant to glyphosate was found in Mississippi, Ohio, and western Tennessee. In a separate experiment examining Tennessee biotypes, a dose response curve demonstrated that four times as much glyphosate was needed to achieve a 50% fresh weight reduction (GR(50)) in resistant biotypes when compared to a susceptible biotype. Resistant biotypes from Tennessee displayed a GR(50) of 1.6 kg/ha as compared to a GR(50) of 0.4 kg/ha in a susceptible horseweed population. Although growth was reduced, the resistant plants did not completely die and could potentially produce seed. Variation in glyphosate resistance was found among the populations tested.

Conyza↗

PubMed2003

Conyzasaponins I-Q, nine new triterpenoid daponins from Conyza blinii.

Nine new triterpenoid saponins, conyzasaponins I-Q (1-9), were isolated from the aerial parts of Conyza blinii. Their structures were established on the basis of extensive 1D and 2D NMR spectra as well as by chemical degradations. Among these compounds, conyzasaponins M-O (5-7) share a common pentasaccharide unit attached to C-28 of the aglycon, 28-O-beta-d-apiofuranosyl-(1-->3)-beta-d-xylopyranosyl-(1-->4)-[beta-d-apiofuranosyl-(1-->3)]-alpha-l-rhamnopyranosyl-(1-->2)-alpha-l-arabinopyranosyl ester, which contains two apiofuranosyl residues. To the best of our knowledge, they are among the few examples of natural products possessing two apiofuranose units in a single sugar chain.

Conyza↗

PubMed2002

Novel sphingolipids from Conyza canadensis.

New sphingolipids, 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)-heptacosdiene (1). 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)-heptacosdiene-1-O-glucopyranoside (2). 1,3-dihydroxy-2-hexanoylamino-(4E)-heptadecene (3). have been isolated from Conyza canadensis, along with five known compounds, p-hydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 3,5-dimethoxybenzoic acid, 3beta-hydroxyolean-12-en-28-oic acid, and 3beta-erythrodiol, isolated for the first time from this species. Their structures were determined by spectroscopic methods ((1)H- and (13)C-NMR, IR and MS) and two dimensional (2D)-NMR experiments.

Conyza↗

PubMed2000

Transient, oxidant-induced antioxidant transcript and enzyme levels correlate with greater oxidant-resistance in paraquat-resistant Conyza bonariensis.

The elucidation of mechanisms plants use to overcome oxidative stress is facilitated where there is intra-specific genetic variability. The differential induction of higher levels of mRNAs, cytosol and chloroplast antioxidant enzyme activities, and proteins occurred after sub-lethal paraquat treatment of the oxidant-resistant biotype of Conyza bonariensis (L.) Cronq. By 6 h after sub-lethal paraquat treatment the activities of superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11), dehydroascorbate reductase (EC 1.8.5), monodehydroascorbate reductase (EC 1.6.5.4), and glutathione peroxidase (EC 1.11.19) had increased, peaking at 24 h and then slowly reverting back to the basal level. Similarly, the levels of mRNAs encoding these enzymes were enhanced by 12 h and peaked at 18-24 h after sub-lethal paraquat treatment. The time courses of the transient elevation of both transcript and antioxidant enzyme levels correlated with a further transient 2.5- to 3.0-fold increase of paraquat resistance, which occurred only in the constitutively resistant biotype. The individual enzymes seem to be part of a coordinately controlled oxidant tolerance in the resistant biotype, utilizing oxidant-induced, increasingly abundant transcript levels, upon which more antioxidant enzymes were synthesized.

Ascorbate Peroxidases↗

PubMed2001

Glycosides and xanthine oxidase inhibitors from Conyza bonariensis.

Fractionation of the xanthine oxidase inhibitory methanol extract of Conyza bonariensis afforded three glycosides, in addition to nine known compounds including amyrin, beta-sitostero1 daucosterol, syringic acid 3-hydroxy-5-methoxybenzoic acid, eugenol 4-O-glucopyranoside, and luteolin, apigenin and takakin 8-O-glucuronide. The structures of the glycosides were established by a combination of spectroscopic methods (IR, MS, 1H and 13C NMR, DEPT, COSY, HMQC and HMBC) as 4-hydroxypyridin-3-carboxylic acid 4-O-glucopyranoside, 8-hydroxy-6,7-dihydrolinalool 8-O-glucopyranoside and bonaroside [viz. 1,3,4,12-tetrahydroxy-2-(9-hexadecenoylamino)octadecane 1-O-glucopyranoside]. The in vitro enzyme assay showed that syringic acid and takakin 8-O-glucuronide displayed weak inhibitory activity against xanthine oxidase with IC50 values of 500+/-41 microM and 170+/-12 microM, respectively.

Asteraceae↗

PubMed2001

Four new triterpenoid saponins from Conyza blinii.

Three new bisdesmosidic saponins named conyzasaponins A, B, and C (1-3) and one new monodesmosidic saponin, conyzasaponin G (4), were isolated from the aerial parts of Conyza blinii. Their structures were elucidated on the basis of extensive NMR (DEPT, DQF-COSY, HOHAHA, HMQC, HMBC, and NOESY) and MS studies. Compounds 1-3 share a common prosapogenin, bayogenin 3-O-beta-D-xylopyranosyl-(1-->3)-beta-D-glucopyranoside, which is identical with conyzasaponin G (4), and differ in the structures of the ester-linked sugar moieties at C-28. Conyzasaponin A (1) is the 28-O-beta-D-apiofuranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl ester, conyzasaponin B (2), the 28-O-beta-D-apiofurano- syl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-[alpha-L-arabinopyranosyl-(1-->3)]-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl ester, and conyzasaponin C (3), the 28-O-alpha-L-rhamnopyranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-[beta-D-apiofuranosyl-(1-->3)]-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl ester of the prosapogenin, respectively.

Carbohydrate Sequence↗

PubMed2001

Antiprotozoal activity of the constituents of Conyza filaginoides.

Bioassay-guided fractionation of the antiprotozoal extract of Conyza filaginoides led to the isolation of three new flavonol caffeoyl glycosides, namely, kaempferol 3-O-(6' '-O-E-caffeoyl)-beta-D-galactopyranoside (1), isorhamnetin 3-O-(6' '-O-E-caffeoyl)-beta-D-galactopyranoside (2), and quercetin 3-O-(6' '-O-E-caffeoyl)-beta-D-glucopyranoside (3). In addition, seven known compounds, erythrodiol (4), beta-caryophyllene-4,5-alpha-oxide (5), astragalin (6), isoquercitrin (7), nicotiflorin (8), narcissin (9), and rutin (10), were obtained. The structures of the new isolates were elucidated by spectroscopic and chemical methods. Compounds were also assessed for antiamoebic and antigiardial activities, but none was significantly active compared to the standard drugs evaluated.

Animals↗

PubMed2000

Bioactive constituents of Conyza albida.

The bioactivity-guided fractionation of an active chloroform extract of Conyza albida led to the isolation of three alkenynes, deca-4,6-diyn-2-(Z)-enoic methyl ester (1), deca-4,6-diyn-2-(Z)-enoic ethyl ester (2) and deca-2,4-diene-4-hydroxy-6-yn-1,4-olide (3), and the terpenoid spathulenol (4), as the active toxic metabolites in the Artemia sp. lethality test. When tested in the KB cell cytotoxicity assay, compounds 1-4 demonstrated IC50 values of 52.2, 38.4, 117.9, and 83.8 microM, respectively. All compounds studied were inactive in the DNA methyl green and DNA strand scission assays, while compounds 3 and 4 showed moderate activity as inhibitors of human topoisomerase I. Compound 2 is reported here for the first time.

Asteraceae↗

PubMed2002

Three pyrone glucosidic derivatives from Conyza albida.

Three new pyrone glucosidic derivatives, together with the known pyromeconic acid glucoside, three acytelenes and two eudesmanes, were obtained from the aerial parts of Conyza albida. The structures were elucidated by high field NMR spectroscopy.

Asteraceae↗