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1.
A structure-activity study to evaluate the effect of 17 guaianolide sesquiterpene lactones (in a range of 100-0.001 microM) on the growth and germination of several mono- and dicotyledon target species is accomplished. Results are compared with those obtained in the same bioassay with an internal standard, the commercial herbicide Logran, to validate the results with a known active formulation and to compare the results with a commercial product to test their potential use as natural herbicide models. Specific conditions for the selective mono- or polyhydroxylation of guaianolides using the SeO(2)/tert-butyl hydroperoxide system are presented and discussed. The high regio- and stereoselectivities of the reaction are explained through the specific structural requirements of the bulky first adduct formed during the ene reaction. These compounds appear to have deeper effects on the growth of either monocots or dicots than the previously tested germacranolides. Otherwise, the lactone group seems to be necessary for the activity, though it does not necessarily need to be unsaturated. However, the presence of a second and easily accessible unsaturated carbonyl system greatly enhances the inhibitory activity. Lipophilicity and the stereochemistry of the possible anchoring sites are also crucial factors for the activity. Finally, the levels of growth inhibition obtained with some compounds on dicots or monocots are totally comparable to those of Logran and allow proposing them as lead compounds.  相似文献   

2.
Plant growth inhibitory effects of acetophenones 1-6, tremetones 7-12, and MeOH and CH(2)Cl(2) extracts from the aerial parts of Baccharis linnearis, Baccharis magellanica, and Baccharis umbelliformis collected in Chile were assayed as growth inhibitory activity in ranges of 10-500 microM and 0.1-150 ppm, respectively. The effects on seedling growth, germination, and respiration of ryegrass, lettuce, green tomato, and red clover weedy target species were measured. In addition to the inhibitory activity on bleaching of crocin induced by alkoxyl radicals, these compounds also demonstrated scavenging properties toward 2,2-diphenyl-1-picrylhydrazyl in thin-layer chromatography autographic and spectrophotometric assays. In addition, acetophenones and tremetones also showed inhibition of H(+) uptake and oxygen uptake respiration in isolated chloroplasts and mitochondria, respectively. Our results indicate that 1, 4, 7-12, and CH(2)Cl(2) extracts interfere with the dicot preemergence properties, mainly energy metabolism of the seeds at the level of respiration. These compounds appear to have selective effects on the radicle more than shoot growth of dicot seeds. Also, the levels of radicle inhibition obtained with some compounds on Physalis ixocarpa and Trifolium pratense are totally comparable to those of ovatifolin, a known natural growth inhibitor. This behavior might be responsible for its plant growth inhibitory properties and its possible role as an allelopathic agent.  相似文献   

3.
A comparative study on the effect of arturin (1), ovatifolin (3), deacetylovatifolin (5), and their 1-acetoxyarturin (2), 8-acetoxyovatifolin (4), 1,10-epoxyovatifolin (6), and 11,13-dihydroovatifolin (7) derivatives, isolated from Podanthus ovatifolius and Podanthus mitiqui, on the seedling growth, germination, and respiration of several monocot and dicot weedy target species was carried out. In addition to the inhibitory activity on the bleaching of crocin induced by alkoxyl radicals, these compounds also displayed scavenging properties toward DPPH in TLC autographic and spectrophotometric assays. The results indicate that ovatifolin (3), deacetylovatifolin (5), epoxyovatifolin (6), dihydroovatifolin (7), and the CH(2)Cl(2) extract interfere with pre-emergence of seedlings at the level of respiration. These compounds appear to have selective effects on the radicle and shoot growth of Physalis ixocarpa and Trifolium pratense. Their allelopathic effects are comparable to those of parthenolide, a know natural growth inhibitor.  相似文献   

4.
Herbicides are released to the environment with potential ecotoxicological risks for mammals. Yeast is a good model to elucidate toxicity mechanisms. We investigated how three commercial herbicides (Proper Energy, Pointer, and Silglif) and their active ingredients (respectively, fenoxaprop-P-ethyl, tribenuron methyl, and glyphosate) can affect biological activities of an oenological Saccharomyces cerevisiae strain, which may be resident on grape vineyards of the same geographical areas where herbicides are used. The use of commercial grade herbicides employed in Italy allowed us to reproduce the same conditions applied in crops; at the same time, assaying pure single active compounds made it possible to compare the effects obtained with commercial formulations. Interestingly, we found that while pure active compounds affect cell growth and metabolism at a lower extent, commercial preparations have a significant major negative influence on yeast biology.  相似文献   

5.
The phytopathogenic fungus Nectria galligena Bres. is the most common canker disease agent of hardwood trees. The terpenoids colletochlorin B, colletorin B, ilicicolin C, E, and F, as well as the phytotoxin alpha,beta-dehydrocurvularin have been isolated from liquid cultures of N. galligena obtained from the xylem of infected apple trees in central Chile. Ilicicolin C and F and alpha,beta-dehydrocurvularin were active against Pseudomonas syringae with IC50 values of 28.5, 28.5, and 14.2 microg/mL, respectively, in the same range as streptomycin and penicillin G (11 and 15 microg/mL, respectively). All of the compounds showed moderate inhibitory activity toward the enzymes acetylcholinesterase (AChE) and beta-glucuronidase. The most active enzyme inhibitors were colletochlorin B and ilicicolin C and E, with IC50 values of 30-36 microg/mL in the AChE assay and 32-43 microg/mL in the beta-glucuronidase test. All of the chlorinated compounds showed some toxicity toward human lung fibroblasts, with IC50 values in the range of 64-120 microg/mL. alpha,beta-Dehydrocurvularin proved to be the most toxic compound, showing IC50 values less than 12 microg/mL. The effect of the isolated compounds on seed germination and radicle and epicotyl growth was assessed in lettuce and millet seeds. At 100 and 200 microg/disk, alpha,beta-dehydrocurvularin significantly reduced radicle length and epicotyl growth in Lactuca sativa. This is the first report on the occurrence of colletochlorin B, colletorin B, ilicicolin C, E, and F, as well as alpha,beta-dehydrocurvularin associated to N. galligena.  相似文献   

6.
A collection of 11 natural and synthetic podolactones have been tested as allelochemicals in a range between 10(-4) and 10(-9) M, and their potential use as natural herbicide models is discussed. Their effects on the germination and growth of the dicots Lactuca sativa (cv. Nigra and cv. Roman), Lepidium sativum, and Lycopersicon esculentum and the monocots Allium cepa, Hordeum vulgare, and Triticum aestivum as standard target species have been studied. An important inhibitory effect on the germination and growth of all tested species (average = 90%) was produced by compounds 9-11 at 10(-4) M. The specific structural requirements related to their activities are studied. On the basis of these results, their use as potential natural herbicide models is proposed.  相似文献   

7.
The aqueous root extract of Ailanthus altissima showed allelopathic activity against radish (Raphanus sativus L. cv. "Saxa"), garden cress (Lepidium sativum L.), and purslane (Portulaca oleracea L.) seeds. A bioassay-oriented purification of active extracts, chromatographic fractions, and compounds demonstrated dose-dependent activity on germination and radicle growth of test seeds; radish seed was the most sensitive to allelochemicals. Active compounds have been isolated: ailanthone, ailanthinone, chaparrine, and ailanthinol B (quassinoid derivatives); the alkaloid 1-methoxycanthin-6-one is not active. The compound with greatest inhibitory activity is ailanthone. The data obtained suggest a possible use of tree-of-heaven root extracts or of its active constituents as natural herbicides.  相似文献   

8.
Abstract

Aerobic rice is a potential water-wise rice production system, but high weed infestation has threatened its sustainability, which demands an efficient and cost-effective weed management technique. Eight commercial herbicide products were applied singly or as tank-mix or in sequence to evaluate their efficacy, rice selectivity and cost-effectiveness in aerobic rice. The study was conducted under field conditions in Malaysia during 2010/2011 following a randomized complete block design. Most of the herbicide treatments provided excellent weed control, and produced much higher net benefit than weedy or weed-free check. None of the herbicides caused significant phytotoxicity to rice plants. Among the herbicide treatments, sequential application of Cyhalofop-butyl+Bensulfuron at early growth stage followed by Bentazon/MCPA at mid growth stage provided the highest weed control efficiency, productivity and net benefit. Application of Bispyribac-sodium at early growth stage followed by Bentazon/MCPA at mid growth stage performed very close to the above-mentioned treatments. Sequential application of Pretilachlor/safener just after seeding followed by Propanil/Thiobencarb at early growth stage also provided satisfactory results in terms of efficacy and economic return. Since manual weeding was not economic, herbicide rotation using the above chemicals may be recommended for effective weed management in aerobic rice.  相似文献   

9.
Interactions of the herbicide sulfentrazone with the cationic surfactants octadecyltrimethylammonium (ODTMA), hexadecyltrimethylammonium (HDTMA), and benzyldimethylhexadecylammonium (BDMHDA) have been studied for the design of slow-release formulations based on sulfentrazone adsorbed on a micelle-montmorillonite complex. Adsorbed amounts of sulfentrazone on ODTMA- and BDMHDA-montmorillonite complexes were 99.2-99.8% of that added, and desorption of herbicide in water during 24 h was low. After 10 washings in funnels with soil, only 2.6% of herbicide was released from ODTMA-montmorillonite formulations versus 100% release from the commercial formulation. The strong binding of sulfentrazone to micelles was confirmed by pH and spectroscopic measurements and was explained by the formation of ionic pairs between cationic surfactant and anionic herbicide. The ODTMA-clay and commercial formulations of sulfentrazone yield almost complete and 40% growth inhibition of green foxtail, respectively, at 700 g of active ingredient/ha. Hence, the slow release from micelle-clay formulations of sulfentrazone promotes its biological activity and reduces environmental contamination.  相似文献   

10.
A series of novel cyanoacrylates containing furan or tetrahydrofuran moieties were synthesized, and their structures were characterized by 1H NMR, elemental analysis, and single-crystal X-ray diffraction analysis. The herbicidal, plant growth regulatory, fungicidal, and antiviral activities of these cyanoacrylates were evaluated. The results of herbicidal activities showed that most of these cyanoacrylates exhibited higher herbicidal activities against dicotyledonous weeds than monocotyl-edonous weeds, and the compounds containing the tetrahydrofuran moiety gave higher herbicidal activities than corresponding furan analogues; (Z)-ethoxyethyl 2-cyano-3-isopropyl-3-(tetrahydrofuran-3-yl)methaneaminoacrylate showed excellent herbicidal activities against amaranth pigweed in postemergence treatment at a dose of 375 g/ha. At the same time, these cyanoacrylates had interesting plant growth regulatory activities, and some compounds stimulated radicle growth of cucumber, whereas some compounds had an inhibitory effect. These cyanoacrylates showed fungicidal activities as well.  相似文献   

11.
The response of Scenedesmus spp. to three phenylureas, namely Maloran, Dicuran, and Patoran was investigated. Chloropyll (a) content, ratio of chlorophyll (a/b), growth rate and dry weight of algae tended to decrease as the concentration of herbicide in the bioassay media was increased. The inhibitory effect of the studied herbicides followed the order; Maloran > Dicuran > Patoran. At low concentration levels, patoran led to an increase in Chl. (a) content, Chl. (a/b) ratio and maximum growth rate. Uptake of the studied compounds by algal cells was at its maximum value in the presence of low herbicide concentrations and tended to decrease as the herbicide concentration was increased. Scenedesmus algal Cells were able to recover and attained their normal growth rate and morphological characteristics when the cells were transferred to a herbicide-free medium. The pH value of the algal media gradually increased as algal growth proceeded. In media containing inhibitory levels of phenylureas, the pH value was unchanged. Statistical analysis indicated that changes in Chl. (a) induced by the herbicides were significant.  相似文献   

12.
A series of aminomethylene-bisphosphonic acid derivatives, previously synthesized and shown to be endowed with herbicidal properties, were evaluated as potential inhibitors of plant glutamine synthetase. The cytosolic form of the enzyme was partially purified from rice cultured cells and assayed in the presence of millimolar concentrations of the compounds by means of three different assay methods, respectively measuring the hemibiosynthetic, the transferase, and the full biosynthetic reactions. Several compounds were found to exert a remarkable inhibition, with I(50) values similar to those obtained under the same conditions with a well-established inhibitor of glutamine synthetase, the herbicide phosphinothricin. Contrary to the reference compound, enzyme kinetics accounted for a reversible inhibition mechanism. The biological activity of the most active derivatives was further characterized by measuring free glutamine levels in cell suspension rice cultures following treatment with the inhibitors. Results confirmed their ability to interfere in vivo with nitrogen metabolism. A preliminary analysis of structure-activity relationship allowed it to be hypothesized that steric rather than electronic factors are responsible for the inhibitory potential of these compounds.  相似文献   

13.
Samples of two soils and two sediments collected at sites originating from mangrove forests in Thailand, were examined in terms of buffering capacity to organic compounds. Atrazine and linuron were used as representative hydrophobic organic compounds for estimating the buffering capacity by observing their adsorptive and desorptive behavior. The buffering capacity could be represented by the distribution of the adsorption ratio (AR) and desorption ratio (DR) as follows: AR (%) = (amount of herbicide adsorbed per unit weight of soil)/(initial amount of herbicide) x 100, and DR (%) = (amount of herbicide desorbed per unit weight of soil after herbicide desorption experiments) / (initial amount of adsorbed herbicide on soil) x 100. The soil under mangrove forests displayed a larger buffering capacity to atrazine and linuron. Compared with 42 soils from Japan, in terms of the adsorption proparty of atrazine and linuron, the mangrove soil ranked in a higher category on the classification of the Japanese soils. Thus, the importance of maintaining or recovering the mangrove forests to promote environmental conservation was emphasized.  相似文献   

14.
Compounds with molecular weights 14 a.m.u. lower than their corresponding parent compounds have been detected in trichothecene standards during gas chromatography-mass spectrometry analysis. The positive ion chemical ionization mass spectra indicated that these compounds were trichothecene homologs lacking a methyl group on the isovaleroxy substituent at the C-8 position. Demethylated derivatives have been found in the standards of T-2, HT-2, and T-2 triol prepared in our laboratory and those obtained from a commercial source.  相似文献   

15.
Herbicides are commonly used on private timberlands in the western United States for site preparation and control of competing vegetation. How non-target soil biota respond to herbicide applications, however, is not thoroughly understood. We tested theeffects of triclorpyr, imazapyr, and sulfometuron methyl on ectomycorrhizal formation in a greenhouse study. Ponderosa pine, Douglas-fir, and white fir seedlings were grown in four forest soils ranging in clay content from 9 to 33% and organic matter content from 3 to 17%, and treated with commercial formulations of each herbicide at 0, 1.0, and 2.0 times the recommended field rate. Many of the possible herbicide-soil combinations resulted in reduced seedling growth. Root development was particularly sensitive to the three herbicides, with an average of 51% fewer root tips compared to the control treatment. The ability of mycorrhizal fungi to infectthe remaining root tips, however, was uninhibited. Mycorrhizal formation was high, averaging 91% of all root tips, regardless of herbicide, application rate, soil type, or conifer species. In agreement, soil microbial biomass and respiratory activity were unaffected by the herbicide treatments. The results show that these herbicides do not alter the capability of mycorrhizal fungi to infect roots, even at concentrations detrimental to seedling growth.  相似文献   

16.
Five ethylcellulose (EC) microencapsulated formulations (MEFs) of norflurazon were prepared and applied in soil to study their mobility, dissipation, activity, and persistence. The results show that the release into water of norflurazon from EC microspheres was retarded when compared with that of commercial herbicide. The mobility of norflurazon from MEFs into soil columns has been greatly diminished in comparison with that of its current commercial formulation (CF). Norflurazon distribution at different depths in the soil was higher in the upper ring (up to 50% of the initial application). In contrast, the residues from commercial norflurazon along the complete soil column were only about 2%. Degradation and bioassay experiments showed that the MEFs had greater persistence (t1/2 values were 7.72 and 30.83 weeks for CF and MEFs, respectively) and herbicidal activity than the commercial formulation. The use of these formulations can be advantageous, because they can minimize the risk of groundwater contamination and permit herbicide use at reduced rates, maintaining the desired concentrations of herbicide in the topsoil layer for longer periods of weed control.  相似文献   

17.
Abstract. Experiments were started in 1967 to investigate the effects of soil mixing on fen peat soil. Peaty topsoil was mixed with mineral subsoil to a maximum depth of 80 cm at two sites, one with a clay subsoil, the other sand. Mixing was done on a commercial scale with a range of implements. After initial increases, yields of arable crops on both mixed soils were subsequently similar to those on unmixed soil. Residual herbicide activity was enhanced on mixed soils, and evidence of peat conservation was obtained at one site. The practice has not been taken up commercially because of the high capital cost of mixing and lack of serious problems which had been predicted following peat wastage.  相似文献   

18.
Avena fatua L. (wild oat) and Lolium rigidum Gaud. (rigid ryegrass) are highly problematic weeds affecting a wide variety of cereal crops worldwide. The fact that both of these weeds have developed resistance to several herbicide groups made them optimal candidates as target organisms for ongoing research about the potential application of allelochemicals and analogue compounds as natural herbicide models. Benzoxazinones, a family of natural allelochemicals present in corn, wheat, and rye, including 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, together with some degradation products, found in crop soils as well as in other systems, and some synthetic analogues of them were tested on wild oat and rigid ryegrass seeds; the results were statistically treated, and some structure-activity relationships, useful in further development of natural herbicide models, were elucidated. The most active compounds were the synthetic benzoxazinone 2-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one and the degradation product 2-aminophenoxazin-3-one, with highly significant inhibition on the development of both weeds. The ecological role of these compounds is discussed by considering both degradability and phytotoxicity. The bioactivity of aminophenoxazines has been correlated by their aqueous solubility-lipophilicity predicted by means of computational methods.  相似文献   

19.
IR 5790, an arylthiadiazolone herbicide structurally related to oxadiargyl and oxadiazon, was synthesized. The herbicidal activity and mode of action of IR 5790 were investigated. This herbicide has broad-spectrum pre-emergence activity against both dicotyledonous and monocotyledonous weeds. The phenotypic responses of susceptible plants, such as interruption of growth and light-dependent development of necrotic areas on the foliage, are consistent with those observed with protoporphyrinogen oxidase-inhibiting herbicides. Tissues exposed to IR 5790 in darkness accumulated protoporphyrin IX, which led to a photodynamic loss of membrane integrity upon exposure to light. Consistent with these physiological symptoms, IR 5790 strongly inhibited protoporphyrinogen oxidase, with an I(50) value of 3 nM. The presence of a sulfur atom did not significantly alter the molecular properties of the thiadiazolone ring, relative to the oxadiazolone ring of oxadiargyl, which explains why IR 5790 has the same mode of action as this herbicide.  相似文献   

20.
The utility of benzoxazinones and some of their synthetic derivatives in the search for new leads for herbicide model development has been explored. The work described focuses on obtaining derivatives that present selectivity in the system Oryza sativa- Echinochloa crus-galli. To achieve this goal the influence of lipophilicity in this system has been studied by preparing 14 ester derivatives at the N-4 position of D-DIBOA along with other compounds with different functionalization and chain lengths at position C-2. These compounds have been tested in the aforementioned system, and the dose-response profiles have been compared. The most active compound was 2-ethyl-4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one, which presented higher selectivity than the specific herbicide Cotanil-35. These results confirm the potential of D-DIBOA as a lead herbicide for the control of Echinochloa spp. in rice crops.  相似文献   

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