典型咪唑啉酮类除草剂的微生物降解研究进展

咪唑啉酮类除草剂是中国广泛应用的除草剂,具有杀草谱广、活性高、选择性强等优点,但其在土壤中残留期长,影响后茬作物.本文综述了典型的咪唑啉酮类除草剂甲氧咪草烟、咪唑乙烟酸和甲咪唑烟酸残留对后茬作物的影响,探究了降解部分咪唑啉酮类除草剂(甲氧咪草烟、咪唑乙烟酸和咪唑烟酸)的微生物所属类群及降解途径,分析了影响微生物降解咪唑...     

Structure-activity relationships of triazinone herbicides on resistant weeds and resistant Chlamydomonas reinhardtii

Weeds resistant to the s-triazine herbicide atrazine also show resistance to the triazinone herbicide metribuzin. However, with highly lipophilic triazinones, thylakoids isolated from atrazine-resistant Amaranthus retroflexus (mutation at position Ser₂₆₄ of the photosystem II D-1 reaction centre protein) in general show a higher pI₅₀ value in photosystem II electron transport than those from the wild type (i.e. negative cross-resistance; ‘supersensitivity’). A quantitative structure–activity relationship (QSAR) can be established, wherein the lipophilicity of the compound plays a major role. In in-vivo experiments, it was found that the triazinone DRW2698 killed resistant Amaranthus retroflexus and Chenopodium album whereas the wild type was almost unaffected. Triazinones were further investigated in five different mutants of Chlamydomonas rheinhardtii (mutations in the D-1 protein at positions Ser₂₆₄, Ala₂₅₁, Leu₂₇₅, Phe₂₅₅, and Val²¹⁹). Inhibitory activity of all triazinones was generally enhanced in the Phe₂₅₅ mutant but decreased in the Val₂₁₉ mutant. In the other mutants, biological activity was decreased when position 3 of the triazinone was substituted by CH₃, OCH₃, SCH₃, NHCH₃ or N(CH₃)₂. However, negative cross-resistance was again observed when this position was occupied by free thiol. It is therefore suggested that these two groups of triazinones orient themselves differently within the herbicide binding niche of the photosystem II D-1 protein.     

Cross-resistance to imidazolinone herbicides in chlorsulfuron-resistant Raphanus raphanistrum

Raphanus raphanistrum L has evolved widespread resistance to sulfonylureas in the Western Australia (WA) wheat belt. With the introduction of imidazolinone-tolerant (IT) wheat (Tritcum aestivum L) and IT canola (Brassica napus L) in the WA wheat belt, it is important to understand the status of cross-resistance in this weed to sulfonylurea and imidazolinone (Imi) herbicides. A study was conducted to examine cross-resistance between chlorsulfuron and Imi herbicides (a mixture of imazapic and imazapyr) in 46 R raphanistrum populations collected from across the WA wheat belt. Plants were treated with herbicides and assessed for phytotoxicity under glasshouse conditions. Of the 46 R raphanistrum populations, 32 were resistant to chlorsulfuron and four were resistant to imazapic + imazapyr. Of the 70% chlorsulfuron-resistant populations, 13% showed cross-resistance to imazapic + imazapyr. However, the cross-resistant populations treated with imazapic + imazapyr showed a lower resistance level than the chlorsulfuron-treated populations. These results suggest that weed populations with such cross-resistance will not be controlled effectively by Imi herbicides. Although the resistance levels of the cross-resistant populations to Imi herbicides were low, the cross-resistance levels of R raphanistrum should be determined before growing IT crops, particularly IT canola.     

Structure-activity relationships of pheromonostasis induced by ACCase-inhibitor herbicides in the moth Helicoverpa armigera

Many moth sex pheromone blends are derived from fatty acids and their production is regulated by a Pheromone Biosynthesis Activating Neuropeptide (PBAN). In prior work we showed that the herbicide Diclofop-acid, an acetyl-coenzyme A carboxylase (ACCase) inhibitor, inhibits PBAN-induced sex pheromone production in vitro. In this work we extend our study showing that several other herbicides, belonging to the 2-aryloxyphenoxypropionate (‘FOP’) and the cyclohexandione-oxime (‘DIM’) families significantly inhibit pheromone production by adult females whilst survival is unaffected by treatment. Enzyme activity in vitro and kinetic analysis revealed a K_m of 0.35 μM with K_i values of 0.1 and 0.28 μM due to Tralkoxydim and Diclofop inhibition, respectively. Inhibitory activity on PBAN-induced pheromone production by all herbicides tested revealed a potency order: Tralkoxydim > Clodinafop > Cycloxidim > Haloxyfop > Diclofop > Fenoxaprop > Fluazifop > Quizalofop, Quizalofop being inactive. Differences in inhibition efficiencies may be attributed to different binding sites on the enzyme or to the polarity and solubility of these compounds.     

Fenbendazole. I. Structure-activity relationships

Substitution of alkyl benzimidazol-2-ylcarbamates by phenoxy- or phenylthio-groups in the 5-position results in an increase in anthelmintic activity. The biological spectrum is altered by substitution of the phenyl ring. A sulphonic ester substituent in the 5-position of the benzimidazole nucleus also increases anthelmintic activity.     

Structure-activity relationship of herbicides inhibiting ACh-induced contractions in a molluscan smooth muscle

Certain herbicides are known to influence the muscle function of molluscs. The penis-retractor muscle complex (PRM complex) of the edible snail, Helix pomatia, is a suitable test object for studying these side effects in smooth muscle, because sequential contractions can be induced in vitro by adding and removing acetylcholine (ACh). In the presence of herbicidal amides, carbamates, and ureas (concentration, 10^?4 mol/liter) the muscle tension was found to be reduced to a variable extent. In contrast, the relaxing effect of herbicidal phenoxycarbonic acids was weak. The inhibitory properties of the herbicides tested were correlated with the electron-withdrawing properties of certain substituents. These substituents are bound to an amino function. Their structure is either aromatic (amides, biscarbamates, carbamates, ureas), aliphatic (thiocarbamates), or cycloaliphatic (cycloat). The structure-activity relationship is comparable with that found for herbicidal activity in plants.     

Structure-activity relationships in a group of imidazole-1-carboxamides

Detailed structure-activity studies in a series of substituted imidazole-1-carboxamides culminated in the synthesis of N-alkyl-N-phenoxyalkyl substituted compounds and, eventually, prochloraz, a compound shown to give excellent broad-spectrum disease control in cereals. Subsequently, evidence was obtained which suggests that its mode of action is through the inhibition of ergosterol biosynthesis or, more specifically, through inhibition of sterol C-14 demethylation.     

Structure-activity relationships of insecticidal amides from Piper guineense root

The structure-activity relationships between five amides previously isolated from the root extract of Piper guineense Schum and Thonn were studied. The methyl-terminated amides, pellitorine and kalecide, were found to be more polar and caused higher knockdown, but showed less lethal action against insects than their methylenedioxyphenyl-terminated counterparts, pipercide and guineensine. Guineensinamide showed weak activity and this was correlated with higher unsaturation and the presence of a pyrrolidyl group in the molecule. There was an association between the polarity of the amides and the recovery of the insects from their effects, much more recovery being observed with the methylterminated than with the methylenedioxyphenyl-terminated amides. Electrophysiological investigations of the effects of pellitorine and pipercide on miniature excitatory postsynaptic potentials (MEPSPs) from the locust retractor unguis nerve-muscle preparation showed that the amides caused a reduction in both the frequency and amplitude of MEPSPs, pipercide being between 100 and 1000 times more effective than pellitorine. An action of the amides on presynaptic transmission is suggested. The effects of pipercide and pellitorine on the isolated nerve-muscle preparation were correlated with the symptoms of poisoning at the whole animal level.     

Structure-activity relationships in triorganotin biocides: The influence of the anionic radical

Bioassay data are reported for seven triorganotin compounds (R₃SnX), in which R=phenyl, cyclohexyl, or 2-methyl-2-phenylpropyl, and × is the anionic form of the organic chelating ligands quinolin-8-ol, quinoline-8-thiol, 1,3-diphenylpropane-1,3-dione, or 3-hydroxyflavone, when tested against an organophosphorus-resistant species of the two-spotted spider mite (Tetranychus urticae), the potato blight fungus (Phytophthora infestans), and the vine downy mildew fungus (Plasmopara viticola). The relationship between the activity and the co-ordination number of the tin atom is discussed, and it is shown that the anionic group × can, in some instances significantly affect the biological properties.     

Structure-activity relationships in a series of new antifungal nitroalcohol derivatives

The structure-antifungal activity correlations of 23 new nitroalcohol derivatives (1-substituted-2-nitropropane-1, 3-diols, their ethers and esters) were investigated using a generalised quantitative structure-activity relationships (QSAR) method, combining Golender and Rozenblit's logico-structural approach and the Free-Wilson and Hansch analyses. Based on results obtained from principal component analysis, the in-vitro activities against Helminthosporium sativum, the inhibition of germination and of growth could be assumed to be governed by a common mechanism. It is suggested that the antifungal activity of the compounds studied is determined mainly by the presence or absence of an aromatic ring (unsubstituted, or bearing a hydrophobic group that is small in bulk and electron-attracting) at position 1, of a (potential) double bond between carbon atoms 1 and 2, and of an acyloxy group at position 3. Among these factors, the double bond seems to be the most important, and the mechanism of the antifungal action is probably dependent on the reactivity of this bond towards thiol groups of endogenous substances.     

Structure-activity relationships of pyrethroids based on direct action on nerve

The structure-activity relationships of 30 synthetic pyrethroids have been studied by measurements of their direct action on isolated crayfish nerve cord. The concentrations of pyrethroids used to increase the frequency of spontaneous discharges to 200% of the control (NS₂₀₀), those to decrease the frequency back to the control level, and those to further decrease the frequency to 10% of the control were measured as indexes of the nerve action. These values did not necessarily run parallel with those for the lethal dose 50 or the knock-down 50. Large differences in NS₂₀₀ were found among optical isomers of tetramethrin and phenothrin, and there was a synergism with respect to the nerve stimulating action between (+) and (?) forms of tetramethrin. (+)-trans-Permethrin was unique in that it exhibited a potent insecticidal action with a very weak nerve action. It is necessary to compare the direct action on the target site for the purpose of establishing the true structure-activity relationships of synthetic pyrethroids.     

Structure-activity relationships of 1,2,3-benzothiadiazole insecticide synergists as inhibitors of microsomal oxidation

The activities of 47 substituted 1,2,3-benzothiadiazoles as inhibitors of microsomal epoxidation and/or hydroxylation in enzyme preparations from rat liver or armyworm (Spodoptera eridania) gut have been evaluated. Many were found to be effective inhibitors of microsomal oxidation, the most active being the 6-butyl and 6-propoxy derivatives with I₅₀ values of 4.9 × 10^?7 and 7.0 × 10^?7M, respectively, for the epoxidation reaction. Regression analyses have established that activity of the 5-, 6-, and 5,6-substituted compounds can be satisfactorily described in equations in terms of π², π, and σ whereas that of the 4-substituted derivatives depends on π and the steric parameter E₈.     

咪唑啉酮类除草剂的应用及降解

咪唑啉酮类除草剂虽具有高效广谱的特点,但有较长的残留活性,长期使用会造成作物药害,并且会制约正常的作物轮作。因此,如何解决其残留问题已成为目前的重要课题。本文介绍了咪唑啉酮类除草剂的种类和特性,阐述了此类除草剂在杂草体内的作用方式、代谢机制、应用情况及其在土壤中的降解途径,并对该类除草剂的应用与降解研究进行了展望。     

Structure-activity relationships of carboxamide fungicides and the succinic dehydrogenase complex of Cryptococcus laurentii and Ustilago maydis

The systemic fungicide, carboxin (5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxanilide) and a variety of carboxamide compounds exhibit a marked specificity for Basidiomycete fungi. This unique specificity resides in the mitochondrial succinic dehydrogenase complex (SDC) of sensitive Basidiomycetes such as Ustilago maydis, the corn smut fungus. The present study examines in detail the structure-activity relationships of 93 carboxamide compounds and the SDC of two carboxin-sensitive organisms, U. maydis and a Basidiomycetous yeast, Cryptococcus laurentii. It has been possible to elucidate substantially the requirement in molecular structure needed for inhibition of the mitochondrial SDC. With few exceptions, a good correlation exists between the inhibitory activity of carboxamides towards the SDC of U. maydis and C. laurentii and the inhibition of growth of carboxamide-sensitive fungi, both in vitro and in vivo on the diseased plant. The structure-activity results were used as a basis for the synthesis of new, fungicidally-active carboxamides. The compounds found to be most active against the mycelial growth of Rhizoctonia solani were also tested on spore germination or mycelial growth of non-Basidiomycete fungi. Three carboxanilides (3-methyl-thiophene-2-carboxanilide, 3′-methyl-2-methylbenzanilide and 3′-methyl-2-ethylbenzanilide) had a fungitoxic spectrum which extended beyond Basidiomycetes. The spectrum of fungicidal activity of carboxanilides appears to be altered not only by substitution in the aniline ring, but by the nature of the ring attached to the carbonyl. No correlation was found between the inhibitory activity of oxathiins and benzanilides and their calculated partition coefficients.     

Structure-activity relationships in fungitoxicants related to triforine and chloraniformethan. III. A quantitative hansch analysis

Quantitative structure-activity relationships in several series of fungitoxic N-(1-substituted-2,2,2-trichloroethyl)formamides and bis[1-(2,2,2-trichloroethyl)formamides] were investigated by the Hansch method, employing partitioning data determined by reversed-phase thin-layer chromatography and electronic parameters calculated by the Hückel Molecular Orbital method. The activity of compounds applied as root-drenches against Erysiphe graminis on barley correlated with their partitioning properties alone, but electronic properties of the aromatic derivatives were also influential in leaf-spray tests. Possible factors governing the activity of the compounds are discussed. It is tentatively proposed that the biologically active centre of triforine and related aliphatic compounds includes the XCHNHCO grouping (where X = heteroatom), whereas that of chloraniformethan and its aryl analogues incorporates the grouping RXCHNHCO (where RX = a conjugated system capable of accepting pi-electrons from an electron donating receptor).     

Structure-activity relationships of 1,2,3-benzothiadiazoles as synergists for carbaryl against the house fly (Musca domestica)

Fifty six 1,2,3-benzothiadiazoles and related compounds were evaluated as carbaryl synergists against the house fly (Musca domestica). Many of these were excellent synergists, the most active being those containing various combinations of halogen, alkyl, or alkoxy substituents in the 5- and/or 6-positions of the ring.Regression analysis on the data from 14 compounds for which substituents constants were available established that synergistic activity can be satisfactorily described by equations in terms of the hydrophobic bonding constant (π) and the homolytic free radical constant (σ ·).The results with compounds related to the 1,2,3-benzothiadiazoles suggest that synergistic activity is associated primarily with the diazosulfide moiety.     

Structure-activity relationships in a group of azoles,with special reference to 1,3-dioxolan-2-ylmethyl derivatives

Substituted imidazoles and substituted 1,2,4-triazoles are active to varying degrees in the control of fungi pathogenic to plants, animals and man. The relationship between chemical structure and their antifungal activity, both in-vitro and in-vivo, is reviewed.