(2E,4Z )-Decadienoic acid and (2E,4Z,7Z )-decatrienoic acid,two herbicidal metabolites from Streptomyces viridochromogenes Tü 6105

Two fatty acids, (2E,4Z)-decadienoic acid and (2E,4Z,7Z)-decatrienoic acid, the latter being described for the first time as a natural product, were detected in the culture filtrate of Streptomyces viridochromogenes Tü 6105 by HPLC-diode array screening, purified by chromatographic methods and structurally elucidated by NMR techniques. Both metabolites show strong herbicidal activity against Lemna minor and Lepidium sativum. The herbicidal activities of the isolated compounds were compared with those of similar fatty acids and derivatives. © 1999 Society of Chemical Industry     

Screening,identification, and observation of infection process of a herbicidal fungal strain HY-02

This study clarified the herbicidal activity, crop safety, classification status, and infection process of herbicidal strain HY-02, and laid a foundation for its development and utilization. Strain HY-02 was isolated from the leaves of Rumex patientia L. by the tissue isolation method. The pathogenicity of the strain to six broadleaf weeds and the safety for four common crops were determined by spray inoculation. The taxonomic status of HY-02 was determined by morphology and molecular biology, and the infection process was confirmed by scanning electron microscopy. In vitro leaf experiments showed that strain HY-02 was pathogenic to six broadleaf weeds, Polygonum aviculare L., Elsholtzia densa Benth., Chenopodium album L., Polygonum lapathifolium L., Amaranthus retroflexus L., and Malva verticillata L. The pot experiment of weeds found that the pathogenicity rates for P. aviculare, E. densa, C. album, P. lapathifolium, A. retroflexus, and M. verticillata were 100.00%, 94.44%, 95.24%, 83.33%, 73.02%, and 40.00%, respectively. Strain HY-02 seemed safe for four crops (Hordeum vulgare L., Triticum aestivum L., Vicia faba L., and Pisum sativum L.), but not for Brassica napus L. The strain was identified as Alternaria alternata (Fries) Keissler. Scanning electron microscope observations showed that hyphae invaded leaf tissues from the stomata by destroying epidermal cells. Hyphae rapidly grew and invaded living tissues by obtaining nutrients from the tissues, destroying the whole leaf tissues, and finally forming reticular lesions. Therefore, the HY-02 strain has the potential to be developed into microbial biocontrol agents for weed control.     

Herbicidal activity of derivatives of 9-aminofluoren-9-ylphosphonic acid

A series of derivatives of 9-aminofluoren-9-ylphosphonic acid (phosphonic analogues of morphactins) were synthesized and screened for herbicidal activity against Lepidium sativum, Cucumis sativus and Lycopersicon esculentum. Ethyl 9-(N-alkylamino)fluoren-9-yl(phenyl)phosphinates appeared to be equipotent with glyphosate and thus may be recognized as new lead compounds for further structural modifications.     

Mode of action of new diethylamines in lycopene cyclase inhibition and in photosystem II turnover

The new bleaching herbicidal compound N,N‐diethyl‐N‐(2‐undecynyl)amine (NDUA) is identified here as an inhibitor of lycopene cyclase and is compared with the known cyclase inhibitors N,N‐diethyl‐N‐[2‐(4‐chlorophenylthio)ethyl]amine (CPTA) and N,N‐diethyl‐N‐[2‐(4‐methylphenoxy)ethyl]amine (MTPA). HPLC separation of chloroplast pigments shows lycopene accumulation in NDUA treated tissue. Variation in chain length of the undecynylamine moeity of NDUA from 7 to 21 C atoms reveals an optimum of 11 to 14 C atoms for herbicidal activity. A series of seven further analogues of NDUA and CPTA reveals the structural elements necessary for inhibition of lycopene cyclase. The effect of NDUA derivatives on photosynthesis has been studied in Chlamydomonas reinhardtii. Photosynthesis is highly sensitive, particularly towards the C14 and longer chain length analogues at nanomolar concentrations. It is shown that the breakdown of photosynthesis by NDUA is due to interference with the turnover of the D1 protein of the photosystem II reaction centre that requires the continous biosynthesis of the two reaction‐centre β‐carotene moieties in the reassembly phase. The D1 protein disappearance is most marked under strong light conditions. The depletion of photosystem II occurs before total pigment bleaching. This newly recognized mechanism in herbicidal activity is also the basis for the mode of action of other lycopene cyclase inhibitors as well as phytoene desaturase inhibitors. © 2001 Society of Chemical Industry     

Synthesis and herbicidal potential of substituted aurones

BACKGROUND: With the objective of exploring the herbicidal activity of substituted aurones, a series of 4,6‐disubstituted and 4,5,6‐trisubstituted aurones were synthesised, and their herbicidal activities against Brassica campestris L. and Echinochloa crusgalli (L.) Beauv. were evaluated in laboratory bioassays. Effects of some of the compounds were evaluated on seed germination. The most active compounds in the laboratory were evaluated in the greenhouse. RESULTS: The compounds were characterised by ¹H NMR, ¹³C NMR and HRMS; some of them were further identified by IR. A (Z)‐configuration was assigned to the aurones, based on spectroscopic and crystallographic data. Bioassay results of root growth showed that the aurones had a moderate herbicidal activity against the dicotyledonous plant Brassica campestris. (Z)‐2‐Phenylmethylene‐4,6‐dimethoxy‐3(2H)‐benzofuranone(6o) was the most active compound, with 81.3 and 88.5% inhibition at 10 and 100 µg ml^?1 respectively, equal to the activity of mesotrione. Some of the aurones possessed some inhibition of germination on several plant species. For glasshouse tests, the substituted aurones had lower herbicidal activity than metolachlor and mesotrione. CONCLUSION: It is possible that aurone derivatives, which possess structures different from those of the commercial herbicides, may become novel lead compounds for the development of herbicides against dicotyledonous weeds with further structure modification. Copyright © 2012 Society of Chemical Industry     

Plant growth regulating properties of 1-amino-1-methylethylphosphonic acid and its derivatives

Seventeen derivatives of 1-amino-1-methylethylphosphonic acid were synthesised and evaluated for plant-growth-regulating activity using Cucumis sativus and Triticum aestivum. The tested compounds exerted either moderate herbicidal action or stimulated plant growth. The structure-activity relationships were similar to those observed earlier for the derivatives of 9-aminofluoren-9-ylphosphonic acids (phosphonic analogues of morphactins).     

异香豆素噁二唑类化合物的合成及除草活性

为了寻找具有较高除草活性的异香豆素类化合物,设计合成了16个新型异香豆素噁二唑类化合物4a～4p,其结构均经核磁共振氢谱、碳谱及高分辨质谱确证。初步除草活性测定结果表明,部分目标化合物在500 mg/L下对马唐Digitaria sanguinalis L.和反枝苋Amaranthusretroflexus L.具有一定的除草活性,其中化合物4j（4-[5-（4-氯-苯基）-[1,2,4]二唑-3-基]-3-己基-6,7-二甲氧基异香豆素）的活性最好,对马唐和反枝苋的致死率分别为64%和62%。     

阿魏酸衍生物的合成及其除草活性测定

为从天然产物中获取新的除草活性成分,通过化学合成的方法对分离自瓜果腐霉Pythium aphanidermatum代谢产物中的阿魏酸进行了结构改造,并采用小杯法,以马唐、马齿苋和播娘蒿为供试杂草对所得化合物进行了除草活性测定。结果显示:所合成的4-羟基-3-甲氧基肉桂酸乙酯、4-羟基-3-甲氧基肉桂酸邻氯苯胺、4-羟基-3-甲氧基肉桂酸酰肼、4-羟基-3-甲氧基肉桂酸叔丁酯和4-乙酰氧基-3-甲氧基肉桂酸5种化合物的回收率分别为96.81%、97.39%、82.20%、75.67%和98.29%。4-羟基-3-甲氧基肉桂酸酰肼和4-乙酰氧基-3-甲氧基肉桂酸对马齿苋胚根的抑制活性最强,IC50分别为87.50 mg/L和74.86 mg/L,其余3种活性相对较弱;4-羟基-3-甲氧基肉桂酸乙酯和4-乙酰氧基-3-甲氧基肉桂酸分别在500 mg/L和1 000 mg/L浓度下可完全抑制播娘蒿和马齿苋胚根、芽的生长,而4-羟基-3-甲氧基肉桂酸邻氯苯胺则在1 000 mg/L浓度下可完全抑制播娘蒿胚根的生长。表明在阿魏酸分子中的不同位点引入适当的基团结构可以提高或者降低阿魏酸分子的除草活性,并获得新的除草活性物质。     

棉籽壳中除草活性物质提取及鉴定

为了开发利用棉籽壳中的除草活性物质，分别以无水乙醇、正丁醇、石油醚和乙酸乙酯为溶剂，采用索氏提取法对棉籽壳中的活性物质进行了提取，并对各溶剂粗提物进行了除草活性测定。结果发现:用无水乙醇提取的粗提物对稗草生长的抑制活性最高，经气相色谱-质谱(GC-MS)联用分析，发现该粗提物中主要含有甘油、三环己基3-烯-6-辛酮、4-乙烯基-2-甲氧基苯酚、(邻甲基苯酚)-2-溴-2氯-乙酰酯、十四酸、十四酸乙酯、十六烷酸、辛酸异戊酯和亚油酸9种化合物。进一步的除草活性测定结果表明，亚油酸、辛酸异戊酯、4-乙烯基-2-甲氧基苯酚和(邻甲基苯酚)-2-溴-2氯-乙酰酯4种化合物对稗草表现出一定的除草活性，其中亚油酸活性最强，其IC₅₀值为14.5 mg/L。     

Phosphonic analogues of morphactins. Part IV: 9-aminofluoren-9-ylphosphine oxides

9-Aminofluoren-9-ylphosphine oxides and the corresponding 9-hydroxy analogues were synthesised and evaluated for herbicidal activity using Spirodela oligorrhiza (Kurz.) Hegelm. All the test compounds were highly active at concentrations of about 10 μM and were comparable with the corresponding phosphonic esters.     

含肟醚并取代异 NFDA1唑环的氨基甲酸酯类化合物的合成及生物活性

为寻找具有优异生物活性的氨基甲酸酯类化合物,根据活性亚结构拼接原理,将取代异 NFDA1 唑和肟醚基团引入多菌灵结构中,以取代苯甲醛 (1) 和2-氯苄胺(3) 为起始原料,经多步反应设计合成了10个未见文献报道的含肟醚并取代异 NFDA1 唑的氨基甲酸酯类化合物,其结构经 1H NMR 和 MS 确证。初步生物活性测定结果表明,部分目标化合物不仅具有一定的杀菌活性,同时还具有较好的除草活性。其中,活体盆栽试验结果表明,化合物11b对黄瓜霜霉病Pseudoperonospora cubensis 的相对防效为90%,对黄瓜白粉病Sphaerotheca fuliginea 的相对防效达95%,低于对照药剂多菌灵;除草活性皿测法表明,化合物11c和11j 200 mg/L下对靶标作物的根、茎抑制率均达80%以上,与对照药剂异丙酯草醚活性相当。盆栽法表明,150 g/hm2下,化合物11c和11j对繁缕Stellaria media苗前和苗后的抑制率均在70%以上,低于异丙酯草醚。此类化合物的构效关系有待进一步研究。     

Modeling root absorption and translocation of 5-substituted analogs of the imidazolinone herbicide,imazapyr

Quantitative structure-activity relationships (QSAR) were developed between the physicochemical parameters of the 5-substituent of a series of analogs of the imidazolinone herbicide, imazapyr, and root absorption, translocation, inhibition of acetohydroxyacid synthase (AHAS), and herbicidal activity of the analogs. An optimum substituent lipophilicity (π = 1.85–2–3) for root absorption was identified for corn (Zea mays L.) and sunflower (Helianthus annuus L.). Translocation from roots to shoots was greatest for those analogs having either highly nonpolar or highly polar 5-substituents, indicating that both symplastic and apopiastic mechanisms may be functioning. In addition, translocation from roots was positively correlated with electron-withdrawing parameters of the 5-substituent, and a possible mechanism governing this relationship is discussed. Modeling in vitro AHAS inhibition was not successful, but models were developed for herbicidal activity as measured in an Arabidopsis thaliana (L.) Hevnh. bioassay. The whole-plant models described an optimum substituent lipophilicity (π = 0 71) which probably reflected the influence of this parameter on the component processes of absorption and translocation. Whole-plant activity was also greater for analogs having electron-donating 5-substituents; this result suggests that electron donation may be important for metabolism, or more likely, for AHAS inhibition.     

Investigation of an emulsifiable oil adjuvant and its components on the activity of a new grass herbicide by factorial experimentation

The herbicidal activity of a new compound [(±)-(EZ}-2-[1-allyloxy-imino)propyr]-3-hydroxy-6-(4-cyanophenyl)cyclohex-2-ene-1-one] (I) , selective to broad-leaf plants, and partially selective in some cereal crops was enhanced by an emulsifiable paraffinic oil (HVI 60E). In order to determine the amount of HVI 60E to be applied with an emulsifiable concentrate of I (IE) a factorial herbicidal assay involving six concentrations of I and five concentrations of HVI 60E (both sets including zero concentration) was conducted to obtain response surfaces of herbicidal activity. The total selectivity of IE in broad-leaf species remained for all HVI 60E concentrations. The activity against grass weeds, except Poa annua L., increased markedly with increasing HVI 60E concentration and enhancement of performance of IE by HVI 60E in broad-leaf crops could be pursued without fear of crop phytotoxicity. However, the increases in activity against grass weeds were accompanied by increases in phytotoxicity against cereal crops. The response surfaces of Echinochloa crus-galli(L.) Beauv. and Zea mays L. were coincident and this result terminated further testing in this outlet. However, the response surfaces of Avena fatua L. and Triticum aestivum L. were reasonably well separated. Further tests in this outlet and in broad-leaf crops are planned around optimum cost-performance ratios derived from combinations with cost-response surfaces. The results of a further lest showed that both components (oil and emulsifier) of HVI 60E were approximately equivalent in adjuvant enhancement activity and so, on cost grounds, a crop oil (low emulsifier content) would be preferred over a crop oil concentrate (high emulsifier content).     

10种N-取代氨基香豆素的合成及生物活性

基于结构拼接思想,设计合成了10个N-取代氨基香豆素类化合物,并测定了其抑菌及除草活性。6-硝基香豆素经Fe/NH4Cl还原得6-氨基香豆素,再与不同醛缩合得Schiff碱,最后经硼氢化钠还原制得10个N-取代氨基香豆素类化合物(4a~4J),其中9个未见文献报道,其结构均经红外光谱、核磁共振氢谱和质谱确认。抑菌活性测试结果表明,所有化合物对苹果腐烂病菌Valsa mali、葡萄白腐病菌Coniothyrium diplodiella、棉花枯萎病菌Fusarium oxysporium和柑橘炭疽病菌Citrusanthrax bacteria均有一定抑制作用,其中 4e 的抑菌活性最强,对苹果腐烂病菌和柑橘炭疽病菌的EC50值分别为7.53和12.93 mg/L,对其余2种植物病原菌的EC50值均小于25 mg/L;化合物 4f 次之,对苹果腐烂病菌和葡萄白腐病菌的EC50值均约为11 mg/L。除草活性测试结果表明,除 4f 外,所有目标化合物均有一定除草作用,其中 4c 的活性最强,100 mg/L下对反枝苋Amaranthus retroflexus种子根、茎生长的抑制率均为99%。     

4-羟基-3-甲氧基肉桂酸乙酯的生物活性及其除草作用机制

为明确以天然产物阿魏酸为母体进行化学结构改造得到的化合物4-羟基-3-甲氧基肉桂酸乙酯的生物活性及其除草机制,利用茎叶喷雾法和小杯法测定其对马唐和反枝苋的生物活性,基于生理生化指标及功能基因表达量对其除草作用机制进行研究。结果表明:4-羟基-3-甲氧基肉桂酸乙酯对马唐茎叶鲜重抑制中浓度IC50为46.27 mg/L;对反枝苋胚根和芽的IC50分别为129.94 mg/L和147.33 mg/L,且在500 mg/L浓度处理时可抑制反枝苋种子萌发;对拟南芥根长的IC50为43.82 mg/L,在160 mg/L浓度处理时拟南芥几乎停止生长、叶片发黄、根毛堆积。该化合物以1 000 mg/L浓度处理马唐叶片2、3、8 h后,电导率较对照组分别增加了22.70%、18.46%和25.62%;1 000 mg/L浓度处理下叶绿素a/b为2.43,较对照的3.62显著下降;处理后叶表微观结构观察发现化合物浓度越大,植物叶片表皮毛倒伏和褶皱越严重;拟南芥AT4G04820基因表达量显著下降,在处理45 min时下降最显著,与对照组相差42.52倍,微管蛋白含量下降,造成微管解离,从而抑制植物生长。表明4-羟基-3-甲氧基肉桂酸乙酯具有较强的除草活性,可能通过破坏细胞结构、抑制光合作用及阻止根生长等途径使杂草生长受到抑制甚至死亡。     

Suppression of Cyperus rotundus L. in carrots with night applications of nitrofen or herbicidal oil*

Selective control or suppression of Cyperus rotundus L. in carrot (Daucus carota L.) was investigated in Brazil using post-emergence applications of nitrofen (2,4-dichlorophenyl 4-nitrophcnyl ether) or a herbicidal oil (11–7% aromatics). Night applications of nitrofen in water, nitrofen in the herbicidal oil and the herbicidal oil alone were more effective in suppressing the growth of C. rotundus foliage than day applications. Nitrofen and the herbicidal oil were, respectively, 50 and 30% more active in suppressing C. rotundus during the warm, wet season (October to March) than the cool, dry season (April to September) in Viçosa. Night applications of nitrofen (1, 2 and 4 kg/ha) in water and the herbicidal oil alone (100, 200 and 400 1/ha) suppressed C. rotundus by 60% or more, and resulted in similar carrot yields to the hand-weeded control. Combinations of nitrofen in the herbicidal oil were more effective in suppressing C. rotundus than either herbicide applied alone, but the combinations tested were toxic to the carrots. Elimination du Cyperus rotundus L. dans les cultures de carrottes au moyen d'applications nocturnes de nitrofène ou d'une huile herbicide..     

The rational design of the optically active wild oat herbicide L-flamprop-isopropyl

An esterase, that has been partially purified from oat tissues, catalyses the hydrolysis of the wild oat herbicide benzoylprop-ethyl and of the related esters of N-benzoyl-N-(3-chloro-4-fluorophenyl)-DL -alanine, including flamprop-methyl and flampropisopropyl. The enzyme is virtually stereospecific for the L -isomers in the racemic mixtures. Hydrolysis of flamprop-methyl in oat tissues shows similar enantiomeric discrimination, but the ethyl and isopropyl ester analogues are converted in vivo to the free acid with very little overall stereoselectivity. Oat tissues must, therefore, contain another enzyme, labile to isolation, that acts on the D -isomers of the higher esters. This was confirmed by showing that it is possible to manipulate the stereoselectivity of the de-esterification of the ethyl ester in vivo by selective inhibition of either the L -isomer pathway with paraoxon (diethyl 4-nitrophenyl phosphate), or the D -isomer route with piperonyl butoxide. The relationship of these findings to the superior herbicidal performance of the L -isomers of these esters, relative to their racemates, is discussed.     

Characterization of new photosynthesis-inhibiting imidazolidine derivatives. 1. Interpretation of post-emergence herbicidal performance from photosynthesis-inhibiting activity and systemicity

An attempt was made to account for quantitatively measured herbicidal performance of foliage-applied 5-hydroxy-3-methyl-2–oxo-imidazolidine-1-carboxamide derivatives by their photosynthesis-inhibiting activity and systemicity. Photosynthesis-inhibiting activity was estimated from the increase of chlorophyll fluorescence intensity in Chlorella vulgaris Beijer cells measured by a microplate scanner, and systemicity was also evaluated by computer-aided chlorophyll fluorescence imaging. The highest herbicidal performance was recorded for N-cyclohexyl-5-hydroxy-3-methyl-2-oxo-imidazo～idine-l-carboxamide, a compound with the second strongest photosynthesis-inhibiting activity and intermediate systemicity. Though neither photosynthesis-inhibiting activity nor systemicity showed significant correlation with the actual herbicidal performance in simple regression analyses, a high predictability was found for a multiple regression on both parameters as two independent variables, suggesting that these two factors work cooperatively in the field performance.     

Characterization of new photosynthesis-inhibiting imidazolidine derivatives. 2. Interpretation of pre-emergence herbicidal performance from photosyghesis-inhibiting activity and soil adsorption coefficient

Ruling factors governing pre-emergence herbicidal activity were analysed for 16 photosynthesis-inhibiting 5-hydroxy-3-methyl-2–oxo-imidazolidine-1-carboxamide derivatives. Herbicidal performance was quantified by the reduction in area of experimental weed vegetation, measured by a computer-aided image analysis system. A system for fluorometric estimation of photosynthesis inhibitor concentration in aqueous solution greatly facilitated determination of the soil adsorption coefficients (K_d). Maximum herbicidal performance was found for N-sec-butyl-5-hydroxy-3-methyl-2-oxo-imidazolidine-1-carboxamide, a compound with the second lowest soil adsorptivity and average photosynthesis-inhibiting activity. A multiple regression analysis suggested that herbicidal performance of the soil-applied imidazolidine derivatives was determined by a balance between K_d and photosynthesis-inhibiting activity. In the present experimental system, however, the main influence was attributed to K_d.     

Dimethoxypyrimidines as Novel Herbicides. Part 2. Synthesis and Herbicidal Activity of O-Pyrimidinylsalicylates and Analogues

A new series of the O-pyrimidinylsalicylates was synthesized and their herbicidal activity was examined. Some of these compounds showed very strong herbicidal activity under pre- and post-emergent treatment conditions against various kinds of grass and broadleaf weeds. Among these compounds, O-(4, 6-dimethoxypyrimidin-2-yl) salicylic acid and its methyl ester were found to exhibit the highest activity. The herbicidal symptoms observed after the treatments included early cessation of plant growth followed by chlorosis, necrosis and plant death. The symptoms were similar to those caused by sulfonylureas and imidazolinones, which inhibit branched-chain amino acid biosynthesis.