Li-hui Zhang

The Extraction, Isolation and Identification of Exudates from the Roots of Flaveria bidentis

Large amounts of ”Flaveria bidentiss” root culturing solution were obtained by using DFT (deep flow technique) equipment and these solution which was vacuum concentrated (10, 20 mg mL^(-1)) can have a certain inhibition on ”Triticum aestivum”, ”Cucumis sativus”, ”Raphanus sativus”, ”Amaranthus retroflexus”, ”Setaria viridis”, ”Chenopodium album”, ”Echinochloa crusgalli” and ”Chloris virgata”. This outcome suggested some active compounds in the root exudates of ”Flaveria bidentis” can inhibit the germination, seedling elongation and root length. The dichloromethane extract of root exudates was identificated by GC-MS, and 29 kinds of compounds, including esters, hydrocarbons, ketones, thiazole, amines, etc. were obtained and the phthalate n-octyl ester, phthalate 2-ethylhexyl ester were proved to be allelochemicals. The culturing solution of root exudates was separated through the resin column and silica gel column and a component inhibiting seedling height, root length and fresh weight of wheat was got. There were 6 kinds of organic compounds in this component including dioctyl phthalate, 1,2-phthalate, mono(2-ethylhexyl) ester by GC-MS.

Isolation, Identification, and Herbicidal Activity of Metabolites Produced by Pseudomonas aeruginosa CB-4

Abstract CB-4, a bacterial strain with highly effective herbicidal activity, was isolated from infected corn leaves. Through morphology, physiological and biochemical tests, and 16S ribosomal DNA gene sequencing methods, CB-4 was identified as Pseudomonas aeruginosa . We conducted activity-evaluation experiments in the laboratory to assess the herbicidal potential of metabolites produced by strain CB-4. Crude extracts of strain CB-4 have high inhibition activity on Digitaria sanguinalis. In general, the root and shoot growth parameters of D. sanguinalis were significantly reduced by metabolites of strain CB-4. The IC 50 of the culture filtrate extracts for the radicula and coleoptile of D. sanguinalis were 0.299 and 0.210 mg mL −1 , respectively. Component 2 of the herbicidal activity of the crude toxin from strain CB-4 was successfully purified for the first time by using high-speed counter current chromatography with a two-phase solvent system composed of petroleum ether-ethyl acetate-methanol-water (4:5:4:5, v/v) and high-performance liquid chromatography. We concluded that the metabolites of strain CB-4 have the potential to be developed as a microbe-based herbicide.

Purification and Structural Analysis of a Selective Toxin Fraction Produced by the Plant Pathogen Setosphaeria turcica

Thirteen fractions from the pathogenic plant fungus Setosphaeria turcica race 1 were separated and collected using high performance liquid chromatography (HPLC). Their toxic activities were assayed through leaf puncturing on corn differentials (OH43, OH43Ht1, OH43Ht2, and OH43HtN), and the results revealed that eight fractions were toxic and fraction 6 was specifically toxic to OH43Ht1, which could be taken as a gene-selective toxin fraction. Fraction 6 was finely purified via HPLC and condensed by freeze desiccation. Its chemical structure was analyzed with EI-MS, IR, HMBC, 1H-NMR, and two-dimensional NMR. The results suggested that fraction 6 contained an unsaturated double bond, carbonyl and methylene groups with molecular weight of 142.

Isolation and Structural Indentification of Herbicidal Toxin Fractions Produced by Pythium aphanidermatum

Abstract In order to understand the compsition and structure of herbicidal component of Pythium aphanidermatum, the isolation and structural indentification were researched. The culture filtrate was extracted by ethyl acetate, petroleum, and chloroform with the same volume respectively and the activity of the crude toxin was bioassayed. The toxin was separated by using the method of thin layer chromatography (TLC), then the main fraction was separated by HPLC, and the structure was analyzed by the sepctrum of IR, 13C-NMR and 1HNMR. The results showed that the ethyl acetate extracts had the strongest herbicidal activity. Using the method of TLC, the bioassay results showed that the extracts with Rf 0.19 had the strongest effect on weeds and the inhibition to Digitaria sanguinalis and Amaranthus retroflexus reached five levels, and the component was proved to be dimethyl o-phthalate from the spectrum of IR, 13C-NMR and 1HNMR, which was one of the components from the toxin, and it had herbicidal activity.

Isolation and Structural Speculation of Herbicide-Active Compounds from the Metabolites of Pythium aphanidermatum

Natural herbicides, or environment-friendly bioherbicides have been attracted more and more attentions. Isolation and structural identification of natural herbicide-active compounds from plant pathogens has been proved to be an effective approach for novel lead discovery of the pesticide development. In this study, the metabolites of the mutant strain PAM1, which obtained from PA1 of Pythium aphanidermatum (Eds.) Fitzp by ultraviolet radiation were separated and identified by HPLC, NMR, and IR. The results revealed that three active compounds including 4-hydroxy-3-methoxycinnamic acid and two indole derivatives, exhibited inhibition activity on the elongation of radical and coleoptile of Digtaria sanguinalis (L.) Scop.

The Herbicidal Activity of Mutant Isolates from Botrytis cinerea

Fifteen mutant isolates were obtained by ultraviolet mutation from parent isolate Botrytis cinerea BC-4. Among them three mutant isolates, BC4-1, BC4-2, and BC4-15, showed strong herbicidal activity. BC4-1 showed maximum herbicidal activity for inhibition of germination and growth of Digitaria sanguinalis L. and Amaranthus retroflexus L. The results also showed that herbicidal activity was influenced by differing pH of PD media, with pH value of 4.0 being the optimum. The crude toxin was extracted using chloroform, petroleum ether, and ethyl acetate, respectively, and the ethyl acetate extracts showed the strongest inhibitory activity on the germination and growth of D. sanguinalis L. and A. retroflexus L. Using HPLC, one fraction with an absorption peak at 271 nm was separated from the crude toxin. This fraction could strongly inhibit the growth of D. sanguinalis L. at a concentration of 100 mg L^(-1) and could completely inhibit the seed germination of D. sanguinalis L. and A. retroflexus L. at a concentration of 50 mg L^(-1).

Isolation and identification of Serratia marcescens Ha1 and herbicidal activity of Ha1 ‘pesta’ granular formulation

Abstract A total of 479 bacterial strains were isolated from brine (Bohai, Qinhuangdao City, Hebei Province, China). Bioassay results indicated that 4 strains named Ha1, Ha17, Ha38, and Ha384 had herbicidal activity. And strain Ha1 had the highest effective herbicidal activity. As a result, this study aims to identify strain Ha1, characterize its physiological and biological activities, evaluate the herbicidal activity of its metabolites, and develop a ‘pesta’ formulation and assess its effectiveness on Digitaria sanguinalis. Ha1 was identified as Serratia marcescens based on 16S rDNA sequencing. This strain has a flagellum, a diameter of 0.5 to 0.8 μm, and a length of 0.9 to 2.0 μm. The indole test shows positive results, and the catalase enzyme exhibits strong positive reactions. Results further showed that the inhibitory concentration (IC50) of the crude extracts to D. sanguinalis radicula and coleoptile were 3.332 and 2.828 mg mL−1, respectively. Both the suppression of D. sanguinalis and the cell viability of the Ha1 formulation in ‘pesta’ were higher when stored at 4°C than at (25±2)°C. These results indicated that S. marcescens Ha1 can potentially be used as a biocontrol agent against D. sanguinalis.

Isolation and Structural Identification of Herbicidal Active Substance from Root of Flaveria bident (L.) Kuntze

Abstract In order to understand the composition and structure of herbicidal active substance from the root of Flaveria bidentis (L.) Kuntze, the isolation and structural identification were researched in this paper. The crude extract from the root of F. bidentis (L.) Kuntze was extracted by petroleum ether, ethyl acetate, and water saturation of n-butyl alcohol, respectively, and the extraction fluid was separated by using the method of TLC, then the main fraction was separated by HPLC, and the structure of the herbicidal active substance was analyzed by LC-MS, elemental analysis and 1H-NMR. The results showed that the petroleum extraction had the strongest herbicidal activity, and the purple blue stripe separated by TLC had the strongest effect on Digitaria sanguinalis. The herbicidal active substance was identified as α-terthienyl according to the data of LC-MS, elemental analysis and 1H-NMR.

Analysis of the herbicidal mechanism of 4-hydroxy-3-methoxy cinnamic acid ethyl ester using iTRAQ and real-time PCR

Absolute quantitation (iTRAQ) is the latest development in the new quantitative proteomics technology for high-throughput identification and quantitation of proteins. The mechanisms underlying the 4-hydroxy-3-methoxy cinnamic acid ethyl ester treatment in Arabidopsis thaliana was investigated. Deficiency-induced changes in the protein profile of A. thaliana caused by this compound were analyzed using iTRAQ and quantitative real-time PCR. A total of 2909 proteins were quantified, of which 49 and 34 proteins were upregulated and downregulated, respectively, in the experimental plants compared with the controls. Treatment results showed that numerous proteins were involved in photosystemII, energy metabolism, and cell structure formation. Based on the upregulated and downregulated proteins, high amount of AT4G21280 protein acted on the oxygen-evolving enhancer protein 3-1, while low amount of AT1G10340 protein affected the catabolic process of the photosystemII-associated light-harvesting complex II. We selected these proteins to preliminarily verify the expression of proteins using quantitative real-time PCR to provide a reliable basis for further studies after proteomics analysis. Results show that the combined use of iTRAQ and quantitative real-time PCR provides an effective method to study proteins, leading to the determination of a new herbicide mechanism.