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    Effects of natural herbicide from tagetes erecta on echinochloa crus-galli (L.) beauv
    (2018-01-01)
    Wichittrakarn, P.
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    We studied the inhibitory effects of leaves extracts of Tagetes erecta on weed-seed germination and the mechanisms involved. Hydroethanolic crude extract (OR) from Tagetes erecta dried leaves was partitioned into four fractions: hydrolyzed (HY), aqueous (AQ), neutral (NE) and acidic (AE). The inhibitory effects of crude extracts and its fractions were evaluated on germination and seedlings growth of Echinochloa crus-galli (L.) Beauv. The total phenolic and flavonoid contents of each fraction were also determined. Germination and seedling growth were drastically inhibited by HY and AE followed by NE, OR and AQ. The HY and AE fractions had higher concentrations of both phenolics and flavonoids than other fractions. The HY fraction was selected as most potent for development as natural herbicide due to its high yield and strong inhibitory effects. The HY fraction was formulated into a soluble concentrate product (SCT) and its inhibition potential and modes of action were investigated. The SCT drastically inhibited the seed germination of E. crus-galli, inhibiting both imbibition, α-amylase activity and also seedling growth. Cytogenetic bioassays of SCT on root-tip cells of Allium cepa L. showed that it inhibited the mitosis and thereby the cell division. It is likely that a natural herbicide may be developed from the hydrolyzed fraction of a hydroethanolic extract of Mexican marigold leaves.
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    Structure-Activity Relationship Study of Xanthoxyline and Related Small Methyl Ketone Herbicides
    Xanthoxyline (1), a small natural methyl ketone, was previously reported as a plant growth inhibitor. In this research, related methyl ketones bearing electron-donating and electron-withdrawing groups, together with heteroaromatics, were investigated against seed germination and seedling growth of Chinese amaranth (Amaranthus tricolor L.) and barnyard grass [Echinochloa crus-galli (L.) Beauv]. The structure-activity relationships (SARs) of methyl ketone herbicides were clarified, and which types and positions of substituents were crucially important for activity were also clarified. Indole derivatives, namely, 3-acetylindole (43) and 3-acetyl-7-azaindole (44) were found to be the most active methyl ketones that highly suppressed plant growth at low concentrations. The molecular docking on the 4-hydroxyphenylpyruvate dioxygenase (HPPD) enzyme indicated that carbonyl, aromatic, and azaindole were key interactions of HPPD inhibitors. This finding would be useful for the development of small ketone herbicides.
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    Allelopathic potential of subfractions from aqueous extract of spirulina platensis and denatured c-phycocyanin
    In this laboratory bioassay, crude aqueous extract of Spirulina platensis (Nordst) Geitl. was extracted with 90% aqueous ethanol and 80% aqueous ethanol to achieve three subfractions, green powder (F1), pale-green powder (F2) and deep-blue powder (F3). Each of these subfractions was evaluated for allelopathic activity on Chinese amaranth (Amaranthus tricolor L.) and barnyardgrass (Echinochloa crus-galli (L.) Beauv.). The plant seeds were germinated in vials with three subfractions (250-2000 mg/l concentrations) and distilled water was used as a negative control. The results indicated that subfraction F3 had the highest inhibitory effect on both of the tested plants. All subfractions had an absorbance ratio (A620/A280) lower than the original aqueous extract, suggesting that a denaturation event of the C-phycocyanin (C-PC) component had occurred during the extraction process. After heating a commercial C-PC solution at 90<sup>o</sup>C for 3 h, the absorbance ratio changed to 0.46, and likewise allelopathic assay revealed that the decolorized C-PC solution retained its allelopathic potential on the tested plants. To confirm these findings, S. platensis powder was extracted with distilled water at 90<sup>o</sup>C for 3 h and tested for its allelopathic potential using standard Petri dish assay at concentrations of 0.625-5%. The results showed that the hot aqueous extract had an absorbance ratio of 0.38, and its allelopathic activities were similar to those of the aqueous extract. Furthermore, it was found that although C-PC in aqueous extractions denatured, it still retained its allelopathic potential on the tested plants.
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    Potential allelopathic effects of Suregada multiflorum and the influence of soil type on its residue's efficacy
    (2010-09-01) ;
    Boonleom, Chaninat
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    Thitavasanta, Sompop
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    This experiment was conducted to determine the potential allelopathic effects of the aqueous extracts and dried leaf powder of Suregada multiflorum and to find the herbicidal effects of its granule on the weed species, barnyardgrass (Echinochloa crus-galli) and slender amaranth (Amaranthus viridis), in various growth media (germination paper, sand, and soil). Observations in this study demonstrated that the potential and magnitude of their inhibitory effects varied among the plant parts. The leaves and branches possessed the strongest inhibition levels, followed by the bark. The aqueous extract from the leaves of S. multiflorum had a remarkably stronger inhibitory effect on the germination and growth of slender amaranth, compared with barnyardgrass; when applied at the concentration of 100-g-L<sup>-1</sup>, it completely inhibited the germination and initial seedling growth of slender amaranth. In addition, all the treatments of the dried leaf powder had stronger inhibition effects than the aqueous extract. Interestingly, the inhibitory effects of the dried leaf granule of S. multiflorum were stronger than the effects of the dried leaf powder at equal rates. The degree of inhibitory effect of the S. multiflorum granule, applied in various growing media, can be classified in order of decreasing inhibition as germination paper = sand > clay soil. The present study indicates that the S. multiflorum granule product that was developed in this research has the potential to provide a powerful organic herbicide for controlling slender amaranth. © 2010 The Authors. Journal compilation © 2010 Weed Science Society of Japan.
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    Inhibitory effects of a variety of aldehydes on Amaranthus tricolor l. And echinochloa crus-galli (L.) beauv.
    Thirty-seven commercial aldehydes containing aliphatic chains and aromatic rings as well as heteroaromatic rings were evaluated for their inhibitory activities against Chinese amaranth (Amaranthus tricolor L.) and barnyardgrass (Echinochloa crus-galli (L.) Beauv). Polysorbate 80 (Tween<sup>fi</sup> 80) was used as a surfactant and the research was preliminarily conducted at 400 µM of all aldehydes. Among these aldehydes, (E)-cinnamaldehyde (7) showed the greatest inhibitory effect on seed germination, shoot and root growth of Chinese amaranth by 54.55%, 75.53%, and 85.13% respectively. Similarly, (E)-crotonaldehyde (5), a related α,β-unsaturated aldehyde, inhibited the germination and seedling growth of the tested species at a high percentage. Apart from these two unsaturated aldehydes, no other aliphatic aldehydes had a harmful effect on Chinese amaranth. In terms of benzaldehyde (6), it had no effect on the tested plant; however, many of its derivatives displayed some inhibitory activity. Furthermore, for the ten common heteroaromatic aldehydes, picolinaldehyde (32) had a high inhibitory effect on Chinese amaranth which closely related to the effect of (E)-crotonaldehyde (5) and (E)-cinnamaldehyde (7), whereas, other heteroaromatic aldehydes showed lower effects. In the case of a monocot plant, barnyardgrass, no tested aldehydes reduced seed germination, however, (E)-cinnamaldehyde (7), 2,4,6-trimethoxybenzaldehyde (16) and 4-(dimethylamino)benzaldehyde (24) could inhibit the seedling growth of the plant with low to moderate levels. The herbicidal effects of the most active aldehydes were then further investigated in order to find the minimum concentration of these aldehydes suppressing the germination and growth of the tested plants. At concentrations as low as 50–100 µM some aldehydes could inhibit the seedling growth of the tested species. The structure-activity relationship (SAR) study reported here demonstrates the chemical clues governing the inhibitory activity of aldehydes which could be utilized in the development of highly effective herbicides in the near future.
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    Development of a Melia azedarach L. based natural herbicide: formulation and efficacy studies
    (2025-08-01)
    Wichittrakarn, Pattharin
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    Manichart, Nutcha
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    This study evaluated the phytotoxic activity of Melia azedarach L. leaf extract against Echinochloa crus-galli and Phaseolus lathyroides. Crude extracts were obtained using sequential solvent separation, of which the dichloromethane fraction exhibited the highest phytotoxicity for both weed species. However, P. lathyroides appeared more sensitive to the extracts compared to E. crus-galli. GC-MS analysis of the dichloromethane crude extract identified phytol (29.14 %), linolenic acid (21.74 %), and palmitic acid (7.20 %) as the main chemical components. Three formulations, a soluble liquid (SL), pellet, and wettable powder, were developed and evaluated for their effects on seed germination and seedling growth. The SL formulation showed the highest efficacy in inhibiting germination (p < 0.05). Further testing of its pre-emergence utility via soil application in greenhouse conditions confirmed the herbicidal efficacy, effectively suppressing P. lathyroides emergence (36.8 % over control) and reducing growth parameters. Mechanistic assays showed the SL product to affect seed imbibition, α-amylase activity, and cell division in a dose-dependent manner, suggesting these as potential mechanisms of action. This study highlights the potential of a M. azedarach-based SL product as an alternative to synthetic herbicides, potentially leading to the development of a new botanical herbicide.
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    Bioassay-Guided Extraction and Isolation of Natural Herbicides from Dried Zanthoxylum limonella Alston Fruits
    Weeds are problematic plant species around the world. Various strategies exist for controlling weeds, but chemical treatment remains the preferred method, particularly when using natural substances. In this research, a crude aqueous-methanol extract from dried Zanthoxylum limonella fruits was acid-base partitioned into four fractions: neutral extract (NE), acid extract (AE), basic extract (BE), and aqueous extract (AQ). These fractions were further separated into seventeen subfractions: NEF1 to NEF7, AEF1 to AEF5, and BEF1 to BEF5, which were then tested for herbicidal activity against the growth of Chinese amaranth (Amaranthus tricolor) and barnyard grass (Echinochloa crus-galli). Active subfractions were isolated via column chromatography and identified using spectroscopic methods, yielding seven active compounds: xanthoxyline (1), tambulin (2), atanine (3), prudomestin (4), skimmianine (5), p-methoxybenzoic acid (6), and methyl caffeate (7). Compounds 2–7 had not been previously reported in Z. limonella. Xanthoxyline (1) was identified as the most potent botanical herbicide, fully inhibiting seed germination of Chinese amaranth and barnyard grass. This compound also decreased seed imbibition and α-amylase activity in both species. Molecular docking studies on the α-amylase enzyme (PDB ID: 1BG9) revealed that the aromatic, hydroxy, and carbonyl groups of xanthoxyline (1) interact with the enzyme's active sites.
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    Evaluation of allelopathic, decomposition and cytogenetic activities of Jasminum officinale L. f. var. grandiflorum (L.) Kob. on bioassay plants
    Methanolic extracts prepared from dried leaves of Jasminum officinale f. var. grandiflorum (L.) Kob. (Spanish jasmine) inhibited seed germination and stunted both root and shoot length of the weeds Echinochloa crus-galli (L.) Beauv. and Phaseolus lathyroides L. The main active compound was isolated and determined by spectral data as a secoiridoid glucoside named oleuropein. In addition, a decrease in allelopathic efficacy appeared as the decomposition periods increased. The mitotic index in treated onion root tips decreased with increasing concentrations of the extracts and longer periods of treatment. Likewise, the mitotic phase index was altered in onion incubated with crude extract. Furthermore, crude extract produced mitotic abnormalities resulting from its action on chromatin organization and mitotic spindle. © 2010 Elsevier Ltd. All rights reserved.
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    Effects of Spirulina platensis and C-phycocyanin on seed germination and seedling growth of two monocot and dicot plants
    (2010-01-01) ;
    Chotsaeng, P.
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    In laboratory bioassay the allelopathic effects of Spirulina platensis (nordst) Geitl. were investigated on Chinese amaranth (Amaranthus tricolor L.), Chinese mustard (Brassica campestris var. chinensis), barnyardgrass (Echinochloa crus-galli [L.] Beauv.) and rice (Oryza sativa L.). The seeds were germinated in Petri dishes with aqueous extract (0.625-5% concentrations) and crude organic extract (250-4000 ppm concentrations) distilled water used as control. All aqueous extracts influenced the seed germination and seedling growth of dicotyledons (A. tricolor and B. campestris). The aqueous extract of 1.25% and 2.50% concentration completely inhibited the germination in dicots. In monocots (barnyardgrass and rice), the aqueous extract of 2.50% concentration inhibited the root length, while the 5% concentration completely inhibited their germination and seedling shoot length. The UV-VIS spectra indicated that the aqueous extract contained C-phycocyanin (C-PC), with a purity ratio (A <inf>620</inf>/A<inf>280</inf>) of 1.17. The allelopathic activity of biologically active protein pigment, C-PC, was assayed on seed germination and seedling growth at 62.50-1000 ppm concentrations. At 1000 ppm, this compound was most inhibitory to shoot and root length of A. tricolor and B. campestris, but there was no effect on germination. The crude ethyl acetate extract was most inhibitory to dicots, but all three crude organic extracts were not inhibitory to monocots.
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    Allelopathic potential of Chinese rice flower (aglaia odorata Lour.) as organic herbicide
    (2009-01-01) ;
    Poonpaiboonpipat, T.
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    Phuwiwat, W.
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    Mongkolaussavaratana, T.
    The aqueous extracts of leaf and branches of Aglaia odorata inhibited the germination and seedling growth of bamyardgrass (Echinochloa crus-galli (L.) Beauv.) and wild pea (Phaseolus lathyroides L.) over the control. Besides its dry leaf powder (31.25, 62.5, 125 and 250 mg/plate) was more inhibitory to these parameters than aqueous extract. Furthermore, the inhibitory effects of dried leaf pellets of Chinese rice flower were more stronger than dried leaf powders at equal rates. The pellets applied at 0.5 ton ha<sup>-1</sup> dose as soil surface mulch inhibited the seedlings emrgence of banyardgrass and wild pea by 67% and 2%, respectively. Thus the Chinese rice flower pellets has the potential to act as organic herbicide for control of bamyardgrass weed.