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    Bioassay-Guided Extraction and Isolation of Natural Herbicides from Dried Zanthoxylum limonella Alston Fruits
    (2025-01-01)
    Chotpatiwetchkul, Warot
    ;
    Charoenying, Patchanee
    ;
    Teerarak, Montinee
    ;
    Meesin, Jatuporn
    ;
    Jongkon, Nathjanan
    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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    Phosphate-solubilizing bacteria from upland rice (Oryza sativa L.) rhizosphere and their tricalcium phosphate solubilizing abilities
    (2018-12-01)
    Cavite, H. J.M.
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    Mactal, A. G.M.
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    Cruz, J. A.
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    Khermkhan, J.
    Insoluble forms of phosphorus (P) may be converted to soluble P by phosphate-solubilizing organisms living different soil ecosystems to make them available for plant roots to be absorbed. In this study, isolation of rhizobacteria and screening of their ability for phosphate solubilization was done. A total of 25 isolates were obtained from upland rice rhizosphere in Isabela province, Philippines. Measuring the solubilizing efficiency revealed that seven out of 25 isolates were found to be promising phosphate-solubilizers showing clearing zone around the colony. Moreover, phosphorus solubilization index (PSI) of the isolates ranged from 1.25 to 1.60 and results obtained are higher than other observations indicating that strains of bacteria isolated are effective phosphate-solubilizers. Furthermore, these PSB could serve as efficient biofertilizer candidates for improving the P nutrition of the crop. This observation can be a promising contribution to cropping system of upland rice, which is constrained by drought leading to inefficient P acquisition. If further developed, this can be eco-friendly and prove to be cost effective strategy to improve upland rice production particularly in the Philippines.
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    A hybrid ring coupler quasi-optical antenna-mixer
    (2009-01-17)
    Janin, Suwan
    ;
    Sripimanwat, Keattisak
    ;
    Phongcharoenpanich, Chuwong
    ;
    Krairiksh, Monai
    This paper proposes a hybrid ring coupler quasi-optical antenna-mixer for mitigating local oscillator retransmission. By demonstrating at K-band, the antenna element consists of back-to-back aperture coupled inverted square patch antenna to couple the RF signal at 18.8 GHz to the sigma port of a hybrid ring mixer while the LO signal at 17.5 GHz is coupled to the delta port. The HSCH-9101 Schottky diodes are used to transform the RF signal to the intermediate frequency signal at 1.3 GHz. The results show that the RF/LO isolation is better than 29 dB at 18.19 GHz, and the isotropic conversion loss of the down converted signal is better than 16 dB at 19.25 GHz. The application of the interest is an inverse measurement technique for dielectric property determination. © 2007 Elsevier GmbH. All rights reserved.
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    Isolation and screening of chitosanase producing microorganisms
    (2006-10-01)
    Wangtueai, Sutee
    ;
    Worawattanamateekul, Wanchai
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    Sangjindavong, Mathana
    ;
    Naranong, Nuanphan
    ;
    Sirisansaneeyakul, Sarote
    A total of 183 isolates of microorganisms were collected from forest soil with the shrimp wastes deposited. The selected four bacterial isolates with high activity of chitosanolytic enzymes on chitosanase detected agar plates (CDA-plates) were TP11.03, TP11.22, TP12.24 and KU22.13. Among them, the potential isolate TP12.24 was identified as Bacillus cereus which produced the highest amount of chitosanase on M9-Chitosan medium.