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Design, Synthesis, and Herbicidal Activity of Novel Dihydrochalcones Derived from Flavokawains and Their Analogs
(2026-05-01)
Poprom, Suriyaphong
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Meesin, Jatuporn
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Chotpatiwetchkul, Warot
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Waratchareeyakul, Watcharee
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Chotsaeng, Nawasit
Weeds are a major cause of crop production losses worldwide, and environmentally friendly chemical control based on natural or semisynthetic compounds has attracted increasing attention. In this study, flavokawains, a class of natural chalcones, and their analogues were converted into dihydrochalcones (1–27) via Pd-catalyzed hydrogenation. The herbicidal activities of these compounds were evaluated against Chinese amaranth (Amaranthus tricolor) and barnyard grass (Echinochloa crus-galli). Several compounds significantly inhibited seed germination and seedling growth in both species. Herbicidal activity was strongly influenced by the type and position of aromatic substituents, with electron-withdrawing groups and meta substitution providing higher activity. The meta-chloro derivative (15) exhibited the highest activity, markedly inhibiting seed germination as well as shoot and root growth. Further investigation of its mode of action revealed that this compound interfered with seed imbibition, inhibited α-amylase activity, and affected membrane integrity and malondialdehyde (MDA) levels in A. tricolor in a concentration-dependent manner. These findings provide valuable insights for the development of natural product-derived herbicides.
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Synergistic Adulticidal Activity of Lemongrass (Cymbopogon citratus), Star Anise (Illicium verum), Nutmeg (Myristica fragrans) Essential Oil and Their Components Against the Housefly (Musca domestica) and Their Safety for Key Non-Target Organisms
(2026-04-01)
Passara, Hataichanok
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Laosinwattana, Chamroon
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Moungthipmalai, Tanapoom
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Murata, Kouhei
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Soonwera, Mayura
Botanical insecticides containing a mixture of plant essential oils (EOs) are considered suitable for the management of houseflies (M. domestica). The adulticidal efficacies of single EOs and mixtures of EOs, including lemongrass (C. citratus), star anise (I. verum), nutmeg (M. fragrans), and their components (geranial, trans-anethole, and α-pinene), against houseflies were determined in comparison to 2% (w/v) α-cypermethrin as the positive control and distilled water as the negative control. The mixture of star anise EO (1%) + geranial (1%) was the most effective adulticide, superseding single EOs, other combinations of EOs, and its active component, α-cypermethrin, and distilled water. This mixture was highly synergistic and was found to be over 74% more toxic than all single EOs and almost 2.6 times more toxic than α-cypermethrin. Furthermore, the tested EOs did not cause mortality in guppies (P. reticulata) or earthworms (E. fetida), and caused a maximum of 48% mortality in honeybees (A. mellifera) at 24 h; by contrast, α-cypermethrin led to 100% mortality in honeybees within 0.5 h and in guppies and earthworms within 24 h, although it had low toxicity toward houseflies. Thus, a mixture of star anise EO + geranial is a promising source of EO-derived insecticides for housefly control that is also safe for important non-target species.
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Herbicidal Activity of the Invasive Weed Malachra capitata L.: Growth Stage Dependence, Bioassay-Guided Fractionation, and Physiological Effects on Seed Germination
(2026-03-01)
Wichittrakarn, Pattharin
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Sathuwijarn, Sirichai
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Manichart, Nutcha
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Yoneyama, Kaori
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Sikhao, Potjana
The invasive weed Malachra capitata is unsuitable for human or animal consumption but has recently attracted attention for potential alternative uses. In this study, the allelopathic potential of M. capitata for weed control was investigated, as were its allelopathic effects on selected crops. The influence of plant developmental stage on its phytotoxic activity was also assessed. In addition, the physiological effects of the extract on seed germination were investigated. Aqueous leaf extracts were obtained across a range of growth stages and evaluated using seed germination and seedling growth bioassays, followed by bioassay-guided fractionation and GC-MS analysis. Leaves extracts collected at 35 days after planting exhibited the strongest inhibitory activity. Dicot plant species (Phaseolus lathyroides, Cucumis sativus, Brassica oleracea, and B. chinensis) were more susceptible to M. capitata extracts than grassy species (Echinochloa crus-galli, Zea mays, and Oryza sativa), indicating selective phytotoxicity. In pot experiments, application of leaf residues as surface mulch at rates of 100, 200, and 400 g/m2 significantly reduced P. lathyroides emergence by 11.25%, 35.00%, and 71.25%, respectively. Bioassay-guided fractionation indicated the ethyl acetate-soluble acidic fraction to contain the active allelochemicals. This inhibition was associated with reduced water uptake and suppression of α-amylase activity during seed germination. The most abundant GC-MS detectable components of the acidic fraction were octadecane (12.45%), eicosane (9.74%), and hexadecane (9.60%). Overall, these findings highlight the allelopathic potential of M. capitata, providing a foundation for further applied research and supporting its valorization for sustainable weed management.
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High-Energy Emulsified Clove Essential Oil Nanoemulsion as a Natural Herbicidal Product: Germination Suppression and Seed Structure Alteration in Echinochloa crus-galli
(2026-03-01)
Sikhao, Potjana
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Somala, Naphat
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Manichart, Nutcha
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Dimak, Jantra
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Poonpaiboonpipat, Thanatsan
Clove (Syzygium aromaticum (L.) Merr. & L.M. Perry) essential oil (EO)-based nanoemulsions may have a promising future in eco-friendly herbicide development. Clove EO was found to have a high eugenol content of 87.27%. Organic-solvent-free nanoemulsions using clove EO as a bioactive ingredient were fabricated using ultrasonication and microfluidization emulsification methods. Fourier-transform infrared spectroscopy confirmed that both emulsification methods did not affect the EO components. The droplet size of optimized nanoemulsions was determined using dynamic light scattering. The smallest size of 66.9 nm was obtained by microfluidization at 20,000 psi and eight passes. Additionally, the smallest droplet size for a sonicated nanoemulsion was 103.9 nm, obtained by ultrasonication at 20% for 6 min. Transmission electron microscopy confirmed the droplet sizes of both optimized nanoemulsions. In a storage test, both optimized nanoemulsions were stored at 4 °C for at least four weeks. Finally, both nanoemulsions were evaluated on pre-emergence herbicidal activities against Echinochloa crus-galli. The results showed that both nanoemulsions inhibited E. crus-galli germination and seedling growth, and additionally, inhibited seed imbibition and α-amylase activity. Micro-morphological and ultrastructural analysis was observed using a scanning electron microscope and an energy dispersive X-ray spectrometer (SEM-EDS). SEM-EDS micrographs of the treated seeds showed that the seed structure was damaged, especially the endosperm, leading to the inhibition of seed germination.
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Terpenoid Mixtures as Repellents Against the American Cockroach: Their Synergy and Low Toxicity Against Non-Target Species
(2026-01-01)
Passara, Hataichanok
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Moungthipmalai, Tanapoom
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Laosinwattana, Chamroon
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Sittichok, Sirawut
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Murata, Kouhei
The repellent activities (Periplaneta americana) of lone and binary mixtures of terpenoids—geranial, trans-anethole, and trans-cinnamaldehyde—against adult American cockroaches were evaluated in this study. The respective efficacies of these mixtures were compared with that of 12% (w/w) DEET. Safety bioassays for all formulations on non-target species, namely, earthworms (Eudrilus eugeniae) and guppy fish (Poecilia reticulata), were conducted to identify natural compounds with repellent efficacy equal to or surpassing that of DEET while ensuring ecological safety for non-target organisms such as fish and earthworms. All mixtures (RC<inf>50</inf> of 0.3 to 1.6 µL/cm3) were more effective than all lone terpenoids (RC<inf>50</inf> of 6.2 to 9.1 µL/cm3) and DEET (RC<inf>50</inf> of 3.0 µL/cm3), demonstrating strong synergy, with an increased repellent value (IV) of 79 to 96%. The strongest repellency, 98.0% at 72 h and an RC<inf>50</inf> of 0.3 µL/cm3, was achieved using geranial + trans-cinnamaldehyde (1:1). This mixture was 5.9 to 10 times more effective as a repellent than DEET. The toxicity of every lone terpenoid and terpenoid mixture to non-target species was low; hence, these mixtures can be considered safe, whereas DEET was highly toxic to non-target species (100% mortality). The terpenoid mixture geranial + trans-cinnamaldehyde showed strong repellency against P. americana.
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Allelopathic Sugarcane Leaf Litter and Its Potential Use as Soil Mulching for Weed Management in Sugarcane Cultivation
(2026-01-01)
Krumsri, Ramida
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Poonpaiboonpipat, Thanatsan
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Samaksaman, Ukrit
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Nuengchamnong, Nitra
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Laosinwattana, Chamroon
Sugarcane leaves, both green and fallen, left after harvest, are agricultural residues containing compounds that inhibit weed germination and seedling growth. This study evaluated their allelopathic effects and mulching potential for weed control. Experimental results using seeds of Ipomoea pes-tigridis and Dactyloctenium aegyptium suggest that the aqueous extract from sugarcane leaf litter reduces seedling growth. When compared to mulch made from extracted sugarcane leaves, mulch made from nonextracted leaves considerably decreased weed emergence and biomass in the pot experiment. It appears that the weed suppression was not just due to the mulching but also to the allelochemicals that were still present in the unprocessed leaves. Weed germination and seedling rates appeared to be lowered, possibly due to the presence of allelochemicals, especially phenolic compounds. Under sugarcane production conditions, field experiments were conducted to evaluate the effects of soil mulching using sugarcane leaf litter applied at rates of 4, 8 and 12 t ha−1. As a soil mulch, sugarcane leaf litter resulted in reduced weed density and biomass compared to typical agricultural practices, with weed control efficacy improving at higher rates of application. For instance, mulching rates of 8 and 12 t ha−1 resulted in respective sugarcane outputs of 104.2 and 111.6 t ha−1, whereas mechanical, manual and no weeding respectively yielded 81.25, 126.88 and 31.25 t ha−1. Based on these findings, the utilisation of sugarcane leaf litter as a soil mulch can reduce weed seed germination and growth, and can therefore be considered as an agroecological practice to be included in sustainable weed management strategies.
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Ultrasonic emulsification of Cananga odorata nanoemulsion formulation for enhancement of herbicidal potential
(2025-12-01)
Laosinwattana, Chamroon
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Somala, Naphat
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Dimak, Jantra
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Teerarak, Montinee
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Chotsaeng, Nawasit
A nanoemulsion was fabricated from Cananga odorata essential oil (EO) and stabilized by incorporation of Tween 80 using ultrasonication. The major constituents of the EO were benzyl benzoate, linalool, and phenylmethyl ester. Differing sonication amplitude (20–60%) and time (2–10 min) were assessed for effects on nanoemulsion droplet size and polydispersity index (PI). The smallest droplet size of 43.98 nm (PI 0.222) was obtained using 40% amplitude for 8 min; this nanoemulsion was evaluated for its droplet characteristics and pre-emergence herbicidal activities on Amaranthus tricolor. FT-IR confirmed ultrasonic emulsification to not affect the EO components. Regarding stability, storage at 4 °C was determined appropriate, with droplet size changing slightly after five weeks. Assays of herbicidal potential showed the coarse emulsion and nanoemulsion to both reduce A. tricolor germination and growth, with the nanoemulsion being more effective at a given concentration and the difference in effectivity correlating to droplet size. Remarkably, treatment with 250 ppm nanoemulsion and coarse emulsion respectively resulted in 100% and 63.75% germination inhibition. Both emulsions decreased seed imbibition and alpha-amylase activity. The highest relative electrolyte leakage was achieved in seed treated with the nanoemulsion. Therefore, this ultrasonic-based nanoemulsion may have utility as bioherbicide alternative.
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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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Laosinwattana, Chamroon
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Charoenying, Patchanee
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Sikhao, Potjana
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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Binary Mixtures of Essential Oils: Potent Housefly Adulticides That Are Safe Against Non-Target Species
(2025-08-01)
Passara, Hataichanok
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Sittichok, Sirawut
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Moungthipmalai, Tanapoom
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Laosinwattana, Chamroon
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Murata, Kouhei
In this study, we investigated the insecticidal potential of Eucalyptus globulus Labill. and Cymbopogon citratus Stapf essential oils (EOs), both alone and in synergistic blends with their primary active compounds, against adult houseflies (Musca domestica L.). Toxicity assessments were also conducted on non-target organisms—dwarf honeybees (Apis florea Fabricius) and guppies (Poecilia reticulata Peters)—to evaluate environmental safety. All binary EO mixtures demonstrated superior efficacy compared to individual EOs and the synthetic pyrethroid α-cypermethrin (1% positive control). The most potent formulation, combining 2.5% (v/v) geranial with 2.5% (v/v) E. globulus EO, exhibited a synergistic effect, achieving complete fly mortality (LT<inf>50</inf>: 0.06 h). This mixture’s mortality index significantly exceeded those of single-component formulations, with a mortality index of 0.22, confirming greater toxicity to flies than α-cypermethrin. Importantly, all the tested EOs and their blends were non-toxic to honeybees and guppies; in comparison, α-cypermethrin caused significant harm. These findings highlight the 2.5% (v/v) geranial + 2.5% (v/v) E. globulus EO blend as a highly effective and environmentally friendly alternative to conventional insecticides. Further research is recommended to optimize its formulation for practical use in sustainable fly management.
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Formulation and evaluation of nanoemulsions from Jasminum officinale essential oil for controlling postharvest browning and maintaining quality in jasmine (Jasminum sambac) flowers
(2025-01-01)
Yeamsuriyotai, Kittiya
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Pradabkun, Natthamon
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Manichart, Nutcha
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Yonsawad, Nipaporn
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Khamchatra, Na Monrug
The jasmine (Jasminum sambac (L.) Aiton) flower has delicate petals, resulting in rapid browning after harvest. The aim of this study was to search for an innovative postharvest treatment for delaying browning of jasmine petals using plant essential oils. J. officinale L. f. var. grandiflorum (L.) essential oil was found to reduce peroxidase activity in jasmine flower by 44.21% in the in vitro condition. The antioxidant activities and chemical composition of J. officinale essential oil were subsequently characterized. The essential oil exhibited the ability to scavenge 2,2-diphenyl-1-picrylhydrazil (DPPH) radicals with a 50% inhibition (EC<inf>50</inf>) value of 6.72 ± 0.89 mg/mL, a chelating effect with EC<inf>50</inf> value of 7.42 ± 1.59 mg/mL, and reducing power with EC<inf>0.5</inf> value of 14.89 ± 0.73 mg/mL. GC-MS analysis detected 29 compounds in the oil, with benzyl alcohol (20.68%) and benzyl acetate (19.87%) predominating. As plant essential oils have restricted water solubility, an oil-in-water emulsion was formulated using a spontaneous emulsification method. The resulting J. officinale essential oil naonoemulsion (JEN) had an oil droplet size of 70.2 ± 0.39 nm and a narrow polydispersity index. In vivo testing confirmed the inhibitory effects of JEN on jasmine flower browning and relevant enzyme activities. Jasmine flowers were soaked in various concentrations of JEN for 5 min, packed in polyethylene plastic bags, and stored in a refrigerator at 10 ± 3°C with relative humidity 66 ± 5%. Flowers treated with 1 and 2 mg/mL JEN showed effective delay of petal browning and maintained good quality with minimum flower opening index, high freshness score, and high color retention index. JEN treatment also reduced phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) activities, indicating postponement of the browning process. In addition, scanning electron microscopy micrographs of treated flower epidermis cells revealed delayed cell wall collapse, indicating retention of intact cells. Taken together, these results support JEN as a potential preventative of enzymatic browning and hence petal browning in jasmine flower.

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