Prodrug is a biologically inactive substance, which decomposes enzymatically and releases the original drug after applied to a biological system. Prodrug is designed to correct some flaws in an original ingredient. This article addresses molecular designs in the neonicotinoid class from a prodrug aspect. Oxadiazine modification of the clothianidin molecule into thiamethoxam is the successful application of hydrolysis of acetal-type prodrugs. N-Alkyl imidacloprid derivatives designed to impart lipophilicity were reported to be dealkylated to imidacloprid by P450 oxidation. Improvement of the photostability of nitromethylene neonicotinoids has been attempted by constructing their Mannich base. Crown ether conjugation to imidacloprid is an expansion to provide the original insecticide with amphiphilic properties. Prodrug lead modification will be a promising approach to break new ground for the neonicotinoid insecticide class.

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A novel series of sulfonanilides having a pyrimidinyl-containing group at the 2′-position was prepared and their herbicidal activities against paddy weeds and selectivity against rice plants were assessed. The structure-activity relationships were probed by substitution of the sulfonyl group, bridge and benzene ring. Among the sulfonamides, difluoromethyl compound showed comparatively high activity and a broad spectrum to control weeds, including Echinochloa oryzicola. The most preferable substitution position on the benzene ring was in the 6-position and the lower alkyl group showed high herbicidal activity and a broad weed control spectrum, and among the compounds tested, the methoxymethyl group was the best. In respect of the bridge moiety, the hydroxyl group was the best. Among the compounds examined, 2′-[(4,6-dimethoxypyrimidin-2-yl)(hydroxy)methyl]-1,1-difluoro-6′-(methoxymethyl)methanesulfonanilide, applied at rates between 4 to 16 g a.i./ha, showed excellent pre-emergence herbicidal activity with a broad spectrum against grass, sedge and broadleaf weeds without injury to rice plants.

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Pyroxasulfone has been shown to be a potent inhibitor of very-long-chain fatty acid elongase (VLCFAE) of plants; therefore, it is categorized within the K3 group of herbicides. In this paper, we studied the properties of pyroxasulfone as a VLCFAE inhibitor in more detail by examination of its inhibitory effects on VLCFAEs from some plants. Pyroxasulfone inhibited microsomal VLCFAE activities of rice, Italian ryegrass, barnyard millet, wheat, corn and soybean with time-independent reversible inhibition. There were differences in the inhibitory potencies against VLCFAEs between pyroxasulfone-susceptible plants (rice, Italian ryegrass and barnyard millet) and pyroxasulfone-tolerant plants (wheat, corn and soybean). This result confirmed that the difference in the sensitivities of VLCFAEs to pyroxasulfone was one of the factors involved in the selectivity of pyroxasulfone between crops and weeds. We succeeded in preparing recombinant VLCFAEs of Arabidopsis (FAE1) and rice (Q6F365) using yeast and rice cultured cells and constructed each assay system. VLCFAE activities of FAE1 and Q6F365 were potently inhibited by pyroxasulfone; however, a critical difference was found in the inhibition manner between FAE1 and Q6F365. Pyroxasulfone inhibited FAE1 in a time-dependent manner, whereas it inhibited Q6F365 in a time-independent manner. The time-independent reversible inhibition of rice Q6F365 and microsomal VLCFAEs of plants proposes a new inhibition mechanism of VLCFAEs by pyroxasulfone.

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We studied the retention and elimination of cumyluron by the brackish water bivalve Corbicula japonica. Although a large concentration of cumyluron was rapidly eliminated from the bivalve within the first few days of the depuration phase, the elimination rate decreased and radioactivity (approximately 0.01 ppm) was detected in all tissues of the bivalve even on Day 42 of the depuration phase; however, no tissue-specific retention was observed. Cumyluron was mostly eliminated in an unchanged form, probably because of weak phase I metabolic activity. This may be one of the causes of the long-term retention of cumyluron at a low level in this bivalve.

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Southern corn leaf blight (SCLB) is an important foliar disease of maize and its control depends on resistant cultivars or fungicides. Maneb is the recommended fungicide to control SCLB; however, application of maneb has been increasingly limited due to public concerns about the potential harmful effects of fungicide residues on human health and the environment. Therefore, an alternative approach was explored in this study using a plant activator, probenazole, to control SCLB. Application of probenazole provided effective control of SCLB under greenhouse conditions. For practical use, using probenazole at a practical rate (1.8 kg a.i./ha) was demonstrated to effectively suppress SCLB under field conditions. In addition, the effect of probenazole treatment on the growth of maize was examined. Compared with the untreated control, leaf length, leaf width, plant height, and the fresh and dry weights of probenazole-treated corn plants were not influenced; therefore, it is suggested that application of probenazole could be an alternative to control SCLB.

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Antibacterial activity of alkyl gallates and their analogs against Ralstonia solanacearum was examined. Methyl gallate showed the strongest activity among the alkyl gallates; activity decreased as the carbon number of esters increased. This tendency of alkyl gallates to act against R. solanacearum was dissimilar to its previously reported action against Gram-negative and Gram-positive bacteria and fungi. Among related compounds with a differing position and number of phenolic hydroxyl groups, methyl 2,3-dihydroxybenzoate showed comparable or slightly stronger activity than methyl gallate. Geraniin, one of the characteristic secondary metabolites produced by Geranium spp., showed moderate activity.

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The dose response of the biological parameters of the model river biofilm, consisting of two diatom strains and three bacterial strains on the glass surface, was examined with atrazine. Good correlations (r²=0.90–0.93) between the atrazine log concentration and the relative increase rates of microbial cell numbers and the amount of chlorophyll a in the model biofilm formation were shown, and similar EC₅₀ values for the biological parameters including esterase activity were tentatively obtained as an endpoint. The results suggested that this model biofilm could be used for testing the potential effects of pesticides on natural river biofilms at a community level with high reproducibility.

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A bis-demethoxy curcumin microemulsion was successfully prepared using the method of pseudo-ternary phase diagrams combined with an orthogonal test in a 3-phase system (O phase=active ingredient; S phase=surfactants; W phase=water). The best transparent region for preparing the bis-demethoxy curcumin microemulsion was formed when Termul-200 (an alkylphenol polyether block copolymer emulsifier) and sodium dodecyl benzene sulfonate (SDBS) (4 : 1 w/w) were used as surfactants (S phase), isopropanol (30% in S phase) as a co-surfactant, and a bis-demethoxy curcumin DMF solution (30%) as the active ingredient (O phase). According to the infinite dilution region of the best phase diagram, the best ratio among O, S and W phases for preparing the bis-demethoxy curcumin microemulsion was a weight ratio of 4.5 : 20 : 75.5. Stability tests showed that all the indicators of our prepared microemulsion met the storage stability criteria. Our results suggested that the combination of the pseudo-ternary phase diagram and orthogonal test analysis provided an effective approach for designing a microemulsion formulation.

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Methyl (4-trifluoromethoxy)phenylcarbamate, the key intermediate for the synthesis of various excellent pesticides, was synthesized using two new, convenient methods with excellent yield and low cost compared to existing methods. We achieved a yield of over 95%, nearly quantitative in some cases. Our synthesis methods were also applied to other aniline derivatives to obtain the desired products with high yields. All reactions were conducted under mild conditions and very pure products were obtained. This method should be very useful in indoxacarb manufacturing, lowering the costs and avoiding excessive pollution.

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Pyribencarb is a novel benzylcarbamate-type fungicide having excellent activity against a wide range of plant pathogenic fungi, especially gray mold diseases caused by Botrytis cinerea. The primary target site of pyribencarb is the Qo site of cytochrome b in the electron transfer system of the respiratory chain. The inhibitory effects of pyribencarb to cytochrome b enzyme on the transfer system of a QoI-resistant strain of B. cinerea are stronger than those of other QoI fungicides. Pyribencarb exhibited adequate control in greenhouse trials when QoI-resistant strains were inoculated. We have developed a practical method for evaluating the sensitivity of B. cinerea to pyribencarb. The final concentrations of pyribencarb in the PDA medium were set at 1 and 100mg a.i. per liter with 1mM salicylhydroxamic acid (SHAM). The isolates that were completely inhibited at 1mg a.i. per liter of pyribencarb were “sensitive strains,” and the isolates that were inhibited by more than 80% at 100mg a.i. per liter of pyribencarb were “weakly resistant strains.” In our assays so far, no strains with mycelial growth inhibition rates of less than 80% at 100mg per liter of pyribencarb have ever been found. In the event that such strains should be found in the future, it will be necessary to monitor their sensitivity to pyribencarb using an in vivo assay.

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The beet armyworm (Spodoptera exigua (Hübner)) is one of the most important vegetable pests in Thailand. After 24 hr of both dipping and sprayer bioassay, estimation of LC₅₀ of the ethyl acetate extract of Jatropha gossypifolia senescent leaves demonstrated toxicity to secondary instar S. exigua larvae because in this stage most armyworm start to move to other plants and it is also the first susceptible stage for toxicity tests. Ricinine, the main alkaloid separated from ethyl acetate crude extract, showed toxicity on secondary instar larvae by the sprayer method with an LC₅₀ of 3,215 ppm whereas the LC₅₀ value for ethyl acetate crude extract is 8,644 ppm. Thus, the ethyl acetate crude extract of Jatropha gossypifolia senescent leaves may have ricinine as the active ingredient and may be used as an alternative choice for the minimal application of chemical insecticides for Spodoptera exigua.

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The fact that the surfactant, octylphenol polyethoxylates (OPEO_n), selectively solubilized epicuticular wax suggested the enhanced performance of foliar-applied agrochemicals. The biodegradation process of OPEO_n by exo-terminal oxidation and subsequent ether cleavage of the EO chain was precisely characterized by the identification of the key intermediate and the cloned alcohol oxidase. Environmental elements, such as Ca²⁺, Mg²⁺ and Fe³⁺, may influence the activity and rate of biodegradation in the environment. A highly reliable method for phylogenetic analysis at the strain level was developed using ribosomal subunit proteins, as theoretical biomarkers, encoded in the S10-spc-alpha operon with a validation procedure.

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Biologically active small molecules have increasingly been used in plant biology to dissect and understand biological systems. Plant hormones are essential factors for normal plant growth and therefore the regulation of their functions causes marked changes in plant phenotypes. Since small molecules that bind to biosynthesis enzymes and reduce their ability can mimic mutations in plant hormone biosynthesis, plant hormone biosynthesis inhibitors are now widely used in plant physiology and genetics.

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