The degradation of [phenoxy-U-¹⁴C] fenothiocarb (FC) in Okitsu alluvial and Ibaraki volcanic ash soils was studied under upland and flooded conditions. Fenothiocarb was more rapidly degraded under upland conditions than under flooded conditions. In Okitsu soil under upland conditions, the degradation of ¹⁴C-fenothiocarb was slightly enhanced when the soil was pre-treated with non-radioactive fenothiocarb, while it was retarded when the soil was sterilized. ¹⁴CO₂ was gradually liberated in two soils under upland conditions, where the half-lives of fenothiocarb were 8 and 15 days for Okitsu and Ibaraki soils, respectively. The soil bound ¹⁴C-residues were found in the humic acid, fulvic acid and fumin fractions. Nine degradation products were observed in both soils under upland and flooded conditions, which were identified as fenothiocarb sulfoxide, 4′-hydroxy-fenothiocarb, N-formyl-fenothiocarb, monodesmethyl-fenothiocarb, didesmethyl-fenothiocarb, methyl 4-phenoxybutyl sulfoxide, methyl 4-phenoxybutyl sulfone, phenoxyacetic acid and 4-phenoxybutylsulfonic acid.

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The translocation and metabolism of ¹⁴C-fenothiocarb [S-(4-[¹⁴C (U)] phenoxybutyl) N, N-dimethylthiocarbamate] were studied using citrus such as summer orange seedlings and mandarin orange trees with fruit under greenhouse conditions. Very little ¹⁴C-fenothiocarb was translocated when applied on the middle of upper or lower surface of leaf, and its limited translocation to an upward direction was found when applied to stem. When it was sprayed to mandarin orange trees, the initial concentration of radioactivity in the leaves and fruit rinds was 26.3 and 4.7ppm, respectively. The radioactivity dissipated more rapidly in the leaves than in the rinds with the half-lives of fenothiocarb being estimated 1.6 and 12 days, respectively. The concentration of radioactivity in the edible part of fruit increased with time, but that equivalent to fenothiocarb remained 43 to 46ppb at the mature stage. Orange juice from the edible part contained water-soluble metabolites. The major metabolites identified in the leaves, rinds and edible fruit were 6-O-malonyl-β-D-glucoside of N-hydroxymethyl-fenothiocarb, N-formyl-fenothiocarb and glycoside conjugates of phenol, respectively. The minor ones were identified as fenothiocarb sulfoxide, N-hydroxymethyl-fenothiocarb, monodesmethyl-fenothiocarb and 4′-hydroxy-fenothiocarb.

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The degradation of the sulfoxide of fenothiocarb (S-4-phenoxybutyl N, N-dimethylthiocarbamate), an acaricide for the control of citrus red mites, was studied in Okitsu alluvial and Ibaraki volcanic ash soils under upland conditions using [phenoxy-U-¹⁴C]-preparation. Fenothiocarb sulfoxide disappeared very rapidly, with its residue in both soils less than 1% of the applied dose 7 days after treatment. Radioactivity in aqueous methanol extracts, evolved ¹⁴CO₂, and bound ¹⁴C-residues were 48.7, 5.3 and 44.7% in Okitsu soil, and 24.8, 6.9 and 69.6% in Ibaraki soil, respectively. In both soils, the evolution pattern of ¹⁴CO₂ was similar and the formation of bound residues was relatively high especially so in Ibaraki volcanic ash soil. Methyl 4-phenoxybutylsulfone, bis(4-phenoxybutyl)thiolsulfinate, methyl 4-phenoxybutylsulfoxide and 4-phenoxybutylsulfonic acid were identified as major degradation products in both soils. Fenothiocarb, bis(4-phenoxybutyl)disulfide and phenoxyacetic acid were also identified as relatively minor products. Fenothiocarb sulfoxide disappeared much faster than fenothiocarb, and the fenothiocarb sulfoxide-treated soils formed more bound residues.

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The photodegradation of ¹⁴C-fenothiocarb [S-(4-phenoxy-U-¹⁴C) butyl N, N-dimethylthiocarbamate] on a silica gel plate exposed to sunlight was studied. Radioactivity on the plate dissipated slowly with time. After 72hr exposure (Sept. to Oct.), 34% of fenothiocarb remained, and its half-life was estimated as approximately 45hr. Twelve photodegradation products were detected by two-dimensional thin-layer chromatography. Among twelve, products identified were S-4-phenoxybutyl N-formyl-N-methylthiocarbamate, S-4-phenoxybutyl N-methylthiocarbamate, bis(4-phenoxybutyl)thiolsulfinate, bis(4-phenoxybutyl)thiolsulfonate, fenothiocarb sulfoxide and 4-phenoxybutylsulfonic acid. A primary photochemical reaction seems to be the oxidation of sulfur to form fenothiocarb sulfoxide, followed by the cleavage of ester linkage and the oxidation or the dimerization of 4-phenoxy-butylsulfenic acid intermediate. Moreover, the oxidation of N-methyl moiety of fenothiocarb is suggested as the second photochemical reaction of fenothiocarb.

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A new phytoalexin, oryzalexin D, was isolated as a group of oryzalexins from blastinfected rice (Oryza sativa) leaves. The structure of oryzalexin D was confirmed as 3, 7-dihydroxy-(+)-sandaracopimaradiene by UV, MS, ¹H-NMR and optical rotation. Oryzalexin D significantly inhibited spore germination of Pyricularia oryzae at 100ppm.

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Antifungal and plant growth regulating activities of enantiomers of (E)-1-(2, 4-dichlorophenyl)-4, 4-dimethyl-2-(1, 2, 4-triazol-1-yl)-1-penten-3-ol (S-3308L) were examined. In a nutrient agar medium, the R(-) isomer was more fungitoxic than the S(+) isomer against fungal species belonging to the Ascomycotina, Basidiomycotina and Deuteromycotina. However, against the Oomycetous fungi, the R(-) isomer was not so fungitoxic as against the other fungal species. There was not a clear difference in fungitoxicity between the R(-) and S(+) isomers. In pot-trials, the R(-) isomer controlled economically important plant diseases when sprayed preventively or curatively, whereas the S(+) isomer was less effective. The R(-) isomer also showed protective activity in vapor phase and systemic, whereas the S(+) isomer exhibited stronger plant growth regulating activity than the R(-) isomer on cucumber seedlings.

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The absorption, translocation and metabolism of ¹⁴C-orbencarb [S-(2-chlorobenzyl-U-¹⁴C) N, N-diethylthiocarbamate] were studied in cotton plants. The absorption and translocation of radioactivity from ¹⁴C-orbencarb applied onto the soil surface increased with time. When a leaf or stem of cotton seedlings was topically applied with ¹⁴C-orbencarb, the radioactivity was translocated to the whole plant. At the mature stage, 3.4% of the applied radioactivity was absorbed in the plants and 0.1% was found in the seeds, while 44.6% remained in the soil. ¹⁴C-Orbencarb was rapidly metabolized in both the cotton plants and the soil, and gradually transformed to the water-soluble metabolites. Major metabolites identified were methyl 2-chlorobenzyl sulfone, monodesethyl-orbencarb, 2-chlorophenylmethanesulfonic acid and 2-chlorobenzyl alcohol in free or conjugated form, and relatively minor metabolites were methyl 2-chlorobenzyl sulfoxide, didesethyl-orbencarb, orbencarb sulfoxide and 2-chlorobenzoic acid also free or conjugated form.

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Adjuvant activities of surfactants for maleic hydrazide diethanolamine salt, a tobacco desuckering agent, were investigated by examining their chemical structure and physico-chemical properties. The correlation between the surfactants' chemical structure and phytotoxicity against tobacco leaves was not recognized, but it was found that the surfactants with carbon number 12 or 18:1 in the alkyl group had high adjuvant activities. The physico-chemical properties of the surfactants and adjuvant activities closely correlated in maximum concentration without phytotoxicity and moisture absorption capacity, but there was no correlation in surface tension, contact angle, HLB (hydrophilic lipophilic balance) and pH. High adjuvant activities were also recognized in some humectants. Findings show it is necessary to select the surfactants with high moisture absorption capacity which can be used at a high concentration without phytotoxicity, if we want to add the adjuvant effects to the traditional wetting agents.

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Relationships between the chemical structure of 61 organophosphorus (OP) insecticides and the degree of resistance in the OP-resistant rice stem borer, Chilo suppressalis WALKER, were studied. The resistant strain necessarily showed high levels of resistance to various types of OP insecticides containing the aryl (including the aromatic heterocyclic group) ester bond, such as fenitrothion, cyanophos, pirimiphos-methyl, chlorpyrifos-methyl, pirimiphos-ethyl, EPN, isofenphos, and their oxons. Resistance was higher to dimethyl esters than to their diethyl homologs, and the highest resistance ratios were found with heterocyclic esters. In contrast, essentially no resistance to OP insecticides having the ester bond with aliphatic enol and thioalcohol, such as malathion, phenthoate, azinphos-methyl, malaoxon, tetrachlorvinphos, and monocrotophos was observed. It is, therefore, concluded that a P-O-aryl bond in OP insecticides is prerequisite for the resistance.

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The metabolism of [¹⁴C] benfuracarb [2, 3-dihydro-2, 2-dimethyl-7-benzofuranyl N-[N-[2-(ethoxycarbonyl)ethyl]-N-isopropylsulfenamoyl]-N-methylcarbamate] was studied in houseflies 0.5, 2, 4 and 24hr after topical application. The penetration of [¹⁴C]benfuracarb was relatively rapid and 64.8% of the radioactivity was found in the internal fractions after 24hr. Benfuracarb was easily decomposed to form carbofuran which, in turn, was oxidized at the 3-position of the ring and the N-methyl group. These oxidized metabolites were then converted to conjugates. Major metabolites were carbofuran [2, 3-dihydro-2, 2-dimethyl-7-benzofuranyl methylcarbamate] and 3-hydroxy-carbofuran followed by N-hydroxymethyl-carbofuran, 3-keto-carbofuran, 3-hydroxy-carbofuran phenol, 3-hydroxy-N-hydroxymethyl-carbofuran and 3-keto-N-hydroxymethyl-carbofuran. Several minor metabolites were also detected. The appreciable amounts of carbofuran accumulated internally in the houseflies indicate its role as the toxic agent.

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The herbicide isouron [3-(5-tert-butyl-3-isoxazolyl)-1, 1-dimethylurea] was rapidly metabolized in soils with upland moisture under anaerobic conditions through replacing air with nitrogen gas. The half-life of isouron was 1 month in Toyohama soil and 2 months in Kanuma soil, respectively. Isouron disappeared completely after 2 months in Toyohama soil and 3 months in Kanuma soil. A degradation product was 1-(1-amino-4, 4-dimethyl-3-oxo-1-pentenyl)-3, 3-dimethylurea formed by reductive cleavage of the isoxazole ring. The main degradation pathway was the formation of the metabolite in the soil under anaerobic conditions. A great number of organisms which degrade isouron reductively existed in anaerobic soil. This fact indicates that the anaerobic microorganisms play an important role for the reductive degradation of isouron in the soil under anaerobic conditions. The reductive product was degraded easily in soil under both aerobic and anaerobic conditions to disappear within 3-5 days after the application.

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As a measure to control pyrethroid resistant houseflies, the synergistic effect of piperonyl butoxide (PB), an inhibitor of cytochrome P-450 dependent monooxygenase system (MFO), was evaluated. When a mixture of various pyrethroids and PB (1:4 ratio, w/w) was applied topically, a remarkable decrease in LD₅₀ values was observed indicating a clearcut synergism. A comparison of the synergistic effect of PB on susceptible CSMA and Mashiko-res 10 strains demonstrated a far greater effect on the latter strain, suggesting that degradation by MFO plays an important role in the resistance mechanism. The mixture also demonstrated an excellent result in controlling pyrethroid-resistant houseflies when applied by an aerial spray in a hog farm in Mashiko. Selection of Mashiko 83-resl strain with a mixture of resmethrin and PB in the laboratory did not develop resistance to the mixture nor did it further increase the resistance level to the pyrethroid.

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Fenpropathrin (α-cyano-3-phenoxybenzyl 2, 2, 3, 3-tetramethylcyclopropanecarboxylate) was examined for toxicity to mites and for effect upon fecundity, paralyzing action and repellency. Fenpropathrin was highly toxic to adults of carmine mite, Tetranychus cinnabarinus BOISDUVAL and citrus red mite, Panonychus citri MCGREGOR, and its ovicidal activity was comparable to that of dicofol and amitraz. It weakened the feeding activity of adult mites, and consequently reduced the number of eggs laid. It also showed characteristic repellency which induced changes in mite's behavior on the host plants. Carmine mites treated with fenpropathrin at low concentrations moved away from treated leaves. When treated with fenpropathrin at 0.16ppm, mites hung on threads from the leaves, and this “spinning down” increased with the dose. The decrease in the number of mites leaving treated leaves at higher concentrations was attributed to the quick paralyzing action by fenpropathrin. More carmine mites spun down from completely treated plants than from partially treated ones, where they had a choice between treated and untreated parts of each plant. Most of the citrus red mites treated with 25ppm and 50ppm fenpropathrin spun down from the host plants within 9hr.

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A strain of bacteria able to degrade isouron [3-(5-tert-butyl-3-isoxazolyl)-1, 1-dimethyl-urea] reductively was isolated from the perfusate in soil perfusion culture. When the bacteria were cultured in a 5% yeast extract medium containing isouron at 28°C without shaking, isouron was metabolized to 1-(1-amino-4, 4-dimethyl-3-oxo-1-pentenyl)-3, 3-dimethylurea during 6-day incubation. The strain of the bacteria was identified as Pseudomonas putida. The curing test and extraction of plasmid DNA from the cells seemed to show that the bacteria have no plasmid. The bacteria also reduced an isouron's related compound, 3-(5-tert-butyl-3-isoxazolyl)-1-methylurea to 1-(1-amino-4, 4-dimethyl-3-oxo-1-pentenyl)-3-methylurea. 3-(5-tert-Butyl-isoxazolyl)urea and 5-tert-butyl-3-aminoisoxazole were slightly metabolized by the bacteria, but no degradation products were detected by thin-layer chromatography and densitometry.

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Pretreatment with the microsomal oxidase inhibitor piperonyl butoxide (pb) greatly improved the topical insecticidal activity of the GABA antagonist, 4-n-propyl-2, 6, 7-trioxa-1-phosphabicyclo[2.2.2]octane 1-oxide (4-n-propyl BP), against the housefly, Musca domestica L., when the synergistic ratio was 313. The insecticidal activity was also enhanced by bypassing the integument with injection without pb pretreatment. When tested by four different methods, the order of the 24-hr LD₅₀ values (μg/fly) for 4-n-propyl BP was: injection, pretreated with pb (0.169)<topical application with pb (0.212)<injection (0.449)<<topical application (66.4). Penetration studies indicated that 4-n-propyl BP caused marked mortality at the internal level of 0.2-0.3μg per fly, although the penetration was slow. The topically applied thiono and phosphite analogs without pb were approximately as insecticidal as the oxon analog injected. The thiono analog had the lowest 24-hr LD₅₀ value (with pb) among its analogs, which was 0.061μg per fly. The lethal level of the thionate ester in the housefly body was estimated to be one-tenth of that of 4-n-propyl BP. The difference in the internal lethal level between 4-n-propyl BP and its thiono analog seems to be related to the difference in their insecticidal activity when they are topically applied without pb.

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Altericidins (altericidin A, B and C), remarkably inhibited the mycelial growth of Alternaria kikuchiana in a liquid medium at low concentrations. The fifty percent inhibitory concentration (EC₅₀) for the mycelial growth varied widely according to the initial mycelial weight. The higher the initial density, the higher the EC₅₀. However, the ratio of EC₅₀ (μg/ml) to the dry weight inoculum (mg/ml) was 2.8, when the initial mycelial weight ranged from 0.8 to 1.45mg (dry weight/ml), and increased in proportion to the mycelial weight (dry weight) under the conditions tested. Scanning electron micrographs showed partial swelling, rupture and exfoliation in the outer cell wall layer of conidium of A. kikuchiana when treated with various concentrations of altericidins. The conidium bursted when treated at a higher concentration of 40ppm. When the hyphae were treated with 20ppm altericidins for 6hr, some of the cells heavily shrunk, and others became empty and flattened. The leakage of cellular constituents was also observed in sporidium of Ustilago maydis treated with 20ppm altericidins for 3hr. These results suggest that altericidins act on the cell wall.

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The insecticidal activities of chiral isomers of isofenphos (O-ethyl O-2-isopropoxycarbonylphenyl N-isopropylphosphoramidothioate) and isofenphos-oxon were examined with reference to their activation in rat liver microsomal-NADPH system. The chiral isomers of isofenphos and Isofenphos-oxon were completely separated by using HPLC with a mixture of n-hexane and 2-propanol on a CHIRALCEL OC column. To the housefly and adzuki bean weevil, the (+)-isomers of both the compounds were more toxic than the (-)-isomers. Especially, to the housefly the (+)-isomer of isofenphos-oxon was approximately 83.5-fold more toxic than the (-)-isomer. To both insects fenitrothion, the (+)-isomer and racemate of isofenphos were almost similar in insecticidal activity, although (-)-isofenphos was somewhat weaker. The I₅₀ values of both chiral isomers of isofenphos-oxon for acetylcholinesterase (AChE) of the housefly head and adzuki bean weevil, however, were higher than 10^-3M. After the chiral isomers of isofenphos-oxon were incubated with the rat liver microsomal system in the presence of NADPH, the (+)-isomer became to inhibit AChE of housefly head stronger than the (-)-isomer; the I₅₀ values were 1.47×10^-7M, 6.19×10^-5M and 9.61×10^-7M for the (+)-, (-)- and racemic isofenphos-oxons, respectively. When piperonyl butoxide (PB) was added to the microsomal-NADPH system, inhibition of AChE activity by the (+)- and racemic isofenphos-oxon was reduced. The data suggested that the (+)-isomer was easily bioactivated by the microsomal-NADPH system though the difference of affinity to AChE between bioactivated chiral isomers should be taken into consideration.

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The leakage of cellular constituents from Alternaria kikuchiana and Ustilago maydis treated with altericidins was investigated. Altericidins induced the leakage of ¹⁴C-labeled substances from mycelia and conidia of A. kikuchiana or sporidia of U. maydis preincubated with ¹⁴C-protein hydrolysate or ¹⁴C-glucose. The large amount of labeled substances leaked out into ambient solution within the first 1hr of incubation. The leakage of protein from mycelia and anthrone-positive substance from conidia of A. kikuchiana was also induced remarkably by altericidins. The former leakage reached the maximum 4 to 6hr after incubation with 20ppm altericidins and the latter 4hr after incubation with 8ppm altericidins. In the case of sporidia of U. maydis, the leakage of ninhydrin-positive substance, anthrone-positive substance and protein from the cells was clearly induced by 4ppm altericidins. The leakage of cellular constituents corresponded to the observation by scanning electron microscope reported previously. These results suggest that altericidins act on cell wall of fungi, induce change of the membrane permeability, and consequently kill them.

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To get some information on the primary site of action of quizalofop-ethyl (ethyl 2-[4-(6-chloro-2-quinoxalinyloxy) phenoxy]propionate), effects on the growth of several intact plants and callus tissues and on the disruption of cellular membranes of stembase segments excised from untreated and herbicide-treated corn seedlings were studied using both (R)-(+)- and (S)-(-)-enantiomers of the herbicide. The growth of susceptible plants such as rice, oat and corn, was drastically reduced by the foliar application of the (R)-enantiomer at a dose of 6.25μg/plant, while the (S)-enantiomers showed only a little effect at a dose of 100μg/plant. Both ¹⁴C-labeled enantiomers showed similar translocation behavior in corn and barnyardgrass seedlings. The results suggested that receptor chirality is the source of the differential activities between the enantiomers.

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For quantitative SAR studies of 2-[4-(2-quinoxalinyloxy)phenoxy] propanoic acid derivatives, the correlation between partition coefficient (log P) and retention volume (log V_R) in HPLC was investigated. It was found that log V_R in HPLC was a useful and convenient alternative to the log P for this series of compounds. Quantitative SAR studies were carried out using the retention volume as a hydrophobic parameter. The shoot growth inhibiting activity against rice plants (Oryza sativa) decreased with an increase in the lipophilicity of their ester moiety.

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[in Japanese]

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[in Japanese]

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The urea herbicide isouron [3-(5-tert-butyl-3-isoxazolyl)-1, 1-dimethylurea] was reductively degraded to 1-(1-amino-4, 4-dimethyl-3-oxo-1-pentenyl)-3, 3-dimethylurea (designated as enaminoketone hereafter) by Pseudomonas putida. The bacterium completely metabolized isouron within a week when it was cultured in a 5% yeast extract medium at 28°C without shaking, but hardly metabolized it in the other media such as a 5% beef extract medium. The result suggested that the bacterium required a certain component of yeast extract to degrade isouron and that the chemical could be degraded by many kinds of bacteria if a yeast extract medium was used for bacterial culture.
In this paper, the reductive degradation of isouron by bacteria was investigated using bacteria isolated from an upland soil and general bacteria stocked in our laboratory.

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For several years, our research group at Sumitomo has been conducting an extensive search for new biologically active natural products. Some of the isolated natural products could be looked upon as prototype models for synthetic research to develop new agrochemicals. In this paper, the followings are described as examples of our research: (i) The extract of black pepper fruits (Piper nigrum L.) exhibited strong insecticidal activity against several pests. A new amide, N-isobutyl-1, 1-(3, 4-methylenedioxyphenyl)-2E, 4E, 10E-2, 4, 10-undecatrienamide (pipercide), as well as two structurally related amides, were isolated as insecticidal principles. From the results of synthetic studies, N-isobutyl-12-(3-trifluoromethylphenoxy)-2E, 4E-2, 4-dodecadienamide was found to have especially potent activity. This amide, as well as the amides from pepper plants, exhibited notable paralyzing effects and lethal activity against pyrethroid-resistant houseflies. Electro-physiological studies using the central nerve cord of the American cockroach demonstrated that these amides are neurotoxic compounds. (ii) The chloroform extract of the stems and leaves of May apple (Podophyllum peltatum L.) showed fungicidal activity against rice blast. Three new 2-pyrones (podoblastin A, B and C) were isolated as fungicidal components and their structures were determined by synthesis. Fungicidal activities against rice blast were greatly improved by structural modifications, and 3-(2-oxodecanyl)-4-hydroxy-6-n-propyl-5, 6-dihydropyran-2-one was selected as the most potent compound. The preventive effect of this compound against rice blast was most successful, however the curative and systemic effects require further improvement. (iii) A biphenyl (3, 5-dimethoxy-4-hydroxybiphenyl, aucuparin), as well as a new dibenzofuran (2, 4-dimethoxy-3-hydroxydibenzofuran, eriobofuran), were isolated as phytoalexins from fungi-infected loquat trees (Eriobotrya japonica L.). The structure of eriobofuran was determined by synthesis. Eriobofuran exhibited fungicidal activity against Pestalotia funerea (phytopathogenic fungi to loquat), however it did not show any activity against several fungi which are non-pathogenic to loquat. The biological significance of the self-induction of the phytoalexins in the loquat tree was considered in relation to plant resistance against fungal attack.

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A number of aminosulfenyl, sulfinyl and alkoxysulfenyl derivatives of methylcarbamate insecticide were synthesized by appropriate substitution of the proton on the carbamyl nitrogen atom, and their insecticidal activity and toxicity to mice were examined. The toxicological properties of the original methylcarbamate were markedly affected by derivatization, resulting generally in substantial improvement in mammalian toxicity and retention or improvement in insecticidal activity. Some of the derivatives demonstrated greater residual effectiveness, and were less phytotoxic to crops. Metabolism of two carbofuran derivatives, i. e., benfuracarb and carbosulfan, in use or under development was examined. In plants and houseflies, both derivatized carbamates were metabolized mainly to carbofuran and related oxidation products, while degradation to phenolic products was the principal route of metabolism in rats. The results indicate that the selective toxicity of the derivative between insects and mammals is attributable to different pathways of metabolism. Studies on the behavior of carbosulfan in different environments showed that carbosulfan dissolved in the solvent containing various acids was transformed into the same alteration products, giving carbofuran, polysulfide derivatives of carbosulfan and biscarbofuran polysulfides as major products. Most of the polysulfide derivatives showed good insecticidal activity and all of them were less toxic to mice than carbofuran. These polysulfide derivatives were also formed in the rat stomach following oral administration of carbosulfan, indicating the contribution of the polysulfide derivatives to lower mammalian toxicity of carbosulfan. In virtually all of the derivatives were less effective inhibitors of acetylcholinesterase than the parent carbamates.

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