Electron spin resonance (ESR) spectroscopy coupled with the spin-trapping or chemicalquenching method was applied to identify the reactive oxygen species generated by irradiation of aqueous humic acid solution. Upon xenon lamp irradiation of aqueous humic acid in the presence of spin trap 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO), a spin adduct (DMPO-OH) of hydroxyl radical with DMPO was detected. Formation of the DMPO-OH was sensitive to superoxide dismutase, dioxygen and hydroxyl radical scavengers, indicating the formation of superoxide anion and hydroxyl radicals. The irradiation of aqueous humic acid solution in the presence of 2, 2, 6, 6-tetramethyl-4-piperidinol resulted in the formation of 2, 2, 6, 6-tetramethylpiperidine-1-oxyl-4-ol (TEMPOL) nitroxide radical. The ESR signal intensity of the TEMPOL radical was enhanced in deuterium oxide, and reduced in the presence of sodium azide and 1, 4-diazabicyclo-[2.2.2]octane (DABCO), indicating the formation of singlet molecular oxygen. The generation of hydrogen peroxide was confirmed spectrophotometrically based on the peroxidase-catalyzed oxidation of leuco crystal violet.

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Eighty-four 3-[(substituted phenylamino)carbonyl]-2-pyrazinecarboxylic acids (3) and the same numbers of N-(substituted phenyl)pyrazine-2, 3-dicarboximides (4) were synthesized starting from various substituted anilines and 2, 3-pyrazinedicarboxylic anhydrides prepared by the condensation of diaminomaleonitrile with 1, 2-diketones, and examined for biological activities. Five compounds of 4 showed certain protective activity against rice bacterial leaf blight and eight compounds of 4 protective activity against rice blast.

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1-Hydroxyethylphosphinic acid, its esters and salts were found to be effective against downy mildew on cucumber both in a foliar spray test and in a soil drench test. These compounds showed not only preventive activity but also curative activity. They were also effective against late blight on potato and phytophthora blight on cucumber. Among them, Ca (II) and Al (III) salts of the acid seemed most promising from the viewpoints of higher antifungal potency and lower phytotoxicity.

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Insecticidal activity of several O-(or S)-aryl O-ethyl isopropylphosphoramidothioates and bioactivation of their oxon homologs by the rat liver microsomal NADPH system were examined. Insecticidal activity and selectivity of the phosphoramidothioates to insects were different depending on substituted groups on the phenyl ring. Strong insecticidal activity was found in the phosphoramidothioates having a cyano or nitro substituted phenyl group. A parallel relationship was not found between insecticidal activity of the phosphoramidothioates and AChE inhibition of their oxon homologs after bioactivation. Although orthocyano and nitro-substituted phenyl phosphoramidothioates showed almost the same insecticidal activity as the para-cyano and nitro derivatives, AChE inhibition activity of their oxon homologs was distinctly different between ortho and para substitutions.

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[¹⁴C]Lindane (γ-HCH) applied as Nexit-fl. formulation at the recommended dose onto potato plants, grown outdoors in lysimeters, formed [¹⁴C]bound (nonextractable with acetone and methanol) residues. Attempts were made to release these bound residues from the foliage by chemical solubilization with BF₃-MeOH. Besides the polar unknown compounds, a remarkable amount (0.25mg/kg) of [¹⁴C]lindane was identified by cochromatography and GC-MS analysis.

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The influence of cyclic imide herbicides and the diphenyl ether oxyfluorfen on growth, content of photosynthetic pigments and degradation of chloroplast components was investigated using autotrophic (light) and heterotrophic (glucose-grown, dark) Scenedesmus cells. These phytotoxic compounds inhibited growth and decreased the content of chlorophylls and carotenoids in both types of cells. Assays of twenty active analogs using either autotrophic or heterotrophic cultures revealed that the correlations between these three physiological parameters were highly significant and similar. Furthermore, these correlations were found in accordance with root-growth inhibition of Echinochloa (sawa millet) seedlings and greenhouse pot tests using different weeds. Using autotrophic Scenedesmus cells incubated in the light, peroxidation was measured by substantial ethane production, concurrently by a decrease of the level of chlorophylls and carotenoids. Presence of the photosynthetic inhibitor diuron counteracted the effects. In dark-incubated heterotrophic cultures no ethane formation was detected. Essentially the same findings were obtained with the peroxidizing diphenyl ether oxyfluorfen. No immediate inhibition by cyclic imides was found on photosynthesis and respiration at concentrations far exceeding the pI₅₀-values for growth inhibition. Our comparative data on different sets of aforementioned parameters suggest that the same basic phytotoxic mechanism(s) prevail in the two types of microalga cultures as well as in Echinochloa roots and higher plants. It is assumed that cyclic imides and nitrodiphenyl ethers induce radicalic reactions, both in the light and in the dark, by affecting crucial enzymes and metabolic pathways including chlorophyll-formation step(s).

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Comparative metabolism of 3-hydroxy-5-methylisoxazole (hymexazol) and its plant metabolites, 3-β-D-glucopyranosyloxy-5-methylisoxazole (hymexazol O-glucoside, HOG) and 2-β-D-glucopyranosyl-5-methyl-4-isoxazolin-3-one (hymexazol N-glucoside, HNG), labeled with ¹⁴C at the 3 position of the isoxazole ring, was studied in male rats given a single oral dose. HOG and HNG, both of which have the same aglycone, showed a remarkable difference in absorption, excretion and metabolism. After HOG administration more than 90% of radioactivity was excreted into urine, 45% of which was eliminated as unchanged HOG. After HNG administration 47% and 46% of radioactivity were excreted into urine and feces, respectively, and most of the radioactivity in feces and 26% (12% of the dose) of the radioactivity in urine were excreted as unchanged HNG. Urinary metabolites of HOG were composed of hymexazol, 5-methyl-3-isoxazolyl sulfate (HS) and 3-β-D-glucopyranuronosyloxy-5-methylisoxazole (HG) while those of HNG were hymexazol, HS, HG, (-)-erythro-(2R, 3R)-dihydroxybutyramide (DBA) and acetoacetamide (AAA).

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Metabolism of 2-β-D-glucopyranosyloxy-5-methyl-4-isoxazolin-3-one (hymexazol N-glucoside, HNG) in male rats was studied. ¹⁴C-HNG intravenously or intraperitoneally dosed was excreted unchanged into urine, showing that rat tissues are not involved in the metabolism of HNG. In in vitro metabolism, HNG was biotransformed to 3-hydroxy-5-methylisoxazole (hymexazol) by rat cecal microflora under an anaerobic condition, and hymexazol was further metabolized to acetoacetamide (AAA), while AAA remained unchanged. When AAA was orally or intravenously or intraperitoneally administered to rats, AAA was in every case biodegraded to (-)-erythro-(2R, 3R)-dihydroxybutyramide (DBA) as a major metabolite, indicating that AAA was metabolized to DBA in rat tissues. Our study showed that orally administered HNG was biotransformed in the gastrointestinal tract to hymexazol and AAA, which were rapidly absorbed, metabolized mainly to 5-methyl-3-isoxazolyl sulfate, 3-β-D-glucopyranuronosyloxy-5-methylisoxazole and DBA, and then these metabolites were excreted into urine.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Sex pheromone activity of synthetic periplanone-A (PA) and its epimer (EPA) was bioassayed in six species of genera Periplaneta and Blatta. The activity of PA was about one thousandth that of periplanone-B (PB) in males of P. americana, and that of EPA was a further one thousandth lower than that of PA. PA, EPA and mixtures of PA and PB showed low pheromone activity in males of P. joponica, P. brunnea, P. australasiae and B. orientalis.

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Aryl methyl phosphorochloridothionates (AMPC) were found as two-step phosphorylation reagents. The 4-nitrophenyl and 2, 6-dichloro-4-methylphenyl derivatives (MNPC and CMPC) were resolved into optically active enantiomers to synthesize optical isomers of ten kinds of insecticidal 1, 3, 2-oxazaphospholidine 2-sulfides and two kinds of 1, 3, 2-benzodioxaphosphorin 2-sulfides, including the commercial insecticide salithion. Of all the 4-substituted oxazaphospholidines, (S)_c(R)_p isomers showed the highest insecticidal activity, followed by (S)_c(S)_p>(R)_c(R)_p>(R)_c(S)_p and for 5-phenyl oxazaphospholidine, (R)_c(R)_p>(R)_c(S)_p>(S)_c(R)_p>(S)_c(S)_p. (S)_c-configuration in the 4-substituted oxazaphospholidine and (R)_c in the 5-phenyl derivative appear essential for a high insecticidal activity, consistent with L- and D-configuration of natural amino acids and octopamine, respectively. In the benzodioxaphosphorins, the (S)_p configuration was favorable for a high insecticidal activity. The oxidative desulfurization of salithion by MCPBA produced an isomerized product (S-benzyl salithion) with racemization as well as the expected salioxon with retention of configuration. Bis(4-chloro-2-ethylphenyl) phenylphosphonate was metabolically transformed into the corresponding cyclic (predominantly cis) ester in houseflies in vivo. The (+)-enantiomer of sulprofos, resolved by acid-catalyzed ethanolysis of the diastereoisomer of proline derivative, was more toxic than (-)-enantiomer to houseflies. The chiral specificity was reversed relative to potency as inhibitor of housefly head AChE activity. Most of phosphorothiolates were activated to more potent inhibitors of electric eel AChE on coincubation with a mouse liver microsomal oxidase system. (-)-Sulprofos oxon sulfone was the exception, undergoing stereoselective detoxification when unwashed microsomes were used. Isofenphos was bioactivated by MFOs in two steps that ultimately gave N-desisopropyl isofenphos oxon, a product with 2300-fold greater inhibitory potency than isofenphos oxon toward housefly head AChE. The isofenphos isomers, resolved on a chiral HPLC column, had the same stereospecificity for MFO-activated anti-AChE activity and toxicity to houseflies, possibly due to enantiomeric differences in AChE inhibitory potency.

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The metabolism studies of tetramethrin, phenothrin, cyphenothrin, fenpropathrin and fenvalerate were carried out in mammals and they were metabolized similarly by oxidation at the acid and alcohol moieties, cleavage of ester linkage, conjugation of the resultant products with glucuronic acid, sulfuric acid or amino acids, and/or conversion of the CN group to thiocyanate and carbon dioxide. Although there were significant differences observed in extents of cleavage of ester bond and oxidation between the trans- and cis-isomers, no remarkable difference was observed in the metabolic fates among the optical isomers of tetramethrin and phenothrin. On the other hand, comparative metabolism study of the four optical isomers of fenvalerate showed that, of the four isomers, only the [2R, αS]-isomer produced a lipophilic conjugate which was identified as an ester of the acid moiety of this isomer with cholesterol (CPIA-cholesterol ester). This conjugate was somewhat persistent in tissues, particularly adrenal, liver, lymph node and spleen. This conjugate seems to be produced via transesterification catalyzed by microsomal carboxyesterase(s), but not via any of the three biosynthetic pathways of endogenous cholesterol esters (ACAT, LCAT and cholesterol esterase). The stereoselective formation of CPIA-cholesterol from the [2R, αS]-isomer seems to be due to stereoselectivity of the carboxyesterase(s). This conjugate is demonstrated to be a causative agent of granulomatous changes observed in the liver, spleen and/or lymph node of animals fed fenvalerate and the [2R, αS]-isomer subacutely, but not fed the other isomers. Some of fenvalerate analogs produced cholesterol ester conjugates and there was good relationship between formation of cholesterol ester conjugates and incidence of granulomatous changes. It is probable that more detailed examination of metabolites of xenobiotics in excreta and tissues will lead to the discovery of other examples of lipophilic conjugates including cholesterol esters.

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