Synthesis and biological activity of furanyl anti-juvenile hormonal compounds

Twenty-one synthetic compounds, containing one or more furan rings, were demonstrated to possess anti-juvenile hormone (AJH) activity as evidenced by their induction of premature metamorphosis in the milkweed bug, Oncopeltus fasciatus (Dallas) by contact, topical application or fumigation. The ED₅₀ of the four most active analogs required to induce precocious metamorphosis from 3rd-instar nymphs by residue contact in a Petri dish compared favorably with that of precocene II (6,7-dimethoxy-2,2-dimethyl 2H-chromene) a naturally occurring phytochemical AJH. Precocious metamorphosis was fully reversible by co-treatment with juvenile hormone (JH III) or JH analogs, demonstrating that the observed AJH activity resulted from an induced deficiency of juvenile hormone.     

Synthesis and precocious-metamorphosis-inducing activity of 3-pyridyl ethers

A new series of 5-(substituted phenoxy)pentyl 3-pyridyl ethers induced precocious metamorphosis in larvae of the silkworm, Bombyx mori. Both 2- and 4-pyridyl ethers were inactive, indicating that the 3-pyridine moiety was essential for the activity. Octyl, dodecyl and farnesyl 3-pyridyl ethers had no activity. Among the compounds tested so far, 5-(4-propylphenoxy)pentyl 3-pyridyl ether showed the highest activity. The activity fell off with increasing or decreasing length of the carbon chain between two oxygen atoms. Introduction of a methyl group at the 6 position of the pyridine ring completely eliminated the activity. Precocious metamorphosis induced by 3-pyridyl ethers was fully reversible by a simultaneous application of a small amount of tebufenozide, an ecdysteroid agonist, or methoprene, a JH agonist. © 1998 SCI.     

Cytochrome P-450 Inducers and Inhibitors Interfering with Ecdysone 20-Monooxygenases and Their Activities during Postembryonic Development of Neobellieria bullata Parker

The cytochrome P-450-dependent microsomal and mitochondrial ecdysone 20-monooxygenase systems convert ecdysone into 20-hydroxyecdysone. The microsomal fraction of fat bodies of zero h wandering stage fleshfly larvae (Neobellieria bullata; Diptera: Sarcophagidae) has a high ecdysone 20- monooxygenase activity. The effects of cytochrome P-450 inhibitors were investigated in vitro on microsomal ecdysone 20-monooxygenase. Metyrapone, fenarimol and certain imidazole derivatives (KK-42, KK-110, KK-135 and PIM) are strong inhibitors. The IC₅₀ value of KK-110, which is the strongest inhibitor, is 2 × 10^?7 M. A triazolyl and two cyclopropylamine derivatives have low activity. The activities of different NADPH-cytochrome c (P-450) reductase inhibitors were also assessed; diquat dibromide is a moderate inhibitor of microsomal ecdysone 20-monooxygenase, while paraquat dichloride has no activity. In-vivo experiments with cytochrome P-450 inducers and inhibitors gave the following results: (a) fenarimol, FI-121, precocene-2 caused “permanent” first-instar larvae; (b) barbital, phenobarbital and their sodium salts caused significant delay in larval development; (c) PIM, PTM, metyrapone, KK-42, KK-135, J-2710, RH 5849 and colchicine caused moulting disturbances; (d) J-2710, PIM, PTM, KK-42, KK-135, RH 5849 and colchicine caused lethal spiracle and mandible malformation; (e) KK-110, fenarimol, barbital and phenobarbital caused precocious pupariation.     

Laboratory evaluation of the effects of Manilkara subsericea (Mart.) Dubard extracts and triterpenes on the development of Dysdercus peruvianus and Oncopeltus fasciatus

BACKGROUND: Studies were carried out to evaluate the effects of Manilkara subsericea extracts and triterpenes on the development of two species of agricultural pest insects, Oncopelus fasciatus and Dysdercus peruvianus. RESULTS: All treatments of insects with M. subsericea extracts induced mortality, delayed development and inhibited moulting. Some extracts assayed (FH, FB and FD in D. peruvianus, and FH, FB and FEA in O. fasciatus) also produced body deformities in the few adults that emerged. Other extracts (FH, FEA, FB, FD and LET in both insects), however, induced either permanent (overaged) or extranumerary nymphs, both of which were unable to achieve the adult stage and reproductive status. The insects were also treated with triterpenes (α‐ and β‐amyrin acetates) which showed high lethality at 30 days after treatment and delayed the intermoult period so that overaged nymphs were detected. CONCLUSION: The results indicate that extracts and triterpenes from Manilkara subsericea act as potent growth inhibitors of phytophagous hemipteran nymphs. It is also concluded that the mixture of several different molecules in the extracts used produces synergic effects that do not occur after using the triterpenes (PFT) alone. These secondary metabolites in the M. subsericea extracts can potentially be used in integrated control programmes against crop pests. Copyright © 2012 Society of Chemical Industry     

Effects of dimehypo (disodium 2-methylaminotrimethylene di thiosulfonate) on growth and cocooning of the silkworm,Bombyx mori (Lepidoptera: Saturnidae)

Dimehypo (disodium 2-methylaminotrimethylene di thiosulfonate), is an insecticide used on rice and other crops in China. However, contamination of mulberry leaves with this has been implicated in a reduction of silk production. The acute and chronic toxicity of dimehypo to Bombyx mori L over the partial life cycle of the organism was determined based on survival, growth and cocooning of two strains of silkworm larvae. A change in the ultrastructure of the posterior silk gland cell was also observed in this study. The results showed that the growth and development of tested larvae was impeded and their life cycle was prolonged in both strains. It was also found that dimehypo was extremely harmful to the cocooning of B mori. Ultrastructural evidence suggests that adverse effects of dimehypo arise as a result of changes in the biosynthesis of fibroin and in the physiological activity of the posterior silk gland cell. The maximum acceptable daily dose of dimehypo based on growth and cocooning of B mori is less than 1.7 × 10⁻⁶ µg day⁻¹ in spring-reared larvae and less than 1.7 × 10⁻⁸ µg day⁻¹ in autumn-reared larvae. © 1999 Society of Chemical Industry     

Imidazole derivative KK-42 reduces ecdysteroid titers and interferes with reproductive processes in adult females of Tenebrio molitor

KK-42, an imidazole derivative considered as potent inhibitor of ecdysteroid biosynthesis, was tested on adult females of Tenebrio molitor. The compound was applied topically (0.1, 1, 5, and 10 μg/insect) on 0- or 2-day-old adult females or added to the culture medium (1 and 10 μM) of ovaries. To test the effect of KK-42 on the reproduction capacity, ovaries were explanted from 2- and 4-day-old females corresponding, respectively, to follicles at the beginning and the end of vitellogenesis. KK-42 treatment reduced the fecundity and the longevity of females, and in addition, it delayed oviposition and affected growth and development of oocytes as evidenced by measurements of the ovarian weight, the number of oocytes per ovaries, and the size of the basal follicle. Hence, the effects were stronger in newly emerged females compared to 2-day-old females. Interestingly, RH-0345, an ecdysteroid agonist, could partly restore the effects on reproductive events induced by KK-42. In a second series of experiments using an enzyme immunoassay to measure ecdysteroid titers, KK-42 reduced the amounts of ecdysteroids in ovaries after application on newly emerged adult females. In 2-day-old females, it caused a significant effect with the highest doses. In addition, the compound significantly reduced the amounts of ecdysteroid released into the culture medium by ovaries explanted from 2- or 4-day-old females. The results are discussed in relation to the mode of action of KK-42 on reproduction.     

Inhibition of juvenile hormone biosynthesis and methyl farnesoate epoxidase activity by 1,5-disubstituted imidazoles in the cockroach,Diploptera punctata

Seventeen substituted imidazoles were tested as inhibitors of juvenile hormone (JH) III synthesis by cockroach corpora allata in an in-vitro radio-chemical assay. Most of these 1,5-disubstituted imidazoles were highly potent, with IC₅₀ values of less than 100nM. The compounds differed in their ability to cause an accumulation of the precursor methyl farnesoate in the glands. Four of the imidazoles were tested by topical application to previtellogenic adult females, and all caused a significant inhibition of JH synthesis and an accumulation of intraglandular methyl farnesoate for at least three days after treatment. Methyl farnesoate epoxidase activity of homogenates of corpora allata was inhibited by the compounds TH -14 and TH -27. This P450-dependent epoxidase activity was inhibited at less than 10 nM. The results show that the 1,5-disubstituted imidazoles are powerful inhibitors of the last step of juvenile synthesis in this cockroach.     

Identification of novel juvenile-hormone signaling activators via high-throughput screening with a chemical library

Juvenile hormone (JH) is an insect-specific hormone that regulates molting and metamorphosis. Hence, JH signaling inhibitors (JHSIs) and activators (JHSAs) can be used as effective insect growth regulators (IGRs) for pest management. In our previous study, we established a high-throughput screening (HTS) system for exploration of novel JHSIs and JHSAs using a Bombyx mori cell line (BmN_JF&AR cells) and succeeded in identifying novel JHSIs from a chemical library. Here, we searched for novel JHSAs using this system. The four-step HTS yielded 10 compounds as candidate JHSAs; some of these compounds showed novel basic structures, whereas the others were composed of a 4-phenoxyphenoxymethyl skeleton, the basic structure of several existing JH analogs (pyriproxyfen and fenoxycarb). Topical application of seven compounds to B. mori larvae significantly prolonged the larval period, suggesting that the identified JHSAs may be promising IGRs targeting the JH signaling pathway.     

Synthesis of substituted benzyl 2-methyl-2-phenylpropyl ethers and their moth-proofing activity on wool against larvae of Anthrenus fasciatus

Synthesis of new moth-proofing agents is necessary to overcome the damage caused by clothes moths and carpet beetles to hosiery and upholstery. In the present paper substituted benzyl 2-methyl-2-phenylpropyl ethers were synthesised and evaluated for moth-proofing activity. Two compounds were found to provide protection against larvae of Anthrenus fasciatus at levels of 1.0 and 10 g kg⁻¹ respectively. The introduction of a methyl group in the para position of the benzene ring attached to C₂ of the 2-methylpropyl chain (ring A) increased moth-proofing activity. The introduction of a phenoxy ring at the meta position of the benzyl nucleus (ring B) also increased activity, while the presence of a nitro group on the benzyl nucleus (ring B) decreased activity. © 1999 Society of Chemical Industry     

Assessment of species specificity of moulting accelerating compounds in Lepidoptera: comparison of activity between Bombyx mori and Spodoptera littoralis by in vitro reporter and in vivo toxicity assays

BACKGROUND: Dibenzoylhydrazine analogues have been developed successfully as a new group of insect growth regulators, called ecdysone agonists or moulting accelerating compounds. A notable feature is their high activity against lepidopteran insects, raising the question as to whether species‐specific analogues can be isolated. In this study, the specificity of ecdysone agonists was addressed through a comparative analysis in two important lepidopterans, the silkworm Bombyx mori L. and the cotton leafworm Spodoptera littoralis (Boisd.). RESULTS: When collections of non‐steroidal ecdysone agonists containing different mother structures (dibenzoylhydrazine, acylaminoketone, tetrahydroquinoline) were tested, in vitro reporter assays showed minor differences using cell lines derived from both species. However, when compounds with high ecdysone agonist activity were examined in toxicity assays, larvicidal activity differed considerably. Of note was the identification of three dibenzoylhydrazine analogues with > 100‐fold higher activity against Bombyx than against Spodoptera larvae. CONCLUSION: The present study demonstrated that species‐specific ecdysone‐agonist‐based insecticides can be developed, but their species specificity is not based on differences in the activation of the ecdysone receptor but rather on unidentified in vivo parameters such as permeability of the cuticle, uptake/excretion by the gut or metabolic detoxification. Copyright © 2010 Society of Chemical Industry     

The response of pyriproxyfen-resistant and susceptible Bemisia tabaci Genn (Homoptera: Aleyrodidae) to pyriproxyfen and fenoxycarb alone and in combination with piperonyl butoxide

Pyriproxyfen was effective against susceptible Bemisia tabaci eggs at a LC₅₀ of 0.003 mg litre⁻¹ and against nymphs at 0.02 mg litre⁻¹. In comparison, eggs of a laboratory selected, pyriproxyfen-resistant B tabaci strain, originating in an Israeli greenhouse, exhibited 6500-fold resistance and nymphs exhibited 1100-fold resistance. Eggs and nymphs of a strain from an Israeli sunflower field exhibited 450 and 210-fold resistance in comparison to the susceptible standard. Fenoxycarb was generally less effective than pyriproxyfen against B tabaci eggs and nymphs but was unaffected by pyriproxyfen resistance. Piperonyl butoxide (PB) was antagonistic to pyriproxyfen, and this increased with increasing pyriproxyfen resistance. PB had no effect on the toxicity of fenoxycarb. Collectively, these data imply that the modes of action of pyriproxyfen and fenoxycarb are distinct, despite the structural similarities of these molecules. Possible reasons for the antagonism of PB against pyriproxyfen are discussed. © 1999 Society of Chemical Industry     

苏云金芽胞杆菌一新菌株的鉴定及其杀虫活性

为分离并鉴定对亚洲玉米螟具有高毒力的苏云金芽胞杆菌菌种,通过棋盘式采集法从吉林省农业科学院试验田土壤中分离获得野生菌株,进行了形态、生化特性、伴孢晶体观察及基因型鉴定,并测定了其对3种鳞翅目害虫的室内生物活性。结果显示:该菌株在LB培养基上为圆形、暗白色菌落,边缘不整齐,革兰氏染色阳性,产生的伴孢晶体形状多为不规则形。16S r DNA序列与苏云金芽胞杆菌属的NBRC 13865同源性达99%;该菌株为cry2+cry9复合基因型,编码氨基酸序列与Cry2Ab和Cry9Ea蛋白同源性分别为94%和99%,鉴定为苏云金芽胞杆菌,命名为JN001。该菌株对亚洲玉米螟具有较高毒性,以1.0×109个/m L菌体浓度接种3龄幼虫72 h后,其校正死亡率为95.06%,致死中浓度(LC50)为4.12×103个/m L菌体,而对斜纹夜蛾和粘虫毒性较弱,接种72 h后校正死亡率分别为12.88%和7.34%。表明该菌株是1株对亚洲玉米螟具有较强毒力的苏云金芽胞杆菌新菌株,具有较好的开发利用潜力。     

黄带犀猎蝽对斜纹夜蛾3、4龄幼虫的捕食功能反应

为明确黄带犀猎蝽Sycanus croceovittatus对斜纹夜蛾Spodoptera litura的控害潜能,在实验室条件下对黄带犀猎蝽3~5龄若虫和雌雄成虫对斜纹夜蛾3、4龄幼虫的捕食功能反应、搜寻效应和自身密度干扰反应进行研究。结果表明,黄带犀猎蝽对斜纹夜蛾幼虫的捕食功能反应均符合Hol-ling II型和Holling III型2种模型;在拟合Holling II模型中,黄带犀猎蝽3~5龄若虫和雌雄成虫对斜纹夜蛾3龄幼虫的日均最大捕食量分别为2.78、4.17、4.35、12.50和8.33头,控害效能分别为5.53、6.54、8.78、14.75和10.42;对斜纹夜蛾4龄幼虫的日均最大捕食量分别为2.56、2.86、3.85、3.57和4.35头,控害效能分别为2.23、3.94、4.54、11.32和5.70,其中雌成虫的控害效能最大。在拟合Hol-ling III模型中,对斜纹夜蛾3龄幼虫的日均最大捕食量分别为2.75、4.10、4.32、10.76和7.41头,最佳寻找密度分别为1.19、2.03、1.73、5.28和3.88头/盒;对斜纹夜蛾4龄幼虫的日均最大捕食量分别为2.38、2.78、3.55、3.58和4.00头,最佳寻找密度分别为1.83、1.50、2.06、0.95和2.10头/盒。搜寻效应与害虫密度呈负相关;种内干扰效应与天敌密度呈正相关。表明黄带犀猎蝽成虫对斜纹夜蛾3、4龄幼虫的捕食能力优于黄带犀猎蝽若虫。     

A biochemical approach to potentiate the activity ofBacillus thuringiensis against corn borers

Due to the fact that the persistence ofBacillus thuringiensis (B.t.) is very short in the field as affected by exposure to ultraviolet radiation, some biochemical approaches have been adopted in an attempt to increase potentiation of the pathogen against the two lepidopterous corn borers,Chilo agamemnon andOstrinia nubilalis. These approaches were based on the incorporation of some selected non-toxic chemical compounds with different modes of action with the endotoxin ofB.t. fed to the larvae and thus resulting in its potentiation. Among the compounds tested, some representatives of inorganic salts, organic acids, protein and lipid solubilizing agents, amino acids and amides showed an obvious potentiation to the endotoxin activity against the target insects. Inorganic salts, such as, calcium oxide, calcium carbonate, zinc sulphate and potassium carbonate at 0.1% potentiated the activity of the product Dipel 2X (B.t. var.kurstaki) against the two tested species in varying degrees. With regard to protein solubilzing agents, urea, sodium thioglycollate and EDTA enhanced the potency ofB.t. againstO. nubilalis with a fold increase of 1.4–2.3. The lipid emulsifying agent Tween 80 (0.5%), caused 1.3 fold increase in the potency ofB.t. With respect toC. agamemnon, sodium thioglycollate and EDTA (0.1%) were effective in potentiating the activity ofB.t. with fold increase of 3.1 and 1.2, respectively, while urea caused a decrease in the potency ofB.t as compared with the control. The lipid emulsifying agent Tween 80 (0.5%) caused 1.3 fold increase in the potency ofB.t. The potentiating effect of aromatic compounds is not obvious with respect to the tested insect species. With amino acids and amides, it appears that some of the tested compounds enhanced the potency ofB.t. against the tested insect species but in varying degrees. The mode of action of the tested compounds has been discussed in the light of the results obtained.     

含酰腙结构的新型吡唑酰胺衍生物对小菜蛾的生物活性

采用浸虫法、夹毒叶片法和叶碟法分别测定了13个含酰腙结构的新型吡唑酰胺衍生物对小菜蛾3龄幼虫的触杀、胃毒和拒食活性。结果表明:该类化合物对小菜蛾3龄幼虫具有较高的胃毒和拒食活性,其中苯环上含有氯原子、且酰腙一端的取代基含有杂原子且体积较小的化合物 H7的胃毒和拒食活性最好,明显高于对照药剂毒死蜱。H7 72 h胃毒作用LC50值为0.6 mg/L(毒死蜱的LC50值为7.4 mg/L);有10个化合物的拒食活性高于毒死蜱,其中 H7 48 h的拒食中浓度(AFC50) 最低,为0.6 mg/L,明显低于毒死蜱(AFC50=6.5 mg/L)。供试化合物对小菜蛾3龄幼虫均无触杀活性。     

Insecticidal and repellent properties of nine volatile constituents of essential oils against the American cockroach,Periplaneta americana (L.)

The toxic and repellent properties of nine major constituents of essential oils, comprising benzene derivatives and terpenes, were evaluated against Periplaneta americana (L.). Contact and fumigant toxicities to adult females and repellency to nymphs were determined. The decreasing order of knockdown activity via contact was methyl-eugenol>isosafrole=eugenol>safrole. The killing effect via contact was in the order eugenol=methyl-eugenol=isosafrole>safrole. Fumigant toxicity was only observed for safrole and isosafrole, with safrole being the more potent. Isoeugenol and the tested terpenes had neither contact nor fumigant toxic effect. The decreasing order of repellency to nymphs was safrole>isosafrole>methyl-eugenol=α-pinene> eugenol>isoeugenol. The benzene derivatives were generally more toxic and repellent to P. americana than the terpenes. The distance of the side chain double bond from the aromatic ring and the substitution of a methoxy group to these compounds appeared to be important determinants of their toxicity and repellency. © 1998 Society of Chemical Industry     

Ecdysteroid titers and molting aberrations in last-stage Oncopeltus nymphs treated with insect growth regulators

The ecdysteroid titers of insect growth regulator (IGR)-treated and untreated large milkweed bug nymphs, Oncopeltus fasciatus (Dallas) (Heteroptera: Lygaeidae), were determined by radioimmunoassay. All of the IGRs tested affected the ecdysteroid levels and the ecdysis of both sexes in some way. AI3-63604, a juvenile hormone mimic, accelerated ecdysteroid production and its subsequent decline, shortened the stadium, and induced a supernumerary nymphal molt. Diflubenzuron had no effect on the onset of ecdysteroid production but slightly retarded the decline in ecdysteroid titers before adult ecdysis, and the ecdysis was incomplete. Ecdysteroid production was delayed and erratic in nymphs treated with azadirachtin and AI3-63967, but the effect on ecdysis was different for each compound. Azadirachtin caused incomplete adult ecdysis, whereas AI3-63967 completely prevented any attempts at ecdysis. The large peak of exdysteroid activity associated with apolysis was absent in starved insects, and they made no attempt to ecdyse.     

Suppression of Reproduction in Poekilocerus pictus (F.) using Penfluron and Diflubenzuron

Abstract

Penfluron and diflubenzuron, both chitin synthesis inhibitors known to be highly effective against nymphs of Poekilocerus pictus (F.), were tested against the adult for their possible effects upon reproduction. These compounds were found to have the maximum effect, when no eggs were laid, if both sexes were treated. The eggs of treated males × untreated females did not hatch and those of treated females × untreated males gave rise to nymphs which died before reaching maturity.     

氟铃脲对韭菜迟眼蕈蚊不同虫态的致毒特点及毒力

为明确氟铃脲对韭菜迟眼蕈蚊不同虫态的致毒特点及毒力,采用胃毒触杀联合毒力法、药液定量滴加法及药膜法分别对韭菜迟眼蕈蚊卵、幼虫、蛹、成虫进行了生物测定。结果表明,经氟铃脲处理的0.5~1、1.5~2和2.5~3日龄韭菜迟眼蕈蚊卵至孵化24 h后,LC_(50)依次为2.27、1.60和0.64 mg/L,对1.5~3日龄卵的毒力高于对0.5~1日龄卵;经氟铃脲处理的2日龄卵、2龄幼虫、4龄幼虫、1日龄和3日龄蛹至羽化时LC_(50)分别为0.06、0.30、0.34、24.05和27.42 mg/L,毒力程度随韭菜迟眼蕈蚊发育而逐步下降;对蛹和成虫毒力较低,100 mg/L氟铃脲染毒1、3日龄蛹的羽化率分别高于10%和20%;药膜法100、1 000 mg/L氟铃脲处理成虫24 h,校正死亡率低于20%。研究表明,氟铃脲对韭菜迟眼蕈蚊各虫态的生长发育均有不利影响,抑制卵的孵化并导致初孵幼虫存活率降低;对幼虫毒杀作用较慢,对蛹及成虫阶段毒力较低。