Juvenile hormones mimics

Stable in acidic, neutral and basic aqueous solutions Pale yellowish solid, faint characteristic odor Flash point 119°C (Pensky-Martens closed tester) Pyriproxyfen is an insect growth regulator which acts both as an ovacide and as an inhibitor of development (juvenile hormone mimic) against white flies, scale, and psylla. The specificity of pyriproxyfen, and its low mammalian toxicity, allow for some variation in application timing. For example, the lack of toxicity to bees allows pyriproxyfen to be applied during bloom on apple trees, and its low mammalian toxicity allows for a very short pre-harvest interval on citrus The residue definition is for pyriproxyfen alone... 

The pest mosquito Aedes nigromacul Ls of the vast San Joaquin valley of California went resistant to organochlorines by 1951, to parathion by 1960, to fenthion by 1965, and to chlorpyrifos (Dursban) by 1970. At present reliance is placed on larvicidal oils, the juvenile-hormone mimic methoprene (Altosid) and the insect growth regulator diflubenzuron (Dimilin), — and on better management of surplus irrigation water. Residual sprays for housefly control, at first so spectacular with the organochlorines, had to move into the OP compounds, which were then knocked out in... 

The multiresistant strains now extant also show a certain cross-tolerance, but not resistance, to the third-generation insecticides such as the juvenile-hormone mimics and other so-called insect growth regulators, as was found in strains of the housefly, flour beetle and tobacco budworm. Resistance to the JH mimic methoprene and Monsanto-585 has been induced by laboratory selection of Culex taxsalis (28) and Culex pipiens (29), and to Monsanto-585 in Culex quinquefasstatus (30). Whatever insect or IGR is chosen, the result of exposure to selective doses in successive generations is usually the development of resistance, repeating our previous experience with chemosterilants, and the... 

An example of increasing the efficiency by decreasing the flow rate is shown on a pellicular silica gel column in Figure 6-5a. (This figure was shown previously as Fig. 4-15.) This is the separation of a cis and trans isomer of synthetically prepared juvenile hormone mimics which are separated in the normal-phase mode. (Juvenile hormone mimics are used to stop or retard the maturation process of insects and, hopefully, control the insect population.) The presence of benzene is probably residue from the reaction solvent. At 2 mL/min the first peak corresponds to 5000 plates and the last peak corresponds to 2300 plates. By lowering the flow rate to 0.5 mL/min, there is a corresponding increase in efficiency in the separation. With the additional efficiency at the slower flow rate, it is possible to observe a small, additional shoulder (peak) under the first peak. However this was done at the expense of increased time (a factor of 4). 

FIGURE 6-5. Effect of flow rate upon the separation, (a) Normal-phase separation of juvenile hormone mimics. Column Corasil II (silica), 2 mm x 183 cm. Mobile phase ethyl ether/hexane (1/199). Detector UV Flow rate 2.0 mL/min and 0.5 mL/ min. (b) GPC separation of phthalates. Column 100 A juStyragel, 8 mm x 30 cm. Mobile phase tetrahydrofuran. Detector RI Sample dioctylphthalates dibutylph-thalate, diethylphthalate, and dimethylphthalate. Flow rate shown on chromatogram. 

The existence of a cytosolic epoxide hydrolase was first indicated by its ability to hydrolyze analogs of insect juvenile hormone not readily hydrolyzed by microsomal epoxide hydrolase. Subsequent studies demonstrated a unique cytosolic enzyme catalytically and structurally distinct from the microsomal enzyme. It appears probable that the cytosolic enzyme is peroxisomal in origin. Both enzymes are broadly nonspecific and have many substrates in common. It is clear, however, that many substrates hydrolyzed well by cytosolic epoxide hydrolase are hydrolyzed poorly by microsomal epoxide hydrolase and vice versa. For example, l-(4 -ethylphenoxy)-3,7-dimethy I -6,7-epoxy-//7//i,v-2-octene, a substituted geranyl epoxide insect juvenile hormone mimic, is hydrolyzed 10 times more rapidly by the cytosolic enzyme than by the microsomal one. In any series, such as the substituted styrene oxides, the trans configuration is hydrolyzed more rapidly by the cytosolic epoxide hydrolase than is the cis isomer. At the same time, it should remembered that in this and other series,... 

Synthetic pyrethroids, avermectins, juvenile hormone mimics, biological pesticides 1985- Genetically engineered organisms... 

Although juvenile hormone itself is too unstable in light and too expensive to synthesize for use in controlling insect populations, related compounds, called juvenile hormone mimics, have been used effectively. The best known example is called methoprene, sold under such trade... 

Methoprene is the common name for a racemic mixture of two enantiomers (R and S in a ratio of 1 1). The activity of the compound as a juvenile hormone mimic is restricted to the S enantiomer. 

Solomon, K.R., Bowlus, SB., Metcalf, K.l.. and Kauenellenbogen. J.A. (1973 . The effect of piperouyi hutoxide and triorhocresyl phosphate on the activity of juvenile hormone mimics and their sulfur isusteres in Tenebrio moiitor L., and Oncvpefitts fiisciatus (Dallas). Life Set. 13,733 742. 

The activity of methoprene against T. mnlunr has been shown to be increased by the addition of PBO (Solomon et al., 1973). Resistant . aixtanvttm adults have been found to metabolize PBO and juvenile hormone mimics more quickly than susceptible strains by attacking the methylene group (Rowlands and Dyte, 1979) The larvae were more resistant to both the hormone mimic and high levels of PBO. 

Dyte, C.E., Forster, R. and Aggarwal, S. (1976) The rust-red flour beetle. Resistance to juvenile hormone mimics. Pest Infestation Control, 1971-73, 79-80. 

Fleas on animals can be controlled by methoprene (11.45), a juvenile hormone mimic that prevents the conversion of larvae into pupae.177 Another chemical, lufenuron (11.46) is given to the animal orally. Any flea that bites the animal becomes sterile by inhibition of the development of chitin, a vital polymer in the exoskeleton. These chemicals should have minimal effects on other species. 

Juvenile hormone agonists as pesticides Methoprene is a juvenile hormone mimic preventing metamorphosis and is used to control a wide variety of insects, especially Diptera and Pharaoh s... 

The N-[4-(benzyloxy)benzyl]anilides obtained by DeMilo and Redfern (1979) proved to be highly effective juvenile hormone mimics, though their structure does not reflect even the intention of preparing terpene inspired juvenoids. The most effective member of this class was N-[4-(3-chlorobenzyl)oxy]benzyl-2,6-difluoro-aniline (69). 

Ethyl-4-[2-(t-butylcarbonyloxy)butoxy] benzoate (ETB, ZR-2646, 71) occupies an intermediate position between the juvenile hormone mimics and the antijuvenile hormones to be discussed later. It acts as an anti-JH at low doses and as a JH mimic at high doses. The nature of this JH agonist/antagonist action is not understood, yet its interference with the induction of juvenile hormone esterase seems to elucidate at least partly its action on insects (Staal, 1977 Sparks et al., 1979). 

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