Juvenile mimics

Bhan P, Pande B S, Soman R, Damodaran N P, Sukh Dev 1984 Products active on Arthropod-V. Insect juvenile mimics (Part 5) Sesquiterpene acids having JH activity from wood of Cedrus deodara Loud. Tfetrahedron 40 2961-2965... 

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... 

For Instance, many terpene derivatives mimic insect hormone actioa Juvabione (15) is the classical example of a juvenile hormone (JH) mimic that prevents egg maturation in Pyrrhocoris bugs. Aromatic terpene ethers (16), methylene dloxyphenyl terpene ethers (17), and other farnesyl derivatives also have JH activity and the latter ones (18) also cause sterility in Pyrrhocoris. For the most part JH active terpenes are among the sesquiterpenes but several monoterpenes also have insect sterilizing effects (19. 20). The acyclic monoterpene cltral reduces the fertility of rats by causing follicular degeneration (21). 

It Is apparent from our Investigations of prenylated qulnones from desert annuals, that these compounds are not only potent skin sensitizers but also potential Insecticides, The toxicity of the prenylated qulnones is in part due to their lipophiliclty which permits the compounds to penetrate the cuticle and alkylate Important metabolic enzymes. Another possible explanation for their antijuvenile action is that the prenylated qulnones are transformed Into a qulnone methlde species which mimic the juvenile hormones (JH) and possibly interfere with the production of JH or deactivate the hormones. 

Several terpenoid compounds serve as juvenile hormones (or mimics) and ecydsones respectively ( ) in insects. 

Retinoic Acid Receptor. Most of the biological effects of retinoids are mediated through the retinoic acid receptor (RAR) and the retinoid X receptor (RXR). Both all-/ran.s-retinoic acid and 9-d.v-rctinoic acid serve as agonists of RAR, while only 9-d.v-rctinoic acid functions as an agonist of RXR. The functional RAR exists as a heterodimer with RXR, while functional RXR exists as a homodimer. Methoprene is a juvenile hormone III analogue that mimics the activity of this insect hormone. 

Methoprene and fenoxycarb mimic the action of insect juvenile hormone in molting and reproduction, and have low toxicity to mammals. Exposure at molting produces deformed insects having mixed larval/pupal or larval/adult morphologies, and they disrupt reproductive physiology in adults to effectively serve as a method of birth control. 

Several authors have investigated the role of juvenile hormone (JH) in hydrocarbon signatures. Sledge et al. (2004) performed one such study based on measuring the size of the corpora allata as an indicator of JH levels. Since caste determination depends strictly on the colony social structure, it can be assumed that topical JH application mimics natural caste development and thus modifies the cuticular caste-specific odor. Based on this assumption,... 

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... 

In moving to other classes of JH analogs, major departures from the farnesane skeleton have been reported in the form of phenyl ethers (22, Z3,2 ), cyclohexenes such as juvabione (25), and small peptides (26) as an extreme case of completely selective action on one family of bugs. The latter compounds are most remarkable for the pronounced differential activity of their optical enantiomers, in which one antipode is several thousand times more active biologically than the other (2 7). In connection with the peptides, it should be noted that there is no formal proof that these compounds exert their action as true mimics of juvenile hormones at the target tissue level. One may well ask whether these peptides act directly on the corpora allata glands as allatotropins. 

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... 

Juvenile hormone (JH) is a necessary chemical at certain times in insect development, but becomes toxic when present during metamorphosis, i.e., when normal JH titers are low. JH mimics (methoprene, hydroprene, fenoxycarb, and pyriproxyfen) act similar to JH and exhibit the highest toxicity when applied at the onset of metamorphosis. 

Juvenile hormone receptor Juvenoids, fenoxycarb, pryriproxyfen JH mimics... 

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... 

The use of juvenile hcamone mimics to control certain insect populations the use of organometaUic reagents to synthesize the C,g juvenile hormone (Opener, Section 20.10C)... 

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