Insect juvenile hormones

Insect juvenile hormone Insect repellents Insect resistance Insects... 

Cinnamyl—sesamol ethers, eg (35), are useful as insect chemosterilants (111). 3,4-Methylenedioxyphenyl-3-halo-2-propynyl ethers (36, X = halogen) are synergists for carbamate insecticides (112). HaloaLkyl or haloalkenyl ethers, eg (37), show acaricidal and insect juvenile hormone activity (113). The first total synthesis of gibbereUic acid was from 2-methoxy-6-aLkoxyethyl-l,4-benzoquinone, a derivative of hydroxyhydroquinone (114). 

Both enantiomers of the biologically active Bower s compound, a potent analogue of an insect juvenile hormone [103] (Scheme 18) were prepared using Aspergillus sp. cells in 96% ee. Interestingly, biological tests showed that the (6i )-antipode was about ten times more active than the (6S)-counterpart against the yellow meal worm Tenebrio molitor. 

Figure 5. Structures of the Insect Juvenile Hormone 3 and a Commercially Available Analog, Methoprene...

In addition to its role as an intermediate in cholesterol biosynthesis, isopentenyl pyrophosphate is the activated precursor of a huge array of biomolecules with diverse biological roles (Fig. 21-48). They include vitamins A, E, and K plant pigments such as carotene and the phytol chain of chlorophyll natural rubber many essential oils (such as the fragrant principles of lemon oil, eucalyptus, and musk) insect juvenile hormone, which controls metamorphosis dolichols, which serve as lipid-soluble carriers in complex polysaccharide synthesis and ubiquinone and plastoquinone, electron carriers in mitochondria and chloroplasts. Collectively, these molecules are called isoprenoids. More than... 

Ashok M., Turner C. and Wilson T. G. (1998) Insect juvenile hormone resistance gene homology with the bHLH-PAS family of transcriptional regulators. Proc. Natl. Acad. 

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. 

Sources of propionate for the biogenesis of the ethyl-branched insect juvenile hormones Role of isoleucine and valine. Proc. Natl. Acad. Sci. USA, 84,... 

Fluoroketone analogues are also inhibitors of esterases. For example, the difluoro-ketone analogue 36 of sn-glycerol phospholipids is a potent competitive inhibitor of phospholipase A27 while the trifluoromethyl ketone 37 analogue of an insect juvenile hormone 38 is a potent and selective inhibitor of juvenile hormone esterase78. 

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,... 

Much interest has been shown in the biosynthesis of insect juvenile hormones (62 R1, R2 = Me or Et). In adult male moths, [l-14C]propionate was specifically incorporated into juvenile hormone I [JH-1, (62 R1 = R2 = Et)], and tracer was only found at, and equally distributed between, C-7 and C-ll.90 Application of [2-14C]-and [3-14C]-propionate led to extensive randomization of label, which suggests that C-2 and C-3 formed in propionate catabolism can be re-used as smaller fragments, whilst C-l is either removed from propionate in a metabolically active form or is highly diluted. Ternary complexes of brain, corpora cardiaca, and corpora allata from the tobacco budworm Heliothis virescens produced labelled JH-I and JH-II (62 R1 = Et, R2 = Me) when incubated with L-[Me-14C]methionine or sodium [l-l4C]propionate.91 Partial degradation of the juvenile hormones showed that in JH-I portions a and /3 (62) had incorporated one atom of tracer from each propionate, whereas fraction y was unlabelled, and in JH-II only fraction a was... 

Chromenes (Phe a-pyran) include encecalin (a phototoxic antimicrobial from various Asteraceae) and the phloroglucinol derivative mallotochromene (cytotoxic and an HIV-1 reverse transcriptase inhibitor). Precocene 1 (7-methoxy-2,2-dimethylchromene) and pre-cocene 2 (6,7-dimethoxy-2,2-dimethylchromene) produced by Ageratum species (Asteraceae) inhibit the production of insect juvenile hormone (JH) as a result of suicidal conversion of these pro-toxins to cytotoxic derivatives by the JH-producing insect cells. 

The molting and other hormonal activities of the ecdysteroids are, of course, modulated by the titer of the insect juvenile hormone and the two materials typically function in close concert with one another in dictating insect molting and metamorphosis as well as in reproductive maturation (21). 

The three major, known insect juvenile hormones (JH I, JH II and JH III) (Figure 6) are all methyl esters of terminally epoxi-dized homologs of farnesoic acid. They are present in varying amounts in different insects at different stages of development and it has been suggested, though not determined, that they may play different hormonal roles. 

In the Design of Inhibitors of Insect Juvenile Hormone Biosynthesis... 

A CA epoxidase perhaps identical to the precocene epoxidase biosynthesizes Insect juvenile hormones (JH) from the analogous inactive oleflnic precursor, and the enzyme activity appears higher in precocene-sensitive species (32). Subsequent detoxification of JH occurs primarily by EHs and esterases in peripheral tissues, and preliminary information does not indicate major differences for JH degradation routes between chewing and sucking herbivores, or insect carnivores (33,34). More study of the role of detoxification in regulating the action of JH in target tissues is required. 

Methoprene, a juvenile hormone analog, is structurally similar to insect juvenile hormones (Figure 4.11) such as juvenile hormone III. It is used for control of mosquitoes (floodwater mosquitoes, 2-4 instars), cigarette beetles, horn flies, fungus gnats (on mushroom), fleas, etc. The oral LD50 for methoprene in rats is >34,600 mg/kg. 

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