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  • 1
    ISSN: 1573-1561
    Keywords: Host-plant resistance ; α-tomatine ; sterols ; sterol esters ; Lycopersicon esculentum ; Heliothis zea ; Lepidoptera ; Noctuidae ; parasitoids ; Hyposoter exiguae ; Hymenoptera ; Ichneumonidae ; secondary compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The solitary, endoparasitic ichneumonid,Hyposoter exiguae (Viereck) is a parasitoid of the tomato fruitworm,Heliothis zea (Boddie). However, the parasitoid is deleteriously affected by the tomato glycoalkaloid, α-tomatine, ingested from hosts (H. zea) fed on artificial diets or semipurified extracts of tomato plants that contained α-tomatine. α-Tomatine causes prolonged larval development; disruption or prevention of pupal eclosion; deformation of antennal, abdominal, and genital structures; and reduction in adult weight and longevity of the parasitoid. These toxic effects are exacerbated when the dietary dose of α-tomatine is increased from 12 μmol to 20 μmol/g dry wt of diet. However, the toxicity of α-tomatine is attenuated in parasitoids reared from hosts fed on artificial diets that contain equimolar or supramolar amounts of 3β-OH-sterols admixed with α-tomatine. Further, the toxicity of extracts from the foliage of different cultivars of tomatoes toH. exiguae is contingent upon the composite levels of α-tomatine and total phytosterol (free and esterified). Cultivars with a low total sterol-tomatine ratio are more toxic toH. exiguae. The possible mode of action of α-tomatine toxicity toH. exiguae by disruption of sterol metabolism is discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 13 (1987), S. 1759-1770 
    ISSN: 1573-1561
    Keywords: Castanospermine ; 6-epicastanospermine ; deoxynojirimycin ; cellobiase ; lactase ; maltase ; sucrase ; trehalase ; endosymbiote ; insect-plant interactions ; allelochemicals ; Homoptera ; Coleoptera ; Lepidoptera ; Diptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The indolizidine alkaloid, castanospermine (1,6,7,8-tetrahydroxy-octahydroindolizidine—a stereochemical mimic of glucose found in the Australian legumeCastanospermum australe), differentially inhibited cellobiose, lactose, maltose, sucrose, and trehalose hydrolyzing enzymes from a broad taxonomic spectrum of insects (19 species from 12 different families). It was a potent inhibitor of cellobiase activity of all insects tested (50% inhibition at 〈3.2 × 10−5 M castanospermine). With one exception, it also inhibited lactase activity of all insects examined. Only in the sap-feeding Homoptera did castanospermine inhibit all disaccharidase activities assayed. Trehalase activity of the Lepidoptera and Diptera was generally inhibited by castanospermine, whereas inhibition of trehalase activity of the Coleoptera by castanospermine was exiguous or not detectable. Castanospermine was a significant feeding deterrent towards pea aphids,Acyrthosiphon pisum, with an ED50 of 1 × 10−4 M in artificial diets. Two compounds stereochemically related to castanospermine, deoxynojirimycin and 6-epicastanospermine, were each slightly active at deterring the feeding of green peach aphids,Myzus persicae, (ED50=2.5 × 10−3 M) and greenbugs,Schizaphis graminum (ED50=5 × 10−3 M), respectively. Among the insects studied there was no distinct relationship between enzyme inhibition and adaptation to host plants containing castanospermine or other toxic alkaloids.
    Type of Medium: Electronic Resource
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