The exact analysis of the ABC type absorption due to the -CH20H group of 3j3-acetoxy-5j3,6[3-oxidocholestan-19-01 provides two vicinal HCOH coupling constants for dihedral angles of 80" and 160". A least squares fit of these and previous data in the literature to a "Karplus" relation provides values for the coefficients in such an equation. The theoretical justification for such a relation has been obtained by extended Hiickel molecular orbital calculations for methanol with different dihedral angles. The practical limitations in, and applications of the relation are discussed. An effect of solvent on the vicinal coupling constants is also noted and discussed.

Factors contributing to resistance of maize to infestation by the corn weevilSitophilus zeamais were investigated in four populations of indigenous and improved maize from Belize. Resistance was related to the antifeedant properties of grain as well as sugar content and mechanical hardness. Grain extracts of all populations of maize significantly reduced insect feeding on treated artificial diets when compared to control diets. Consumption of treated diets was negatively correlated with phenolic content of the grain extract. An analysis by GC-MS indicated that ferulic acid andp-coumaric acid were the principal phenolics present in the extracts, and insect feeding was strongly deterred when pure substances were added to insect diets. Fluorescence associated with ferulic acid and related compounds in grain sections was located in the pericarp and aleurone layer and was especially intense in the most resistant grain variety.

Analogues of the Cyclic Hydroxamic Acid 2,4-Dihydroxy-7-methoxy-2.Zf-l,4-benzoxazin-3-one: Decomposition to Benzoxazolinones and Reaction with /8-Mercaptoethanol

Azadirachtin, a triterpenoid substance from the neem tree, Azadirachta indica A. Juss., Meliaceae, was evaluated for its antifeedant and insecticidal properties to the European corn borer Ostrinia nubilalis Hübner. The 50% protective concentration for larval feeding on treated corn disks (PC50) was 3.5 ppm for neonate larvae and 24 ppm for third instar larvae. Azadirachtin severely reduced larval growth at 1 and 10 ppm in a meridic diet and eventually caused 100% mortality at 10 ppm and 90% at 1 ppm. At 0.1 ppm azadirachtin showed no significant effect on larvae but altered the sex ratio in favor of male moths during adult emergence and arrested oviposition of female moths. Nutritional indices for naive and habituated third instar larvae suggested that reduction of growth was due to toxicity as shown by a lowered efficiency of conversion in the azadirachtin treated groups, rather than changes in digestibility. No clear evidence of tolerance was observed in the habituated group. The data suggest that at 10 ppm azadirachtin is an effective botanical insecticide for control of O. nubilalis. RÉSUMÉ Propriétés anti‐appètantes et insecticides de l'azadirachtine envers la pyrale du maïs, Ostrinia nubilalis On a examiné les propriétés anti‐appétantes et insecticides de l'azadirachtine, une substance triterpénoïde provenant d'Azadirachta indica envers la pyrale du maïs Ostrinia nubilalis. La concentration effective pour causer 50% d'inhibition de l'alimentation larvaire (PC50) sur des disques foliaires a été de 3.5 ppm pour les larves de premier stade et de 24 μg/8 pour celle de troisième stade. L'azadirachtine a sévèrement réduit la croissance larvaire à des concentrations de 1 et 10 ppm dans une diète méridique et, éventuellement, a causé 100% de mortalité à 10 ppm et 90% à 1 ppm. A 0.1 ppm l'azadirachtine n'a pas eu d'effet significatif sur les larves maïs a modifié l'indice de masculinité en faveur des mâles au moment de l'émergence et a empêché l'oviposition chez les femelles. Les indices nutritionnels pour les larves naïves de troisième âge et celles ayant subi une accoutumance suggèrent que la réduction de croissance est le résultat d'une intoxication comme le démontre une efficacité réduite de transformation chez les groupes traités à l'azadirachtine, plutôt que des changements de digestibilité. Il n'y a pas d'évidence claire de tolérance dans le groupe ayant subi l'accoutumance. Les résultats suggèrent qu'à 10 ppm l'azadirachtine est un insecticide botanique efficace envers O. nubilalis.

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